diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2f0d7542..511d6b5 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3960,12 +3960,16 @@
 {
 	struct cg_cgroup_link *link;
 
+	read_lock(&css_set_lock);
 	list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
 		struct css_set *cg = link->cg;
-		if (atomic_read(&cg->refcount) > 0)
+		if (cg && (atomic_read(&cg->refcount) > 0)) {
+			read_unlock(&css_set_lock);
 			return 0;
+		}
 	}
 
+	read_unlock(&css_set_lock);
 	return 1;
 }