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fsnotify: fix UAF from FS_ERROR event on a shutting down filesystem

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Protect against use after free when filesystem calls fsnotify_sb_error()
during fs shutdown.

Move freeing of sb->s_fsnotify_info to destroy_super_work(), because it
may be accessed from fs shutdown context.

Reported-by: syzbot+5e3f9b2a67b45f16d4e6@syzkaller.appspotmail.com
Suggested-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/linux-fsdevel/20240416173211.4lnmgctyo4jn5fha@quack3/
Fixes: 07a3b8d0bf ("fsnotify: lazy attach fsnotify_sb_info state to sb")
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20240416181452.567070-1-amir73il@gmail.com>
This commit is contained in:
Amir Goldstein 2024-04-16 21:14:52 +03:00 committed by Jan Kara
parent a5e57b4d37
commit 795bb82d12
3 changed files with 10 additions and 1 deletions
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6
fs/notify/fsnotify.c
View File

@ -103,7 +103,11 @@ void fsnotify_sb_delete(struct super_block *sb)
WARN_ON(fsnotify_sb_has_priority_watchers(sb, FSNOTIFY_PRIO_CONTENT));
WARN_ON(fsnotify_sb_has_priority_watchers(sb,
FSNOTIFY_PRIO_PRE_CONTENT));
kfree(sbinfo);
}
void fsnotify_sb_free(struct super_block *sb)
{
kfree(sb->s_fsnotify_info);
}
/*

1
fs/super.c
View File

@ -274,6 +274,7 @@ static void destroy_super_work(struct work_struct *work)
{
struct super_block *s = container_of(work, struct super_block,
destroy_work);
fsnotify_sb_free(s);
security_sb_free(s);
put_user_ns(s->s_user_ns);
kfree(s->s_subtype);

4
include/linux/fsnotify_backend.h
View File

@ -576,6 +576,7 @@ extern int __fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data
extern void __fsnotify_inode_delete(struct inode *inode);
extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
extern void fsnotify_sb_delete(struct super_block *sb);
extern void fsnotify_sb_free(struct super_block *sb);
extern u32 fsnotify_get_cookie(void);
static inline __u32 fsnotify_parent_needed_mask(__u32 mask)
@ -880,6 +881,9 @@ static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
static inline void fsnotify_sb_delete(struct super_block *sb)
{}
static inline void fsnotify_sb_free(struct super_block *sb)
{}
static inline void fsnotify_update_flags(struct dentry *dentry)
{}