When checking IsDangling make sure image is not in manifest list

Currently when we run podman image prune or podman images --filter
dangling

It is pruning images that are in a local manifest. These images are
not dangling because they are currently in use by a named manifest list.

You can create this situation simply by doing

echo "from scratch" > /tmp/Containerfile
id=$(podman build /tmp)
podman manifest create test $id
podman image prune --force
podman image exists $id

Will return an error since the image was pruned.  Now the local manifest
test is broken.

Signed-off-by: Daniel J Walsh <[email protected]>

Author: rhatdan

libimage/image.go

@@ -206,7 +206,10 @@ func (i *Image) isDangling(ctx context.Context, tree *layerTree) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	return len(children) == 0, nil
+	if len(children) != 0 {
+		return false, nil
+	}
+	return !tree.manifestDigests[i.Digest()], nil
 }
 
 // IsIntermediate returns true if the image is an intermediate image, that is

libimage/layer_tree.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/containers/storage"
 	storageTypes "github.com/containers/storage/types"
+	digest "github.com/opencontainers/go-digest"
 	ociv1 "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/sirupsen/logrus"
 )
@@ -22,6 +23,8 @@ type layerTree struct {
 	// emptyImages do not have any top-layer so we cannot create a
 	// *layerNode for them.
 	emptyImages []*Image
+
+	manifestDigests map[digest.Digest]bool
 }
 
 // node returns a layerNode for the specified layerID.
@@ -102,8 +105,9 @@ func (r *Runtime) newFreshLayerTree() (*layerTree, error) {
 // The caller is responsible for (layers, images) being consistent.
 func (r *Runtime) newLayerTreeFromData(images []*Image, layers []storage.Layer) (*layerTree, error) {
 	tree := layerTree{
-		nodes:    make(map[string]*layerNode),
-		ociCache: make(map[string]*ociv1.Image),
+		nodes:           make(map[string]*layerNode),
+		ociCache:        make(map[string]*ociv1.Image),
+		manifestDigests: make(map[digest.Digest]bool),
 	}
 
 	// First build a tree purely based on layer information.
@@ -124,6 +128,15 @@ func (r *Runtime) newLayerTreeFromData(images []*Image, layers []storage.Layer)
 		topLayer := img.TopLayer()
 		if topLayer == "" {
 			tree.emptyImages = append(tree.emptyImages, img)
+			if manifestList, _ := img.IsManifestList(context.TODO()); manifestList {
+				mlist, err := img.ToManifestList()
+				if err != nil {
+					return nil, err
+				}
+				for _, digest := range mlist.list.Digests() {
+					tree.manifestDigests[digest] = true
+				}
+			}
 			continue
 		}
 		node, exists := tree.nodes[topLayer]

pkg/manifests/manifests.go

@@ -50,6 +50,7 @@ type List interface {
 
 	findDocker(instanceDigest digest.Digest) (*manifest.Schema2ManifestDescriptor, error)
 	findOCIv1(instanceDigest digest.Digest) (*v1.Descriptor, error)
+	Digests() []digest.Digest
 }
 
 type list struct {
@@ -677,3 +678,11 @@ func (l *list) Instances() []digest.Digest {
 	}
 	return instances
 }
+
+func (l *list) Digests() []digest.Digest {
+	var digests []digest.Digest
+	for i := range l.docker.Manifests {
+		digests = append(digests, l.docker.Manifests[i].Digest)
+	}
+	return digests
+}