Merge pull request #48050 from luxas/fix_rbac_configmaps

Automatic merge from submit-queue

kubeadm: Expose only the cluster-info ConfigMap in the kube-public ns

**What this PR does / why we need it**:

Noticed a bug; we should only expose the `cluster-info` ConfigMap.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

Fixes: https://github.com/kubernetes/kubeadm/issues/320

**Special notes for your reviewer**:

Cherrypick-candidate for v1.8 cc @dchen1107 
Not blocking the release though...

**Release note**:

```release-note
NONE
```
@jbeda @pipejakob @timothysc @kubernetes/sig-cluster-lifecycle-pr-reviews

cmd/kubeadm/app/phases/apiconfig/clusterroles.go

@@ -105,7 +105,7 @@ func createRoles(clientset *clientset.Clientset) error {
 				Namespace: metav1.NamespacePublic,
 			},
 			Rules: []rbac.PolicyRule{
-				rbachelper.NewRule("get").Groups("").Resources("configmaps").RuleOrDie(),
+				rbachelper.NewRule("get").Groups("").Resources("configmaps").Names("cluster-info").RuleOrDie(),
 			},
 		},
 	}