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| author | Christian Brauner <brauner@kernel.org> | 2025-04-14 22:13:33 +0200 |
|---|---|---|
| committer | Christian Brauner <brauner@kernel.org> | 2025-04-15 11:32:34 +0200 |
| commit | c86b300b1ea35959a6e2a63a6497226a6ea90b67 (patch) | |
| tree | a58eff52db91c26b171ad1485d0988ec1f8091cc /fs | |
| parent | ddee68c499f76ae47c011549df5be53db0057402 (diff) | |
| download | ath-c86b300b1ea35959a6e2a63a6497226a6ea90b67.tar.gz | |
fs: add kern_path_locked_negative()
The audit code relies on the fact that kern_path_locked() returned a
path even for a negative dentry. If it doesn't find a valid dentry it
immediately calls:
audit_find_parent(d_backing_inode(parent_path.dentry));
which assumes that parent_path.dentry is still valid. But it isn't since
kern_path_locked() has been changed to path_put() also for a negative
dentry.
Fix this by adding a helper that implements the required audit semantics
and allows us to fix the immediate bleeding. We can find a unified
solution for this afterwards.
Link: https://lore.kernel.org/20250414-rennt-wimmeln-f186c3a780f1@brauner
Fixes: 1c3cb50b58c3 ("VFS: change kern_path_locked() and user_path_locked_at() to never return negative dentry")
Reported-and-tested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/namei.c | 65 |
1 files changed, 49 insertions, 16 deletions
diff --git a/fs/namei.c b/fs/namei.c index 8510ff53f12e5..267ac9c22dd27 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1665,27 +1665,20 @@ static struct dentry *lookup_dcache(const struct qstr *name, return dentry; } -/* - * Parent directory has inode locked exclusive. This is one - * and only case when ->lookup() gets called on non in-lookup - * dentries - as the matter of fact, this only gets called - * when directory is guaranteed to have no in-lookup children - * at all. - * Will return -ENOENT if name isn't found and LOOKUP_CREATE wasn't passed. - * Will return -EEXIST if name is found and LOOKUP_EXCL was passed. - */ -struct dentry *lookup_one_qstr_excl(const struct qstr *name, - struct dentry *base, - unsigned int flags) +static struct dentry *lookup_one_qstr_excl_raw(const struct qstr *name, + struct dentry *base, + unsigned int flags) { - struct dentry *dentry = lookup_dcache(name, base, flags); + struct dentry *dentry; struct dentry *old; - struct inode *dir = base->d_inode; + struct inode *dir; + dentry = lookup_dcache(name, base, flags); if (dentry) - goto found; + return dentry; /* Don't create child dentry for a dead directory. */ + dir = base->d_inode; if (unlikely(IS_DEADDIR(dir))) return ERR_PTR(-ENOENT); @@ -1698,7 +1691,24 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name, dput(dentry); dentry = old; } -found: + return dentry; +} + +/* + * Parent directory has inode locked exclusive. This is one + * and only case when ->lookup() gets called on non in-lookup + * dentries - as the matter of fact, this only gets called + * when directory is guaranteed to have no in-lookup children + * at all. + * Will return -ENOENT if name isn't found and LOOKUP_CREATE wasn't passed. + * Will return -EEXIST if name is found and LOOKUP_EXCL was passed. + */ +struct dentry *lookup_one_qstr_excl(const struct qstr *name, + struct dentry *base, unsigned int flags) +{ + struct dentry *dentry; + + dentry = lookup_one_qstr_excl_raw(name, base, flags); if (IS_ERR(dentry)) return dentry; if (d_is_negative(dentry) && !(flags & LOOKUP_CREATE)) { @@ -2762,6 +2772,29 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct return d; } +struct dentry *kern_path_locked_negative(const char *name, struct path *path) +{ + struct filename *filename __free(putname) = getname_kernel(name); + struct dentry *d; + struct qstr last; + int type, error; + + error = filename_parentat(AT_FDCWD, filename, 0, path, &last, &type); + if (error) + return ERR_PTR(error); + if (unlikely(type != LAST_NORM)) { + path_put(path); + return ERR_PTR(-EINVAL); + } + inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); + d = lookup_one_qstr_excl_raw(&last, path->dentry, 0); + if (IS_ERR(d)) { + inode_unlock(path->dentry->d_inode); + path_put(path); + } + return d; +} + struct dentry *kern_path_locked(const char *name, struct path *path) { struct filename *filename = getname_kernel(name); |