diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index f684c82efc2e..79682c23407c 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -914,6 +914,8 @@ int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param)
 	opt = fs_parse(fc, &cgroup1_fs_parameters, param, &result);
 	if (opt == -ENOPARAM) {
 		if (strcmp(param->key, "source") == 0) {
+			if (fc->source)
+				return invalf(fc, "Multiple sources not supported");
 			fc->source = param->string;
 			param->string = NULL;
 			return 0;