Merge pull request #208 from rhvgoyal/config-rootfsPropagation

Create container_private, container_slave and container_shared modes for rootfsPropagation

libcontainer/configs/config.go

@@ -92,8 +92,8 @@ type Config struct {
 	// bind mounts are writtable.
 	Readonlyfs bool `json:"readonlyfs"`
 
-	// Privatefs will mount the container's rootfs as private where mount points from the parent will not propogate
-	Privatefs bool `json:"privatefs"`
+	// Specifies the mount propagation flags to be applied to /.
+	RootPropagation int `json:"rootPropagation"`
 
 	// Mounts specify additional source and destination paths that will be mounted inside the container's
 	// rootfs and mount namespace if specified

libcontainer/integration/exec_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"io/ioutil"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strconv"
 	"strings"
@@ -1014,3 +1015,238 @@ func TestSTDIOPermissions(t *testing.T) {
 		t.Fatalf("stderr should equal be equal %q %q", actual, "hi")
 	}
 }
+
+func unmountOp(path string) error {
+	if err := syscall.Unmount(path, syscall.MNT_DETACH); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Launch container with rootfsPropagation in rslave mode. Also
+// bind mount a volume /mnt1host at /mnt1cont at the time of launch. Now do
+// another mount on host (/mnt1host/mnt2host) and this new mount should
+// propagate to container (/mnt1cont/mnt2host)
+func TestRootfsPropagationSlaveMount(t *testing.T) {
+	var mountPropagated bool
+	var dir1cont string
+	var dir2cont string
+
+	dir1cont = "/root/mnt1cont"
+
+	if testing.Short() {
+		return
+	}
+	rootfs, err := newRootfs()
+	ok(t, err)
+	defer remove(rootfs)
+	config := newTemplateConfig(rootfs)
+
+	config.RootPropagation = syscall.MS_SLAVE | syscall.MS_REC
+
+	// Bind mount a volume
+	dir1host, err := ioutil.TempDir("", "mnt1host")
+	ok(t, err)
+	defer os.RemoveAll(dir1host)
+
+	// Make this dir a "shared" mount point. This will make sure a
+	// slave relationship can be established in container.
+	err = syscall.Mount(dir1host, dir1host, "bind", syscall.MS_BIND|syscall.MS_REC, "")
+	ok(t, err)
+	err = syscall.Mount("", dir1host, "", syscall.MS_SHARED|syscall.MS_REC, "")
+	ok(t, err)
+	defer unmountOp(dir1host)
+
+	config.Mounts = append(config.Mounts, &configs.Mount{
+		Source:      dir1host,
+		Destination: dir1cont,
+		Device:      "bind",
+		Flags:       syscall.MS_BIND | syscall.MS_REC})
+
+	// TODO: systemd specific processing
+	f := factory
+
+	container, err := f.Create("testSlaveMount", config)
+	ok(t, err)
+	defer container.Destroy()
+
+	stdinR, stdinW, err := os.Pipe()
+	ok(t, err)
+
+	pconfig := &libcontainer.Process{
+		Args:  []string{"cat"},
+		Env:   standardEnvironment,
+		Stdin: stdinR,
+	}
+
+	err = container.Start(pconfig)
+	stdinR.Close()
+	defer stdinW.Close()
+	ok(t, err)
+
+	// Create mnt1host/mnt2host and bind mount itself on top of it. This
+	// should be visible in container.
+	dir2host, err := ioutil.TempDir(dir1host, "mnt2host")
+	ok(t, err)
+	defer os.RemoveAll(dir2host)
+
+	err = syscall.Mount(dir2host, dir2host, "bind", syscall.MS_BIND, "")
+	defer unmountOp(dir2host)
+	ok(t, err)
+
+	// Run "cat /proc/self/mountinfo" in container and look at mount points.
+	var stdout2 bytes.Buffer
+
+	stdinR2, stdinW2, err := os.Pipe()
+	ok(t, err)
+
+	pconfig2 := &libcontainer.Process{
+		Args:   []string{"cat", "/proc/self/mountinfo"},
+		Env:    standardEnvironment,
+		Stdin:  stdinR2,
+		Stdout: &stdout2,
+	}
+
+	err = container.Start(pconfig2)
+	stdinR2.Close()
+	defer stdinW2.Close()
+	ok(t, err)
+
+	// Wait for process
+	stdinW2.Close()
+	waitProcess(pconfig2, t)
+	stdinW.Close()
+	waitProcess(pconfig, t)
+
+	mountPropagated = false
+	dir2cont = filepath.Join(dir1cont, filepath.Base(dir2host))
+
+	propagationInfo := string(stdout2.Bytes())
+	lines := strings.Split(propagationInfo, "\n")
+	for _, l := range lines {
+		linefields := strings.Split(l, " ")
+		if len(linefields) < 5 {
+			continue
+		}
+
+		if linefields[4] == dir2cont {
+			mountPropagated = true
+			break
+		}
+	}
+
+	if mountPropagated != true {
+		t.Fatalf("Mount on host %s did not propagate in container at %s\n", dir2host, dir2cont)
+	}
+}
+
+// Launch container with rootfsPropagation 0 so no propagation flags are
+// applied. Also bind mount a volume /mnt1host at /mnt1cont at the time of
+// launch. Now do a mount in container (/mnt1cont/mnt2cont) and this new
+// mount should propagate to host (/mnt1host/mnt2cont)
+
+func TestRootfsPropagationSharedMount(t *testing.T) {
+	var dir1cont string
+	var dir2cont string
+
+	dir1cont = "/root/mnt1cont"
+
+	if testing.Short() {
+		return
+	}
+	rootfs, err := newRootfs()
+	ok(t, err)
+	defer remove(rootfs)
+	config := newTemplateConfig(rootfs)
+	config.RootPropagation = syscall.MS_PRIVATE
+
+	// Bind mount a volume
+	dir1host, err := ioutil.TempDir("", "mnt1host")
+	ok(t, err)
+	defer os.RemoveAll(dir1host)
+
+	// Make this dir a "shared" mount point. This will make sure a
+	// shared relationship can be established in container.
+	err = syscall.Mount(dir1host, dir1host, "bind", syscall.MS_BIND|syscall.MS_REC, "")
+	ok(t, err)
+	err = syscall.Mount("", dir1host, "", syscall.MS_SHARED|syscall.MS_REC, "")
+	ok(t, err)
+	defer unmountOp(dir1host)
+
+	config.Mounts = append(config.Mounts, &configs.Mount{
+		Source:      dir1host,
+		Destination: dir1cont,
+		Device:      "bind",
+		Flags:       syscall.MS_BIND | syscall.MS_REC})
+
+	// TODO: systemd specific processing
+	f := factory
+
+	container, err := f.Create("testSharedMount", config)
+	ok(t, err)
+	defer container.Destroy()
+
+	stdinR, stdinW, err := os.Pipe()
+	ok(t, err)
+
+	pconfig := &libcontainer.Process{
+		Args:  []string{"cat"},
+		Env:   standardEnvironment,
+		Stdin: stdinR,
+	}
+
+	err = container.Start(pconfig)
+	stdinR.Close()
+	defer stdinW.Close()
+	ok(t, err)
+
+	// Create mnt1host/mnt2cont.  This will become visible inside container
+	// at mnt1cont/mnt2cont. Bind mount itself on top of it. This
+	// should be visible on host now.
+	dir2host, err := ioutil.TempDir(dir1host, "mnt2cont")
+	ok(t, err)
+	defer os.RemoveAll(dir2host)
+
+	dir2cont = filepath.Join(dir1cont, filepath.Base(dir2host))
+
+	// Mount something in container and see if it is visible on host.
+	var stdout2 bytes.Buffer
+
+	stdinR2, stdinW2, err := os.Pipe()
+	ok(t, err)
+
+	// Provide CAP_SYS_ADMIN
+	processCaps := append(config.Capabilities, "CAP_SYS_ADMIN")
+
+	pconfig2 := &libcontainer.Process{
+		Args:         []string{"mount", "--bind", dir2cont, dir2cont},
+		Env:          standardEnvironment,
+		Stdin:        stdinR2,
+		Stdout:       &stdout2,
+		Capabilities: processCaps,
+	}
+
+	err = container.Start(pconfig2)
+	stdinR2.Close()
+	defer stdinW2.Close()
+	ok(t, err)
+
+	// Wait for process
+	stdinW2.Close()
+	waitProcess(pconfig2, t)
+	stdinW.Close()
+	waitProcess(pconfig, t)
+
+	defer unmountOp(dir2host)
+
+	// Check if mount is visible on host or not.
+	out, err := exec.Command("findmnt", "-n", "-f", "-oTARGET", dir2host).CombinedOutput()
+	outtrim := strings.TrimSpace(string(out))
+	if err != nil {
+		t.Logf("findmnt error %q: %q", err, outtrim)
+	}
+
+	if string(outtrim) != dir2host {
+		t.Fatalf("Mount in container on %s did not propagate to host on %s. finmnt output=%s", dir2cont, dir2host, outtrim)
+	}
+}

libcontainer/rootfs_linux.go

@@ -13,6 +13,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/docker/docker/pkg/mount"
 	"github.com/docker/docker/pkg/symlink"
 	"github.com/opencontainers/runc/libcontainer/cgroups"
 	"github.com/opencontainers/runc/libcontainer/configs"
@@ -420,14 +421,89 @@ func mknodDevice(dest string, node *configs.Device) error {
 	return syscall.Chown(dest, int(node.Uid), int(node.Gid))
 }
 
+func getMountInfo(mountinfo []*mount.MountInfo, dir string) *mount.MountInfo {
+	for _, m := range mountinfo {
+		if m.Mountpoint == dir {
+			return m
+		}
+	}
+	return nil
+}
+
+// Get the parent mount point of directory passed in as argument. Also return
+// optional fields.
+func getParentMount(rootfs string) (string, string, error) {
+	var path string
+
+	mountinfos, err := mount.GetMounts()
+	if err != nil {
+		return "", "", err
+	}
+
+	mountinfo := getMountInfo(mountinfos, rootfs)
+	if mountinfo != nil {
+		return rootfs, mountinfo.Optional, nil
+	}
+
+	path = rootfs
+	for {
+		path = filepath.Dir(path)
+
+		mountinfo = getMountInfo(mountinfos, path)
+		if mountinfo != nil {
+			return path, mountinfo.Optional, nil
+		}
+
+		if path == "/" {
+			break
+		}
+	}
+
+	// If we are here, we did not find parent mount. Something is wrong.
+	return "", "", fmt.Errorf("Could not find parent mount of %s", rootfs)
+}
+
+// Make parent mount private if it was shared
+func rootfsParentMountPrivate(config *configs.Config) error {
+	sharedMount := false
+
+	parentMount, optionalOpts, err := getParentMount(config.Rootfs)
+	if err != nil {
+		return err
+	}
+
+	optsSplit := strings.Split(optionalOpts, " ")
+	for _, opt := range optsSplit {
+		if strings.HasPrefix(opt, "shared:") {
+			sharedMount = true
+			break
+		}
+	}
+
+	// Make parent mount PRIVATE if it was shared. It is needed for two
+	// reasons. First of all pivot_root() will fail if parent mount is
+	// shared. Secondly when we bind mount rootfs it will propagate to
+	// parent namespace and we don't want that to happen.
+	if sharedMount {
+		return syscall.Mount("", parentMount, "", syscall.MS_PRIVATE, "")
+	}
+
+	return nil
+}
+
 func prepareRoot(config *configs.Config) error {
 	flag := syscall.MS_SLAVE | syscall.MS_REC
-	if config.Privatefs {
-		flag = syscall.MS_PRIVATE | syscall.MS_REC
+	if config.RootPropagation != 0 {
+		flag = config.RootPropagation
 	}
 	if err := syscall.Mount("", "/", "", uintptr(flag), ""); err != nil {
 		return err
 	}
+
+	if err := rootfsParentMountPrivate(config); err != nil {
+		return err
+	}
+
 	return syscall.Mount(config.Rootfs, config.Rootfs, "bind", syscall.MS_BIND|syscall.MS_REC, "")
 }
 
@@ -469,6 +545,13 @@ func pivotRoot(rootfs, pivotBaseDir string) error {
 	}
 	// path to pivot dir now changed, update
 	pivotDir = filepath.Join(pivotBaseDir, filepath.Base(pivotDir))
+
+	// Make pivotDir rprivate to make sure any of the unmounts don't
+	// propagate to parent.
+	if err := syscall.Mount("", pivotDir, "", syscall.MS_PRIVATE|syscall.MS_REC, ""); err != nil {
+		return err
+	}
+
 	if err := syscall.Unmount(pivotDir, syscall.MNT_DETACH); err != nil {
 		return fmt.Errorf("unmount pivot_root dir %s", err)
 	}