kyverno/examples/Validate/check_hostpath.yaml

apiVersion : kubepolicy.nirmata.io/v1alpha1
kind: Policy
metadata:
  name: check-host-path
spec:
  rules:
  - name: check-host-path
    resource:
      kinds: 
      - Pod
    validate:
      message: "Host path volumes are not allowed"
      pattern:
        volumes:
        - name: "*"
          hostPath: null