Automatic merge from submit-queue
Fix RBAC authorizer of ServiceAccount
RBAC authorizer assigns a role to a wrong service account.
How to reproduce
1.Create role and rolebinding to allow default user in kube-system namespace to read secrets in kube-system namespace.
```
# kubectl create -f role.yaml
# kubectl create -f binding.yaml
```
```yaml
# role.yaml
kind: Role
apiVersion: rbac.authorization.k8s.io/v1alpha1
metadata:
name: secret-reader
namespace: kube-system
rules:
- apiGroups: [""]
resources: ["secrets"]
verbs: ["get", "watch", "list"]
nonResourceURLs: []
```
```yaml
# binding.yaml
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1alpha1
metadata:
name: read-secrets
namespace: kube-system
subjects:
- kind: ServiceAccount
name: default
namespace: kube-system
roleRef:
kind: Role
namespace: kube-system
name: secret-reader
apiVersion: rbac.authorization.k8s.io/v1alpha1
```
2.Set a credential of default user
```
$ kubectl config set-credentials default_user --token=<token_of_system:serviceaccount:kube-system:default>
$ kubectl config set-context default_user-context --cluster=test-cluster --user=default_user
$ kubectl config use-context default_user-context
```
3.Try to get secrets as default user in kube-system namespace
```
$ kubectl --namespace=kube-system get secrets
the server does not allow access to the requested resource (get secrets)
```
As shown above, default user could not access to secrets.
But if I have kube-system user in default namespace, it is allowed access to secrets.
4.Create a service account and try to get secrets as kube-system user in default namespace
```
# kubectl --namespace=default create serviceaccount kube-system
serviceaccount "kube-system" created
$ kubectl config set-credentials kube-system_user --token=<token_of_system:serviceaccount:default:kube-system>
$ kubectl config set-context kube-system_user-context --cluster=test-cluster --user=kube-system_user
$ kubectl config use-context kube-system_user-context
$ kubectl --namespace=kube-system get secrets
NAME TYPE DATA AGE
default-token-8pyb3 kubernetes.io/service-account-token 3 4d
```
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