llbsolver: fix panic when requesting provenance on nil result

Signed-off-by: Tonis Tiigi <[email protected]>

Author: tonistiigi

frontend/dockerfile/dockerfile_provenance_test.go

@@ -862,3 +862,40 @@ RUN --mount=type=secret,id=mysecret --mount=type=secret,id=othersecret --mount=t
 	require.Equal(t, "default", pred.Invocation.Parameters.SSH[0].ID)
 	require.True(t, pred.Invocation.Parameters.SSH[0].Optional)
 }
+
+func testNilProvenance(t *testing.T, sb integration.Sandbox) {
+	integration.CheckFeatureCompat(t, sb, integration.FeatureProvenance)
+	ctx := sb.Context()
+
+	c, err := client.New(ctx, sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	f := getFrontend(t, sb)
+
+	dockerfile := []byte(`
+FROM scratch
+ENV FOO=bar
+`)
+	dir, err := integration.Tmpdir(
+		t,
+		fstest.CreateFile("Dockerfile", dockerfile, 0600),
+	)
+	require.NoError(t, err)
+
+	_, err = f.Solve(sb.Context(), c, client.SolveOpt{
+		LocalDirs: map[string]string{
+			builder.DefaultLocalNameDockerfile: dir,
+			builder.DefaultLocalNameContext:    dir,
+		},
+		FrontendAttrs: map[string]string{
+			"attest:provenance": "mode=max",
+		},
+		Exports: []client.ExportEntry{
+			{
+				Type: client.ExporterImage,
+			},
+		},
+	}, nil)
+	require.NoError(t, err)
+}

frontend/dockerfile/dockerfile_test.go

@@ -154,6 +154,7 @@ var allTests = integration.TestFuncs(
 	testClientFrontendProvenance,
 	testClientLLBProvenance,
 	testSecretSSHProvenance,
+	testNilProvenance,
 	testSBOMScannerArgs,
 )
 

solver/llbsolver/proc/provenance.go

@@ -32,6 +32,10 @@ func ProvenanceProcessor(attrs map[string]string) llbsolver.Processor {
 				return nil, errors.Errorf("no build info found for provenance %s", p.ID)
 			}
 
+			if cp == nil {
+				continue
+			}
+
 			ref, ok := res.FindRef(p.ID)
 			if !ok {
 				return nil, errors.Errorf("could not find ref %s", p.ID)