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@xxxxxxxxxxxxxxxxxxxxxxxxx Suggested-by: Jan Kara <jack@xxxxxxx> Link: https://lore.kernel.org/linux-fsdevel/20240416173211.4lnmgctyo4jn5fha@quack3/ Fixes: 07a3b8d0bf72 ("fsnotify: lazy attach fsnotify_sb_info state to sb") Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- fs/notify/fsnotify.c | 6 +++++- fs/super.c | 1 + include/linux/fsnotify_backend.h | 4 ++++ 3 files changed, 10 insertions(+), 1 deletion(-) diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index 2ae965ef37e8..ff69ae24c4e8 100644 --- a/fs/notify/fsnotify.c +++ b/fs/notify/fsnotify.c @@ -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); } /* diff --git a/fs/super.c b/fs/super.c index 69ce6c600968..b72f1d288e95 100644 --- a/fs/super.c +++ b/fs/super.c @@ -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); diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h index 7f1ab8264e41..4dd6143db271 100644 --- a/include/linux/fsnotify_backend.h +++ b/include/linux/fsnotify_backend.h @@ -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) {} -- 2.34.1
