diff --git a/[refs] b/[refs]
index 027e3eeced96..08a19d99a5fc 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 61eafb00d55dfbccdfce543c6b60e369ff4f8f18
+refs/heads/master: 3a981f482cc29f7d0aeab509e51ea15519a6e961
diff --git a/trunk/mm/memcontrol.c b/trunk/mm/memcontrol.c
index ac35bccadb7b..f8517cd28feb 100644
--- a/trunk/mm/memcontrol.c
+++ b/trunk/mm/memcontrol.c
@@ -1148,7 +1148,7 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg,
 {
 	if (root_memcg == memcg)
 		return true;
-	if (!root_memcg->use_hierarchy)
+	if (!root_memcg->use_hierarchy || !memcg)
 		return false;
 	return css_is_ancestor(&memcg->css, &root_memcg->css);
 }