From: NeilBrown <neilb@ownmail.net>
To: "Alexander Viro" <viro@zeniv.linux.org.uk>,
"Christian Brauner" <brauner@kernel.org>,
"Amir Goldstein" <amir73il@gmail.com>
Cc: "Jan Kara" <jack@suse.cz>,
linux-fsdevel@vger.kernel.org, Jeff Layton <jlayton@kernel.org>,
Chris Mason <clm@fb.com>, David Sterba <dsterba@suse.com>,
David Howells <dhowells@redhat.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Danilo Krummrich <dakr@kernel.org>,
Tyler Hicks <code@tyhicks.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Chuck Lever <chuck.lever@oracle.com>,
Olga Kornievskaia <okorniev@redhat.com>,
Dai Ngo <Dai.Ngo@oracle.com>, Namjae Jeon <linkinjeon@kernel.org>,
Steve French <smfrench@gmail.com>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Carlos Maiolino <cem@kernel.org>,
John Johansen <john.johansen@canonical.com>,
Paul Moore <paul@paul-moore.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
Stephen Smalley <stephen.smalley.work@gmail.com>,
Ondrej Mosnacek <omosnace@redhat.com>,
Mateusz Guzik <mjguzik@gmail.com>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
Stefan Berger <stefanb@linux.ibm.com>,
"Darrick J. Wong" <djwong@kernel.org>,
linux-kernel@vger.kernel.org, netfs@lists.linux.dev,
ecryptfs@vger.kernel.org, linux-nfs@vger.kernel.org,
linux-unionfs@vger.kernel.org, linux-cifs@vger.kernel.org,
linux-xfs@vger.kernel.org, linux-security-module@vger.kernel.org,
selinux@vger.kernel.org
Subject: [PATCH v6 06/15] VFS: introduce start_creating_noperm() and start_removing_noperm()
Date: Thu, 13 Nov 2025 11:18:29 +1100 [thread overview]
Message-ID: <20251113002050.676694-7-neilb@ownmail.net> (raw)
In-Reply-To: <20251113002050.676694-1-neilb@ownmail.net>
From: NeilBrown <neil@brown.name>
xfs, fuse, ipc/mqueue need variants of start_creating or start_removing
which do not check permissions.
This patch adds _noperm versions of these functions.
Note that do_mq_open() was only calling mntget() so it could call
path_put() - it didn't really need an extra reference on the mnt.
Now it doesn't call mntget() and uses end_creating() which does
the dput() half of path_put().
Also mq_unlink() previously passed
d_inode(dentry->d_parent)
as the dir inode to vfs_unlink(). This is after locking
d_inode(mnt->mnt_root)
These two inodes are the same, but normally calls use the textual
parent.
So I've changes the vfs_unlink() call to be given d_inode(mnt->mnt_root).
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: NeilBrown <neil@brown.name>
--
changes since v2:
- dir arg passed to vfs_unlink() in mq_unlink() changed to match
the dir passed to lookup_noperm()
- restore assignment to path->mnt even though the mntget() is removed.
---
fs/fuse/dir.c | 19 +++++++---------
fs/namei.c | 48 ++++++++++++++++++++++++++++++++++++++++
fs/xfs/scrub/orphanage.c | 11 ++++-----
include/linux/namei.h | 2 ++
ipc/mqueue.c | 32 ++++++++++-----------------
5 files changed, 74 insertions(+), 38 deletions(-)
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 316922d5dd13..a0d5b302bcc2 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -1397,27 +1397,25 @@ int fuse_reverse_inval_entry(struct fuse_conn *fc, u64 parent_nodeid,
if (!parent)
return -ENOENT;
- inode_lock_nested(parent, I_MUTEX_PARENT);
if (!S_ISDIR(parent->i_mode))
- goto unlock;
+ goto put_parent;
err = -ENOENT;
dir = d_find_alias(parent);
if (!dir)
- goto unlock;
+ goto put_parent;
- name->hash = full_name_hash(dir, name->name, name->len);
- entry = d_lookup(dir, name);
+ entry = start_removing_noperm(dir, name);
dput(dir);
- if (!entry)
- goto unlock;
+ if (IS_ERR(entry))
+ goto put_parent;
fuse_dir_changed(parent);
if (!(flags & FUSE_EXPIRE_ONLY))
d_invalidate(entry);
fuse_invalidate_entry_cache(entry);
- if (child_nodeid != 0 && d_really_is_positive(entry)) {
+ if (child_nodeid != 0) {
inode_lock(d_inode(entry));
if (get_node_id(d_inode(entry)) != child_nodeid) {
err = -ENOENT;
@@ -1445,10 +1443,9 @@ int fuse_reverse_inval_entry(struct fuse_conn *fc, u64 parent_nodeid,
} else {
err = 0;
}
- dput(entry);
- unlock:
- inode_unlock(parent);
+ end_removing(entry);
+ put_parent:
iput(parent);
return err;
}
diff --git a/fs/namei.c b/fs/namei.c
index 38dda29552f6..da01b828ede6 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3275,6 +3275,54 @@ struct dentry *start_removing(struct mnt_idmap *idmap, struct dentry *parent,
}
EXPORT_SYMBOL(start_removing);
+/**
+ * start_creating_noperm - prepare to create a given name without permission checking
+ * @parent: directory in which to prepare to create the name
+ * @name: the name to be created
+ *
+ * Locks are taken and a lookup in performed prior to creating
+ * an object in a directory.
+ *
+ * If the name already exists, a positive dentry is returned.
+ *
+ * Returns: a negative or positive dentry, or an error.
+ */
+struct dentry *start_creating_noperm(struct dentry *parent,
+ struct qstr *name)
+{
+ int err = lookup_noperm_common(name, parent);
+
+ if (err)
+ return ERR_PTR(err);
+ return start_dirop(parent, name, LOOKUP_CREATE);
+}
+EXPORT_SYMBOL(start_creating_noperm);
+
+/**
+ * start_removing_noperm - prepare to remove a given name without permission checking
+ * @parent: directory in which to find the name
+ * @name: the name to be removed
+ *
+ * Locks are taken and a lookup in performed prior to removing
+ * an object from a directory.
+ *
+ * If the name doesn't exist, an error is returned.
+ *
+ * end_removing() should be called when removal is complete, or aborted.
+ *
+ * Returns: a positive dentry, or an error.
+ */
+struct dentry *start_removing_noperm(struct dentry *parent,
+ struct qstr *name)
+{
+ int err = lookup_noperm_common(name, parent);
+
+ if (err)
+ return ERR_PTR(err);
+ return start_dirop(parent, name, 0);
+}
+EXPORT_SYMBOL(start_removing_noperm);
+
#ifdef CONFIG_UNIX98_PTYS
int path_pts(struct path *path)
{
diff --git a/fs/xfs/scrub/orphanage.c b/fs/xfs/scrub/orphanage.c
index 9c12cb844231..e732605924a1 100644
--- a/fs/xfs/scrub/orphanage.c
+++ b/fs/xfs/scrub/orphanage.c
@@ -152,11 +152,10 @@ xrep_orphanage_create(
}
/* Try to find the orphanage directory. */
- inode_lock_nested(root_inode, I_MUTEX_PARENT);
- orphanage_dentry = lookup_noperm(&QSTR(ORPHANAGE), root_dentry);
+ orphanage_dentry = start_creating_noperm(root_dentry, &QSTR(ORPHANAGE));
if (IS_ERR(orphanage_dentry)) {
error = PTR_ERR(orphanage_dentry);
- goto out_unlock_root;
+ goto out_dput_root;
}
/*
@@ -170,7 +169,7 @@ xrep_orphanage_create(
orphanage_dentry, 0750);
error = PTR_ERR(orphanage_dentry);
if (IS_ERR(orphanage_dentry))
- goto out_unlock_root;
+ goto out_dput_orphanage;
}
/* Not a directory? Bail out. */
@@ -200,9 +199,7 @@ xrep_orphanage_create(
sc->orphanage_ilock_flags = 0;
out_dput_orphanage:
- dput(orphanage_dentry);
-out_unlock_root:
- inode_unlock(VFS_I(sc->mp->m_rootip));
+ end_creating(orphanage_dentry, root_dentry);
out_dput_root:
dput(root_dentry);
out:
diff --git a/include/linux/namei.h b/include/linux/namei.h
index 6d1069f93ebf..0441f5921f87 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -93,6 +93,8 @@ struct dentry *start_creating(struct mnt_idmap *idmap, struct dentry *parent,
struct qstr *name);
struct dentry *start_removing(struct mnt_idmap *idmap, struct dentry *parent,
struct qstr *name);
+struct dentry *start_creating_noperm(struct dentry *parent, struct qstr *name);
+struct dentry *start_removing_noperm(struct dentry *parent, struct qstr *name);
/**
* end_creating - finish action started with start_creating
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 093551fe66a7..6d7610310003 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -913,13 +913,12 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
goto out_putname;
ro = mnt_want_write(mnt); /* we'll drop it in any case */
- inode_lock(d_inode(root));
- path.dentry = lookup_noperm(&QSTR(name->name), root);
+ path.dentry = start_creating_noperm(root, &QSTR(name->name));
if (IS_ERR(path.dentry)) {
error = PTR_ERR(path.dentry);
goto out_putfd;
}
- path.mnt = mntget(mnt);
+ path.mnt = mnt;
error = prepare_open(path.dentry, oflag, ro, mode, name, attr);
if (!error) {
struct file *file = dentry_open(&path, oflag, current_cred());
@@ -928,13 +927,12 @@ static int do_mq_open(const char __user *u_name, int oflag, umode_t mode,
else
error = PTR_ERR(file);
}
- path_put(&path);
out_putfd:
if (error) {
put_unused_fd(fd);
fd = error;
}
- inode_unlock(d_inode(root));
+ end_creating(path.dentry, root);
if (!ro)
mnt_drop_write(mnt);
out_putname:
@@ -957,7 +955,7 @@ SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
int err;
struct filename *name;
struct dentry *dentry;
- struct inode *inode = NULL;
+ struct inode *inode;
struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
struct vfsmount *mnt = ipc_ns->mq_mnt;
@@ -969,26 +967,20 @@ SYSCALL_DEFINE1(mq_unlink, const char __user *, u_name)
err = mnt_want_write(mnt);
if (err)
goto out_name;
- inode_lock_nested(d_inode(mnt->mnt_root), I_MUTEX_PARENT);
- dentry = lookup_noperm(&QSTR(name->name), mnt->mnt_root);
+ dentry = start_removing_noperm(mnt->mnt_root, &QSTR(name->name));
if (IS_ERR(dentry)) {
err = PTR_ERR(dentry);
- goto out_unlock;
+ goto out_drop_write;
}
inode = d_inode(dentry);
- if (!inode) {
- err = -ENOENT;
- } else {
- ihold(inode);
- err = vfs_unlink(&nop_mnt_idmap, d_inode(dentry->d_parent),
- dentry, NULL);
- }
- dput(dentry);
-
-out_unlock:
- inode_unlock(d_inode(mnt->mnt_root));
+ ihold(inode);
+ err = vfs_unlink(&nop_mnt_idmap, d_inode(mnt->mnt_root),
+ dentry, NULL);
+ end_removing(dentry);
iput(inode);
+
+out_drop_write:
mnt_drop_write(mnt);
out_name:
putname(name);
--
2.50.0.107.gf914562f5916.dirty
next prev parent reply other threads:[~2025-11-13 0:41 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-13 0:18 [PATCH v6 00/15] Create and use APIs to centralise locking for directory ops NeilBrown
2025-11-13 0:18 ` [PATCH v6 01/15] debugfs: rename end_creating() to debugfs_end_creating() NeilBrown
2025-11-13 0:18 ` [PATCH v6 02/15] VFS: introduce start_dirop() and end_dirop() NeilBrown
2025-11-13 0:18 ` [PATCH v6 03/15] VFS: tidy up do_unlinkat() NeilBrown
2025-11-13 0:18 ` [PATCH v6 04/15] VFS/nfsd/cachefiles/ovl: add start_creating() and end_creating() NeilBrown
2025-11-13 0:18 ` [PATCH v6 05/15] VFS/nfsd/cachefiles/ovl: introduce start_removing() and end_removing() NeilBrown
2025-11-13 0:18 ` NeilBrown [this message]
2025-11-30 0:01 ` [PATCH v6 06/15] VFS: introduce start_creating_noperm() and start_removing_noperm() Val Packett
2025-11-30 0:19 ` Al Viro
2025-11-30 22:06 ` [PATCH] fuse: fix conversion of fuse_reverse_inval_entry() to start_removing() NeilBrown
2025-12-01 8:22 ` Amir Goldstein
2025-12-01 8:33 ` Al Viro
2025-12-01 14:03 ` Miklos Szeredi
2025-12-01 17:08 ` Al Viro
2025-12-02 8:46 ` Miklos Szeredi
2025-12-05 13:09 ` Christian Brauner
2025-12-15 14:19 ` Christian Brauner
2025-12-01 8:50 ` NeilBrown
2025-12-01 8:56 ` Al Viro
2026-01-12 9:45 ` Christian Brauner
2025-11-13 0:18 ` [PATCH v6 07/15] smb/server: use end_removing_noperm for for target of smb2_create_link() NeilBrown
2025-11-13 0:18 ` [PATCH v6 08/15] VFS: introduce start_removing_dentry() NeilBrown
2025-11-13 0:18 ` [PATCH v6 09/15] VFS: add start_creating_killable() and start_removing_killable() NeilBrown
2025-11-13 0:18 ` [PATCH v6 10/15] VFS/nfsd/ovl: introduce start_renaming() and end_renaming() NeilBrown
2025-11-13 0:18 ` [PATCH v6 11/15] VFS/ovl/smb: introduce start_renaming_dentry() NeilBrown
2025-11-13 0:18 ` [PATCH v6 12/15] Add start_renaming_two_dentries() NeilBrown
2025-11-17 23:04 ` Paul Moore
2025-11-13 0:18 ` [PATCH v6 13/15] ecryptfs: use new start_creating/start_removing APIs NeilBrown
2025-11-13 0:18 ` [PATCH v6 14/15] VFS: change vfs_mkdir() to unlock on failure NeilBrown
2025-11-13 0:18 ` [PATCH v6 15/15] VFS: introduce end_creating_keep() NeilBrown
2025-11-14 12:24 ` [PATCH v6 00/15] Create and use APIs to centralise locking for directory ops Christian Brauner
2025-11-14 14:05 ` Jeff Layton
2025-11-14 14:23 ` Christian Brauner
2025-11-14 14:52 ` Jeff Layton
2025-11-14 22:00 ` Christian Brauner
2025-11-27 11:11 ` NeilBrown
2025-11-27 11:06 ` NeilBrown
2025-11-14 12:27 ` Christian Brauner
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