Merge pull request #19093 from estesp/userns-root-rework

Allow root non-userns metadata backwards compatibility

daemon/daemon_experimental.go

@@ -10,7 +10,6 @@ import (
 
 	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/api/types/container"
-	"github.com/docker/docker/pkg/directory"
 	"github.com/docker/docker/pkg/idtools"
 )
 
@@ -48,53 +47,36 @@ func setupRemappedRoot(config *Config) ([]idtools.IDMap, []idtools.IDMap, error)
 }
 
 func setupDaemonRoot(config *Config, rootDir string, rootUID, rootGID int) error {
-	// the main docker root needs to be accessible by all users, as user namespace support
-	// will create subdirectories owned by either a) the real system root (when no remapping
-	// is setup) or b) the remapped root host ID (when --root=uid:gid is used)
-	// for "first time" users of user namespaces, we need to migrate the current directory
-	// contents to the "0.0" (root == root "namespace" daemon root)
-	nsRoot := "0.0"
+	config.Root = rootDir
+	// the docker root metadata directory needs to have execute permissions for all users (o+x)
+	// so that syscalls executing as non-root, operating on subdirectories of the graph root
+	// (e.g. mounted layers of a container) can traverse this path.
+	// The user namespace support will create subdirectories for the remapped root host uid:gid
+	// pair owned by that same uid:gid pair for proper write access to those needed metadata and
+	// layer content subtrees.
 	if _, err := os.Stat(rootDir); err == nil {
-		// root current exists; we need to check for a prior migration
-		if _, err := os.Stat(filepath.Join(rootDir, nsRoot)); err != nil && os.IsNotExist(err) {
-			// need to migrate current root to "0.0" subroot
-			// 1. create non-usernamespaced root as "0.0"
-			if err := os.Mkdir(filepath.Join(rootDir, nsRoot), 0700); err != nil {
-				return fmt.Errorf("Cannot create daemon root %q: %v", filepath.Join(rootDir, nsRoot), err)
-			}
-			// 2. move current root content to "0.0" new subroot
-			if err := directory.MoveToSubdir(rootDir, nsRoot); err != nil {
-				return fmt.Errorf("Cannot migrate current daemon root %q for user namespaces: %v", rootDir, err)
-			}
-			// 3. chmod outer root to 755
-			if chmodErr := os.Chmod(rootDir, 0755); chmodErr != nil {
-				return chmodErr
-			}
-		}
-	} else if os.IsNotExist(err) {
-		// no root exists yet, create it 0755 with root:root ownership
-		if err := os.MkdirAll(rootDir, 0755); err != nil {
+		// root current exists; verify the access bits are correct by setting them
+		if err = os.Chmod(rootDir, 0701); err != nil {
 			return err
 		}
-		// create the "0.0" subroot (so no future "migration" happens of the root)
-		if err := os.Mkdir(filepath.Join(rootDir, nsRoot), 0700); err != nil {
+	} else if os.IsNotExist(err) {
+		// no root exists yet, create it 0701 with root:root ownership
+		if err := os.MkdirAll(rootDir, 0701); err != nil {
 			return err
 		}
 	}
 
-	// for user namespaces we will create a subtree underneath the specified root
+	// if user namespaces are enabled we will create a subtree underneath the specified root
 	// with any/all specified remapped root uid/gid options on the daemon creating
 	// a new subdirectory with ownership set to the remapped uid/gid (so as to allow
 	// `chdir()` to work for containers namespaced to that uid/gid)
 	if config.RemappedRoot != "" {
-		nsRoot = fmt.Sprintf("%d.%d", rootUID, rootGID)
-	}
-	config.Root = filepath.Join(rootDir, nsRoot)
-	logrus.Debugf("Creating actual daemon root: %s", config.Root)
-
-	// Create the root directory if it doesn't exists
-	if err := idtools.MkdirAllAs(config.Root, 0700, rootUID, rootGID); err != nil {
-		return fmt.Errorf("Cannot create daemon root: %s: %v", config.Root, err)
+		config.Root = filepath.Join(rootDir, fmt.Sprintf("%d.%d", rootUID, rootGID))
+		logrus.Debugf("Creating user namespaced daemon root: %s", config.Root)
+		// Create the root directory if it doesn't exists
+		if err := idtools.MkdirAllAs(config.Root, 0700, rootUID, rootGID); err != nil {
+			return fmt.Errorf("Cannot create daemon root: %s: %v", config.Root, err)
+		}
 	}
 	return nil
 }

daemon/graphdriver/aufs/aufs.go

@@ -123,7 +123,7 @@ func Init(root string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
 	// Create the root aufs driver dir and return
 	// if it already exists
 	// If not populate the dir structure
-	if err := idtools.MkdirAllAs(root, 0755, rootUID, rootGID); err != nil {
+	if err := idtools.MkdirAllAs(root, 0700, rootUID, rootGID); err != nil {
 		if os.IsExist(err) {
 			return a, nil
 		}
@@ -136,7 +136,7 @@ func Init(root string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
 
 	// Populate the dir structure
 	for _, p := range paths {
-		if err := idtools.MkdirAllAs(path.Join(root, p), 0755, rootUID, rootGID); err != nil {
+		if err := idtools.MkdirAllAs(path.Join(root, p), 0700, rootUID, rootGID); err != nil {
 			return nil, err
 		}
 	}

daemon/graphdriver/overlay/overlay.go

@@ -146,7 +146,7 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
 		return nil, err
 	}
 	// Create the driver home dir
-	if err := idtools.MkdirAllAs(home, 0755, rootUID, rootGID); err != nil && !os.IsExist(err) {
+	if err := idtools.MkdirAllAs(home, 0700, rootUID, rootGID); err != nil && !os.IsExist(err) {
 		return nil, err
 	}