Merge pull request #2197 from aaronlehmann/hash-empty

Avoid nil pointer dereference when copying from image with no layers

cache/contenthash/checksum.go

@@ -91,6 +91,12 @@ type cacheManager struct {
 }
 
 func (cm *cacheManager) Checksum(ctx context.Context, ref cache.ImmutableRef, p string, opts ChecksumOpts, s session.Group) (digest.Digest, error) {
+	if ref == nil {
+		if p == "/" {
+			return digest.FromBytes(nil), nil
+		}
+		return "", errors.Errorf("%s: no such file or directory", p)
+	}
 	cc, err := cm.GetCacheContext(ctx, ensureOriginMetadata(ref.Metadata()), ref.IdentityMapping())
 	if err != nil {
 		return "", nil

client/client_test.go

@@ -66,7 +66,9 @@ type nopWriteCloser struct {
 func (nopWriteCloser) Close() error { return nil }
 
 func TestIntegration(t *testing.T) {
-	mirrors := integration.WithMirroredImages(integration.OfficialImages("busybox:latest", "alpine:latest"))
+	mirroredImages := integration.OfficialImages("busybox:latest", "alpine:latest")
+	mirroredImages["tonistiigi/test:nolayers"] = "docker.io/tonistiigi/test:nolayers"
+	mirrors := integration.WithMirroredImages(mirroredImages)
 
 	integration.Run(t, []integration.Test{
 		testCacheExportCacheKeyLoop,
@@ -93,6 +95,7 @@ func TestIntegration(t *testing.T) {
 		testBasicRegistryCacheImportExport,
 		testBasicLocalCacheImportExport,
 		testCachedMounts,
+		testCopyFromEmptyImage,
 		testProxyEnv,
 		testLocalSymlinkEscape,
 		testTmpfsMounts,
@@ -2944,6 +2947,41 @@ func testCacheMountNoCache(t *testing.T, sb integration.Sandbox) {
 	require.NoError(t, err)
 }
 
+func testCopyFromEmptyImage(t *testing.T, sb integration.Sandbox) {
+	requiresLinux(t)
+	c, err := New(sb.Context(), sb.Address())
+	require.NoError(t, err)
+	defer c.Close()
+
+	for _, image := range []llb.State{llb.Scratch(), llb.Image("tonistiigi/test:nolayers")} {
+		st := llb.Scratch().File(llb.Copy(image, "/", "/"))
+		def, err := st.Marshal(sb.Context())
+		require.NoError(t, err)
+
+		_, err = c.Solve(sb.Context(), def, SolveOpt{}, nil)
+		require.NoError(t, err)
+
+		st = llb.Scratch().File(llb.Copy(image, "/foo", "/"))
+		def, err = st.Marshal(sb.Context())
+		require.NoError(t, err)
+
+		_, err = c.Solve(sb.Context(), def, SolveOpt{}, nil)
+		require.Error(t, err)
+		require.Contains(t, err.Error(), "/foo: no such file or directory")
+
+		busybox := llb.Image("busybox:latest")
+
+		out := busybox.Run(llb.Shlex(`sh -e -c '[ $(ls /scratch | wc -l) = '0' ]'`))
+		out.AddMount("/scratch", image, llb.Readonly)
+
+		def, err = out.Marshal(sb.Context())
+		require.NoError(t, err)
+
+		_, err = c.Solve(sb.Context(), def, SolveOpt{}, nil)
+		require.NoError(t, err)
+	}
+}
+
 // containerd/containerd#2119
 func testDuplicateWhiteouts(t *testing.T, sb integration.Sandbox) {
 	skipDockerd(t, sb)