Create working directory if it doesn't yet exist

PiperOrigin-RevId: 229438125
Change-Id: I58eb0d10178d1adfc709d7b859189d1acbcb2f22

runsc/container/container_test.go

@@ -1699,6 +1699,27 @@ func TestDestroyStarting(t *testing.T) {
 	}
 }
 
+func TestCreateWorkingDir(t *testing.T) {
+	for _, conf := range configs(overlay) {
+		t.Logf("Running test with conf: %+v", conf)
+
+		tmpDir, err := ioutil.TempDir(testutil.TmpDir(), "cwd-create")
+		if err != nil {
+			t.Fatalf("ioutil.TempDir() failed: %v", err)
+		}
+		dir := path.Join(tmpDir, "new/working/dir")
+
+		// touch will fail if the directory doesn't exist.
+		spec := testutil.NewSpecWithArgs("/bin/touch", path.Join(dir, "file"))
+		spec.Process.Cwd = dir
+		spec.Root.Readonly = true
+
+		if err := run(spec, conf); err != nil {
+			t.Fatalf("Error running container: %v", err)
+		}
+	}
+}
+
 // executeSync synchronously executes a new process.
 func (cont *Container) executeSync(args *control.ExecArgs) (syscall.WaitStatus, error) {
 	pid, err := cont.Execute(args)

runsc/container/fs.go

@@ -87,7 +87,7 @@ func setupFS(spec *specs.Spec, conf *boot.Config, bundleDir string) ([]specs.Mou
 		// container.
 		dst, err := resolveSymlinks(spec.Root.Path, m.Destination)
 		if err != nil {
-			return nil, fmt.Errorf("failed to resolve symlinks: %v", err)
+			return nil, fmt.Errorf("resolving symlinks to %q: %v", m.Destination, err)
 		}
 
 		flags := optionsToFlags(m.Options)
@@ -113,6 +113,16 @@ func setupFS(spec *specs.Spec, conf *boot.Config, bundleDir string) ([]specs.Mou
 		rv = append(rv, cpy)
 	}
 
+	if spec.Process.Cwd != "" {
+		dst, err := resolveSymlinks(spec.Root.Path, spec.Process.Cwd)
+		if err != nil {
+			return nil, fmt.Errorf("resolving symlinks to %q: %v", spec.Process.Cwd, err)
+		}
+		if err := os.MkdirAll(dst, 0755); err != nil {
+			return nil, err
+		}
+	}
+
 	// If root is read only, check if it needs to be remounted as readonly.
 	if spec.Root.Readonly {
 		isMountPoint, readonly, err := mountInfo(spec.Root.Path)