diff --git a/fs/namespace.c b/fs/namespace.c
index 39b0644..88aa7dd 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2573,6 +2573,9 @@
 	/* make sure we can reach put_old from new_root */
 	if (!is_path_reachable(real_mount(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;
 	br_write_lock(vfsmount_lock);
 	detach_mnt(new_mnt, &parent_path);
 	detach_mnt(root_mnt, &root_parent);