Fix nil pointer deref in affinity plugin

Both Pod.Spec.Affinity and Pod.Spec.Affinity.NodeAffinity can be nil,
which is properly checked now.

controllers/node_controller_test.go

@@ -553,6 +553,27 @@ var _ = Describe("The affinity plugin", func() {
 
 	})
 
+	It("does not crash if a pod has no affinity set at all", func() {
+		pod := &corev1.Pod{}
+		pod.Namespace = "default"
+		pod.Name = "container"
+		pod.Spec.NodeName = firstNode.Name
+		pod.Spec.Containers = []corev1.Container{
+			{
+				Name:  "nginx",
+				Image: "nginx",
+			},
+		}
+		Expect(k8sClient.Create(context.Background(), pod)).To(Succeed())
+		affinity := impl.Affinity{}
+		result, err := affinity.Check(buildParams(firstNode))
+		Expect(err).To(Succeed())
+		Expect(result).To(BeTrue())
+		result, err = affinity.Check(buildParams(secondNode))
+		Expect(err).To(Succeed())
+		Expect(result).To(BeTrue())
+	})
+
 })
 
 var _ = Describe("The nodecount plugin", func() {

plugin/impl/affinity.go

@@ -99,22 +99,33 @@ func hasAffinityPod(nodeName string, params *plugin.Parameters) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	for _, pod := range podList.Items {
-		for _, preferred := range pod.Spec.Affinity.NodeAffinity.PreferredDuringSchedulingIgnoredDuringExecution {
-			for _, expr := range preferred.Preference.MatchExpressions {
-				affinityPod := expr.Key == constants.StateLabelKey &&
-					expr.Operator == v1.NodeSelectorOpIn &&
-					len(expr.Values) == 1 &&
-					expr.Values[0] == "operational"
-				if affinityPod {
-					return true, nil
-				}
-			}
+	for i := range podList.Items {
+		if hasOperationalAffinity(&podList.Items[i]) {
+			return true, nil
 		}
 	}
 	return false, nil
 }
 
+func hasOperationalAffinity(pod *v1.Pod) bool {
+	if pod.Spec.Affinity == nil || pod.Spec.Affinity.NodeAffinity == nil {
+		return false
+	}
+	nodeAffinity := pod.Spec.Affinity.NodeAffinity
+	for _, preferred := range nodeAffinity.PreferredDuringSchedulingIgnoredDuringExecution {
+		for _, expr := range preferred.Preference.MatchExpressions {
+			affinityPod := expr.Key == constants.StateLabelKey &&
+				expr.Operator == v1.NodeSelectorOpIn &&
+				len(expr.Values) == 1 &&
+				expr.Values[0] == "operational"
+			if affinityPod {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 func (a *Affinity) AfterEval(chainResult bool, params plugin.Parameters) error {
 	return nil
 }