On Tue, Oct 23, 2018 at 12:19:35PM +0100, Alan Jenkins wrote: > I think there's another small hole. It is possible to move a sub-mount from > a detached tree (instead of moving the root of the tree). Then > do_move_mount() calls attach_recursive_mnt() with a non-NULL parent_path. > > This causes it to skip count_mounts(). So, it doesn't count the number of > attached mounts, and it allows you to exceed sysctl_mount_max. That's trivial to repair, fortunately - we just need to check source_mnt->mnt_ns instead of parent_path.
