Restrict control plane scheduling

 1apiVersion: kyverno.io/v1
 2kind: ClusterPolicy
 3metadata:
 4  name: restrict-controlplane-scheduling
 5  annotations:
 6    policies.kyverno.io/title: Restrict control plane scheduling
 7    policies.kyverno.io/category: Sample
 8    policies.kyverno.io/subject: Pod
 9    policies.kyverno.io/description: >-
10      Scheduling non-system Pods to control plane nodes (which run kubelet) is often undesirable
11      because it takes away resources from the control plane components and can represent
12      a possible security threat vector. This policy prevents users from setting a toleration
13      in a Pod spec which allows running on control plane nodes
14      with the taint key `node-role.kubernetes.io/master`.      
15spec:
16  validationFailureAction: audit
17  background: true
18  rules:
19  - name: restrict-controlplane-scheduling-master
20    match:
21      resources:
22        kinds:
23        - Pod
24    validate:
25      message: Pods may not use tolerations which schedule on control plane nodes.
26      pattern:
27        spec:
28          =(tolerations):
29            - key: "!node-role.kubernetes.io/master"
30  - name: restrict-controlplane-scheduling-control-plane
31    match:
32      resources:
33        kinds:
34        - Pod
35    validate:
36      message: Pods may not use tolerations which schedule on control plane nodes.
37      pattern:
38        spec:
39          =(tolerations):
40            - key: "!node-role.kubernetes.io/control-plane"