From: Amir Goldstein Date: Tue, 16 Apr 2024 18:14:52 +0000 (+0300) Subject: fsnotify: fix UAF from FS_ERROR event on a shutting down filesystem X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=795bb82d12a16a4cee42845b0e4c7e3276574e5d;p=linux.git fsnotify: fix UAF from FS_ERROR event on a shutting down filesystem 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 Link: https://lore.kernel.org/linux-fsdevel/20240416173211.4lnmgctyo4jn5fha@quack3/ Fixes: 07a3b8d0bf72 ("fsnotify: lazy attach fsnotify_sb_info state to sb") Reviewed-by: Christian Brauner Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Message-Id: <20240416181452.567070-1-amir73il@gmail.com> --- diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c index 2ae965ef37e85..ff69ae24c4e89 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 71d9779c42b10..81656c7807db8 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 7f1ab8264e41d..4dd6143db2716 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) {}