Reset uid/gid to 0 in build context to fix cache busting issues on ADD/COPY in stream mode

cli/command/image/build.go

@@ -378,13 +378,13 @@ func runBuild(dockerCli command.Cli, options buildOptions) error {
 
 	if s != nil {
 		go func() {
-			logrus.Debugf("running session: %v", s.UUID())
+			logrus.Debugf("running session: %v", s.ID())
 			if err := s.Run(ctx, dockerCli.Client().DialSession); err != nil {
 				logrus.Error(err)
 				cancel() // cancel progress context
 			}
 		}()
-		buildOptions.SessionID = s.UUID()
+		buildOptions.SessionID = s.ID()
 	}
 
 	response, err := dockerCli.Client().ImageBuild(ctx, body, buildOptions)

cli/command/image/build_session.go

@@ -21,6 +21,7 @@ import (
 	"github.com/moby/buildkit/session"
 	"github.com/moby/buildkit/session/filesync"
 	"github.com/pkg/errors"
+	"github.com/tonistiigi/fsutil"
 	"golang.org/x/time/rate"
 )
 
@@ -52,8 +53,20 @@ func addDirToSession(session *session.Session, contextDir string, progressOutput
 	}
 
 	p := &sizeProgress{out: progressOutput, action: "Streaming build context to Docker daemon"}
+	mapUIDAndGID := func(s *fsutil.Stat) bool {
+		s.Uid = uint32(0)
+		s.Gid = uint32(0)
 
-	workdirProvider := filesync.NewFSSyncProvider(contextDir, excludes)
+		return true
+	}
+
+	workdirProvider := filesync.NewFSSyncProvider([]filesync.SyncedDir{
+		{
+			Dir:      contextDir,
+			Excludes: excludes,
+			Map:      mapUIDAndGID,
+		},
+	})
 	session.Allow(workdirProvider)
 
 	// this will be replaced on parallel build jobs. keep the current

cli/command/image/build_session_test.go

@@ -0,0 +1,37 @@
+package image
+
+import (
+	"bytes"
+	"path/filepath"
+	"testing"
+
+	"github.com/docker/docker/pkg/streamformatter"
+	"github.com/gotestyourself/gotestyourself/fs"
+	"github.com/moby/buildkit/session"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAddDirToSession(t *testing.T) {
+	dest := fs.NewDir(t, "test-build-session",
+		fs.WithFile("Dockerfile", `
+			FROM alpine:3.6
+			COPY foo /
+		`),
+		fs.WithFile("foo", "some content", fs.AsUser(65534, 65534)),
+	)
+	defer dest.Remove()
+
+	contextDir := dest.Path()
+	sharedKey, err := getBuildSharedKey(contextDir)
+	require.NoError(t, err)
+
+	var s *session.Session
+	s, err = session.NewSession(filepath.Base(contextDir), sharedKey)
+	require.NoError(t, err)
+
+	syncDone := make(chan error)
+	progressOutput := streamformatter.NewProgressOutput(new(bytes.Buffer))
+	err = addDirToSession(s, contextDir, progressOutput, syncDone)
+	// Needs some assertions here to ensure we reset uid/gid to 0 for example
+	require.NoError(t, err)
+}

vendor.conf

@@ -26,7 +26,8 @@ github.com/mattn/go-shellwords v1.0.3
 github.com/Microsoft/go-winio v0.4.4
 github.com/miekg/pkcs11 df8ae6ca730422dba20c768ff38ef7d79077a59f
 github.com/mitchellh/mapstructure f3009df150dadf309fdee4a54ed65c124afad715
-github.com/moby/buildkit da2b9dc7dab99e824b2b1067ad7d0523e32dd2d9 https://github.com/dmcgowan/buildkit.git
+github.com/moby/buildkit c2dbdeb457ea665699a5d97f79eebfac4ab4726f https://github.com/tonistiigi/buildkit.git
+github.com/tonistiigi/fsutil 1dedf6e90084bd88c4c518a15e68a37ed1370203
 github.com/Nvveen/Gotty a8b993ba6abdb0e0c12b0125c603323a71c7790c https://github.com/ijc25/Gotty
 github.com/opencontainers/go-digest 21dfd564fd89c944783d00d069f33e3e7123c448
 github.com/opencontainers/image-spec v1.0.0
@@ -40,7 +41,6 @@ github.com/spf13/cobra v1.5.1 https://github.com/dnephin/cobra.git
 github.com/spf13/pflag 9ff6c6923cfffbcd502984b8e0c80539a94968b7
 github.com/stevvooe/continuity cd7a8e21e2b6f84799f5dd4b65faf49c8d3ee02d
 github.com/stretchr/testify 4d4bfba8f1d1027c4fdbe371823030df51419987
-github.com/tonistiigi/fsutil 0ac4c11b053b9c5c7c47558f81f96c7100ce50fb
 github.com/xeipuuv/gojsonpointer e0fe6f68307607d540ed8eac07a342c33fa1b54a
 github.com/xeipuuv/gojsonreference e02fc20de94c78484cd5ffb007f8af96be030a45
 github.com/xeipuuv/gojsonschema 93e72a773fade158921402d6a24c819b48aba29d