/* make sure we can reach put_old from new_root */
if (!is_path_reachable(old_mnt, old.dentry, &new))
goto out4;
+ /* make certain new is below the root */
+ if (!is_path_reachable(new_mnt, new.dentry, &root))
+ goto out4;
root_mp->m_count++; /* pin it so it won't go away */
lock_mount_hash();
detach_mnt(new_mnt, &parent_path);