From: Jan Kara jack@suse.cz
commit c915d8f5918bea7c3962b09b8884ca128bfd9b0c upstream.
When inotify_freeing_mark() races with inotify_handle_inode_event() it can happen that inotify_handle_inode_event() sees that i_mark->wd got already reset to -1 and reports this value to userspace which can confuse the inotify listener. Avoid the problem by validating that wd is sensible (and pretend the mark got removed before the event got generated otherwise).
CC: stable@vger.kernel.org Fixes: 7e790dd5fc93 ("inotify: fix error paths in inotify_update_watch") Message-Id: 20230424163219.9250-1-jack@suse.cz Reported-by: syzbot+4a06d4373fd52f0b2f9c@syzkaller.appspotmail.com Reviewed-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/notify/inotify/inotify_fsnotify.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
--- a/fs/notify/inotify/inotify_fsnotify.c +++ b/fs/notify/inotify/inotify_fsnotify.c @@ -65,7 +65,7 @@ int inotify_handle_inode_event(struct fs struct fsnotify_event *fsn_event; struct fsnotify_group *group = inode_mark->group; int ret; - int len = 0; + int len = 0, wd; int alloc_len = sizeof(struct inotify_event_info); struct mem_cgroup *old_memcg;
@@ -81,6 +81,13 @@ int inotify_handle_inode_event(struct fs fsn_mark);
/* + * We can be racing with mark being detached. Don't report event with + * invalid wd. + */ + wd = READ_ONCE(i_mark->wd); + if (wd == -1) + return 0; + /* * Whoever is interested in the event, pays for the allocation. Do not * trigger OOM killer in the target monitoring memcg as it may have * security repercussion. @@ -110,7 +117,7 @@ int inotify_handle_inode_event(struct fs fsn_event = &event->fse; fsnotify_init_event(fsn_event); event->mask = mask; - event->wd = i_mark->wd; + event->wd = wd; event->sync_cookie = cookie; event->name_len = len; if (len)