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Commit 2b71cbf7 authored by Amir Goldstein's avatar Amir Goldstein Committed by Greg Kroah-Hartman
Browse files

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

commit 69562eb0bd3e6bb8e522a7b254334e0fb30dff0c upstream.

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>
[backport to 5.x.y]
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9a6ce27a

fs/notify/fanotify/fanotify_user.c

+20 −2
Original line number Diff line number Diff line
@@ -928,8 +928,11 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid) 
	return 0;

}



static int fanotify_events_supported(struct path *path, __u64 mask)

static int fanotify_events_supported(struct path *path, __u64 mask,

				     unsigned int flags)

{

	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;



	/*

	 * Some filesystems such as 'proc' acquire unusual locks when opening

	 * files. For them fanotify permission events have high chances of
@@ -941,6 +944,21 @@ static int fanotify_events_supported(struct path *path, __u64 mask) 
	if (mask & FANOTIFY_PERM_EVENTS &&

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

		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;



	return 0;

}
@@ -1050,7 +1068,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, 
		goto fput_and_out;



	if (flags & FAN_MARK_ADD) {

		ret = fanotify_events_supported(&path, mask);

		ret = fanotify_events_supported(&path, mask, flags);

		if (ret)

			goto path_put_and_out;

	}