Repository: kubernetes-csi/external-provisioner (go)
Issue: Panic when using unsupported data source
Occurs with version v2.0.4 or with canary.

If you enable the AnyVolumeDataSource feature gate, and create a PVC with a data source that is some CRD other than a snapshot, the external provisioner panics.

I1203 14:04:27.518582       1 connection.go:182] GRPC call: /csi.v1.Controller/CreateVolume
I1203 14:04:27.518600       1 controller.go:869] Started provisioner controller csi.test.net_test-csi-controller-86844bf58c-p5zxh_a0581d73-b8b9-4033-9b0a-87907718bf35!
I1203 14:04:27.518639       1 controller.go:1317] provision "default/pvc1" class "standard": started
I1203 14:04:27.518680       1 controller.go:485] DataSource specified (Hello) is not supported by the provisioner, waiting for an external data populator to create the volume
E1203 14:04:27.518818       1 runtime.go:78] Observed a panic: "invalid memory address or nil pointer dereference" (runtime error: invalid memory address or nil pointer dereference)
goroutine 126 [running]:
k8s.io/apimachinery/pkg/util/runtime.logPanic(0x16ad960, 0x24a3ce0)
	/workspace/vendor/k8s.io/apimachinery/pkg/util/runtime/runtime.go:74 +0xa6
k8s.io/apimachinery/pkg/util/runtime.HandleCrash(0x0, 0x0, 0x0)
	/workspace/vendor/k8s.io/apimachinery/pkg/util/runtime/runtime.go:48 +0x89
panic(0x16ad960, 0x24a3ce0)
	/go/pkg/csiprow.XXXXFoAlfI/go-1.15/src/runtime/panic.go:969 +0x175
sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller.(*ProvisionController).provisionClaimOperation(0xc000484c80, 0x1abbd00, 0xc000046020, 0xc000093c00, 0x1, 0x0, 0x0, 0x1800920)
	/workspace/vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller/controller.go:1420 +0x12da
sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller.(*ProvisionController).syncClaim(0xc000484c80, 0x1abbd00, 0xc000046020, 0x1887340, 0xc000093c00, 0xc0005d7d50, 0x1)
	/workspace/vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller/controller.go:1072 +0x10e
sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller.(*ProvisionController).syncClaimHandler(0xc000484c80, 0x1abbd00, 0xc000046020, 0xc00036ff80, 0x24, 0x414e9b, 0xc00059eca8)
	/workspace/vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller/controller.go:1040 +0xca
sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller.(*ProvisionController).processNextClaimWorkItem.func1(0xc000484c80, 0xc00059ee18, 0x163b640, 0xc000528e30, 0x0, 0x0)
	/workspace/vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller/controller.go:941 +0x11d
sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller.(*ProvisionController).processNextClaimWorkItem(0xc000484c80, 0x1abbd00, 0xc000046020, 0x0)
	/workspace/vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller/controller.go:963 +0x71
sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller.(*ProvisionController).runClaimWorker(0xc000484c80, 0x1abbd00, 0xc000046020)Provision
	/workspace/vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller/controller.go:909 +0x3f
sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller.(*ProvisionController).Run.func1.2()
	/workspace/vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller/controller.go:865 +0x3c
k8s.io/apimachinery/pkg/util/wait.BackoffUntil.func1(0xc0005f7da0)
	/workspace/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:155 +0x5f
k8s.io/apimachinery/pkg/util/wait.BackoffUntil(0xc0005f7da0, 0x1a7e420, 0xc0006044e0, 0x1, 0x0)
	/workspace/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:156 +0xad
k8s.io/apimachinery/pkg/util/wait.JitterUntil(0xc0005f7da0, 0x3b9aca00, 0x0, 0x1, 0x0)
	/workspace/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:133 +0x98
k8s.io/apimachinery/pkg/util/wait.Until(0xc0005f7da0, 0x3b9aca00, 0x0)
	/workspace/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:90 +0x4d
created by sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller.(*ProvisionController).Run.func1
	/workspace/vendor/sigs.k8s.io/sig-storage-lib-external-provisioner/v6/controller/controller.go:865 +0x46a
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x14ffc3a]


What appears to be going on is that that when ProvisionController.provisionClaimOperation() calls csiProvisioner.Provision(), the callee is returning a nil volume and a nil error. That caller assumes that nil error implies that volume is non-nil and tries to dereference it for logging purposes.

Pull request description: Return an error when data source is unsupported
**What type of PR is this?**

/kind bug

**What this PR does / why we need it**:

Fix a panic bug caused by unsupported data source.

**Which issue(s) this PR fixes**:

Fixes #533

**Special notes for your reviewer**:

None

**Does this PR introduce a user-facing change?**:
```release-note
Fix panic when using an external data source
```


Patch:
diff --git a/pkg/controller/controller.go b/pkg/controller/controller.go
index 1edfa0090..4c878557f 100644
--- a/pkg/controller/controller.go
+++ b/pkg/controller/controller.go
@@ -485,11 +485,13 @@ func (p *csiProvisioner) Provision(ctx context.Context, options controller.Provi
 		case pvcKind:
 			rc.clone = true
 		default:
-			klog.Infof("DataSource specified (%s) is not supported by the provisioner, waiting for an external data populator to create the volume", options.PVC.Spec.DataSource.Kind)
 			// DataSource is not VolumeSnapshot and PVC
-			// Wait for an external data populator to create the volume
-			p.eventRecorder.Event(options.PVC, v1.EventTypeNormal, "Provisioning", fmt.Sprintf("Waiting for a volume to be created by an external data populator"))
-			return nil, controller.ProvisioningFinished, nil
+			// Assume external data populator to create the volume, and there is no more work for us to do
+			p.eventRecorder.Event(options.PVC, v1.EventTypeNormal, "Provisioning", fmt.Sprintf("Assuming an external populator will provision the volume"))
+			return nil, controller.ProvisioningFinished, &controller.IgnoredError{
+				Reason: fmt.Sprintf("data source (%s) is not handled by the provisioner, assuming an external populator will provision it",
+					options.PVC.Spec.DataSource.Kind),
+			}
 		}
 	}
 	if err := p.checkDriverCapabilities(rc); err != nil {


Test patch:
diff --git a/pkg/controller/controller_test.go b/pkg/controller/controller_test.go
index 0f4ac1e51..cc6179520 100644
--- a/pkg/controller/controller_test.go
+++ b/pkg/controller/controller_test.go
@@ -1799,7 +1799,7 @@ func TestProvision(t *testing.T) {
 				},
 			},
 			expectState:      controller.ProvisioningFinished,
-			expectErr:        false,
+			expectErr:        true,
 			skipCreateVolume: true,
 		},
 	}