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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull procfs updates from Christian Brauner:
- Revamp fs/filesystems.c
The file was a mess with a hand-rolled linked list in desperate need
of a cleanup. The filesystems list is now RCU-ified, /proc files can
be marked permanent from outside fs/proc/, and the string emitted
when reading /proc/filesystems is pre-generated and cached instead of
pointer-chasing and printfing entry by entry on every read.
The file is read frequently because libselinux reads it and is linked
into numerous frequently used programs (even ones you would not
suspect, like sed!). Scalability also improves since reference
maintenance on open/close is bypassed.
open+read+close cycle single-threaded (ops/s):
before: 442732
after: 1063462 (+140%)
open+read+close cycle with 20 processes (ops/s):
before: 606177
after: 3300576 (+444%)
A follow-up patch adds missing unlocks in some corner cases and
tidies things up.
- Relax the mount visibility check for subset=pid mounts
When procfs is mounted with subset=pid, all static files become
unavailable and only the dynamic pid information is accessible. In
that case there is no point in imposing the full mount visibility
restrictions on the mounter - everything that can be hidden in procfs
is already inaccessible. These restrictions prevented procfs from
being mounted inside rootless containers since almost all container
implementations overmount parts of procfs to hide certain
directories.
As part of this /proc/self/net is only shown in subset=pid mounts for
CAP_NET_ADMIN, reconfiguring subset=pid is rejected, the
SB_I_USERNS_VISIBLE superblock flag is replaced with an
FS_USERNS_MOUNT_RESTRICTED filesystem flag, fully visible mounts are
recorded in a list, and the mount restrictions are finally
documented.
- Protect ptrace_may_access() with exec_update_lock in procfs
Most uses of ptrace_may_access() in procfs should hold
exec_update_lock to avoid TOCTOU issues with concurrent privileged
execve() (like setuid binary execution).
This fixes the easy cases - the owner and visibility checks and the
FD link permission checks - with the gnarlier ones to follow later.
* tag 'vfs-7.2-rc1.procfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
fs: fix ups and tidy ups to /proc/filesystems caching
proc: protect ptrace_may_access() with exec_update_lock (FD links)
proc: protect ptrace_may_access() with exec_update_lock (part 1)
docs: proc: add documentation about mount restrictions
proc: handle subset=pid separately in userns visibility checks
proc: prevent reconfiguring subset=pid
proc: subset=pid: Show /proc/self/net only for CAP_NET_ADMIN
fs: cache the string generated by reading /proc/filesystems
sysfs: remove trivial sysfs_get_tree() wrapper
fs: RCU-ify filesystems list
fs: move SB_I_USERNS_VISIBLE to FS_USERNS_MOUNT_RESTRICTED
proc: allow to mark /proc files permanent outside of fs/proc/
namespace: record fully visible mounts in list
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc vfs updates from Christian Brauner:
"Features:
- Reduce pipe->mutex contention by pre-allocating pages outside the
lock in anon_pipe_write().
anon_pipe_write() called alloc_page() once per page while holding
pipe->mutex. The allocation can sleep doing direct reclaim and runs
memcg charging, which extends the critical section and stalls any
concurrent reader on the same mutex. Now up to 8 pages are
pre-allocated before the mutex is taken, leftovers are recycled
into the per-pipe tmp_page[] cache before unlock, and any remainder
is released after unlock, keeping the allocator out of the critical
section on both sides. On a writers x readers sweep with 64KB
writes against a 1 MB pipe throughput improves 6-28% and average
write latency drops 5-22%; under memory pressure - when the cost of
holding the mutex across reclaim is highest - throughput improves
21-48% and latency drops 17-33%. The microbenchmark is added to
selftests.
- uaccess/sockptr: fix the ignored_trailing logic in
copy_struct_to_user() to behave as documented and the usize check
in copy_struct_from_sockptr() for user pointers, and add
copy_struct_{from,to}_bounce_buffer() and copy_struct_to_sockptr()
helpers for upcoming users (IPPROTO_SMBDIRECT, IPPROTO_QUIC).
- bpf: add a sleepable bpf_real_inode() kfunc that resolves the real
inode backing a dentry via d_real_inode(). On overlayfs the inode
attached to the dentry doesn't carry the underlying device
information; this is used by the filesystem restriction BPF program
that was merged into systemd.
- docs: add guidelines for submitting new filesystems, motivated by
the maintenance burden abandoned and untestable filesystems impose
on VFS developers, blocking infrastructure work like folio
conversions and iomap migration.
Fixes:
- libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()
and drop the now-redundant assignments in callers. This began as a
one-line dma-buf fix for a path_noexec() warning; a pseudo
filesystem has no reason not to set SB_I_NOEXEC. All init_pseudo()
callers were audited: the only visible effect is on dma-buf where
SB_I_NOEXEC silences the warning.
- Handle set_blocksize() failures in legacy filesystems (bfs, hpfs,
qnx4, jfs, befs, affs, isofs, minix, ntfs3, omfs). Mounting a
device with a sector size > PAGE_SIZE crashed roughly half of them;
the rest had the same missing error handling pattern. Plus a
follow-up releasing the superblock buffer_head when setting the
minix v3 block size fails.
- mount: honour SB_NOUSER in the new mount API.
- fs/fcntl: fix a SOFTIRQ-unsafe lock order in fasync signaling by
switching the process-group paths of send_sigio() and send_sigurg()
from read_lock(&tasklist_lock) to RCU, matching the single-PID
path.
- vfs: add an FS_USERNS_DELEGATABLE flag and set it for NFS, fixing
delegated NFS mounts (fsopen() in a container with the mount
performed by a privileged daemon) that broke when non-init
s_user_ns was tied to FS_USERNS_MOUNT.
- selftests/namespaces: fix a hang in nsid_test where an unreaped
grandchild kept the TAP pipe write-end open, a waitpid(-1) race in
listns_efault_test, and a false FAIL on kernels without listns()
where the tests should SKIP.
- filelock: fix the break_lease() stub signature for
CONFIG_FILE_LOCKING=n.
- init/initramfs_test: wait for the async initramfs unpacking before
running; the test and do_populate_rootfs() share the parser state.
- fs/coredump: reduce redundant log noise in
validate_coredump_safety().
- iomap: pass the correct length to fserror_report_io() in
__iomap_write_begin().
- backing-file: fix the backing_file_open() kerneldoc.
Cleanups:
- initramfs: refactor the cpio hex header parsing to use hex2bin()
instead of the hand-rolled simple_strntoul() which is reverted, and
extend the initramfs KUnit tests to cover header fields with 0x
prefixes.
- Replace __get_free_pages() and friends with kmalloc()/kzalloc()
across quota, proc, ocfs2/dlm, nilfs2, nfs, nfsd, libfs, jfs, jbd2,
isofs, fuse, select, namespace, configfs, binfmt_misc, bfs, and the
do_mounts init code - part of the larger work of replacing page
allocator calls with kmalloc().
- Use clear_and_wake_up_bit() in unlock_buffer() and
journal_end_buffer_io_sync() instead of open-coding the sequence.
- Drop unused VFS exports: unexport drop_super_exclusive(), remove
start_removing_user_path_at(), and fold __start_removing_path()
into start_removing_path().
- fs/read_write: narrow the __kernel_write() export with
EXPORT_SYMBOL_FOR_MODULES().
- vfs: uapi: retire octal and hex constants in favor of (1 << n) for
the O_ flags. Finding a free bit for a new flag across the
architectures was needlessly hard with the mixed bases.
- dcache: add extra sanity checks of dead dentries in dentry_free()
via a new DENTRY_WARN_ONCE() that also prints d_flags.
- iov_iter: use kmemdup_array() in dup_iter() to harden the
allocation against multiplication overflow.
- fs/pipe: write to ->poll_usage only once.
- vfs: remove an always-taken if-branch in find_next_fd().
- dcache: use kmalloc_flex() for struct external_name in __d_alloc().
- namei: use QSTR() instead of QSTR_INIT() in path_pts().
- sync_file_range: delete dead S_ISLNK code.
- Comment fixes: retire a stale comment in fget_task_next() and fix
assorted spelling mistakes"
* tag 'vfs-7.2-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (73 commits)
backing-file: fix backing_file_open() kerneldoc parameter
iomap: pass the correct len to fserror_report_io in __iomap_write_begin
vfs: add FS_USERNS_DELEGATABLE flag and set it for NFS
filelock: fix break_lease() stub signature for CONFIG_FILE_LOCKING=n
vfs: uapi: retire octal and hex numbers in favor of (1 << n) for O_ flags
bpf: add bpf_real_inode() kfunc
fs/read_write: Do not export __kernel_write() to the entire world
libfs: drop redundant SB_I_NOEXEC/SB_I_NODEV in init_pseudo() callers
libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()
mount: honour SB_NOUSER in the new mount API
fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling
selftests/pipe: add pipe_bench microbenchmark
fs/pipe: pre-allocate pages outside pipe->mutex in anon_pipe_write
fs: retire stale comment in fget_task_next()
fs: fix spelling mistakes in comment
bfs: replace get_zeroed_page() with kzalloc()
binfmt_misc: replace __get_free_page() with kmalloc()
configfs: replace __get_free_pages() with kzalloc()
fs/namespace: use __getname() to allocate mntpath buffer
fs/select: replace __get_free_page() with kmalloc()
...
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open_tree(..., OPEN_TREE_NAMESPACE) and
fsmount(..., FSMOUNT_NAMESPACE, ...) currently work on non-directories,
like regular files. That's bad for two reasons:
- It ends up mounting a regular file over the inherited namespace root,
which is a directory; mounting a non-directory over a directory is
normally explicitly forbidden, see for example do_move_mount()
- It causes setns() on the new namespace to set the cwd to a regular
file, which the rest of VFS does not expect
Fix it by restricting create_new_namespace() (which is used by both of
these flags) to directories.
Leave the behavior for OPEN_TREE_CLONE as-is, that seems unproblematic.
Fixes: 9b8a0ba68246 ("mount: add OPEN_TREE_NAMESPACE")
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: stable@kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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may_decode_fh() accesses mount::mnt_ns without holding any locks; that
means the mount can concurrently be unmounted, and the mnt_namespace can
concurrently be freed after an RCU grace period.
This race can happens as follows, assuming that the mount point was
created by open_tree(..., OPEN_TREE_CLONE):
thread 1 thread 2 RCU
__do_sys_open_by_handle_at
do_handle_open
handle_to_path
may_decode_fh
is_mounted
[mount::mnt_ns access]
[mount::mnt_ns access]
__do_sys_close
fput_close_sync
__fput
dissolve_on_fput
umount_tree
class_namespace_excl_destructor
namespace_unlock
free_mnt_ns
mnt_ns_tree_remove
call_rcu(mnt_ns_release_rcu)
mnt_ns_release_rcu
mnt_ns_release
kfree
[mnt_namespace::user_ns access] **UAF**
Fix it by taking rcu_read_lock() around the mount::mnt_ns access, like
in __prepend_path().
Additionally, document the semantics of mount::mnt_ns, and use WRITE_ONCE()
for writers that can race with lockless readers.
This bug is unreachable unless one of the following is set:
- CONFIG_PREEMPTION
- CONFIG_RCU_STRICT_GRACE_PERIOD
because it requires an RCU grace period to happen during a syscall without
an explicit preemption.
This doesn't seem to have interesting security impact; worst-case, it could
leak the result of an integer comparison to userspace (from the level
check in cap_capable()), cause an endless loop, or crash the kernel by
dereferencing an invalid address.
Fixes: 620c266f3949 ("fhandle: relax open_by_handle_at() permission checks")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://patch.msgid.link/20260603-vfs-fhandle-uaf-fix-v2-1-d05db76a5084@google.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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One should *not* be allowed to mount one of those, new API or not.
Reported-by: Denis Arefev <arefev@swemel.ru>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Link: https://patch.msgid.link/20260602020444.GP2636677@ZenIV
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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mnt_warn_timestamp_expiry() allocates memory for a path with
__get_free_page() although there is a dedicated helper for allocation of
file paths: __getname().
Replace __get_free_page() for allocation of a path buffer with __getname().
Christian Brauner <brauner@kernel.org> says:
Pass PATH_MAX (not PAGE_SIZE) to d_path() to match the size that
__getname() actually allocates, and drop the now-unnecessary NULL check
around __putname() since __putname() handles NULL. Both per Jan Kara's
review feedback, acked by the author.
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Link: https://patch.msgid.link/20260523-b4-fs-v1-14-275e36a83f0e@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
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When procfs is mounted with subset=pid, only the dynamic process-related
part of the filesystem remains visible. That part cannot be hidden by
overmounts, so checking whether an existing procfs mount is fully
visible does not make sense for this mode.
At the same time, a subset=pid procfs mount must not be used as evidence
that a later procfs mount would not reveal additional information. It
provides a restricted view of procfs, not the full filesystem view.
Mark subset=pid procfs instances as restricted variants. Ignore
restricted variants when looking for an already-visible mount, and allow
new restricted variants without consulting mnt_already_visible().
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://patch.msgid.link/4d5e760c3d534dd2e05578d119cc408450053a98.1777278334.git.legion@kernel.org
Reviewed-by: Aleksa Sarai <aleksa@amutable.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Whether a filesystem's mounts need to undergo a visibility check in user
namespaces is a static property of the filesystem type, not a runtime
property of each superblock instance. Both proc and sysfs always set
SB_I_USERNS_VISIBLE on their superblocks unconditionally (sysfs does so
on first creation, and subsequent mounts reuse the same superblock).
Move this flag from sb->s_iflags (SB_I_USERNS_VISIBLE) to
file_system_type->fs_flags (FS_USERNS_MOUNT_RESTRICTED) so the intent
is expressed at the filesystem type level where it belongs.
All check sites are updated to test sb->s_type->fs_flags instead of
sb->s_iflags. The SB_I_NOEXEC and SB_I_NODEV flags remain on the
superblock as they are runtime properties set during fill_super.
Link: https://patch.msgid.link/72887c5b6204dc3adf5a53104f0be6bd8bc4f6cd.1777278334.git.legion@kernel.org
Reviewed-by: Aleksa Sarai <aleksa@amutable.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Instead of wading through all the mounts in the mount namespace rbtree
to find fully visible procfs and sysfs mounts, be honest about them
being special cruft and record them in a separate per-mount namespace
list.
Link: https://patch.msgid.link/684859a8e0ac929cb89c1fbe16ce15b30c70eb1f.1777278334.git.legion@kernel.org
Reviewed-by: Aleksa Sarai <aleksa@amutable.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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In the OPEN_TREE_NAMESPACE path vfs_open_tree() resolves a path via
filename_lookup() without holding namespace_lock. Between the lookup
and create_new_namespace() acquiring namespace_lock via
LOCK_MOUNT_EXACT_COPY() another thread can unmount the mount, setting
mnt->mnt_ns to NULL.
When create_new_namespace() then checks !mnt->mnt_ns it incorrectly
takes the swap-and-mntget path that was designed for fsmount()'s
detached mounts. This reuses a mount whose mnt_mp_list is in an
inconsistent state from the concurrent unmount, causing a general
protection fault in __umount_mnt() -> hlist_del_init(&mnt->mnt_mp_list)
during namespace teardown.
Remove the !mnt->mnt_ns special case entirely. Instead, always
duplicate the mount:
- For OPEN_TREE_NAMESPACE use __do_loopback() which will properly
clone the mount or reject it via may_copy_tree() if it was
unmounted in the race window.
- For fsmount() use clone_mnt() directly (via the new MOUNT_COPY_NEW
flag) since the mount is freshly created by vfs_create_mount() and
not in any namespace so __do_loopback()'s IS_MNT_UNBINDABLE,
may_copy_tree, and __has_locked_children checks don't apply.
Reported-by: syzbot+e4470cc28308f2081ec8@syzkaller.appspotmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Allow MOVE_MOUNT_BENEATH to target the caller's rootfs. When the target
of a mount-beneath operation is the caller's root mount, verify that:
(1) The caller is located at the root of the mount, as enforced by
path_mounted() in do_lock_mount().
(2) Propagation from the parent mount would not overmount the target,
to avoid propagating beneath the rootfs of other mount namespaces.
The root-switching is decomposed into individually atomic, locally-scoped
steps: mount-beneath inserts the new root under the old one, chroot(".")
switches the caller's root, and umount2(".", MNT_DETACH) removes the old
root. Since each step only modifies the caller's own state, this avoids
cross-namespace vulnerabilities and inherent fork/unshare/setns races
that a chroot_fs_refs()-based approach would have.
Userspace can use the following workflow to switch roots:
fd_tree = open_tree(-EBADF, "/newroot",
OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC);
fchdir(fd_tree);
move_mount(fd_tree, "", AT_FDCWD, "/",
MOVE_MOUNT_BENEATH | MOVE_MOUNT_F_EMPTY_PATH);
chroot(".");
umount2(".", MNT_DETACH);
Link: https://patch.msgid.link/20260224-work-mount-beneath-rootfs-v1-2-8c58bf08488f@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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When performing a mount-beneath operation the target mount can often be
locked:
unshare(CLONE_NEWUSER | CLONE_NEWNS);
mount --beneath -t tmpfs tmpfs /proc
will fail because the procfs mount on /proc became locked when the mount
namespace was created from the parent mount namespace. Same logic for:
unshare(CLONE_NEWUSER | CLONE_NEWNS);
mount --beneath -t tmpfs tmpfs /
MNT_LOCKED is raised to prevent an unprivileged mount namespace from
revealing whatever is under a given mount. To replace the rootfs we need
to handle that case though.
We can simply transfer the locked mount property from the top mount to
the mount beneath. The new mount we mounted beneath the top mount takes
over the job of the top mount in protecting the parent mount from being
revealed. This leaves us free to allow the top mount to be unmounted.
This also works during mount propagation and also works for the
non-MOVE_MOUNT_BENEATH case:
(1) move_mount(MOVE_MOUNT_BENEATH): @source_mnt->overmount always NULL
(2) move_mount(): @source_mnt->overmount maybe !NULL
For (1) can_move_mount_beneath() rejects overmounted @source_mnt (We
could allow this but whatever it's not really a use-case and it's fugly
to move an overmounted mount stack around. What are you even doing? So
let's keep that restriction.
For (2) we can have @source_mnt overmounted (Someone overmounted us
while we locked the target mount.). Both are fine. @source_mnt will be
mounted on whatever @q was mounted on and @q will be mounted on the top
of the @source_mnt mount stack. Even in such cases we can unlock @q and
lock @source_mnt if @q was locked.
This effectively makes mount propagation useful in cases where a mount
namespace has a locked mount somewhere and we propagate a new mount
beneath it but the mount namespace could never get at it because the old
top mount remains locked. Again, we just let the newly propagated mount
take over the protection and unlock the top mount.
Link: https://patch.msgid.link/20260224-work-mount-beneath-rootfs-v1-1-8c58bf08488f@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add support for creating a mount namespace that contains only a copy of
the root mount from the caller's mount namespace, with none of the
child mounts. This is useful for containers and sandboxes that want to
start with a minimal mount table and populate it from scratch rather
than inheriting and then tearing down the full mount tree.
Two new flags are introduced:
- CLONE_EMPTY_MNTNS for clone3(), using the 64-bit flag space.
- UNSHARE_EMPTY_MNTNS for unshare(), reusing the
CLONE_PARENT_SETTID bit which has no meaning for unshare.
Both flags imply CLONE_NEWNS. For the unshare path,
UNSHARE_EMPTY_MNTNS is converted to CLONE_EMPTY_MNTNS in
unshare_nsproxy_namespaces() before it reaches copy_mnt_ns(), so the
mount namespace code only needs to handle a single flag.
In copy_mnt_ns(), when CLONE_EMPTY_MNTNS is set, clone_mnt() is used
instead of copy_tree() to clone only the root mount. The caller's root
and working directory are both reset to the root dentry of the new
mount.
The cleanup variables are changed from vfsmount pointers with
__free(mntput) to struct path with __free(path_put) because the empty
mount namespace path needs to release both mount and dentry references
when replacing the caller's root and pwd. In the normal (non-empty)
path only the mount component is set, and dput(NULL) is a no-op so
path_put remains correct there as well.
Link: https://patch.msgid.link/20260306-work-empty-mntns-consolidated-v1-1-6eb30529bbb0@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Add FSMOUNT_NAMESPACE flag to fsmount() that creates a new mount
namespace with the newly created filesystem attached to a copy of the
real rootfs. This returns a namespace file descriptor instead of an
O_PATH mount fd, similar to how OPEN_TREE_NAMESPACE works for open_tree().
This allows creating a new filesystem and immediately placing it in a
new mount namespace in a single operation, which is useful for container
runtimes and other namespace-based isolation mechanisms.
The rootfs mount is created before copying the real rootfs for the new
namespace meaning that the mount namespace id for the mount of the root
of the namespace is bigger than the child mounted on top of it. We've
never explicitly given the guarantee for such ordering and I doubt
anyone relies on it. Accepting that lets us avoid copying the mount
again and also avoids having to massage may_copy_tree() to grant an
exception for fsmount->mnt->mnt_ns being NULL.
Link: https://patch.msgid.link/20260122-work-fsmount-namespace-v1-3-5ef0a886e646@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Remove the OPEN_TREE_NAMESPACE flag checking from __do_loopback() and
instead have callers pass CL_COPY_MNT_NS_FILE directly in copy_flags.
Link: https://patch.msgid.link/20260122-work-fsmount-namespace-v1-2-5ef0a886e646@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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If the root of the namespace has an id that's greater than the child
we'd not find it. Handle that case.
Link: https://patch.msgid.link/20260122-work-fsmount-namespace-v1-1-5ef0a886e646@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs fixes from Christian Brauner:
- Fix an uninitialized variable in file_getattr().
The flags_valid field wasn't initialized before calling
vfs_fileattr_get(), triggering KMSAN uninit-value reports in fuse
- Fix writeback wakeup and logging timeouts when DETECT_HUNG_TASK is
not enabled.
sysctl_hung_task_timeout_secs is 0 in that case causing spurious
"waiting for writeback completion for more than 1 seconds" warnings
- Fix a null-ptr-deref in do_statmount() when the mount is internal
- Add missing kernel-doc description for the @private parameter in
iomap_readahead()
- Fix mount namespace creation to hold namespace_sem across the mount
copy in create_new_namespace().
The previous drop-and-reacquire pattern was fragile and failed to
clean up mount propagation links if the real rootfs was a shared or
dependent mount
- Fix /proc mount iteration where m->index wasn't updated when
m->show() overflows, causing a restart to repeatedly show the same
mount entry in a rapidly expanding mount table
- Return EFSCORRUPTED instead of ENOSPC in minix_new_inode() when the
inode number is out of range
- Fix unshare(2) when CLONE_NEWNS is set and current->fs isn't shared.
copy_mnt_ns() received the live fs_struct so if a subsequent
namespace creation failed the rollback would leave pwd and root
pointing to detached mounts. Always allocate a new fs_struct when
CLONE_NEWNS is requested
- fserror bug fixes:
- Remove the unused fsnotify_sb_error() helper now that all callers
have been converted to fserror_report_metadata
- Fix a lockdep splat in fserror_report() where igrab() takes
inode::i_lock which can be held in IRQ context.
Replace igrab() with a direct i_count bump since filesystems
should not report inodes that are about to be freed or not yet
exposed
- Handle error pointer in procfs for try_lookup_noperm()
- Fix an integer overflow in ep_loop_check_proc() where recursive calls
returning INT_MAX would overflow when +1 is added, breaking the
recursion depth check
- Fix a misleading break in pidfs
* tag 'vfs-7.0-rc2.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
pidfs: avoid misleading break
eventpoll: Fix integer overflow in ep_loop_check_proc()
proc: Fix pointer error dereference
fserror: fix lockdep complaint when igrabbing inode
fsnotify: drop unused helper
unshare: fix unshare_fs() handling
minix: Correct errno in minix_new_inode
namespace: fix proc mount iteration
mount: hold namespace_sem across copy in create_new_namespace()
iomap: Describe @private in iomap_readahead()
statmount: Fix the null-ptr-deref in do_statmount()
writeback: Fix wakeup and logging timeouts for !DETECT_HUNG_TASK
fs: init flags_valid before calling vfs_fileattr_get
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This was done entirely with mindless brute force, using
git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'
to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.
Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.
For the same reason the 'flex' versions will be done as a separate
conversion.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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This is the result of running the Coccinelle script from
scripts/coccinelle/api/kmalloc_objs.cocci. The script is designed to
avoid scalar types (which need careful case-by-case checking), and
instead replace kmalloc-family calls that allocate struct or union
object instances:
Single allocations: kmalloc(sizeof(TYPE), ...)
are replaced with: kmalloc_obj(TYPE, ...)
Array allocations: kmalloc_array(COUNT, sizeof(TYPE), ...)
are replaced with: kmalloc_objs(TYPE, COUNT, ...)
Flex array allocations: kmalloc(struct_size(PTR, FAM, COUNT), ...)
are replaced with: kmalloc_flex(*PTR, FAM, COUNT, ...)
(where TYPE may also be *VAR)
The resulting allocations no longer return "void *", instead returning
"TYPE *".
Signed-off-by: Kees Cook <kees@kernel.org>
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The m->index isn't updated when m->show() overflows and retains its
value before the current mount causing a restart to start at the same
value. If that happens in short order to due a quickly expanding mount
table this would cause the same mount to be shown again and again.
Ensure that *pos always equals the mount id of the mount that was
returned by start/next. On restart after overflow mnt_find_id_at(*pos)
finds the exact mount. This should avoid duplicates, avoid skips and
should handle concurrent modification just fine.
Cc: <stable@vger.kernel.org>
Fixed: 2eea9ce4310d8 ("mounts: keep list of mounts in an rbtree")
Link: https://patch.msgid.link/20260129-geleckt-treuhand-4bb940acacd9@brauner
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Fix an oversight when creating a new mount namespace. If someone had the
bright idea to make the real rootfs a shared or dependent mount and it
is later copied the copy will become a peer of the old real rootfs mount
or a dependent mount of it. The namespace semaphore is dropped and we
use mount lock exact to lock the new real root mount. If that fails or
the subsequent do_loopback() fails we rely on the copy of the real root
mount to be cleaned up by path_put(). The problem is that this doesn't
deal with mount propagation and will leave the mounts linked in the
propagation lists.
When creating a new mount namespace create_new_namespace() first
acquires namespace_sem to clone the nullfs root, drops it, then
reacquires it via LOCK_MOUNT_EXACT which takes inode_lock first to
respect the inode_lock -> namespace_sem lock ordering. This
drop-and-reacquire pattern is fragile and was the source of the
propagation cleanup bug fixed in the preceding commit.
Extend lock_mount_exact() with a copy_mount mode that clones the mount
under the locks atomically. When copy_mount is true, path_overmounted()
is skipped since we're copying the mount, not mounting on top of it -
the nullfs root always has rootfs mounted on top so the check would
always fail. If clone_mnt() fails after get_mountpoint() has pinned the
mountpoint, __unlock_mount() is used to properly unpin the mountpoint
and release both locks.
This allows create_new_namespace() to use LOCK_MOUNT_EXACT_COPY which
takes inode_lock and namespace_sem once and holds them throughout the
clone and subsequent mount operations, eliminating the
drop-and-reacquire pattern entirely.
Reported-by: syzbot+a89f9434fb5a001ccd58@syzkaller.appspotmail.com
Fixes: 9b8a0ba68246 ("mount: add OPEN_TREE_NAMESPACE") # mainline only
Link: https://lore.kernel.org/699047f6.050a0220.2757fb.0024.GAE@google.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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If the mount is internal, it's mnt_ns will be MNT_NS_INTERNAL, which is
defined as ERR_PTR(-EINVAL). So, in the do_statmount(), need to check ns
of mount by IS_ERR() and return.
Fixes: 0e5032237ee5 ("statmount: accept fd as a parameter")
Reported-by: syzbot+9e03a9535ea65f687a44@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/698e287a.a70a0220.2c38d7.009e.GAE@google.com/
Signed-off-by: Qing Wang <wangqing7171@gmail.com>
Link: https://patch.msgid.link/20260213103006.2472569-1-wangqing7171@gmail.com
Reviewed-by: Bhavik Sachdev <b.sachdev1904@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs 'struct filename' updates from Al Viro:
"[Mostly] sanitize struct filename handling"
* tag 'pull-filename' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (68 commits)
sysfs(2): fs_index() argument is _not_ a pathname
alpha: switch osf_mount() to strndup_user()
ksmbd: use CLASS(filename_kernel)
mqueue: switch to CLASS(filename)
user_statfs(): switch to CLASS(filename)
statx: switch to CLASS(filename_maybe_null)
quotactl_block(): switch to CLASS(filename)
chroot(2): switch to CLASS(filename)
move_mount(2): switch to CLASS(filename_maybe_null)
namei.c: switch user pathname imports to CLASS(filename{,_flags})
namei.c: convert getname_kernel() callers to CLASS(filename_kernel)
do_f{chmod,chown,access}at(): use CLASS(filename_uflags)
do_readlinkat(): switch to CLASS(filename_flags)
do_sys_truncate(): switch to CLASS(filename)
do_utimes_path(): switch to CLASS(filename_uflags)
chdir(2): unspaghettify a bit...
do_fchownat(): unspaghettify a bit...
fspick(2): use CLASS(filename_flags)
name_to_handle_at(): use CLASS(filename_uflags)
vfs_open_tree(): use CLASS(filename_uflags)
...
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc vfs updates from Christian Brauner:
"This contains a mix of VFS cleanups, performance improvements, API
fixes, documentation, and a deprecation notice.
Scalability and performance:
- Rework pid allocation to only take pidmap_lock once instead of
twice during alloc_pid(), improving thread creation/teardown
throughput by 10-16% depending on false-sharing luck. Pad the
namespace refcount to reduce false-sharing
- Track file lock presence via a flag in ->i_opflags instead of
reading ->i_flctx, avoiding false-sharing with ->i_readcount on
open/close hot paths. Measured 4-16% improvement on 24-core
open-in-a-loop benchmarks
- Use a consume fence in locks_inode_context() to match the
store-release/load-consume idiom, eliminating a hardware fence on
some architectures
- Annotate cdev_lock with __cacheline_aligned_in_smp to prevent
false-sharing
- Remove a redundant DCACHE_MANAGED_DENTRY check in
__follow_mount_rcu() that never fires since the caller already
verifies it, eliminating a 100% mispredicted branch
- Fix a 100% mispredicted likely() in devcgroup_inode_permission()
that became wrong after a prior code reorder
Bug fixes and correctness:
- Make insert_inode_locked() wait for inode destruction instead of
skipping, fixing a corner case where two matching inodes could
exist in the hash
- Move f_mode initialization before file_ref_init() in alloc_file()
to respect the SLAB_TYPESAFE_BY_RCU ordering contract
- Add a WARN_ON_ONCE guard in try_to_free_buffers() for folios with
no buffers attached, preventing a null pointer dereference when
AS_RELEASE_ALWAYS is set but no release_folio op exists
- Fix select restart_block to store end_time as timespec64, avoiding
truncation of tv_sec on 32-bit architectures
- Make dump_inode() use get_kernel_nofault() to safely access inode
and superblock fields, matching the dump_mapping() pattern
API modernization:
- Make posix_acl_to_xattr() allocate the buffer internally since
every single caller was doing it anyway. Reduces boilerplate and
unnecessary error checking across ~15 filesystems
- Replace deprecated simple_strtoul() with kstrtoul() for the
ihash_entries, dhash_entries, mhash_entries, and mphash_entries
boot parameters, adding proper error handling
- Convert chardev code to use guard(mutex) and __free(kfree) cleanup
patterns
- Replace min_t() with min() or umin() in VFS code to avoid silently
truncating unsigned long to unsigned int
- Gate LOOKUP_RCU assertions behind CONFIG_DEBUG_VFS since callers
already check the flag
Deprecation:
- Begin deprecating legacy BSD process accounting (acct(2)). The
interface has numerous footguns and better alternatives exist
(eBPF)
Documentation:
- Fix and complete kernel-doc for struct export_operations, removing
duplicated documentation between ReST and source
- Fix kernel-doc warnings for __start_dirop() and ilookup5_nowait()
Testing:
- Add a kunit test for initramfs cpio handling of entries with
filesize > PATH_MAX
Misc:
- Add missing <linux/init_task.h> include in fs_struct.c"
* tag 'vfs-7.0-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (28 commits)
posix_acl: make posix_acl_to_xattr() alloc the buffer
fs: make insert_inode_locked() wait for inode destruction
initramfs_test: kunit test for cpio.filesize > PATH_MAX
fs: improve dump_inode() to safely access inode fields
fs: add <linux/init_task.h> for 'init_fs'
docs: exportfs: Use source code struct documentation
fs: move initializing f_mode before file_ref_init()
exportfs: Complete kernel-doc for struct export_operations
exportfs: Mark struct export_operations functions at kernel-doc
exportfs: Fix kernel-doc output for get_name()
acct(2): begin the deprecation of legacy BSD process accounting
device_cgroup: remove branch hint after code refactor
VFS: fix __start_dirop() kernel-doc warnings
fs: Describe @isnew parameter in ilookup5_nowait()
fs/namei: Remove redundant DCACHE_MANAGED_DENTRY check in __follow_mount_rcu
fs: only assert on LOOKUP_RCU when built with CONFIG_DEBUG_VFS
select: store end_time as timespec64 in restart block
chardev: Switch to guard(mutex) and __free(kfree)
namespace: Replace simple_strtoul with kstrtoul to parse boot params
dcache: Replace simple_strtoul with kstrtoul in set_dhash_entries
...
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs mount updates from Christian Brauner:
- statmount: accept fd as a parameter
Extend struct mnt_id_req with a file descriptor field and a new
STATMOUNT_BY_FD flag. When set, statmount() returns mount information
for the mount the fd resides on — including detached mounts
(unmounted via umount2(MNT_DETACH)).
For detached mounts the STATMOUNT_MNT_POINT and STATMOUNT_MNT_NS_ID
mask bits are cleared since neither is meaningful. The capability
check is skipped for STATMOUNT_BY_FD since holding an fd already
implies prior access to the mount and equivalent information is
available through fstatfs() and /proc/pid/mountinfo without
privilege. Includes comprehensive selftests covering both attached
and detached mount cases.
- fs: Remove internal old mount API code (1 patch)
Now that every in-tree filesystem has been converted to the new
mount API, remove all the legacy shim code in fs_context.c that
handled unconverted filesystems. This deletes ~280 lines including
legacy_init_fs_context(), the legacy_fs_context struct, and
associated wrappers. The mount(2) syscall path for userspace remains
untouched. Documentation references to the legacy callbacks are
cleaned up.
- mount: add OPEN_TREE_NAMESPACE to open_tree()
Container runtimes currently use CLONE_NEWNS to copy the caller's
entire mount namespace — only to then pivot_root() and recursively
unmount everything they just copied. With large mount tables and
thousands of parallel container launches this creates significant
contention on the namespace semaphore.
OPEN_TREE_NAMESPACE copies only the specified mount tree (like
OPEN_TREE_CLONE) but returns a mount namespace fd instead of a
detached mount fd. The new namespace contains the copied tree mounted
on top of a clone of the real rootfs.
This functions as a combined unshare(CLONE_NEWNS) + pivot_root() in a
single syscall. Works with user namespaces: an unshare(CLONE_NEWUSER)
followed by OPEN_TREE_NAMESPACE creates a mount namespace owned by
the new user namespace. Mount namespace file mounts are excluded from
the copy to prevent cycles. Includes ~1000 lines of selftests"
* tag 'vfs-7.0-rc1.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
selftests/open_tree: add OPEN_TREE_NAMESPACE tests
mount: add OPEN_TREE_NAMESPACE
fs: Remove internal old mount API code
selftests: statmount: tests for STATMOUNT_BY_FD
statmount: accept fd as a parameter
statmount: permission check should return EPERM
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When creating containers the setup usually involves using CLONE_NEWNS
via clone3() or unshare(). This copies the caller's complete mount
namespace. The runtime will also assemble a new rootfs and then use
pivot_root() to switch the old mount tree with the new rootfs. Afterward
it will recursively umount the old mount tree thereby getting rid of all
mounts.
On a basic system here where the mount table isn't particularly large
this still copies about 30 mounts. Copying all of these mounts only to
get rid of them later is pretty wasteful.
This is exacerbated if intermediary mount namespaces are used that only
exist for a very short amount of time and are immediately destroyed
again causing a ton of mounts to be copied and destroyed needlessly.
With a large mount table and a system where thousands or ten-thousands
of containers are spawned in parallel this quickly becomes a bottleneck
increasing contention on the semaphore.
Extend open_tree() with a new OPEN_TREE_NAMESPACE flag. Similar to
OPEN_TREE_CLONE only the indicated mount tree is copied. Instead of
returning a file descriptor referring to that mount tree
OPEN_TREE_NAMESPACE will cause open_tree() to return a file descriptor
to a new mount namespace. In that new mount namespace the copied mount
tree has been mounted on top of a copy of the real rootfs.
The caller can setns() into that mount namespace and perform any
additionally required setup such as move_mount() detached mounts in
there.
This allows OPEN_TREE_NAMESPACE to function as a combined
unshare(CLONE_NEWNS) and pivot_root().
A caller may for example choose to create an extremely minimal rootfs:
fd_mntns = open_tree(-EBADF, "/var/lib/containers/wootwoot", OPEN_TREE_NAMESPACE);
This will create a mount namespace where "wootwoot" has become the
rootfs mounted on top of the real rootfs. The caller can now setns()
into this new mount namespace and assemble additional mounts.
This also works with user namespaces:
unshare(CLONE_NEWUSER);
fd_mntns = open_tree(-EBADF, "/var/lib/containers/wootwoot", OPEN_TREE_NAMESPACE);
which creates a new mount namespace owned by the earlier created user
namespace with "wootwoot" as the rootfs mounted on top of the real
rootfs.
Link: https://patch.msgid.link/20251229-work-empty-namespace-v1-1-bfb24c7b061f@kernel.org
Tested-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Suggested-by: Christian Brauner <brauner@kernel.org>
Suggested-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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just use CLASS(filename_uflags) + filename_lookup()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Remove the "nullfs_rootfs" boot parameter and simply always use nullfs.
The mutable rootfs will be mounted on top of it. Systems that don't use
pivot_root() to pivot away from the real rootfs will have an additional
mount stick around but that shouldn't be a problem at all. If it is
we'll rever this commit.
This also simplifies the boot process and removes the need for the
traditional switch_root workarounds.
Suggested-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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no need to check it in the caller
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Currently pivot_root() doesn't work on the real rootfs because it
cannot be unmounted. Userspace has to do a recursive removal of the
initramfs contents manually before continuing the boot.
Really all we want from the real rootfs is to serve as the parent mount
for anything that is actually useful such as the tmpfs or ramfs for
initramfs unpacking or the rootfs itself. There's no need for the real
rootfs to actually be anything meaningful or useful. Add a immutable
rootfs called "nullfs" that can be selected via the "nullfs_rootfs"
kernel command line option.
The kernel will mount a tmpfs/ramfs on top of it, unpack the initramfs
and fire up userspace which mounts the rootfs and can then just do:
chdir(rootfs);
pivot_root(".", ".");
umount2(".", MNT_DETACH);
and be done with it. (Ofc, userspace can also choose to retain the
initramfs contents by using something like pivot_root(".", "/initramfs")
without unmounting it.)
Technically this also means that the rootfs mount in unprivileged
namespaces doesn't need to become MNT_LOCKED anymore as it's guaranteed
that the immutable rootfs remains permanently empty so there cannot be
anything revealed by unmounting the covering mount.
In the future this will also allow us to create completely empty mount
namespaces without risking to leak anything.
systemd already handles this all correctly as it tries to pivot_root()
first and falls back to MS_MOVE only when that fails.
This goes back to various discussion in previous years and a LPC 2024
presentation about this very topic.
Link: https://patch.msgid.link/20260112-work-immutable-rootfs-v2-3-88dd1c34a204@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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We will soon be able to pivot_root() with the introduction of the
immutable rootfs. Add a wrapper for kernel internal usage.
Link: https://patch.msgid.link/20260112-work-immutable-rootfs-v2-2-88dd1c34a204@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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and the rootfs get mount id one as it always has. Before we actually
mount the rootfs we create an internal tmpfs mount which has mount id
zero but is never exposed anywhere. Continue that "tradition".
Link: https://patch.msgid.link/20260112-work-immutable-rootfs-v2-1-88dd1c34a204@kernel.org
Fixes: 7f9bfafc5f49 ("fs: use xarray for old mount id")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Replace simple_strtoul() with the recommended kstrtoul() for parsing the
'mhash_entries=' and 'mphash_entries=' boot parameters.
Check the return value of kstrtoul() and reject invalid values. This
adds error handling while preserving behavior for existing values, and
removes use of the deprecated simple_strtoul() helper.
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://patch.msgid.link/20251214153141.218953-2-thorsten.blum@linux.dev
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Extend `struct mnt_id_req` to take in a fd and introduce STATMOUNT_BY_FD
flag. When a valid fd is provided and STATMOUNT_BY_FD is set, statmount
will return mountinfo about the mount the fd is on.
This even works for "unmounted" mounts (mounts that have been umounted
using umount2(mnt, MNT_DETACH)), if you have access to a file descriptor
on that mount. These "umounted" mounts will have no mountpoint and no
valid mount namespace. Hence, we unset the STATMOUNT_MNT_POINT and
STATMOUNT_MNT_NS_ID in statmount.mask for "unmounted" mounts.
In case of STATMOUNT_BY_FD, given that we already have access to an fd
on the mount, accessing mount information without a capability check
seems fine because of the following reasons:
- All fs related information is available via fstatfs() without any
capability check.
- Mount information is also available via /proc/pid/mountinfo (without
any capability check).
- Given that we have access to a fd on the mount which tells us that we
had access to the mount at some point (or someone that had access gave
us the fd). So, we should be able to access mount info.
Co-developed-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Bhavik Sachdev <b.sachdev1904@gmail.com>
Link: https://patch.msgid.link/20251129091455.757724-3-b.sachdev1904@gmail.com
Acked-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Currently, statmount() returns ENOENT when caller is not CAP_SYS_ADMIN
in the user namespace owner of target mount namespace. This should be
EPERM instead.
Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Bhavik Sachdev <b.sachdev1904@gmail.com>
Link: https://patch.msgid.link/20251129091455.757724-2-b.sachdev1904@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull fd prepare updates from Christian Brauner:
"This adds the FD_ADD() and FD_PREPARE() primitive. They simplify the
common pattern of get_unused_fd_flags() + create file + fd_install()
that is used extensively throughout the kernel and currently requires
cumbersome cleanup paths.
FD_ADD() - For simple cases where a file is installed immediately:
fd = FD_ADD(O_CLOEXEC, vfio_device_open_file(device));
if (fd < 0)
vfio_device_put_registration(device);
return fd;
FD_PREPARE() - For cases requiring access to the fd or file, or
additional work before publishing:
FD_PREPARE(fdf, O_CLOEXEC, sync_file->file);
if (fdf.err) {
fput(sync_file->file);
return fdf.err;
}
data.fence = fd_prepare_fd(fdf);
if (copy_to_user((void __user *)arg, &data, sizeof(data)))
return -EFAULT;
return fd_publish(fdf);
The primitives are centered around struct fd_prepare. FD_PREPARE()
encapsulates all allocation and cleanup logic and must be followed by
a call to fd_publish() which associates the fd with the file and
installs it into the caller's fdtable. If fd_publish() isn't called,
both are deallocated automatically. FD_ADD() is a shorthand that does
fd_publish() immediately and never exposes the struct to the caller.
I've implemented this in a way that it's compatible with the cleanup
infrastructure while also being usable separately. IOW, it's centered
around struct fd_prepare which is aliased to class_fd_prepare_t and so
we can make use of all the basica guard infrastructure"
* tag 'vfs-6.19-rc1.fd_prepare.fs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (42 commits)
io_uring: convert io_create_mock_file() to FD_PREPARE()
file: convert replace_fd() to FD_PREPARE()
vfio: convert vfio_group_ioctl_get_device_fd() to FD_ADD()
tty: convert ptm_open_peer() to FD_ADD()
ntsync: convert ntsync_obj_get_fd() to FD_PREPARE()
media: convert media_request_alloc() to FD_PREPARE()
hv: convert mshv_ioctl_create_partition() to FD_ADD()
gpio: convert linehandle_create() to FD_PREPARE()
pseries: port papr_rtas_setup_file_interface() to FD_ADD()
pseries: convert papr_platform_dump_create_handle() to FD_ADD()
spufs: convert spufs_gang_open() to FD_PREPARE()
papr-hvpipe: convert papr_hvpipe_dev_create_handle() to FD_PREPARE()
spufs: convert spufs_context_open() to FD_PREPARE()
net/socket: convert __sys_accept4_file() to FD_ADD()
net/socket: convert sock_map_fd() to FD_ADD()
net/kcm: convert kcm_ioctl() to FD_PREPARE()
net/handshake: convert handshake_nl_accept_doit() to FD_PREPARE()
secretmem: convert memfd_secret() to FD_ADD()
memfd: convert memfd_create() to FD_ADD()
bpf: convert bpf_token_create() to FD_PREPARE()
...
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull autofs update from Christian Brauner:
"Prevent futile mount triggers in private mount namespaces.
Fix a problematic loop in autofs when a mount namespace contains
autofs mounts that are propagation private and there is no
namespace-specific automount daemon to handle possible automounting.
Previously, attempted path resolution would loop until MAXSYMLINKS was
reached before failing, causing significant noise in the log.
The fix adds a check in autofs ->d_automount() so that the VFS can
immediately return EPERM in this case. Since the mount is propagation
private, EPERM is the most appropriate error code"
* tag 'vfs-6.19-rc1.autofs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
autofs: dont trigger mount if it cant succeed
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull namespace updates from Christian Brauner:
"This contains substantial namespace infrastructure changes including a new
system call, active reference counting, and extensive header cleanups.
The branch depends on the shared kbuild branch for -fms-extensions support.
Features:
- listns() system call
Add a new listns() system call that allows userspace to iterate
through namespaces in the system. This provides a programmatic
interface to discover and inspect namespaces, addressing
longstanding limitations:
Currently, there is no direct way for userspace to enumerate
namespaces. Applications must resort to scanning /proc/*/ns/ across
all processes, which is:
- Inefficient - requires iterating over all processes
- Incomplete - misses namespaces not attached to any running
process but kept alive by file descriptors, bind mounts, or
parent references
- Permission-heavy - requires access to /proc for many processes
- No ordering or ownership information
- No filtering per namespace type
The listns() system call solves these problems:
ssize_t listns(const struct ns_id_req *req, u64 *ns_ids,
size_t nr_ns_ids, unsigned int flags);
struct ns_id_req {
__u32 size;
__u32 spare;
__u64 ns_id;
struct /* listns */ {
__u32 ns_type;
__u32 spare2;
__u64 user_ns_id;
};
};
Features include:
- Pagination support for large namespace sets
- Filtering by namespace type (MNT_NS, NET_NS, USER_NS, etc.)
- Filtering by owning user namespace
- Permission checks respecting namespace isolation
- Active Reference Counting
Introduce an active reference count that tracks namespace
visibility to userspace. A namespace is visible in the following
cases:
- The namespace is in use by a task
- The namespace is persisted through a VFS object (namespace file
descriptor or bind-mount)
- The namespace is a hierarchical type and is the parent of child
namespaces
The active reference count does not regulate lifetime (that's still
done by the normal reference count) - it only regulates visibility
to namespace file handles and listns().
This prevents resurrection of namespaces that are pinned only for
internal kernel reasons (e.g., user namespaces held by
file->f_cred, lazy TLB references on idle CPUs, etc.) which should
not be accessible via (1)-(3).
- Unified Namespace Tree
Introduce a unified tree structure for all namespaces with:
- Fixed IDs assigned to initial namespaces
- Lookup based solely on inode number
- Maintained list of owned namespaces per user namespace
- Simplified rbtree comparison helpers
Cleanups
- Header Reorganization:
- Move namespace types into separate header (ns_common_types.h)
- Decouple nstree from ns_common header
- Move nstree types into separate header
- Switch to new ns_tree_{node,root} structures with helper functions
- Use guards for ns_tree_lock
- Initial Namespace Reference Count Optimization
- Make all reference counts on initial namespaces a nop to avoid
pointless cacheline ping-pong for namespaces that can never go
away
- Drop custom reference count initialization for initial namespaces
- Add NS_COMMON_INIT() macro and use it for all namespaces
- pid: rely on common reference count behavior
- Miscellaneous Cleanups
- Rename exit_task_namespaces() to exit_nsproxy_namespaces()
- Rename is_initial_namespace() and make argument const
- Use boolean to indicate anonymous mount namespace
- Simplify owner list iteration in nstree
- nsfs: raise SB_I_NODEV, SB_I_NOEXEC, and DCACHE_DONTCACHE explicitly
- nsfs: use inode_just_drop()
- pidfs: raise DCACHE_DONTCACHE explicitly
- pidfs: simplify PIDFD_GET__NAMESPACE ioctls
- libfs: allow to specify s_d_flags
- cgroup: add cgroup namespace to tree after owner is set
- nsproxy: fix free_nsproxy() and simplify create_new_namespaces()
Fixes:
- setns(pidfd, ...) race condition
Fix a subtle race when using pidfds with setns(). When the target
task exits after prepare_nsset() but before commit_nsset(), the
namespace's active reference count might have been dropped. If
setns() then installs the namespaces, it would bump the active
reference count from zero without taking the required reference on
the owner namespace, leading to underflow when later decremented.
The fix resurrects the ownership chain if necessary - if the caller
succeeded in grabbing passive references, the setns() should
succeed even if the target task exits or gets reaped.
- Return EFAULT on put_user() error instead of success
- Make sure references are dropped outside of RCU lock (some
namespaces like mount namespace sleep when putting the last
reference)
- Don't skip active reference count initialization for network
namespace
- Add asserts for active refcount underflow
- Add asserts for initial namespace reference counts (both passive
and active)
- ipc: enable is_ns_init_id() assertions
- Fix kernel-doc comments for internal nstree functions
- Selftests
- 15 active reference count tests
- 9 listns() functionality tests
- 7 listns() permission tests
- 12 inactive namespace resurrection tests
- 3 threaded active reference count tests
- commit_creds() active reference tests
- Pagination and stress tests
- EFAULT handling test
- nsid tests fixes"
* tag 'namespace-6.19-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (103 commits)
pidfs: simplify PIDFD_GET_<type>_NAMESPACE ioctls
nstree: fix kernel-doc comments for internal functions
nsproxy: fix free_nsproxy() and simplify create_new_namespaces()
selftests/namespaces: fix nsid tests
ns: drop custom reference count initialization for initial namespaces
pid: rely on common reference count behavior
ns: add asserts for initial namespace active reference counts
ns: add asserts for initial namespace reference counts
ns: make all reference counts on initial namespace a nop
ipc: enable is_ns_init_id() assertions
fs: use boolean to indicate anonymous mount namespace
ns: rename is_initial_namespace()
ns: make is_initial_namespace() argument const
nstree: use guards for ns_tree_lock
nstree: simplify owner list iteration
nstree: switch to new structures
nstree: add helper to operate on struct ns_tree_{node,root}
nstree: move nstree types into separate header
nstree: decouple from ns_common header
ns: move namespace types into separate header
...
|
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc vfs updates from Christian Brauner:
"Features:
- Cheaper MAY_EXEC handling for path lookup. This elides MAY_WRITE
permission checks during path lookup and adds the
IOP_FASTPERM_MAY_EXEC flag so filesystems like btrfs can avoid
expensive permission work.
- Hide dentry_cache behind runtime const machinery.
- Add German Maglione as virtiofs co-maintainer.
Cleanups:
- Tidy up and inline step_into() and walk_component() for improved
code generation.
- Re-enable IOCB_NOWAIT writes to files. This refactors file
timestamp update logic, fixing a layering bypass in btrfs when
updating timestamps on device files and improving FMODE_NOCMTIME
handling in VFS now that nfsd started using it.
- Path lookup optimizations extracting slowpaths into dedicated
routines and adding branch prediction hints for mntput_no_expire(),
fd_install(), lookup_slow(), and various other hot paths.
- Enable clang's -fms-extensions flag, requiring a JFS rename to
avoid conflicts.
- Remove spurious exports in fs/file_attr.c.
- Stop duplicating union pipe_index declaration. This depends on the
shared kbuild branch that brings in -fms-extensions support which
is merged into this branch.
- Use MD5 library instead of crypto_shash in ecryptfs.
- Use largest_zero_folio() in iomap_dio_zero().
- Replace simple_strtol/strtoul with kstrtoint/kstrtouint in init and
initrd code.
- Various typo fixes.
Fixes:
- Fix emergency sync for btrfs. Btrfs requires an explicit sync_fs()
call with wait == 1 to commit super blocks. The emergency sync path
never passed this, leaving btrfs data uncommitted during emergency
sync.
- Use local kmap in watch_queue's post_one_notification().
- Add hint prints in sb_set_blocksize() for LBS dependency on THP"
* tag 'vfs-6.19-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (35 commits)
MAINTAINERS: add German Maglione as virtiofs co-maintainer
fs: inline step_into() and walk_component()
fs: tidy up step_into() & friends before inlining
orangefs: use inode_update_timestamps directly
btrfs: fix the comment on btrfs_update_time
btrfs: use vfs_utimes to update file timestamps
fs: export vfs_utimes
fs: lift the FMODE_NOCMTIME check into file_update_time_flags
fs: refactor file timestamp update logic
include/linux/fs.h: trivial fix: regualr -> regular
fs/splice.c: trivial fix: pipes -> pipe's
fs: mark lookup_slow() as noinline
fs: add predicts based on nd->depth
fs: move mntput_no_expire() slowpath into a dedicated routine
fs: remove spurious exports in fs/file_attr.c
watch_queue: Use local kmap in post_one_notification()
fs: touch up predicts in path lookup
fs: move fd_install() slowpath into a dedicated routine and provide commentary
fs: hide dentry_cache behind runtime const machinery
fs: touch predicts in do_dentry_open()
...
|
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Christian Brauner <brauner@kernel.org> says:
A variant of the fix sent in [1] was squashed into this commit.
Link: https://lore.kernel.org/20251128035149.392402-1-kartikey406@gmail.com [1]
Reported-by: Deepanshu Kartikey <kartikey406@gmail.com>
Reported-by: syzbot+94048264da5715c251f9@syzkaller.appspotmail.com
Tested-by: syzbot+94048264da5715c251f9@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=94048264da5715c251f9
Link: https://patch.msgid.link/20251123-work-fd-prepare-v4-7-b6efa1706cfd@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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Link: https://patch.msgid.link/20251123-work-fd-prepare-v4-6-b6efa1706cfd@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
Link: https://patch.msgid.link/20251123-work-fd-prepare-v4-5-b6efa1706cfd@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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lookup_mnt_ns() already takes a reference on mnt_ns.
grab_requested_mnt_ns() doesn't need to take an extra reference.
Fixes: 78f0e33cd6c93 ("fs/namespace: correctly handle errors returned by grab_requested_mnt_ns")
Signed-off-by: Andrei Vagin <avagin@google.com>
Link: https://patch.msgid.link/20251122071953.3053755-1-avagin@google.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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In the stock variant the compiler spills several registers on the stack
and employs stack smashing protection, adding even more code + a branch
on exit..
The actual fast path is small enough that the compiler inlines it for
all callers -- the symbol is no longer emitted.
Forcing noinline on it just for code-measurement purposes shows the fast
path dropping from 111 to 39 bytes.
Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://patch.msgid.link/20251114201803.2183505-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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If a mount namespace contains autofs mounts, and they are propagation
private, and there is no namespace specific automount daemon to handle
possible automounting then attempted path resolution will loop until
MAXSYMLINKS is reached before failing causing quite a bit of noise in
the log.
Add a check for this in autofs ->d_automount() so that the VFS can
immediately return an error in this case. Since the mount is propagation
private an EPERM return seems most appropriate.
Suggested by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Ian Kent <raven@themaw.net>
Link: https://patch.msgid.link/20251118024631.10854-2-raven@themaw.net
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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grab_requested_mnt_ns was changed to return error codes on failure, but
its callers were not updated to check for error pointers, still checking
only for a NULL return value.
This commit updates the callers to use IS_ERR() or IS_ERR_OR_NULL() and
PTR_ERR() to correctly check for and propagate errors.
This also makes sure that the logic actually works and mount namespace
file descriptors can be used to refere to mounts.
Christian Brauner <brauner@kernel.org> says:
Rework the patch to be more ergonomic and in line with our overall error
handling patterns.
Fixes: 7b9d14af8777 ("fs: allow mount namespace fd")
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrei Vagin <avagin@google.com>
Link: https://patch.msgid.link/20251111062815.2546189-1-avagin@google.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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Initial namespaces don't modify their reference count anymore.
They remain fixed at one so drop the custom refcount initializations.
Link: https://patch.msgid.link/20251110-work-namespace-nstree-fixes-v1-16-e8a9264e0fb9@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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Stop playing games with the namespace id and use a boolean instead:
* This will remove the special-casing we need to do everywhere for mount
namespaces.
* It will allow us to use asserts on the namespace id for initial
namespaces everywhere.
* It will allow us to put anonymous mount namespaces on the namespaces
trees in the future and thus make them available to statmount() and
listmount().
Link: https://patch.msgid.link/20251110-work-namespace-nstree-fixes-v1-10-e8a9264e0fb9@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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Switch the nstree management to the new combined structures.
Link: https://patch.msgid.link/20251110-work-namespace-nstree-fixes-v1-5-e8a9264e0fb9@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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The initial set of namespace comes with fixed inode numbers making it
easy for userspace to identify them solely based on that information.
This has long preceeded anything here.
Similarly, let's assign fixed namespace ids for the initial namespaces.
Kill the cookie and use a sequentially increasing number. This has the
nice side-effect that the owning user namespace will always have a
namespace id that is smaller than any of it's descendant namespaces.
Link: https://patch.msgid.link/20251029-work-namespace-nstree-listns-v4-15-2e6f823ebdc0@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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Now that we have a common initializer use it for all static namespaces.
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
|
Clang, in particular, is not happy about dead code:
fs/namespace.c:135:37: error: unused function 'node_to_mnt_ns' [-Werror,-Wunused-function]
135 | static inline struct mnt_namespace *node_to_mnt_ns(const struct rb_node *node)
| ^~~~~~~~~~~~~~
1 error generated.
Remove a leftover from the previous cleanup.
Fixes: 7d7d16498958 ("mnt: support ns lookup")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20251024132336.1666382-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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In statmount_string(), most flags assign an output offset pointer (offp)
which is later updated with the string offset. However, the
STATMOUNT_MNT_UIDMAP and STATMOUNT_MNT_GIDMAP cases directly set the
struct fields instead of using offp. This leaves offp uninitialized,
leading to a possible uninitialized dereference when *offp is updated.
Fix it by assigning offp for UIDMAP and GIDMAP as well, keeping the code
path consistent.
Fixes: 37c4a9590e1e ("statmount: allow to retrieve idmappings")
Fixes: e52e97f09fb6 ("statmount: let unset strings be empty")
Cc: stable@vger.kernel.org
Signed-off-by: Zhen Ni <zhen.ni@easystack.cn>
Link: https://patch.msgid.link/20251013114151.664341-1-zhen.ni@easystack.cn
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull fs_context updates from Al Viro:
"Change vfs_parse_fs_string() calling conventions
Get rid of the length argument (almost all callers pass strlen() of
the string argument there), add vfs_parse_fs_qstr() for the cases that
do want separate length"
* tag 'pull-fs_context' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
do_nfs4_mount(): switch to vfs_parse_fs_string()
change the calling conventions for vfs_parse_fs_string()
|
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Pull vfs mount updates from Al Viro:
"Several piles this cycle, this mount-related one being the largest and
trickiest:
- saner handling of guards in fs/namespace.c, getting rid of
needlessly strong locking in some of the users
- lock_mount() calling conventions change - have it set the
environment for attaching to given location, storing the results in
caller-supplied object, without altering the passed struct path.
Make unlock_mount() called as __cleanup for those objects. It's not
exactly guard(), but similar to it
- MNT_WRITE_HOLD done right.
mnt_hold_writers() does *not* mess with ->mnt_flags anymore, so
insertion of a new mount into ->s_mounts of underlying superblock
does not, in itself, expose ->mnt_flags of that mount to concurrent
modifications
- getting rid of pathological cases when umount() spends quadratic
time removing the victims from propagation graph - part of that had
been dealt with last cycle, this should finish it
- a bunch of stuff constified
- assorted cleanups
* tag 'pull-mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (64 commits)
constify {__,}mnt_is_readonly()
WRITE_HOLD machinery: no need for to bump mount_lock seqcount
struct mount: relocate MNT_WRITE_HOLD bit
preparations to taking MNT_WRITE_HOLD out of ->mnt_flags
setup_mnt(): primitive for connecting a mount to filesystem
simplify the callers of mnt_unhold_writers()
copy_mnt_ns(): use guards
copy_mnt_ns(): use the regular mechanism for freeing empty mnt_ns on failure
open_detached_copy(): separate creation of namespace into helper
open_detached_copy(): don't bother with mount_lock_hash()
path_has_submounts(): use guard(mount_locked_reader)
fs/namespace.c: sanitize descriptions for {__,}lookup_mnt()
ecryptfs: get rid of pointless mount references in ecryptfs dentries
umount_tree(): take all victims out of propagation graph at once
do_mount(): use __free(path_put)
do_move_mount_old(): use __free(path_put)
constify can_move_mount_beneath() arguments
path_umount(): constify struct path argument
may_copy_tree(), __do_loopback(): constify struct path argument
path_mount(): constify struct path argument
...
|
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull namespace updates from Christian Brauner:
"This contains a larger set of changes around the generic namespace
infrastructure of the kernel.
Each specific namespace type (net, cgroup, mnt, ...) embedds a struct
ns_common which carries the reference count of the namespace and so
on.
We open-coded and cargo-culted so many quirks for each namespace type
that it just wasn't scalable anymore. So given there's a bunch of new
changes coming in that area I've started cleaning all of this up.
The core change is to make it possible to correctly initialize every
namespace uniformly and derive the correct initialization settings
from the type of the namespace such as namespace operations, namespace
type and so on. This leaves the new ns_common_init() function with a
single parameter which is the specific namespace type which derives
the correct parameters statically. This also means the compiler will
yell as soon as someone does something remotely fishy.
The ns_common_init() addition also allows us to remove ns_alloc_inum()
and drops any special-casing of the initial network namespace in the
network namespace initialization code that Linus complained about.
Another part is reworking the reference counting. The reference
counting was open-coded and copy-pasted for each namespace type even
though they all followed the same rules. This also removes all open
accesses to the reference count and makes it private and only uses a
very small set of dedicated helpers to manipulate them just like we do
for e.g., files.
In addition this generalizes the mount namespace iteration
infrastructure introduced a few cycles ago. As reminder, the vfs makes
it possible to iterate sequentially and bidirectionally through all
mount namespaces on the system or all mount namespaces that the caller
holds privilege over. This allow userspace to iterate over all mounts
in all mount namespaces using the listmount() and statmount() system
call.
Each mount namespace has a unique identifier for the lifetime of the
systems that is exposed to userspace. The network namespace also has a
unique identifier working exactly the same way. This extends the
concept to all other namespace types.
The new nstree type makes it possible to lookup namespaces purely by
their identifier and to walk the namespace list sequentially and
bidirectionally for all namespace types, allowing userspace to iterate
through all namespaces. Looking up namespaces in the namespace tree
works completely locklessly.
This also means we can move the mount namespace onto the generic
infrastructure and remove a bunch of code and members from struct
mnt_namespace itself.
There's a bunch of stuff coming on top of this in the future but for
now this uses the generic namespace tree to extend a concept
introduced first for pidfs a few cycles ago. For a while now we have
supported pidfs file handles for pidfds. This has proven to be very
useful.
This extends the concept to cover namespaces as well. It is possible
to encode and decode namespace file handles using the common
name_to_handle_at() and open_by_handle_at() apis.
As with pidfs file handles, namespace file handles are exhaustive,
meaning it is not required to actually hold a reference to nsfs in
able to decode aka open_by_handle_at() a namespace file handle.
Instead the FD_NSFS_ROOT constant can be passed which will let the
kernel grab a reference to the root of nsfs internally and thus decode
the file handle.
Namespaces file descriptors can already be derived from pidfds which
means they aren't subject to overmount protection bugs. IOW, it's
irrelevant if the caller would not have access to an appropriate
/proc/<pid>/ns/ directory as they could always just derive the
namespace based on a pidfd already.
It has the same advantage as pidfds. It's possible to reliably and for
the lifetime of the system refer to a namespace without pinning any
resources and to compare them trivially.
Permission checking is kept simple. If the caller is located in the
namespace the file handle refers to they are able to open it otherwise
they must hold privilege over the owning namespace of the relevant
namespace.
The namespace file handle layout is exposed as uapi and has a stable
and extensible format. For now it simply contains the namespace
identifier, the namespace type, and the inode number. The stable
format means that userspace may construct its own namespace file
handles without going through name_to_handle_at() as they are already
allowed for pidfs and cgroup file handles"
* tag 'namespace-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (65 commits)
ns: drop assert
ns: move ns type into struct ns_common
nstree: make struct ns_tree private
ns: add ns_debug()
ns: simplify ns_common_init() further
cgroup: add missing ns_common include
ns: use inode initializer for initial namespaces
selftests/namespaces: verify initial namespace inode numbers
ns: rename to __ns_ref
nsfs: port to ns_ref_*() helpers
net: port to ns_ref_*() helpers
uts: port to ns_ref_*() helpers
ipv4: use check_net()
net: use check_net()
net-sysfs: use check_net()
user: port to ns_ref_*() helpers
time: port to ns_ref_*() helpers
pid: port to ns_ref_*() helpers
ipc: port to ns_ref_*() helpers
cgroup: port to ns_ref_*() helpers
...
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull copy_process updates from Christian Brauner:
"This contains the changes to enable support for clone3() on nios2
which apparently is still a thing.
The more exciting part of this is that it cleans up the inconsistency
in how the 64-bit flag argument is passed from copy_process() into the
various other copy_*() helpers"
[ Fixed up rv ltl_monitor 32-bit support as per Sasha Levin in the merge ]
* tag 'kernel-6.18-rc1.clone3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
nios2: implement architecture-specific portion of sys_clone3
arch: copy_thread: pass clone_flags as u64
copy_process: pass clone_flags as u64 across calltree
copy_sighand: Handle architectures where sizeof(unsigned long) < sizeof(u64)
|
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull vfs mount updates from Christian Brauner:
"This contains some work around mount api handling:
- Output the warning message for mnt_too_revealing() triggered during
fsmount() to the fscontext log. This makes it possible for the
mount tool to output appropriate warnings on the command line.
For example, with the newest fsopen()-based mount(8) from
util-linux, the error messages now look like:
# mount -t proc proc /tmp
mount: /tmp: fsmount() failed: VFS: Mount too revealing.
dmesg(1) may have more information after failed mount system call.
- Do not consume fscontext log entries when returning -EMSGSIZE
Userspace generally expects APIs that return -EMSGSIZE to allow for
them to adjust their buffer size and retry the operation.
However, the fscontext log would previously clear the message even
in the -EMSGSIZE case.
Given that it is very cheap for us to check whether the buffer is
too small before we remove the message from the ring buffer, let's
just do that instead.
- Drop an unused argument from do_remount()"
* tag 'vfs-6.18-rc1.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
vfs: fs/namespace.c: remove ms_flags argument from do_remount
selftests/filesystems: add basic fscontext log tests
fscontext: do not consume log entries when returning -EMSGSIZE
vfs: output mount_too_revealing() errors to fscontext
docs/vfs: Remove mentions to the old mount API helpers
fscontext: add custom-prefix log helpers
fs: Remove mount_bdev
fs: Remove mount_nodev
|
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When calling in listmount() mnt_ns_release() may be passed a NULL
pointer. Handle that case gracefully.
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc vfs updates from Christian Brauner:
"This contains the usual selections of misc updates for this cycle.
Features:
- Add "initramfs_options" parameter to set initramfs mount options.
This allows to add specific mount options to the rootfs to e.g.,
limit the memory size
- Add RWF_NOSIGNAL flag for pwritev2()
Add RWF_NOSIGNAL flag for pwritev2. This flag prevents the SIGPIPE
signal from being raised when writing on disconnected pipes or
sockets. The flag is handled directly by the pipe filesystem and
converted to the existing MSG_NOSIGNAL flag for sockets
- Allow to pass pid namespace as procfs mount option
Ever since the introduction of pid namespaces, procfs has had very
implicit behaviour surrounding them (the pidns used by a procfs
mount is auto-selected based on the mounting process's active
pidns, and the pidns itself is basically hidden once the mount has
been constructed)
This implicit behaviour has historically meant that userspace was
required to do some special dances in order to configure the pidns
of a procfs mount as desired. Examples include:
* In order to bypass the mnt_too_revealing() check, Kubernetes
creates a procfs mount from an empty pidns so that user
namespaced containers can be nested (without this, the nested
containers would fail to mount procfs)
But this requires forking off a helper process because you cannot
just one-shot this using mount(2)
* Container runtimes in general need to fork into a container
before configuring its mounts, which can lead to security issues
in the case of shared-pidns containers (a privileged process in
the pidns can interact with your container runtime process)
While SUID_DUMP_DISABLE and user namespaces make this less of an
issue, the strict need for this due to a minor uAPI wart is kind
of unfortunate
Things would be much easier if there was a way for userspace to
just specify the pidns they want. So this pull request contains
changes to implement a new "pidns" argument which can be set
using fsconfig(2):
fsconfig(procfd, FSCONFIG_SET_FD, "pidns", NULL, nsfd);
fsconfig(procfd, FSCONFIG_SET_STRING, "pidns", "/proc/self/ns/pid", 0);
or classic mount(2) / mount(8):
// mount -t proc -o pidns=/proc/self/ns/pid proc /tmp/proc
mount("proc", "/tmp/proc", "proc", MS_..., "pidns=/proc/self/ns/pid");
Cleanups:
- Remove the last references to EXPORT_OP_ASYNC_LOCK
- Make file_remove_privs_flags() static
- Remove redundant __GFP_NOWARN when GFP_NOWAIT is used
- Use try_cmpxchg() in start_dir_add()
- Use try_cmpxchg() in sb_init_done_wq()
- Replace offsetof() with struct_size() in ioctl_file_dedupe_range()
- Remove vfs_ioctl() export
- Replace rwlock() with spinlock in epoll code as rwlock causes
priority inversion on preempt rt kernels
- Make ns_entries in fs/proc/namespaces const
- Use a switch() statement() in init_special_inode() just like we do
in may_open()
- Use struct_size() in dir_add() in the initramfs code
- Use str_plural() in rd_load_image()
- Replace strcpy() with strscpy() in find_link()
- Rename generic_delete_inode() to inode_just_drop() and
generic_drop_inode() to inode_generic_drop()
- Remove unused arguments from fcntl_{g,s}et_rw_hint()
Fixes:
- Document @name parameter for name_contains_dotdot() helper
- Fix spelling mistake
- Always return zero from replace_fd() instead of the file descriptor
number
- Limit the size for copy_file_range() in compat mode to prevent a
signed overflow
- Fix debugfs mount options not being applied
- Verify the inode mode when loading it from disk in minixfs
- Verify the inode mode when loading it from disk in cramfs
- Don't trigger automounts with RESOLVE_NO_XDEV
If openat2() was called with RESOLVE_NO_XDEV it didn't traverse
through automounts, but could still trigger them
- Add FL_RECLAIM flag to show_fl_flags() macro so it appears in
tracepoints
- Fix unused variable warning in rd_load_image() on s390
- Make INITRAMFS_PRESERVE_MTIME depend on BLK_DEV_INITRD
- Use ns_capable_noaudit() when determining net sysctl permissions
- Don't call path_put() under namespace semaphore in listmount() and
statmount()"
* tag 'vfs-6.18-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (38 commits)
fcntl: trim arguments
listmount: don't call path_put() under namespace semaphore
statmount: don't call path_put() under namespace semaphore
pid: use ns_capable_noaudit() when determining net sysctl permissions
fs: rename generic_delete_inode() and generic_drop_inode()
init: INITRAMFS_PRESERVE_MTIME should depend on BLK_DEV_INITRD
initramfs: Replace strcpy() with strscpy() in find_link()
initrd: Use str_plural() in rd_load_image()
initramfs: Use struct_size() helper to improve dir_add()
initrd: Fix unused variable warning in rd_load_image() on s390
fs: use the switch statement in init_special_inode()
fs/proc/namespaces: make ns_entries const
filelock: add FL_RECLAIM to show_fl_flags() macro
eventpoll: Replace rwlock with spinlock
selftests/proc: add tests for new pidns APIs
procfs: add "pidns" mount option
pidns: move is-ancestor logic to helper
openat2: don't trigger automounts with RESOLVE_NO_XDEV
namei: move cross-device check to __traverse_mounts
namei: remove LOOKUP_NO_XDEV check from handle_mounts
...
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Massage listmount() and make sure we don't call path_put() under the
namespace semaphore. If we put the last reference we're fscked.
Fixes: b4c2bea8ceaa ("add listmount(2) syscall")
Cc: stable@vger.kernel.org # v6.8+
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Massage statmount() and make sure we don't call path_put() under the
namespace semaphore. If we put the last reference we're fscked.
Fixes: 46eae99ef733 ("add statmount(2) syscall")
Cc: stable@vger.kernel.org # v6.8+
Signed-off-by: Christian Brauner <brauner@kernel.org>
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It's misplaced in struct proc_ns_operations and ns->ops might be NULL if
the namespace is compiled out but we still want to know the type of the
namespace for the initial namespace struct.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Simply derive the ns operations from the namespace type.
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Just use the common helper we have.
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Make it easier to grep and rename to ns_count.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Stop accessing ns.count directly.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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And drop ns_free_inum(). Anything common that can be wasted centrally
should be wasted in the new common helper.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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There's a lot of information that namespace implementers don't need to
know about at all. Encapsulate this all in the initialization helper.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Assign the reserved MNT_NS_ANON_INO sentinel to anonymous mount
namespaces and cleanup the initial mount ns allocation. This is just a
preparatory patch and the ns->inum check in ns_common_init() will be
dropped in the next patch.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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There's various scenarios where we need to know whether we are in the
initial set of namespaces or not to e.g., shortcut permission checking.
All namespaces expose that information. Let's do that too.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Move the mount namespace to the generic ns lookup infrastructure.
This allows us to drop a bunch of members from struct mnt_namespace.
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Bring in the fix for removing a mount namespace from the mount namespace
rbtree and list.
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Don't cargo-cult the same thing over and over.
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... neither for insertion into the list of instances, nor for
mnt_{un,}hold_writers(), nor for mnt_get_write_access() deciding
to be nice to RT during a busy-wait loop - all of that only needs
the spinlock side of mount_lock.
IOW, it's mount_locked_reader, not mount_writer.
Clarify the comment re locking rules for mnt_unhold_writers() - it's
not just that mount_lock needs to be held when calling that, it must
have been held all along since the matching mnt_hold_writers().
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... from ->mnt_flags to LSB of ->mnt_pprev_for_sb.
This is safe - we always set and clear it within the same mount_lock
scope, so we won't interfere with list operations - traversals are
always forward, so they don't even look at ->mnt_prev_for_sb and
both insertions and removals are in mount_lock scopes of their own,
so that bit will be clear in *all* mount instances during those.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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We have an unpleasant wart in accessibility rules for struct mount. There
are per-superblock lists of mounts, used by sb_prepare_remount_readonly()
to check if any of those is currently claimed for write access and to
block further attempts to get write access on those until we are done.
As soon as it is attached to a filesystem, mount becomes reachable
via that list. Only sb_prepare_remount_readonly() traverses it and
it only accesses a few members of struct mount. Unfortunately,
->mnt_flags is one of those and it is modified - MNT_WRITE_HOLD set
and then cleared. It is done under mount_lock, so from the locking
rules POV everything's fine.
However, it has easily overlooked implications - once mount has been
attached to a filesystem, it has to be treated as globally visible.
In particular, initializing ->mnt_flags *must* be done either prior
to that point or under mount_lock. All other members are still
private at that point.
Life gets simpler if we move that bit (and that's *all* that can get
touched by access via this list) out of ->mnt_flags. It's not even
hard to do - currently the list is implemented as list_head one,
anchored in super_block->s_mounts and linked via mount->mnt_instance.
As the first step, switch it to hlist-like open-coded structure -
address of the first mount in the set is stored in ->s_mounts
and ->mnt_instance replaced with ->mnt_next_for_sb and ->mnt_pprev_for_sb -
the former either NULL or pointing to the next mount in set, the
latter - address of either ->s_mounts or ->mnt_next_for_sb in the
previous element of the set.
In the next commit we'll steal the LSB of ->mnt_pprev_for_sb as
replacement for MNT_WRITE_HOLD.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Take the identical logics in vfs_create_mount() and clone_mnt() into
a new helper that takes an empty struct mount and attaches it to
given dentry (sub)tree.
Should be called once in the lifetime of every mount, prior to making
it visible in any data structures.
After that point ->mnt_root and ->mnt_sb never change; ->mnt_root
is a counting reference to dentry and ->mnt_sb - an active reference
to superblock.
Mount remains associated with that dentry tree all the way until
the call of cleanup_mnt(), when the refcount eventually drops
to zero.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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The logics in cleanup on failure in mount_setattr_prepare() is simplified
by having the mnt_hold_writers() failure followed by advancing m to the
next node in the tree before leaving the loop.
And since all calls are preceded by the same check that flag has been set
and the function is inlined, let's just shift the check into it.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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* mntput() of rootmnt and pwdmnt done via __free(mntput)
* mnt_ns_tree_add() can be done within namespace_excl scope.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Now that free_mnt_ns() works prior to mnt_ns_tree_add(), there's no need for
an open-coded analogue free_mnt_ns() there - yes, we do avoid one call_rcu()
use per failing call of clone() or unshare(), if they fail due to OOM in that
particular spot, but it's not really worth bothering.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Actual removal is done under the lock, but for checking if need to bother
the lockless RB_EMPTY_NODE() is safe - either that namespace had never
been added to mnt_ns_tree, in which case the the node will stay empty, or
whoever had allocated it has called mnt_ns_tree_add() and it has already
run to completion. After that point RB_EMPTY_NODE() will become false and
will remain false, no matter what we do with other nodes in the tree.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... and convert the helper to use of a guard(namespace_excl)
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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we are holding namespace_sem and a reference to root of tree;
iterating through that tree does not need mount_lock. Neither
does the insertion into the rbtree of new namespace or incrementing
the mount count of that namespace.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Comments regarding "shadow mounts" were stale - no such thing anymore.
Document the locking requirements for __lookup_mnt().
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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For each removed mount we need to calculate where the slaves will end up.
To avoid duplicating that work, do it for all mounts to be removed
at once, taking the mounts themselves out of propagation graph as
we go, then do all transfers; the duplicate work on finding destinations
is avoided since if we run into a mount that already had destination found,
we don't need to trace the rest of the way. That's guaranteed
O(removed mounts) for finding destinations and removing from propagation
graph and O(surviving mounts that have master removed) for transfers.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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now it finally can be done.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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argument
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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|
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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argument(s)
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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callers have no business modifying the paths they get
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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... and use that to constify the pointers in callers
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Currently do_lock_mount() has the target path switched to whatever
might be overmounting it. We _do_ want to have the parent
mount/mountpoint chosen on top of the overmounting pile; however,
the way it's done has unpleasant races - if umount propagation
removes the overmount while we'd been trying to set the environment
up, we might end up failing if our target path strays into that overmount
just before the overmount gets kicked out.
Users of do_lock_mount() do not need the target path changed - they
have all information in res->{parent,mp}; only one place (in
do_move_mount()) currently uses the resulting path->mnt, and that value
is trivial to reconstruct by the original value of path->mnt + chosen
parent mount.
Let's keep the target path unchanged; it avoids a bunch of subtle races
and it's not hard to do:
do
as mount_locked_reader
find the prospective parent mount/mountpoint dentry
grab references if it's not the original target
lock the prospective mountpoint dentry
take namespace_sem exclusive
if prospective parent/mountpoint would be different now
err = -EAGAIN
else if location has been unmounted
err = -ENOENT
else if mountpoint dentry is not allowed to be mounted on
err = -ENOENT
else if beneath and the top of the pile was the absolute root
err = -EINVAL
else
try to get struct mountpoint (by dentry), set
err to 0 on success and -ENO{MEM,ENT} on failure
if err != 0
res->parent = ERR_PTR(err)
drop locks
else
res->parent = prospective parent
drop temporary references
while err == -EAGAIN
A somewhat subtle part is that dropping temporary references is allowed.
Neither mounts nor dentries should be evicted by a thread that holds
namespace_sem. On success we are dropping those references under
namespace_sem, so we need to be sure that these are not the last
references remaining. However, on success we'd already verified (under
namespace_sem) that original target is still mounted and that mount
and dentry we are about to drop are still reachable from it via the
mount tree. That guarantees that we are not about to drop the last
remaining references.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Returns the final (topmost) mount in the chain of overmounts
starting at given mount. Same locking rules as for any mount
tree traversal - either the spinlock side of mount_lock, or
rcu + sample the seqcount side of mount_lock before the call
and recheck afterwards.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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That kills the last place where callers of lock_mount(path, &mp)
used path->dentry.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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parent and mountpoint always come from the same struct pinned_mountpoint
now.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Both callers pass it a mountpoint reference picked from pinned_mountpoint
and path it corresponds to.
First of all, path->dentry is equal to mp.mp->m_dentry. Furthermore, path->mnt
is &mp.parent->mnt, making struct path contents redundant.
Pass it the address of that pinned_mountpoint instead; what's more, if we
teach it to treat ERR_PTR(error) in ->parent as "bail out with that error"
we can simplify the callers even more - do_add_mount() will do the right
thing even when called after lock_mount() failure.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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After successful do_lock_mount() call, mp.parent is set to either
real_mount(path->mnt) (for !beneath case) or to ->mnt_parent of that
(for beneath). p is set to real_mount(path->mnt) and after
several uses it's made equal to mp.parent. All uses prior to that
care only about p->mnt_ns and since p->mnt_ns == parent->mnt_ns,
we might as well use mp.parent all along.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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1) pinned_mountpoint gets a new member - struct mount *parent.
Set only if we locked the sucker; ERR_PTR() - on failed attempt.
2) do_lock_mount() et.al. return void and set ->parent to
* on success with !beneath - mount corresponding to path->mnt
* on success with beneath - the parent of mount corresponding
to path->mnt
* in case of error - ERR_PTR(-E...).
IOW, we get the mount we will be actually mounting upon or ERR_PTR().
3) we can't use CLASS, since the pinned_mountpoint is placed on
hlist during initialization, so we define local macros:
LOCK_MOUNT(mp, path)
LOCK_MOUNT_MAYBE_BENEATH(mp, path, beneath)
LOCK_MOUNT_EXACT(mp, path)
All of them declare and initialize struct pinned_mountpoint mp,
with unlock_mount done via __cleanup().
Users converted.
[
lock_mount() is unused now; removed.
Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
]
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Absolute majority of callers are passing the 4th argument equal to
strlen() of the 3rd one.
Drop the v_size argument, add vfs_parse_fs_qstr() for the cases that
want independent length.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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same story as with do_new_mount_fc().
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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do_add_mount() consumes vfsmount on success; just follow it with
conditional retain_and_null_ptr() on success and we can switch
to __free() for mnt and be done with that - unlock_mount() is
in the very end.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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finish_automount() can't use lock_mount() - it treats finding something
already mounted as "quitely drop our mount and return 0", not as
"mount on top of whatever mounted there". It's been open-coded;
let's take it into a helper similar to lock_mount(). "something's
already mounted" => -EBUSY, finish_automount() needs to distinguish
it from the normal case and it can't happen in other failure cases.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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preparations for making unlock_mount() a __cleanup();
can't have path_put() inside mount_lock scope.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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preparations for making unlock_mount() a __cleanup();
can't have path_put() inside mount_lock scope.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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It's enough to check that dentries match; if path->dentry is equal to
m->mnt_root, superblocks will match as well.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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We want to mount beneath the given location. For that operation to
make sense, location must be the root of some mount that has something
under it. Currently we let it proceed if those requirements are not met,
with rather meaningless results, and have that bogosity caught further
down the road; let's fail early instead - do_lock_mount() doesn't make
sense unless those conditions hold, and checking them there makes
things simpler.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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1) checking that location we want to move does point to root of some mount
can be done before anything else; that property is not going to change
and having it already verified simplifies the analysis.
2) checking the type agreement between what we are trying to move and what
we are trying to move it onto also belongs in the very beginning -
do_lock_mount() might end up switching new_path to something that overmounts
the original location, but... the same type agreement applies to overmounts,
so we could just as well check against the original location.
3) since we know that old_path->dentry is the root of old_path->mnt, there's
no point bothering with path_is_overmounted() in can_move_mount_beneath();
it's simply a check for the mount we are trying to move having non-NULL
->overmount. And with that, we can switch can_move_mount_beneath() to
taking old instead of old_path, leaving no uses of old_path past the original
checks.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Both 'parent' and 'ns' are used at most once, no point precalculating those...
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Prior to the call of do_new_mount_fc() the caller has just done successful
vfs_get_tree(). Then do_new_mount_fc() does several checks on resulting
superblock, and either does fc_drop_locked() and returns an error or
proceeds to unlock the superblock and call vfs_create_mount().
The thing is, there's no reason to delay that unlock + vfs_create_mount() -
the tests do not rely upon the state of ->s_umount and
fc_drop_locked()
put_fs_context()
is equivalent to
unlock ->s_umount
put_fs_context()
Doing vfs_create_mount() before the checks allows us to move vfs_get_tree()
from caller to do_new_mount_fc() and collapse it with vfs_create_mount()
into an fc_mount() call.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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|
here a use of __free(path_put) for dropping fs_root is enough to
make guard(mount_locked_reader) fit...
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
All we need here is to follow ->overmount on root mount of namespace...
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
... and document that locking requirements for is_path_reachable().
There is one questionable caller in do_listmount() where we are not
holding mount_lock *and* might not have the first argument mounted.
However, in that case it will immediately return true without having
to look at the ancestors. Might be cleaner to move the check into
non-LSTM_ROOT case which it really belongs in - there the check is
not always true and is_mounted() is guaranteed.
Document the locking environments for is_path_reachable() callers:
get_peer_under_root()
get_dominating_id()
do_statmount()
do_listmount()
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
The reason why it needs only mount_locked_reader is that there's no lockless
accesses of expiry lists.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
... and document the locking requirements of __has_locked_children()
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Currently we are taking mount_writer; what that function needs is
either mount_locked_reader (we are not changing anything, we just
want to iterate through the subtree) or namespace_shared and
a reference held by caller on the root of subtree - that's also
enough to stabilize the topology.
The thing is, all callers are already holding at least namespace_shared
as well as a reference to the root of subtree.
Let's make the callers provide locking warranties - don't mess with
mount_lock in check_for_nsfs_mounts() itself and document the locking
requirements.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
clean fit; namespace_shared due to iterating through ns->mounts.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
clean fit; guards can't be weaker due to umount_tree() call.
Setting emptied_ns requires namespace_excl, but not anything
mount_lock-related.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Clean fit; guards can't be weaker due to umount_tree() calls.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
clean fit; namespace_excl to modify propagation graph
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
clean fit; namespace_excl to modify propagation graph
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
clean fit; namespace_shared due to iterating through ns->mounts.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Clean fit for guards use; guards can't be weaker due to umount_tree() calls.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Note that just as path_put, it should never be done in scope of
namespace_sem, be it shared or exclusive.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
If anything, namespace_lock should be DEFINE_LOCK_GUARD_0, not DEFINE_GUARD.
That way we
* do not need to feed it a bogus argument
* do not get gcc trying to compare an address of static in
file variable with -4097 - and, if we are unlucky, trying to keep
it in a register, with spills and all such.
The same problems apply to grabbing namespace_sem shared.
Rename it to namespace_excl, add namespace_shared, convert the existing users:
guard(namespace_lock, &namespace_sem) => guard(namespace_excl)()
guard(rwsem_read, &namespace_sem) => guard(namespace_shared)()
scoped_guard(namespace_lock, &namespace_sem) => scoped_guard(namespace_excl)
scoped_guard(rwsem_read, &namespace_sem) => scoped_guard(namespace_shared)
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
With the introduction of clone3 in commit 7f192e3cd316 ("fork: add
clone3") the effective bit width of clone_flags on all architectures was
increased from 32-bit to 64-bit, with a new type of u64 for the flags.
However, for most consumers of clone_flags the interface was not
changed from the previous type of unsigned long.
While this works fine as long as none of the new 64-bit flag bits
(CLONE_CLEAR_SIGHAND and CLONE_INTO_CGROUP) are evaluated, this is still
undesirable in terms of the principle of least surprise.
Thus, this commit fixes all relevant interfaces of callees to
sys_clone3/copy_process (excluding the architecture-specific
copy_thread) to consistently pass clone_flags as u64, so that
no truncation to 32-bit integers occurs on 32-bit architectures.
Signed-off-by: Simon Schuster <schuster.simon@siemens-energy.com>
Link: https://lore.kernel.org/20250901-nios2-implement-clone3-v2-2-53fcf5577d57@siemens-energy.com
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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|
Replace 8 leading spaces with a tab to follow kernel coding style.
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Link: https://lore.kernel.org/20250820133424.1667467-1-zhangguopeng@kylinos.cn
Signed-off-by: Christian Brauner <brauner@kernel.org>
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|
When CONFIG_TMPFS is enabled, the initial root filesystem is a tmpfs.
By default, a tmpfs mount is limited to using 50% of the available RAM
for its content. This can be problematic in memory-constrained
environments, particularly during a kdump capture.
In a kdump scenario, the capture kernel boots with a limited amount of
memory specified by the 'crashkernel' parameter. If the initramfs is
large, it may fail to unpack into the tmpfs rootfs due to insufficient
space. This is because to get X MB of usable space in tmpfs, 2*X MB of
memory must be available for the mount. This leads to an OOM failure
during the early boot process, preventing a successful crash dump.
This patch introduces a new kernel command-line parameter,
initramfs_options, which allows passing specific mount options directly
to the rootfs when it is first mounted. This gives users control over
the rootfs behavior.
For example, a user can now specify initramfs_options=size=75% to allow
the tmpfs to use up to 75% of the available memory. This can
significantly reduce the memory pressure for kdump.
Consider a practical example:
To unpack a 48MB initramfs, the tmpfs needs 48MB of usable space. With
the default 50% limit, this requires a memory pool of 96MB to be
available for the tmpfs mount. The total memory requirement is therefore
approximately: 16MB (vmlinuz) + 48MB (loaded initramfs) + 48MB (unpacked
kernel) + 96MB (for tmpfs) + 12MB (runtime overhead) ≈ 220MB.
By using initramfs_options=size=75%, the memory pool required for the
48MB tmpfs is reduced to 48MB / 0.75 = 64MB. This reduces the total
memory requirement by 32MB (96MB - 64MB), allowing the kdump to succeed
with a smaller crashkernel size, such as 192MB.
An alternative approach of reusing the existing rootflags parameter was
considered. However, a new, dedicated initramfs_options parameter was
chosen to avoid altering the current behavior of rootflags (which
applies to the final root filesystem) and to prevent any potential
regressions.
Also add documentation for the new kernel parameter "initramfs_options"
This approach is inspired by prior discussions and patches on the topic.
Ref: https://www.lightofdawn.org/blog/?viewDetailed=00128
Ref: https://landley.net/notes-2015.html#01-01-2015
Ref: https://lkml.org/lkml/2021/6/29/783
Ref: https://www.kernel.org/doc/html/latest/filesystems/ramfs-rootfs-initramfs.html#what-is-rootfs
Signed-off-by: Lichen Liu <lichliu@redhat.com>
Link: https://lore.kernel.org/20250815121459.3391223-1-lichliu@redhat.com
Tested-by: Rob Landley <rob@landley.net>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Pull mount fixes from Al Viro:
"Fixes for several recent mount-related regressions"
* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
change_mnt_propagation(): calculate propagation source only if we'll need it
use uniform permission checks for all mount propagation changes
propagate_umount(): only surviving overmounts should be reparented
fix the softlockups in attach_recursive_mnt()
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do_change_type() and do_set_group() are operating on different
aspects of the same thing - propagation graph. The latter
asks for mounts involved to be mounted in namespace(s) the caller
has CAP_SYS_ADMIN for. The former is a mess - originally it
didn't even check that mount *is* mounted. That got fixed,
but the resulting check turns out to be too strict for userland -
in effect, we check that mount is in our namespace, having already
checked that we have CAP_SYS_ADMIN there.
What we really need (in both cases) is
* only touch mounts that are mounted. That's a must-have
constraint - data corruption happens if it get violated.
* don't allow to mess with a namespace unless you already
have enough permissions to do so (i.e. CAP_SYS_ADMIN in its userns).
That's an equivalent of what do_set_group() does; let's extract that
into a helper (may_change_propagation()) and use it in both
do_set_group() and do_change_type().
Fixes: 12f147ddd6de "do_change_type(): refuse to operate on unmounted/not ours mounts"
Acked-by: Andrei Vagin <avagin@gmail.com>
Reviewed-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Tested-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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In case when we mounting something on top of a large stack of overmounts,
all of them being peers of each other, we get quadratic time by the
depth of overmount stack. Easily fixed by doing commit_tree() before
reparenting the overmount; simplifies commit_tree() as well - it doesn't
need to skip the already mounted stuff that had been reparented on top
of the new mounts.
Since we are holding mount_lock through both reparenting and call of
commit_tree(), the order does not matter from the mount hash point
of view.
Reported-by: "Lai, Yi" <yi1.lai@linux.intel.com>
Tested-by: "Lai, Yi" <yi1.lai@linux.intel.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Fixes: 663206854f02 "copy_tree(): don't link the mounts via mnt_list"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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...because it is not used
Signed-off-by: Askar Safin <safinaskar@zohomail.com>
Link: https://lore.kernel.org/20250811045444.1813009-1-safinaskar@zohomail.com
Reviewed-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
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The lflags value used to look up from_path was overwritten by the one used
to look up to_path.
In other words, from_path was looked up with the wrong lflags value. Fix it.
Fixes: f9fde814de37 ("fs: support getname_maybe_null() in move_mount()")
Signed-off-by: Yuntao Wang <yuntao.wang@linux.dev>
Link: https://lore.kernel.org/20250811052426.129188-1-yuntao.wang@linux.dev
[Christian Brauner <brauner@kernel.org>: massage patch]
Signed-off-by: Christian Brauner <brauner@kernel.org>
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It makes little sense for fsmount() to output the warning message when
mount_too_revealing() is violated to kmsg. Instead, the warning should
be output (with a "VFS" prefix) to the fscontext log. In addition,
include the same log message for mount_too_revealing() when doing a
regular mount for consistency.
With the newest fsopen()-based mount(8) from util-linux, the error
messages now look like
# mount -t proc proc /tmp
mount: /tmp: fsmount() failed: VFS: Mount too revealing.
dmesg(1) may have more information after failed mount system call.
which could finally result in mount_too_revealing() errors being easier
for users to detect and understand.
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/20250806-errorfc-mount-too-revealing-v2-2-534b9b4d45bb@cyphar.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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As described in commit 7a54947e727b ('Merge patch series "fs: allow
changing idmappings"'), open_tree_attr(2) was necessary in order to
allow for a detached mount to be created and have its idmappings changed
without the risk of any racing threads operating on it. For this reason,
mount_setattr(2) still does not allow for id-mappings to be changed.
However, there was a bug in commit 2462651ffa76 ("fs: allow changing
idmappings") which allowed users to bypass this restriction by calling
open_tree_attr(2) *without* OPEN_TREE_CLONE.
can_idmap_mount() prevented this bug from allowing an attached
mountpoint's id-mapping from being modified (thanks to an is_anon_ns()
check), but this still allows for detached (but visible) mounts to have
their be id-mapping changed. This risks the same UAF and locking issues
as described in the merge commit, and was likely unintentional.
Fixes: 2462651ffa76 ("fs: allow changing idmappings")
Cc: stable@vger.kernel.org # v6.15+
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/20250808-open_tree_attr-bugfix-idmap-v1-1-0ec7bc05646c@cyphar.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull namespace updates from Christian Brauner:
"This contains namespace updates. This time specifically for nsfs:
- Userspace heavily relies on the root inode numbers for namespaces
to identify the initial namespaces. That's already a hard
dependency. So we cannot change that anymore. Move the initial
inode numbers to a public header and align the only two namespaces
that currently don't do that with all the other namespaces.
- The root inode of /proc having a fixed inode number has been part
of the core kernel ABI since its inception, and recently some
userspace programs (mainly container runtimes) have started to
explicitly depend on this behaviour.
The main reason this is useful to userspace is that by checking
that a suspect /proc handle has fstype PROC_SUPER_MAGIC and is
PROCFS_ROOT_INO, they can then use openat2() together with
RESOLVE_{NO_{XDEV,MAGICLINK},BENEATH} to ensure that there isn't a
bind-mount that replaces some procfs file with a different one.
This kind of attack has lead to security issues in container
runtimes in the past (such as CVE-2019-19921) and libraries like
libpathrs[1] use this feature of procfs to provide safe procfs
handling functions"
* tag 'vfs-6.17-rc1.nsfs' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
uapi: export PROCFS_ROOT_INO
mntns: use stable inode number for initial mount ns
netns: use stable inode number for initial mount ns
nsfs: move root inode number to uapi
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git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs
Pull misc VFS updates from Christian Brauner:
"This contains the usual selections of misc updates for this cycle.
Features:
- Add ext4 IOCB_DONTCACHE support
This refactors the address_space_operations write_begin() and
write_end() callbacks to take const struct kiocb * as their first
argument, allowing IOCB flags such as IOCB_DONTCACHE to propagate
to the filesystem's buffered I/O path.
Ext4 is updated to implement handling of the IOCB_DONTCACHE flag
and advertises support via the FOP_DONTCACHE file operation flag.
Additionally, the i915 driver's shmem write paths are updated to
bypass the legacy write_begin/write_end interface in favor of
directly calling write_iter() with a constructed synchronous kiocb.
Another i915 change replaces a manual write loop with
kernel_write() during GEM shmem object creation.
Cleanups:
- don't duplicate vfs_open() in kernel_file_open()
- proc_fd_getattr(): don't bother with S_ISDIR() check
- fs/ecryptfs: replace snprintf with sysfs_emit in show function
- vfs: Remove unnecessary list_for_each_entry_safe() from
evict_inodes()
- filelock: add new locks_wake_up_waiter() helper
- fs: Remove three arguments from block_write_end()
- VFS: change old_dir and new_dir in struct renamedata to dentrys
- netfs: Remove unused declaration netfs_queue_write_request()
Fixes:
- eventpoll: Fix semi-unbounded recursion
- eventpoll: fix sphinx documentation build warning
- fs/read_write: Fix spelling typo
- fs: annotate data race between poll_schedule_timeout() and
pollwake()
- fs/pipe: set FMODE_NOWAIT in create_pipe_files()
- docs/vfs: update references to i_mutex to i_rwsem
- fs/buffer: remove comment about hard sectorsize
- fs/buffer: remove the min and max limit checks in __getblk_slow()
- fs/libfs: don't assume blocksize <= PAGE_SIZE in
generic_check_addressable
- fs_context: fix parameter name in infofc() macro
- fs: Prevent file descriptor table allocations exceeding INT_MAX"
* tag 'vfs-6.17-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (24 commits)
netfs: Remove unused declaration netfs_queue_write_request()
eventpoll: fix sphinx documentation build warning
ext4: support uncached buffered I/O
mm/pagemap: add write_begin_get_folio() helper function
fs: change write_begin/write_end interface to take struct kiocb *
drm/i915: Refactor shmem_pwrite() to use kiocb and write_iter
drm/i915: Use kernel_write() in shmem object create
eventpoll: Fix semi-unbounded recursion
vfs: Remove unnecessary list_for_each_entry_safe() from evict_inodes()
fs/libfs: don't assume blocksize <= PAGE_SIZE in generic_check_addressable
fs/buffer: remove the min and max limit checks in __getblk_slow()
fs: Prevent file descriptor table allocations exceeding INT_MAX
fs: Remove three arguments from block_write_end()
fs/ecryptfs: replace snprintf with sysfs_emit in show function
fs: annotate suspected data race between poll_schedule_timeout() and pollwake()
docs/vfs: update references to i_mutex to i_rwsem
fs/buffer: remove comment about hard sectorsize
fs_context: fix parameter name in infofc() macro
VFS: change old_dir and new_dir in struct renamedata to dentrys
proc_fd_getattr(): don't bother with S_ISDIR() check
...
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|
We are holding namespace_sem shared and we have not done any group
id allocations since we grabbed it. Therefore IS_MNT_SHARED(m)
is equivalent to non-zero m->mnt_group_id.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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All places where we call set_mnt_shared() are guaranteed to have
non-zero ->mnt_group_id - either by explicit test, or by having
done successful invent_group_ids() covering the same mount since
we'd grabbed namespace_sem.
The opposite combination (non-zero ->mnt_group_id and !IS_MNT_SHARED())
*is* possible - it means that we have allocated group id, but didn't
get around to set_mnt_shared() yet; such state is transient -
by the time we do namespace_unlock(), we must either do set_mnt_shared()
or unroll the group id allocations by cleanup_group_ids().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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the only difference between it and CL_SLAVE is in this predicate
in clone_mnt():
if ((flag & CL_SLAVE) ||
((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
However, in case of CL_SHARED_TO_SLAVE we have not allocated any
mount group ids since the time we'd grabbed namespace_sem, so
IS_MNT_SHARED() is equivalent to non-zero ->mnt_group_id. And
in case of CL_SLAVE old has come either from the original tree,
which had ->mnt_group_id allocated for all nodes or from result
of sequence of CL_MAKE_SHARED or CL_MAKE_SHARED|CL_SLAVE copies,
ultimately going back to the original tree. In both cases we are
guaranteed that old->mnt_group_id will be non-zero.
In other words, the predicate is always equal to
(flags & (CL_SLAVE | CL_SHARED_TO_SLAVE)) && old->mnt_group_id
and with that replacement CL_SLAVE and CL_SHARED_TO_SLAVE have exact
same behaviour.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Freeing of a namespace must be delayed until after we'd dealt with mount
notifications (in namespace_unlock()). The reasons are not immediately
obvious (they are buried in ->prev_ns handling in mnt_notify()), and
having that free_mnt_ns() explicitly called after namespace_unlock()
is asking for trouble - it does feel like they should be OK to free
as soon as they've been emptied.
Make the things more explicit by setting 'emptied_ns' under namespace_sem
and having namespace_unlock() free the sucker as soon as it's safe to free.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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The only place that really needs to be adjusted is commit_tree() -
there we need to iterate through the copy and we might as well
use next_mnt() for that. However, in case when our tree has been
slid under something already mounted (propagation to a mountpoint
that already has something mounted on it or a 'beneath' move_mount)
we need to take care not to walk into the overmounting tree.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Several flags are updated and checked only under namespace_sem; we are
already making use of that when we are checking them without mount_lock,
but we have to hold mount_lock for all updates, which makes things
clumsier than they have to be.
Take MNT_SHARED, MNT_UNBINDABLE, MNT_MARKED and MNT_UMOUNT_CANDIDATE
into a separate field (->mnt_t_flags), renaming them to T_SHARED,
etc. to avoid confusion. All accesses must be under namespace_sem.
That changes locking requirements for mnt_change_propagation() and
set_mnt_shared() - only namespace_sem is needed now. The same goes
for SET_MNT_MARKED et.al.
There might be more flags moved from ->mnt_flags to that field;
this is just the initial set.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Simplify the rules for mount refcounts. Current rules include:
* being a namespace root => +1
* being someone's child => +1
* being someone's child => +1 to parent's refcount, unless you've
already been through umount_tree().
The last part is not needed at all. It makes for more places where need
to decrement refcounts and it creates an asymmetry between the situations
for something that has never been a part of a namespace and something that
left one, both for no good reason.
If mount's refcount has additions from its children, we know that
* it's either someone's child itself (and will remain so
until umount_tree(), at which point contributions from children
will disappear), or
* or is the root of namespace (and will remain such until
it either becomes someone's child in another namespace or goes through
umount_tree()), or
* it is the root of some tree copy, and is currently pinned
by the caller of copy_tree() (and remains such until it either gets
into namespace, or goes to umount_tree()).
In all cases we already have contribution(s) to refcount that will last
as long as the contribution from children remains. In other words, the
lifetime is not affected by refcount contributions from children.
It might be useful for "is it busy" checks, but those are actually
no harder to express without it.
NB: propagate_mnt_busy() part is an equivalent transformation, ugly as it
is; the current logics is actually wrong and may give false negatives,
but fixing that is for a separate patch (probably earlier in the queue).
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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struct mountpoint has an odd kinda-sorta refcount in it. It's always
either equal to or one above the number of mounts attached to that
mountpoint.
"One above" happens when a function takes a temporary reference to
mountpoint. Things get simpler if we express that as inserting
a local object into ->m_list and removing it to drop the reference.
New calling conventions:
1) lock_mount(), do_lock_mount(), get_mountpoint() and lookup_mountpoint()
take an extra struct pinned_mountpoint * argument and returns 0/-E...
(or true/false in case of lookup_mountpoint()) instead of returning
struct mountpoint pointers. In case of success, the struct mountpoint *
we used to get can be found as pinned_mountpoint.mp
2) unlock_mount() (always paired with lock_mount()/do_lock_mount()) takes
an address of struct pinned_mountpoint - the same that had been passed to
lock_mount()/do_lock_mount().
3) put_mountpoint() for a temporary reference (paired with get_mountpoint()
or lookup_mountpoint()) is replaced with unpin_mountpoint(), which takes
the address of pinned_mountpoint we passed to matching {get,lookup}_mountpoint().
4) all instances of pinned_mountpoint are local variables; they always live on
stack. {} is used for initializer, after successful {get,lookup}_mountpoint()
we must make sure to call unpin_mountpoint() before leaving the scope and
after successful {do_,}lock_mount() we must make sure to call unlock_mount()
before leaving the scope.
5) all manipulations of ->m_count are gone, along with ->m_count itself.
struct mountpoint lives while its ->m_list is non-empty.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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A call of unhash_mnt() is immediately followed by passing its return
value to __put_mountpoint(); the shrink list given to __put_mountpoint()
will be ex_mountpoints when called from umount_mnt() and list when called
from mntput_no_expire().
Replace with __umount_mnt(mount, shrink_list), moving the call of
__put_mountpoint() into it (and returning nothing), adjust the
callers.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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attach new_mnt *before* detaching root_mnt; that way we don't need to keep hold
on the mountpoint and one more pair of unhash_mnt()/put_mountpoint() gets
folded together into umount_mnt().
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Doesn't take much massage, and we no longer need to make sure that
by the time of final mntput() the victim has been removed from the
list. Makes life safer for ->d_automount() instances...
Rules:
* all ->mnt_expire accesses are under mount_lock.
* insertion into the list is done by mnt_set_expiry(), and
caller (->d_automount() instance) must hold a reference to mount
in question. It shouldn't be done more than once for a mount.
* if a mount on an expiry list is not yet mounted, it will
be ignored by anything that walks that list.
* if the final mntput() finds its victim still on an expiry
list (in which case it must've never been mounted - umount_tree()
would've taken it out), it will remove the victim from the list.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
... rather than doing that in do_move_mount(). That's the main
obstacle to moving the protection of ->mnt_expire from namespace_sem
to mount_lock (spinlock-only), which would simplify several failure
exits.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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'attached' serves as a proxy for "source is a subtree of our namespace
and not the entirety of anon namespace"; finish massaging it away.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
... and fold it with unhash_mnt() there - there's no need to retain a reference
to old_mp beyond that point, since by then all mountpoints we were going to add
are either explicitly pinned by get_mountpoint() or have stuff already added
to them.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
move vs. attach is trivially detected as mnt_has_parent(source_mnt)...
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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... and 'beneath' is no longer used there
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
The logics used for tucking under existing mount differs for original
and copies; copies do a mount hash lookup to see if mountpoint to be is
already overmounted, while the original is told explicitly.
But the same logics that is used for copies works for the original,
at which point the only place where we get very close to eliminating
the need of passing 'beneath' flag to attach_recursive_mnt().
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Once attach_recursive_mnt() has created all copies of original subtree,
it needs to put them in place(s).
Steps needed for those are slightly different:
1) in 'move' case, original copy doesn't need any rbtree
manipulations (everything's already in the same namespace where it will
be), but it needs to be detached from the current location
2) in 'attach' case, original may be in anon namespace; if it is,
all those mounts need to removed from their current namespace before
insertion into the target one
3) additional copies have a couple of extra twists - in case
of cross-userns propagation we need to lock everything other the root of
subtree and in case when we end up inserting under an existing mount,
that mount needs to be found (for original copy we have it explicitly
passed by the caller).
Quite a bit of that can be unified; as the first step, make commit_tree()
helper (inserting mounts into namespace, hashing the root of subtree
and marking the namespace as updated) usable in all cases; (2) and (3)
are already using it and for (1) we only need to make the insertion of
mounts into namespace conditional.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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The variant currently in the tree has problems; trying to prove
correctness has caught at least one class of bugs (reparenting
that ends up moving the visible location of reparented mount, due
to not excluding some of the counterparts on propagation that
should've been included).
I tried to prove that it's the only bug there; I'm still not sure
whether it is. If anyone can reconstruct and write down an analysis
of the mainline implementation, I'll gladly review it; as it is,
I ended up doing a different implementation. Candidate collection
phase is similar, but trimming the set down until it satisfies the
constraints turned out pretty different.
I hoped to do transformation as a massage series, but that turns out
to be too convoluted. So it's a single patch replacing propagate_umount()
and friends in one go, with notes and analysis in D/f/propagate_umount.txt
(in addition to inline comments).
As far I can tell, it is provably correct and provably linear by the number
of mounts we need to look at in order to decide what should be unmounted.
It even builds and seems to survive testing...
Another nice thing that fell out of that is that ->mnt_umounting is no longer
needed.
Compared to the first version:
* explicit MNT_UMOUNT_CANDIDATE flag for is_candidate()
* trim_ancestors() only clears that flag, leaving the suckers on list
* trim_one() and handle_locked() take the stuff with flag cleared off
the list. That allows to iterate with list_for_each_entry_safe() when calling
trim_one() - it removes at most one element from the list now.
* no globals - I didn't bother with any kind of context, not worth it.
* Notes updated accordingly; I have not touch the terms yet.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Original rationale for those had been the reduced cost of mntput()
for the stuff that is mounted somewhere. Mount refcount increments and
decrements are frequent; what's worse, they tend to concentrate on the
same instances and cacheline pingpong is quite noticable.
As the result, mount refcounts are per-cpu; that allows a very cheap
increment. Plain decrement would be just as easy, but decrement-and-test
is anything but (we need to add the components up, with exclusion against
possible increment-from-zero, etc.).
Fortunately, there is a very common case where we can tell that decrement
won't be the final one - if the thing we are dropping is currently
mounted somewhere. We have an RCU delay between the removal from mount
tree and dropping the reference that used to pin it there, so we can
just take rcu_read_lock() and check if the victim is mounted somewhere.
If it is, we can go ahead and decrement without and further checks -
the reference we are dropping is not the last one. If it isn't, we
get all the fun with locking, carefully adding up components, etc.,
but the majority of refcount decrements end up taking the fast path.
There is a major exception, though - pipes and sockets. Those live
on the internal filesystems that are not going to be mounted anywhere.
They are not going to be _un_mounted, of course, so having to take the
slow path every time a pipe or socket gets closed is really obnoxious.
Solution had been to mark them as long-lived ones - essentially faking
"they are mounted somewhere" indicator.
With minor modification that works even for ones that do eventually get
dropped - all it takes is making sure we have an RCU delay between
clearing the "mounted somewhere" indicator and dropping the reference.
There are some additional twists (if you want to drop a dozen of such
internal mounts, you'd be better off with clearing the indicator on
all of them, doing an RCU delay once, then dropping the references),
but in the basic form it had been
* use kern_mount() if you want your internal mount to be
a long-term one.
* use kern_unmount() to undo that.
Unfortunately, the things did rot a bit during the mount API reshuffling.
In several cases we have lost the "fake the indicator" part; kern_unmount()
on the unmount side remained (it doesn't warn if you use it on a mount
without the indicator), but all benefits regaring mntput() cost had been
lost.
To get rid of that bitrot, let's add a new helper that would work
with fs_context-based API: fc_mount_longterm(). It's a counterpart
of fc_mount() that does, on success, mark its result as long-term.
It must be paired with kern_unmount() or equivalents.
Converted:
1) mqueue (it used to use kern_mount_data() and the umount side
is still as it used to be)
2) hugetlbfs (used to use kern_mount_data(), internal mount is
never unmounted in this one)
3) i915 gemfs (used to be kern_mount() + manual remount to set
options, still uses kern_unmount() on umount side)
4) v3d gemfs (copied from i915)
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Calls of do_umount() are always preceded by can_umount(), where we'd
done a racy check for mount belonging to our namespace; if it wasn't,
can_unmount() would've failed with -EINVAL and we wouldn't have
reached do_umount() at all.
That check needs to be redone once we have acquired namespace_sem
and in do_umount() we do that. However, that's done in a very odd
way; we check that mount is still in rbtree of _some_ namespace or
its mnt_list is not empty. It is equivalent to check_mnt(mnt) -
we know that earlier mnt was mounted in our namespace; if it has
stayed there, it's going to remain in rbtree of our namespace.
OTOH, if it ever had been removed from out namespace, it would be
removed from rbtree and it never would've re-added to a namespace
afterwards. As for ->mnt_list, for something that had been mounted
in a namespace we'll never observe non-empty ->mnt_list while holding
namespace_sem - it does temporarily become non-empty during
umount_tree(), but that doesn't outlast the call of umount_tree(),
let alone dropping namespace_sem.
Things get much easier to follow if we replace that with (equivalent)
check_mnt(mnt) there. What's more, currently we treat a failure of
that test as "quietly do nothing"; we might as well pretend that we'd
lost the race and fail on that the same way can_umount() would have.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
The underlying rules are simple:
* MNT_SHARED should be set iff ->mnt_group_id of new mount ends up
non-zero.
* mounts should be on the same ->mnt_share cyclic list iff they have
the same non-zero ->mnt_group_id value.
* CL_PRIVATE is mutually exclusive with MNT_SHARED, MNT_SLAVE,
MNT_SHARED_TO_SLAVE and MNT_EXPIRE; the whole point of that thing is to
get a clone of old mount that would *not* be on any namespace-related
lists.
The above allows to make the logics more straightforward; what's more,
it makes the proof that invariants are maintained much simpler.
The variant in mainline is safe (aside of a very narrow race with
unsafe modification of mnt_flags right after we had the mount exposed
in superblock's ->s_mounts; theoretically it can race with ro remount
of the original, but it's not easy to hit), but proof of its correctness
is really unpleasant.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Originally MNT_LOCKED meant only one thing - "don't let this mount to
be peeled off its parent, we don't want to have its mountpoint exposed".
Accordingly, it had only been set on mounts that *do* have a parent.
Later it got overloaded with another use - setting it on the absolute
root had given free protection against umount(2) of absolute root
(was possible to trigger, oopsed). Not a bad trick, but it ended
up costing more than it bought us. Unfortunately, the cost included
both hard-to-reason-about logics and a subtle race between
mount -o remount,ro and mount --[r]bind - lockless &= ~MNT_LOCKED in
the end of __do_loopback() could race with sb_prepare_remount_readonly()
setting and clearing MNT_HOLD_WRITE (under mount_lock, as it should
be). The race wouldn't be much of a problem (there are other ways to
deal with it), but the subtlety is.
Turns out that nobody except umount(2) had ever made use of having
MNT_LOCKED set on absolute root. So let's give up on that trick,
clever as it had been, add an explicit check in do_umount() and
return to using MNT_LOCKED only for mounts that have a parent.
It means that
* clone_mnt() no longer copies MNT_LOCKED
* copy_tree() sets it on submounts if their counterparts had
been marked such, and does that right next to attach_mnt() in there,
in the same mount_lock scope.
* __do_loopback() no longer needs to strip MNT_LOCKED off the
root of subtree it's about to return; no store, no race.
* init_mount_tree() doesn't bother setting MNT_LOCKED on absolute
root.
* lock_mnt_tree() does not set MNT_LOCKED on the subtree's root;
accordingly, its caller (loop in attach_recursive_mnt()) does not need to
bother stripping that MNT_LOCKED on root. Note that lock_mnt_tree() setting
MNT_LOCKED on submounts happens in the same mount_lock scope as __attach_mnt()
(from commit_tree()) that makes them reachable.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
It's always ->mnt_parent of the first one. What the function does is
making a mount (with already set parent and mountpoint) visible - in
mount hash and in the parent's list of children.
IOW, it takes the existing rootwards linkage and sets the matching
crownwards linkage.
Renamed to make_visible(), while we are at it.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
that's the condition we are actually trying to check there...
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
checks if mount is the root of an anonymouns namespace.
Switch open-coded equivalents to using it.
For mounts that belong to anon namespace !mnt_has_parent(mount)
is the same as mount == ns->root, and intent is more obvious in
the latter form.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
mount_is_ancestor(p1, p2) returns true iff there is a possibly
empty ancestry chain from p1 to p2.
Convert the open-coded checks. Unlike those open-coded variants
it does not depend upon p1 not being root...
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
It never made any sense - neither when copy_tree() had been introduced
(2.4.11-pre5), nor at any point afterwards. Mountpoint is meaningless
without parent mount and the root of copied tree has no parent until we get
around to attaching it somewhere. At that time we'll have mountpoint set;
before that we have no idea which dentry will be used as mountpoint.
IOW, copy_tree() should just leave the default value.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
|
Currently it's still possible to run into a pathological situation when
two hashed mounts share both parent and mountpoint. That does not work
well, for obvious reasons.
We are not far from getting rid of that; the only remaining gap is
attach_recursive_mnt() not being careful enough when sliding a tree
under existing mount (for propagated copies or in 'beneath' case for
the original one).
To deal with that cleanly we need to be able to find overmounts
(i.e. mounts on top of parent's root); we could do hash lookups or scan
the list of children but either would be costly. Since one of the results
we get from that will be prevention of multiple parallel overmounts, let's
just bite the bullet and store a (non-counting) reference to overmount
in struct mount.
With that done, closing the hole in attach_recursive_mnt() becomes easy
- we just need to follow the chain of overmounts before we change the
mountpoint of the mount we are sliding things under.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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mnt_set_mountpoint_beneath() consists of attaching new mount side-by-side
with the one we want to mount beneath (by mnt_set_mountpoint()), followed
by mnt_change_mountpoint() shifting the the top mount onto the new one
(by mnt_change_mountpoint()).
Both callers of mnt_set_mountpoint_beneath (both in attach_recursive_mnt())
have the same form - in 'beneath' case we call mnt_set_mountpoint_beneath(),
otherwise - mnt_set_mountpoint().
The thing is, expressing that as unconditional mnt_set_mountpoint(),
followed, in 'beneath' case, by mnt_change_mountpoint() is just as easy.
And these mnt_change_mountpoint() callers are similar to the ones we
do when it comes to attaching propagated copies, which will allow more
cleanups in the next commits.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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simpler that way - all but one caller pass false as 'beneath' argument,
and that one caller is actually happier with the call expanded - the
logics with choice of mountpoint is identical for 'moving' and 'attaching'
cases, and now that is no longer hidden.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Once want_mount_setattr() has returned a positive, it does require
finish_mount_kattr() to release ->mnt_userns. Failing do_mount_setattr()
does not change that.
As the result, we can end up leaking userns and possibly mnt_idmap as
well.
Fixes: c4a16820d901 ("fs: add open_tree_attr()")
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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under it
If we are propagating across the userns boundary, we need to lock the
mounts added there. However, in case when something has already
been mounted there and we end up sliding a new tree under that,
the stuff that had been there before should not get locked.
IOW, lock_mnt_tree() should be called before we reparent the
preexisting tree on top of what we are adding.
Fixes: 3bd045cc9c4b ("separate copying and locking mount tree on cross-userns copies")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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collect_mounts() has several problems - one can't iterate over the results
directly, so it has to be done with callback passed to iterate_mounts();
it has an oopsable race with d_invalidate(); it creates temporary clones
of mounts invisibly for sync umount (IOW, you can have non-lazy umount
succeed leaving filesystem not mounted anywhere and yet still busy).
A saner approach is to give caller an array of struct path that would pin
every mount in a subtree, without cloning any mounts.
* collect_mounts()/drop_collected_mounts()/iterate_mounts() is gone
* collect_paths(where, preallocated, size) gives either ERR_PTR(-E...) or
a pointer to array of struct path, one for each chunk of tree visible under
'where' (i.e. the first element is a copy of where, followed by (mount,root)
for everything mounted under it - the same set collect_mounts() would give).
Unlike collect_mounts(), the mounts are *not* cloned - we just get pinning
references to the roots of subtrees in the caller's namespace.
Array is terminated by {NULL, NULL} struct path. If it fits into
preallocated array (on-stack, normally), that's where it goes; otherwise
it's allocated by kmalloc_array(). Passing 0 as size means that 'preallocated'
is ignored (and expected to be NULL).
* drop_collected_paths(paths, preallocated) is given the array returned
by an earlier call of collect_paths() and the preallocated array passed to that
call. All mount/dentry references are dropped and array is kfree'd if it's not
equal to 'preallocated'.
* instead of iterate_mounts(), users should just iterate over array
of struct path - nothing exotic is needed for that. Existing users (all in
audit_tree.c) are converted.
[folded a fix for braino reported by Venkat Rao Bagalkote <venkat88@linux.ibm.com>]
Fixes: 80b5dce8c59b0 ("vfs: Add a function to lazily unmount all mounts from any dentry")
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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VFS has switched to i_rwsem for ten years now (9902af79c01a: parallel
lookups actual switch to rwsem), but the VFS documentation and comments
still has references to i_mutex.
Signed-off-by: Junxuan Liao <ljx@cs.wisc.edu>
Link: https://lore.kernel.org/72223729-5471-474a-af3c-f366691fba82@cs.wisc.edu
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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Apart from the network and mount namespace all other namespaces expose a
stable inode number and userspace has been relying on that for a very
long time now. It's very much heavily used API. Align the mount
namespace and use a stable inode number from the reserved procfs inode
number space so this is consistent across all namespaces.
Link: https://lore.kernel.org/20250606-work-nsfs-v1-3-b8749c9a8844@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
|
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Pull mount fixes from Al Viro:
"Various mount-related bugfixes:
- split the do_move_mount() checks in subtree-of-our-ns and
entire-anon cases and adapt detached mount propagation selftest for
mount_setattr
- allow clone_private_mount() for a path on real rootfs
- fix a race in call of has_locked_children()
- fix move_mount propagation graph breakage by MOVE_MOUNT_SET_GROUP
- make sure clone_private_mnt() caller has CAP_SYS_ADMIN in the right
userns
- avoid false negatives in path_overmount()
- don't leak MNT_LOCKED from parent to child in finish_automount()
- do_change_type(): refuse to operate on unmounted/not ours mounts"
* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
do_change_type(): refuse to operate on unmounted/not ours mounts
clone_private_mnt(): make sure that caller has CAP_SYS_ADMIN in the right userns
selftests/mount_setattr: adapt detached mount propagation test
do_move_mount(): split the checks in subtree-of-our-ns and entire-anon cases
fs: allow clone_private_mount() for a path on real rootfs
fix propagation graph breakage by MOVE_MOUNT_SET_GROUP move_mount(2)
finish_automount(): don't leak MNT_LOCKED from parent to child
path_overmount(): avoid false negatives
fs/fhandle.c: fix a race in call of has_locked_children()
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Ensure that propagation settings can only be changed for mounts located
in the caller's mount namespace. This change aligns permission checking
with the rest of mount(2).
Reviewed-by: Christian Brauner <brauner@kernel.org>
Fixes: 07b20889e305 ("beginning of the shared-subtree proper")
Reported-by: "Orlando, Noah" <Noah.Orlando@deshaw.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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What we want is to verify there is that clone won't expose something
hidden by a mount we wouldn't be able to undo. "Wouldn't be able to undo"
may be a result of MNT_LOCKED on a child, but it may also come from
lacking admin rights in the userns of the namespace mount belongs to.
clone_private_mnt() checks the former, but not the latter.
There's a number of rather confusing CAP_SYS_ADMIN checks in various
userns during the mount, especially with the new mount API; they serve
different purposes and in case of clone_private_mnt() they usually,
but not always end up covering the missing check mentioned above.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reported-by: "Orlando, Noah" <Noah.Orlando@deshaw.com>
Fixes: 427215d85e8d ("ovl: prevent private clone if bind mount is not allowed")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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... and fix the breakage in anon-to-anon case. There are two cases
acceptable for do_move_mount() and mixing checks for those is making
things hard to follow.
One case is move of a subtree in caller's namespace.
* source and destination must be in caller's namespace
* source must be detachable from parent
Another is moving the entire anon namespace elsewhere
* source must be the root of anon namespace
* target must either in caller's namespace or in a suitable
anon namespace (see may_use_mount() for details).
* target must not be in the same namespace as source.
It's really easier to follow if tests are *not* mixed together...
Reviewed-by: Christian Brauner <brauner@kernel.org>
Fixes: 3b5260d12b1f ("Don't propagate mounts into detached trees")
Reported-by: Allison Karlitskaya <lis@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
|
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Mounting overlayfs with a directory on real rootfs (initramfs)
as upperdir has failed with following message since commit
db04662e2f4f ("fs: allow detached mounts in clone_private_mount()").
[ 4.080134] overlayfs: failed to clone upperpath
Overlayfs mount uses clone_private_mount() to create internal mount
for the underlying layers.
The commit made clone_private_mount() reject real rootfs because
it does not have a parent mount and is in the initial mount namespace,
that is not an anonymous mount namespace.
This issue can be fixed by modifying the permission check
of clone_private_mount() following [1].
Reviewed-by: Christian Brauner <brauner@kernel.org>
Fixes: db04662e2f4f ("fs: allow detached mounts in clone_private_mount()")
Link: https://lore.kernel.org/all/20250514190252.GQ2023217@ZenIV/ [1]
Link: https://lore.kernel.org/all/20250506194849.GT2023217@ZenIV/
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Kazuma Kondo <kazuma-kondo@nec.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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9ffb14ef61ba "move_mount: allow to add a mount into an existing group"
breaks assertions on ->mnt_share/->mnt_slave. For once, the data structures
in question are actually documented.
Documentation/filesystem/sharedsubtree.rst:
All vfsmounts in a peer group have the same ->mnt_master. If it is
non-NULL, they form a contiguous (ordered) segment of slave list.
do_set_group() puts a mount into the same place in propagation graph
as the old one. As the result, if old mount gets events from somewhere
and is not a pure event sink, new one needs to be placed next to the
old one in the slave list the old one's on. If it is a pure event
sink, we only need to make sure the new one doesn't end up in the
middle of some peer group.
"move_mount: allow to add a mount into an existing group" ends up putting
the new one in the beginning of list; that's definitely not going to be
in the middle of anything, so that's fine for case when old is not marked
shared. In case when old one _is_ marked shared (i.e. is not a pure event
sink), that breaks the assumptions of propagation graph iterators.
Put the new mount next to the old one on the list - that does the right thing
in "old is marked shared" case and is just as correct as the current behaviour
if old is not marked shared (kudos to Pavel for pointing that out - my original
suggested fix changed behaviour in the "nor marked" case, which complicated
things for no good reason).
Reviewed-by: Christian Brauner <brauner@kernel.org>
Fixes: 9ffb14ef61ba ("move_mount: allow to add a mount into an existing group")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Holding namespace_sem is enough to make sure that result remains valid.
It is *not* enough to avoid false negatives from __lookup_mnt(). Mounts
can be unhashed outside of namespace_sem (stuck children getting detached
on final mntput() of lazy-umounted mount) and having an unrelated mount
removed from the hash chain while we traverse it may end up with false
negative from __lookup_mnt(). We need to sample and recheck the seqlock
component of mount_lock...
Bug predates the introduction of path_overmount() - it had come from
the code in finish_automount() that got abstracted into that helper.
Reviewed-by: Christian Brauner <brauner@kernel.org>
Fixes: 26df6034fdb2 ("fix automount/automount race properly")
Fixes: 6ac392815628 ("fs: allow to mount beneath top mount")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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may_decode_fh() is calling has_locked_children() while holding no locks.
That's an oopsable race...
The rest of the callers are safe since they are holding namespace_sem and
are guaranteed a positive refcount on the mount in question.
Rename the current has_locked_children() to __has_locked_children(), make
it static and switch the fs/namespace.c users to it.
Make has_locked_children() a wrapper for __has_locked_children(), calling
the latter under read_seqlock_excl(&mount_lock).
Reviewed-by: Christian Brauner <brauner@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Fixes: 620c266f3949 ("fhandle: relax open_by_handle_at() permission checks")
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull automount updates from Al Viro:
"Automount wart removal
A bunch of odd boilerplate gone from instances - the reason for
those was the need to protect the yet-to-be-attched mount from
mark_mounts_for_expiry() deciding to take it out.
But that's easy to detect and take care of in mark_mounts_for_expiry()
itself; no need to have every instance simulate mount being busy by
grabbing an extra reference to it, with finish_automount() undoing
that once it attaches that mount.
Should've done it that way from the very beginning... This is a
flagday change, thankfully there are very few instances.
vfs_submount() is gone - its sole remaining user (trace_automount)
had been switched to saner primitives"
* tag 'pull-automount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
kill vfs_submount()
saner calling conventions for ->d_automount()
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Pull mount propagation fix from Al Viro:
"6.15 allowed mount propagation to destinations in detached trees;
unfortunately, that breaks existing userland, so the old behaviour
needs to be restored.
It's not exactly a revert - the original behaviour had a bug, where
existence of detached tree might disrupt propagation between locations
not in detached trees. Thankfully, userland did not depend upon that
bug, so we want to keep the fix"
* tag 'pull-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
Don't propagate mounts into detached trees
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All versions up to 6.14 did not propagate mount events into detached
tree. Shortly after 6.14 a merge of vfs-6.15-rc1.mount.namespace
(130e696aa68b) has changed that.
Unfortunately, that has caused userland regressions (reported in
https://lore.kernel.org/all/CAOYeF9WQhFDe+BGW=Dp5fK8oRy5AgZ6zokVyTj1Wp4EUiYgt4w@mail.gmail.com/)
Straight revert wouldn't be an option - in particular, the variant in 6.14
had a bug that got fixed in d1ddc6f1d9f0 ("fix IS_MNT_PROPAGATING uses")
and we don't want to bring the bug back.
This is a modification of manual revert posted by Christian, with changes
needed to avoid reintroducing the breakage in scenario described in
d1ddc6f1d9f0.
Cc: stable@vger.kernel.org
Reported-by: Allison Karlitskaya <lis@redhat.com>
Tested-by: Allison Karlitskaya <lis@redhat.com>
Acked-by: Christian Brauner <brauner@kernel.org>
Co-developed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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