Merge tag 'fsnotify_for_v6.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull fsnotify fix from Jan Kara:
 "A fix for fanotify to disallow creating of mount or superblock marks
  for kernel internal pseudo filesystems"

* tag 'fsnotify_for_v6.5-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fanotify: disallow mount/sb marks on kernel internal pseudo fs

1 files changed, 14 insertions, 0 deletions

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 95d7d8790bc36a..f69c451018e33d 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1623,6 +1623,20 @@ static int fanotify_events_supported(struct fsnotify_group *group,
 		return -EINVAL;
 
 	/*
+	 * mount and sb marks are not allowed on kernel internal pseudo fs,
+	 * like pipe_mnt, because that would subscribe to events on all the
+	 * anonynous pipes in the system.
+	 *
+	 * SB_NOUSER covers all of the internal pseudo fs whose objects are not
+	 * exposed to user's mount namespace, but there are other SB_KERNMOUNT
+	 * fs, like nsfs, debugfs, for which the value of allowing sb and mount
+	 * mark is questionable. For now we leave them alone.
+	 */
+	if (mark_type != FAN_MARK_INODE &&
+	    path->mnt->mnt_sb->s_flags & SB_NOUSER)
+		return -EINVAL;
+
+	/*
 	 * We shouldn't have allowed setting dirent events and the directory
 	 * flags FAN_ONDIR and FAN_EVENT_ON_CHILD in mask of non-dir inode,
 	 * but because we always allowed it, error only when using new APIs.