c8d/list: Ignore unexpected image target

Don't fail-fast when encountering an image that targets an unexpected
descriptor (neither a manifest nor index). Log a warning instead.

Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>

daemon/containerd/image_list.go

@@ -301,6 +301,13 @@ func (i *ImageService) imageSummary(ctx context.Context, img images.Image, platf
 		return nil
 	})
 	if err != nil {
+		if errors.Is(err, errNotManifestOrIndex) {
+			log.G(ctx).WithFields(log.Fields{
+				"error": err,
+				"image": img.Name,
+			}).Warn("unexpected image target (neither a manifest nor index)")
+			return nil, nil, nil
+		}
 		return nil, nil, err
 	}
 

daemon/containerd/image_list_test.go

@@ -101,6 +101,9 @@ func TestImageList(t *testing.T) {
 	emptyIndex, err := specialimage.EmptyIndex(blobsDir)
 	assert.NilError(t, err)
 
+	configTarget, err := specialimage.ConfigTarget(blobsDir)
+	assert.NilError(t, err)
+
 	cs := &blobsDirContentStore{blobs: filepath.Join(blobsDir, "blobs/sha256")}
 
 	for _, tc := range []struct {
@@ -150,6 +153,16 @@ func TestImageList(t *testing.T) {
 				assert.Check(t, is.Len(all, 2))
 			},
 		},
+		{
+			// Make sure an invalid image target doesn't break the whole operation
+			name:   "one good image, second has config as a target",
+			images: imagesFromIndex(multilayer, configTarget),
+			check: func(t *testing.T, all []*imagetypes.Summary) {
+				assert.Check(t, is.Len(all, 1))
+
+				assert.Check(t, is.Equal(all[0].ID, multilayer.Manifests[0].Digest.String()))
+			},
+		},
 	} {
 		tc := tc
 		t.Run(tc.name, func(t *testing.T) {

internal/testutils/specialimage/configtarget.go

@@ -0,0 +1,33 @@
+package specialimage
+
+import (
+	"github.com/containerd/containerd/platforms"
+	"github.com/distribution/reference"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// ConfigTarget creates an image index with an image config being used as an
+// image target instead of a manifest or index.
+func ConfigTarget(dir string) (*ocispec.Index, error) {
+	const imageRef = "config:latest"
+
+	ref, err := reference.ParseNormalizedNamed(imageRef)
+	if err != nil {
+		return nil, err
+	}
+
+	desc, err := writeJsonBlob(dir, ocispec.MediaTypeImageConfig, ocispec.Image{
+		Platform: platforms.MustParse("linux/amd64"),
+		Config: ocispec.ImageConfig{
+			Env: []string{"FOO=BAR"},
+		},
+	})
+	if err != nil {
+		return nil, err
+	}
+	desc.Annotations = map[string]string{
+		"io.containerd.image.name": ref.String(),
+	}
+
+	return ociImage(dir, ref, desc)
+}

internal/testutils/specialimage/multilayer.go

@@ -102,19 +102,24 @@ func singlePlatformImage(dir string, ref reference.Named, manifest ocispec.Manif
 		}
 	}
 
-	idx := ocispec.Index{
-		Versioned: specs.Versioned{SchemaVersion: 2},
-		MediaType: ocispec.MediaTypeImageIndex,
-		Manifests: []ocispec.Descriptor{manifestDesc},
-	}
-	if err := writeJson(idx, filepath.Join(dir, "index.json")); err != nil {
-		return nil, err
-	}
 	if err := writeJson(legacyManifests, filepath.Join(dir, "manifest.json")); err != nil {
 		return nil, err
 	}
 
-	err = os.WriteFile(filepath.Join(dir, "oci-layout"), []byte(`{"imageLayoutVersion": "1.0.0"}`), 0o644)
+	return ociImage(dir, ref, manifestDesc)
+}
+
+func ociImage(dir string, ref reference.Named, target ocispec.Descriptor) (*ocispec.Index, error) {
+	idx := ocispec.Index{
+		Versioned: specs.Versioned{SchemaVersion: 2},
+		MediaType: ocispec.MediaTypeImageIndex,
+		Manifests: []ocispec.Descriptor{target},
+	}
+	if err := writeJson(idx, filepath.Join(dir, "index.json")); err != nil {
+		return nil, err
+	}
+
+	err := os.WriteFile(filepath.Join(dir, "oci-layout"), []byte(`{"imageLayoutVersion": "1.0.0"}`), 0o644)
 	if err != nil {
 		return nil, err
 	}