Merge pull request #385 from crosbymichael/userns-updates

Make usernamespaces work without sidecar process

Author: Mrunal Patel

error.go

@@ -57,11 +57,3 @@ type Error interface {
 	// Returns the error code for this error.
 	Code() ErrorCode
 }
-
-type initError struct {
-	Message string `json:"message,omitempty"`
-}
-
-func (i initError) Error() string {
-	return i.Message
-}

generic_error.go

@@ -11,8 +11,8 @@ import (
 
 var errorTemplate = template.Must(template.New("error").Parse(`Timestamp: {{.Timestamp}}
 Code: {{.ECode}}
-{{if .Err }}
-Message: {{.Err.Error}}
+{{if .Message }}
+Message: {{.Message}}
 {{end}}
 Frames:{{range $i, $frame := .Stack.Frames}}
 ---
@@ -28,6 +28,7 @@ func newGenericError(err error, c ErrorCode) Error {
 	return &genericError{
 		Timestamp: time.Now(),
 		Err:       err,
+		Message:   err.Error(),
 		ECode:     c,
 		Stack:     stacktrace.Capture(1),
 	}
@@ -41,19 +42,21 @@ func newSystemError(err error) Error {
 		Timestamp: time.Now(),
 		Err:       err,
 		ECode:     SystemError,
+		Message:   err.Error(),
 		Stack:     stacktrace.Capture(1),
 	}
 }
 
 type genericError struct {
 	Timestamp time.Time
 	ECode     ErrorCode
-	Err       error
+	Err       error `json:"-"`
+	Message   string
 	Stack     stacktrace.Stacktrace
 }
 
 func (e *genericError) Error() string {
-	return fmt.Sprintf("[%d] %s: %s", e.ECode, e.ECode, e.Err)
+	return fmt.Sprintf("[%d] %s: %s", e.ECode, e.ECode, e.Message)
 }
 
 func (e *genericError) Code() ErrorCode {

linux_console.go

@@ -12,13 +12,9 @@ import (
 	"github.com/docker/libcontainer/label"
 )
 
-const (
-	containerConsolePath string = "/dev/console"
-)
-
 // NewConsole returns an initalized console that can be used within a container by copying bytes
 // from the master side to the slave that is attached as the tty for the container's init process.
-func NewConsole() (Console, error) {
+func NewConsole(uid, gid int) (Console, error) {
 	master, err := os.OpenFile("/dev/ptmx", syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_CLOEXEC, 0)
 	if err != nil {
 		return nil, err
@@ -30,6 +26,12 @@ func NewConsole() (Console, error) {
 	if err := unlockpt(master); err != nil {
 		return nil, err
 	}
+	if err := os.Chmod(console, 0600); err != nil {
+		return nil, err
+	}
+	if err := os.Chown(console, uid, gid); err != nil {
+		return nil, err
+	}
 	return &linuxConsole{
 		slavePath: console,
 		master:    master,
@@ -78,16 +80,10 @@ func (c *linuxConsole) Close() error {
 func (c *linuxConsole) mount(rootfs, mountLabel string, uid, gid int) error {
 	oldMask := syscall.Umask(0000)
 	defer syscall.Umask(oldMask)
-	if err := os.Chmod(c.slavePath, 0600); err != nil {
-		return err
-	}
-	if err := os.Chown(c.slavePath, uid, gid); err != nil {
-		return err
-	}
 	if err := label.SetFileLabel(c.slavePath, mountLabel); err != nil {
 		return err
 	}
-	dest := filepath.Join(rootfs, containerConsolePath)
+	dest := filepath.Join(rootfs, "/dev/console")
 	f, err := os.Create(dest)
 	if err != nil && !os.IsExist(err) {
 		return err

linux_container.go

@@ -147,7 +147,6 @@ func (c *linuxContainer) newInitProcess(p *Process, cmd *exec.Cmd, parentPipe, c
 		if cmd.SysProcAttr.Credential == nil {
 			cmd.SysProcAttr.Credential = &syscall.Credential{}
 		}
-		t = "_LIBCONTAINER_INITTYPE=userns"
 	}
 	cmd.Env = append(cmd.Env, t)
 	cmd.SysProcAttr.Cloneflags = cloneFlags

linux_factory.go

@@ -166,9 +166,7 @@ func (l *LinuxFactory) StartInitialization(pipefd uintptr) (err error) {
 			// ensure that any data sent from the parent is consumed so it doesn't
 			// receive ECONNRESET when the child writes to the pipe.
 			ioutil.ReadAll(pipe)
-			if err := json.NewEncoder(pipe).Encode(initError{
-				Message: err.Error(),
-			}); err != nil {
+			if err := json.NewEncoder(pipe).Encode(newSystemError(err)); err != nil {
 				panic(err)
 			}
 		}

linux_init.go

@@ -21,10 +21,8 @@ import (
 type initType string
 
 const (
-	initSetns       initType = "setns"
-	initStandard    initType = "standard"
-	initUserns      initType = "userns"
-	initUsernsSetup initType = "userns_setup"
+	initSetns    initType = "setns"
+	initStandard initType = "standard"
 )
 
 type pid struct {
@@ -67,14 +65,6 @@ func newContainerInit(t initType, pipe *os.File) (initer, error) {
 		return &linuxSetnsInit{
 			config: config,
 		}, nil
-	case initUserns:
-		return &linuxUsernsInit{
-			config: config,
-		}, nil
-	case initUsernsSetup:
-		return &linuxUsernsSideCar{
-			config: config,
-		}, nil
 	case initStandard:
 		return &linuxStandardInit{
 			config: config,

linux_process.go

@@ -4,13 +4,11 @@ package libcontainer
 
 import (
 	"encoding/json"
-	"fmt"
 	"io"
 	"os"
 	"os/exec"
 	"syscall"
 
-	log "github.com/Sirupsen/logrus"
 	"github.com/docker/libcontainer/cgroups"
 	"github.com/docker/libcontainer/system"
 )
@@ -145,28 +143,12 @@ func (p *initProcess) start() error {
 	if err := p.createNetworkInterfaces(); err != nil {
 		return newSystemError(err)
 	}
-	// Start the setup process to setup the init process
-	if p.cmd.SysProcAttr.Cloneflags&syscall.CLONE_NEWUSER != 0 {
-		parent, err := p.newUsernsSetupProcess()
-		if err != nil {
-			return newSystemError(err)
-		}
-		if err := parent.start(); err != nil {
-			if err := parent.terminate(); err != nil {
-				log.Warn(err)
-			}
-			return err
-		}
-		if _, err := parent.wait(); err != nil {
-			return newSystemError(err)
-		}
-	}
 	if err := p.sendConfig(); err != nil {
 		return newSystemError(err)
 	}
 	// wait for the child process to fully complete and receive an error message
 	// if one was encoutered
-	var ierr *initError
+	var ierr *genericError
 	if err := json.NewDecoder(p.parentPipe).Decode(&ierr); err != nil && err != io.EOF {
 		return newSystemError(err)
 	}
@@ -229,26 +211,6 @@ func (p *initProcess) createNetworkInterfaces() error {
 	return nil
 }
 
-func (p *initProcess) newUsernsSetupProcess() (parentProcess, error) {
-	parentPipe, childPipe, err := newPipe()
-	if err != nil {
-		return nil, newSystemError(err)
-	}
-	cmd := exec.Command(p.cmd.Args[0], p.cmd.Args[1:]...)
-	cmd.ExtraFiles = []*os.File{childPipe}
-	cmd.Dir = p.cmd.Dir
-	cmd.Env = append(cmd.Env,
-		fmt.Sprintf("_LIBCONTAINER_INITPID=%d", p.pid()),
-		fmt.Sprintf("_LIBCONTAINER_INITTYPE=userns_setup"),
-	)
-	return &setnsProcess{
-		cmd:        cmd,
-		childPipe:  childPipe,
-		parentPipe: parentPipe,
-		config:     p.config,
-	}, nil
-}
-
 func (p *initProcess) signal(s os.Signal) error {
 	return p.cmd.Process.Signal(s)
 }

linux_rootfs.go

@@ -35,52 +35,49 @@ var baseMounts = []*configs.Mount{
 		Destination: "/dev/pts",
 		Device:      "devpts",
 		Flags:       syscall.MS_NOSUID | syscall.MS_NOEXEC,
-		Data:        "newinstance,ptmxmode=0666,mode=620,gid=5",
+		Data:        "newinstance,ptmxmode=0666,mode=0620,gid=5",
 	},
 }
 
 // setupRootfs sets up the devices, mount points, and filesystems for use inside a
 // new mount namespace.
 func setupRootfs(config *configs.Config) (err error) {
 	if err := prepareRoot(config); err != nil {
-		return err
+		return newSystemError(err)
 	}
 	for _, m := range append(baseMounts, config.Mounts...) {
 		if err := mount(m, config.Rootfs, config.MountLabel); err != nil {
-			return err
+			return newSystemError(err)
 		}
 	}
 	if err := createDevices(config); err != nil {
-		return err
+		return newSystemError(err)
 	}
 	if err := setupPtmx(config); err != nil {
-		return err
+		return newSystemError(err)
 	}
 	// stdin, stdout and stderr could be pointing to /dev/null from parent namespace.
-	// Re-open them inside this namespace.
-	// FIXME: Need to fix this for user namespaces.
-	if !config.Namespaces.Contains(configs.NEWUSER) {
-		if err := reOpenDevNull(config.Rootfs); err != nil {
-			return err
-		}
+	// re-open them inside this namespace.
+	if err := reOpenDevNull(config.Rootfs); err != nil {
+		return newSystemError(err)
 	}
 	if err := setupDevSymlinks(config.Rootfs); err != nil {
-		return err
+		return newSystemError(err)
 	}
 	if err := syscall.Chdir(config.Rootfs); err != nil {
-		return err
+		return newSystemError(err)
 	}
 	if config.NoPivotRoot {
 		err = msMoveRoot(config.Rootfs)
 	} else {
 		err = pivotRoot(config.Rootfs, config.PivotDir)
 	}
 	if err != nil {
-		return err
+		return newSystemError(err)
 	}
 	if config.Readonlyfs {
 		if err := setReadonly(); err != nil {
-			return err
+			return newSystemError(err)
 		}
 	}
 	syscall.Umask(0022)
@@ -202,13 +199,32 @@ func createDevices(config *configs.Config) error {
 
 // Creates the device node in the rootfs of the container.
 func createDeviceNode(rootfs string, node *configs.Device) error {
-	var (
-		dest   = filepath.Join(rootfs, node.Path)
-		parent = filepath.Dir(dest)
-	)
-	if err := os.MkdirAll(parent, 0755); err != nil {
+	dest := filepath.Join(rootfs, node.Path)
+	if err := os.MkdirAll(filepath.Dir(dest), 0755); err != nil {
 		return err
 	}
+	if err := mknodDevice(dest, node); err != nil {
+		if os.IsExist(err) {
+			return nil
+		}
+		if err != syscall.EPERM {
+			return err
+		}
+		// containers running in a user namespace are not allowed to mknod
+		// devices so we can just bind mount it from the host.
+		f, err := os.Create(dest)
+		if err != nil && !os.IsExist(err) {
+			return err
+		}
+		if f != nil {
+			f.Close()
+		}
+		return syscall.Mount(node.Path, dest, "bind", syscall.MS_BIND, "")
+	}
+	return nil
+}
+
+func mknodDevice(dest string, node *configs.Device) error {
 	fileMode := node.FileMode
 	switch node.Type {
 	case 'c':
@@ -218,13 +234,10 @@ func createDeviceNode(rootfs string, node *configs.Device) error {
 	default:
 		return fmt.Errorf("%c is not a valid device type for device %s", node.Type, node.Path)
 	}
-	if err := syscall.Mknod(dest, uint32(fileMode), node.Mkdev()); err != nil && !os.IsExist(err) {
-		return fmt.Errorf("mknod %s %s", node.Path, err)
-	}
-	if err := syscall.Chown(dest, int(node.Uid), int(node.Gid)); err != nil {
-		return fmt.Errorf("chown %s to %d:%d", node.Path, node.Uid, node.Gid)
+	if err := syscall.Mknod(dest, uint32(fileMode), node.Mkdev()); err != nil {
+		return err
 	}
-	return nil
+	return syscall.Chown(dest, int(node.Uid), int(node.Gid))
 }
 
 func prepareRoot(config *configs.Config) error {
@@ -251,16 +264,8 @@ func setupPtmx(config *configs.Config) error {
 		return fmt.Errorf("symlink dev ptmx %s", err)
 	}
 	if config.Console != "" {
-		uid, err := config.HostUID()
-		if err != nil {
-			return err
-		}
-		gid, err := config.HostGID()
-		if err != nil {
-			return err
-		}
 		console := newConsoleFromPath(config.Console)
-		return console.mount(config.Rootfs, config.MountLabel, uid, gid)
+		return console.mount(config.Rootfs, config.MountLabel, 0, 0)
 	}
 	return nil
 }