Commit 69562eb0 authored by Amir Goldstein's avatar Amir Goldstein Committed by Jan Kara
Browse files

fanotify: disallow mount/sb marks on kernel internal pseudo fs 

Hopefully, nobody is trying to abuse mount/sb marks for watching all
anonymous pipes/inodes.

I cannot think of a good reason to allow this - it looks like an
oversight that dated back to the original fanotify API.

Link: https://lore.kernel.org/linux-fsdevel/20230628101132.kvchg544mczxv2pm@quack3/


Fixes: 0ff21db9 ("fanotify: hooks the fanotify_mark syscall to the vfsmount code")
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Reviewed-by: default avatarChristian Brauner <brauner@kernel.org>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Message-Id: <20230629042044.25723-1-amir73il@gmail.com>
parent a901a356

fs/notify/fanotify/fanotify_user.c

+14 −0
Original line number Original line Diff line number Diff line
@@ -1622,6 +1622,20 @@ static int fanotify_events_supported(struct fsnotify_group *group, 
	    path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)

	    path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM)

		return -EINVAL;

		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

	 * 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,

	 * flags FAN_ONDIR and FAN_EVENT_ON_CHILD in mask of non-dir inode,