Make Mount.Type optional for bind mounts

According to the OCI spec Mount.Type is an optional field and it
defaults to "bind" when any of "bind" or "rbind" is included in
Mount.Options.

Also fix the shim to remove bind/rbind from options when mount is
converted from bind to tmpfs inside the Sentry.

Fixes #2330
Fixes #3274

PiperOrigin-RevId: 371996891

4 files changed, 76 insertions, 63 deletions

diff --git a/runsc/boot/controller.go b/runsc/boot/controller.go
index 05b721b28..9b270cbf2 100644
--- a/runsc/boot/controller.go
+++ b/runsc/boot/controller.go
@@ -402,7 +402,7 @@ func (cm *containerManager) Restore(o *RestoreOpts, _ *struct{}) error {
 	ctx := k.SupervisorContext()
 	mntr := newContainerMounter(&cm.l.root, cm.l.k, cm.l.mountHints, kernel.VFS2Enabled)
 	if kernel.VFS2Enabled {
-		ctx, err = mntr.configureRestore(ctx, cm.l.root.conf)
+		ctx, err = mntr.configureRestore(ctx)
 		if err != nil {
 			return fmt.Errorf("configuring filesystem restore: %v", err)
 		}
diff --git a/runsc/boot/fs.go b/runsc/boot/fs.go
index 3c0cef6db..bf4a41f77 100644
--- a/runsc/boot/fs.go
+++ b/runsc/boot/fs.go
@@ -232,7 +232,7 @@ func parseMountOption(opt string, allowedKeys ...string) (bool, error) {
 
 // mountDevice returns a device string based on the fs type and target
 // of the mount.
-func mountDevice(m specs.Mount) string {
+func mountDevice(m *specs.Mount) string {
 	if m.Type == bind {
 		// Make a device string that includes the target, which is consistent across
 		// S/R and uniquely identifies the connection.
@@ -256,6 +256,8 @@ func mountFlags(opts []string) fs.MountSourceFlags {
 			mf.NoAtime = true
 		case "noexec":
 			mf.NoExec = true
+		case "bind", "rbind":
+			// These are the same as a mount with type="bind".
 		default:
 			log.Warningf("ignoring unknown mount option %q", o)
 		}
@@ -486,9 +488,9 @@ func (m *mountHint) isSupported() bool {
 // For now enforce that all options are the same. Once bind mount is properly
 // supported, then we should ensure the master is less restrictive than the
 // container, e.g. master can be 'rw' while container mounts as 'ro'.
-func (m *mountHint) checkCompatible(mount specs.Mount) error {
+func (m *mountHint) checkCompatible(mount *specs.Mount) error {
 	// Remove options that don't affect to mount's behavior.
-	masterOpts := filterUnsupportedOptions(m.mount)
+	masterOpts := filterUnsupportedOptions(&m.mount)
 	replicaOpts := filterUnsupportedOptions(mount)
 
 	if len(masterOpts) != len(replicaOpts) {
@@ -512,7 +514,7 @@ func (m *mountHint) fileAccessType() config.FileAccessType {
 	return config.FileAccessShared
 }
 
-func filterUnsupportedOptions(mount specs.Mount) []string {
+func filterUnsupportedOptions(mount *specs.Mount) []string {
 	rv := make([]string, 0, len(mount.Options))
 	for _, o := range mount.Options {
 		if isSupportedMountFlag(mount.Type, o) {
@@ -576,7 +578,7 @@ func newPodMountHints(spec *specs.Spec) (*podMountHints, error) {
 	return &podMountHints{mounts: mnts}, nil
 }
 
-func (p *podMountHints) findMount(mount specs.Mount) *mountHint {
+func (p *podMountHints) findMount(mount *specs.Mount) *mountHint {
 	for _, m := range p.mounts {
 		if m.mount.Source == mount.Source {
 			return m
@@ -679,7 +681,8 @@ func (c *containerMounter) mountSubmounts(ctx context.Context, conf *config.Conf
 	root := mns.Root()
 	defer root.DecRef(ctx)
 
-	for _, m := range c.mounts {
+	for i := range c.mounts {
+		m := &c.mounts[i]
 		log.Debugf("Mounting %q to %q, type: %s, options: %s", m.Source, m.Destination, m.Type, m.Options)
 		if hint := c.hints.findMount(m); hint != nil && hint.isSupported() {
 			if err := c.mountSharedSubmount(ctx, mns, root, m, hint); err != nil {
@@ -714,7 +717,7 @@ func (c *containerMounter) checkDispenser() error {
 func (c *containerMounter) mountSharedMaster(ctx context.Context, conf *config.Config, hint *mountHint) (*fs.Inode, error) {
 	// Map mount type to filesystem name, and parse out the options that we are
 	// capable of dealing with.
-	fsName, opts, useOverlay, err := c.getMountNameAndOptions(conf, hint.mount)
+	fsName, opts, useOverlay, err := c.getMountNameAndOptions(conf, &hint.mount)
 	if err != nil {
 		return nil, err
 	}
@@ -734,7 +737,7 @@ func (c *containerMounter) mountSharedMaster(ctx context.Context, conf *config.C
 		mf.ReadOnly = true
 	}
 
-	inode, err := filesystem.Mount(ctx, mountDevice(hint.mount), mf, strings.Join(opts, ","), nil)
+	inode, err := filesystem.Mount(ctx, mountDevice(&hint.mount), mf, strings.Join(opts, ","), nil)
 	if err != nil {
 		return nil, fmt.Errorf("creating mount %q: %v", hint.name, err)
 	}
@@ -796,13 +799,14 @@ func (c *containerMounter) createRootMount(ctx context.Context, conf *config.Con
 
 // getMountNameAndOptions retrieves the fsName, opts, and useOverlay values
 // used for mounts.
-func (c *containerMounter) getMountNameAndOptions(conf *config.Config, m specs.Mount) (string, []string, bool, error) {
+func (c *containerMounter) getMountNameAndOptions(conf *config.Config, m *specs.Mount) (string, []string, bool, error) {
+	specutils.MaybeConvertToBindMount(m)
+
 	var (
 		fsName     string
 		opts       []string
 		useOverlay bool
 	)
-
 	switch m.Type {
 	case devpts.Name, devtmpfs.Name, procvfs2.Name, sysvfs2.Name:
 		fsName = m.Type
@@ -836,7 +840,7 @@ func (c *containerMounter) getMountNameAndOptions(conf *config.Config, m specs.M
 	return fsName, opts, useOverlay, nil
 }
 
-func (c *containerMounter) getMountAccessType(conf *config.Config, mount specs.Mount) config.FileAccessType {
+func (c *containerMounter) getMountAccessType(conf *config.Config, mount *specs.Mount) config.FileAccessType {
 	if hint := c.hints.findMount(mount); hint != nil {
 		return hint.fileAccessType()
 	}
@@ -847,7 +851,7 @@ func (c *containerMounter) getMountAccessType(conf *config.Config, mount specs.M
 // be readonly, a lower ramfs overlay is added to create the mount point dir.
 // Another overlay is added with tmpfs on top if Config.Overlay is true.
 // 'm.Destination' must be an absolute path with '..' and symlinks resolved.
-func (c *containerMounter) mountSubmount(ctx context.Context, conf *config.Config, mns *fs.MountNamespace, root *fs.Dirent, m specs.Mount) error {
+func (c *containerMounter) mountSubmount(ctx context.Context, conf *config.Config, mns *fs.MountNamespace, root *fs.Dirent, m *specs.Mount) error {
 	// Map mount type to filesystem name, and parse out the options that we are
 	// capable of dealing with.
 	fsName, opts, useOverlay, err := c.getMountNameAndOptions(conf, m)
@@ -921,7 +925,7 @@ func (c *containerMounter) mountSubmount(ctx context.Context, conf *config.Confi
 
 // mountSharedSubmount binds mount to a previously mounted volume that is shared
 // among containers in the same pod.
-func (c *containerMounter) mountSharedSubmount(ctx context.Context, mns *fs.MountNamespace, root *fs.Dirent, mount specs.Mount, source *mountHint) error {
+func (c *containerMounter) mountSharedSubmount(ctx context.Context, mns *fs.MountNamespace, root *fs.Dirent, mount *specs.Mount, source *mountHint) error {
 	if err := source.checkCompatible(mount); err != nil {
 		return err
 	}
@@ -946,7 +950,7 @@ func (c *containerMounter) mountSharedSubmount(ctx context.Context, mns *fs.Moun
 
 // addRestoreMount adds a mount to the MountSources map used for restoring a
 // checkpointed container.
-func (c *containerMounter) addRestoreMount(conf *config.Config, renv *fs.RestoreEnvironment, m specs.Mount) error {
+func (c *containerMounter) addRestoreMount(conf *config.Config, renv *fs.RestoreEnvironment, m *specs.Mount) error {
 	fsName, opts, useOverlay, err := c.getMountNameAndOptions(conf, m)
 	if err != nil {
 		return err
@@ -994,7 +998,8 @@ func (c *containerMounter) createRestoreEnvironment(conf *config.Config) (*fs.Re
 
 	// Add submounts.
 	var tmpMounted bool
-	for _, m := range c.mounts {
+	for i := range c.mounts {
+		m := &c.mounts[i]
 		if err := c.addRestoreMount(conf, renv, m); err != nil {
 			return nil, err
 		}
@@ -1009,7 +1014,7 @@ func (c *containerMounter) createRestoreEnvironment(conf *config.Config) (*fs.Re
 			Type:        tmpfsvfs2.Name,
 			Destination: "/tmp",
 		}
-		if err := c.addRestoreMount(conf, renv, tmpMount); err != nil {
+		if err := c.addRestoreMount(conf, renv, &tmpMount); err != nil {
 			return nil, err
 		}
 	}
@@ -1068,7 +1073,7 @@ func (c *containerMounter) mountTmp(ctx context.Context, conf *config.Config, mn
 			// another user. This is normally done for /tmp.
 			Options: []string{"mode=01777"},
 		}
-		return c.mountSubmount(ctx, conf, mns, root, tmpMount)
+		return c.mountSubmount(ctx, conf, mns, root, &tmpMount)
 
 	default:
 		return err
diff --git a/runsc/boot/fs_test.go b/runsc/boot/fs_test.go
index b4f12d034..09ffda628 100644
--- a/runsc/boot/fs_test.go
+++ b/runsc/boot/fs_test.go
@@ -244,7 +244,7 @@ func TestGetMountAccessType(t *testing.T) {
 			}
 			mounter := containerMounter{hints: podHints}
 			conf := &config.Config{FileAccessMounts: config.FileAccessShared}
-			if got := mounter.getMountAccessType(conf, specs.Mount{Source: source}); got != tst.want {
+			if got := mounter.getMountAccessType(conf, &specs.Mount{Source: source}); got != tst.want {
 				t.Errorf("getMountAccessType(), want: %v, got: %v", tst.want, got)
 			}
 		})
diff --git a/runsc/boot/vfs.go b/runsc/boot/vfs.go
index 7d8fd0483..c1828bd3d 100644
--- a/runsc/boot/vfs.go
+++ b/runsc/boot/vfs.go
@@ -46,6 +46,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/runsc/config"
+	"gvisor.dev/gvisor/runsc/specutils"
 )
 
 func registerFilesystems(k *kernel.Kernel) error {
@@ -362,33 +363,33 @@ func (c *containerMounter) mountSubmountsVFS2(ctx context.Context, conf *config.
 
 	for i := range mounts {
 		submount := &mounts[i]
-		log.Debugf("Mounting %q to %q, type: %s, options: %s", submount.Source, submount.Destination, submount.Type, submount.Options)
+		log.Debugf("Mounting %q to %q, type: %s, options: %s", submount.mount.Source, submount.mount.Destination, submount.mount.Type, submount.mount.Options)
 		var (
 			mnt *vfs.Mount
 			err error
 		)
 
-		if hint := c.hints.findMount(submount.Mount); hint != nil && hint.isSupported() {
-			mnt, err = c.mountSharedSubmountVFS2(ctx, conf, mns, creds, submount.Mount, hint)
+		if hint := c.hints.findMount(submount.mount); hint != nil && hint.isSupported() {
+			mnt, err = c.mountSharedSubmountVFS2(ctx, conf, mns, creds, submount.mount, hint)
 			if err != nil {
-				return fmt.Errorf("mount shared mount %q to %q: %v", hint.name, submount.Destination, err)
+				return fmt.Errorf("mount shared mount %q to %q: %v", hint.name, submount.mount.Destination, err)
 			}
 		} else {
 			mnt, err = c.mountSubmountVFS2(ctx, conf, mns, creds, submount)
 			if err != nil {
-				return fmt.Errorf("mount submount %q: %w", submount.Destination, err)
+				return fmt.Errorf("mount submount %q: %w", submount.mount.Destination, err)
 			}
 		}
 
 		if mnt != nil && mnt.ReadOnly() {
 			// Switch to ReadWrite while we setup submounts.
 			if err := c.k.VFS().SetMountReadOnly(mnt, false); err != nil {
-				return fmt.Errorf("failed to set mount at %q readwrite: %w", submount.Destination, err)
+				return fmt.Errorf("failed to set mount at %q readwrite: %w", submount.mount.Destination, err)
 			}
 			// Restore back to ReadOnly at the end.
 			defer func() {
 				if err := c.k.VFS().SetMountReadOnly(mnt, true); err != nil {
-					panic(fmt.Sprintf("failed to restore mount at %q back to readonly: %v", submount.Destination, err))
+					panic(fmt.Sprintf("failed to restore mount at %q back to readonly: %v", submount.mount.Destination, err))
 				}
 			}()
 		}
@@ -401,8 +402,8 @@ func (c *containerMounter) mountSubmountsVFS2(ctx context.Context, conf *config.
 }
 
 type mountAndFD struct {
-	specs.Mount
-	fd int
+	mount *specs.Mount
+	fd    int
 }
 
 func (c *containerMounter) prepareMountsVFS2() ([]mountAndFD, error) {
@@ -410,15 +411,18 @@ func (c *containerMounter) prepareMountsVFS2() ([]mountAndFD, error) {
 	// undocumented assumption that FDs are dispensed in the order in which
 	// they are required by mounts.
 	var mounts []mountAndFD
-	for _, m := range c.mounts {
-		fd := -1
+	for i := range c.mounts {
+		m := &c.mounts[i]
+		specutils.MaybeConvertToBindMount(m)
+
 		// Only bind mounts use host FDs; see
 		// containerMounter.getMountNameAndOptionsVFS2.
+		fd := -1
 		if m.Type == bind {
 			fd = c.fds.remove()
 		}
 		mounts = append(mounts, mountAndFD{
-			Mount: m,
+			mount: m,
 			fd:    fd,
 		})
 	}
@@ -428,7 +432,7 @@ func (c *containerMounter) prepareMountsVFS2() ([]mountAndFD, error) {
 
 	// Sort the mounts so that we don't place children before parents.
 	sort.Slice(mounts, func(i, j int) bool {
-		return len(mounts[i].Destination) < len(mounts[j].Destination)
+		return len(mounts[i].mount.Destination) < len(mounts[j].mount.Destination)
 	})
 
 	return mounts, nil
@@ -444,16 +448,16 @@ func (c *containerMounter) mountSubmountVFS2(ctx context.Context, conf *config.C
 		return nil, nil
 	}
 
-	if err := c.makeMountPoint(ctx, creds, mns, submount.Destination); err != nil {
-		return nil, fmt.Errorf("creating mount point %q: %w", submount.Destination, err)
+	if err := c.makeMountPoint(ctx, creds, mns, submount.mount.Destination); err != nil {
+		return nil, fmt.Errorf("creating mount point %q: %w", submount.mount.Destination, err)
 	}
 
 	if useOverlay {
-		log.Infof("Adding overlay on top of mount %q", submount.Destination)
+		log.Infof("Adding overlay on top of mount %q", submount.mount.Destination)
 		var cleanup func()
 		opts, cleanup, err = c.configureOverlay(ctx, creds, opts, fsName)
 		if err != nil {
-			return nil, fmt.Errorf("mounting volume with overlay at %q: %w", submount.Destination, err)
+			return nil, fmt.Errorf("mounting volume with overlay at %q: %w", submount.mount.Destination, err)
 		}
 		defer cleanup()
 		fsName = overlay.Name
@@ -465,32 +469,34 @@ func (c *containerMounter) mountSubmountVFS2(ctx context.Context, conf *config.C
 	target := &vfs.PathOperation{
 		Root:  root,
 		Start: root,
-		Path:  fspath.Parse(submount.Destination),
+		Path:  fspath.Parse(submount.mount.Destination),
 	}
 	mnt, err := c.k.VFS().MountAt(ctx, creds, "", target, fsName, opts)
 	if err != nil {
-		return nil, fmt.Errorf("failed to mount %q (type: %s): %w, opts: %v", submount.Destination, submount.Type, err, opts)
+		return nil, fmt.Errorf("failed to mount %q (type: %s): %w, opts: %v", submount.mount.Destination, submount.mount.Type, err, opts)
 	}
-	log.Infof("Mounted %q to %q type: %s, internal-options: %q", submount.Source, submount.Destination, submount.Type, opts.GetFilesystemOptions.Data)
+	log.Infof("Mounted %q to %q type: %s, internal-options: %q", submount.mount.Source, submount.mount.Destination, submount.mount.Type, opts.GetFilesystemOptions.Data)
 	return mnt, nil
 }
 
 // getMountNameAndOptionsVFS2 retrieves the fsName, opts, and useOverlay values
 // used for mounts.
 func (c *containerMounter) getMountNameAndOptionsVFS2(conf *config.Config, m *mountAndFD) (string, *vfs.MountOptions, bool, error) {
-	fsName := m.Type
+	fsName := m.mount.Type
 	useOverlay := false
-	var data []string
-	var iopts interface{}
+	var (
+		data         []string
+		internalData interface{}
+	)
 
-	verityData, verityOpts, verityRequested, remainingMOpts, err := parseVerityMountOptions(m.Options)
+	verityData, verityOpts, verityRequested, remainingMOpts, err := parseVerityMountOptions(m.mount.Options)
 	if err != nil {
 		return "", nil, false, err
 	}
-	m.Options = remainingMOpts
+	m.mount.Options = remainingMOpts
 
 	// Find filesystem name and FS specific data field.
-	switch m.Type {
+	switch m.mount.Type {
 	case devpts.Name, devtmpfs.Name, proc.Name, sys.Name:
 		// Nothing to do.
 
@@ -499,7 +505,7 @@ func (c *containerMounter) getMountNameAndOptionsVFS2(conf *config.Config, m *mo
 
 	case tmpfs.Name:
 		var err error
-		data, err = parseAndFilterOptions(m.Options, tmpfsAllowedData...)
+		data, err = parseAndFilterOptions(m.mount.Options, tmpfsAllowedData...)
 		if err != nil {
 			return "", nil, false, err
 		}
@@ -511,35 +517,35 @@ func (c *containerMounter) getMountNameAndOptionsVFS2(conf *config.Config, m *mo
 			// but unlikely to be correct in this context.
 			return "", nil, false, fmt.Errorf("9P mount requires a connection FD")
 		}
-		data = p9MountData(m.fd, c.getMountAccessType(conf, m.Mount), true /* vfs2 */)
-		iopts = gofer.InternalFilesystemOptions{
-			UniqueID: m.Destination,
+		data = p9MountData(m.fd, c.getMountAccessType(conf, m.mount), true /* vfs2 */)
+		internalData = gofer.InternalFilesystemOptions{
+			UniqueID: m.mount.Destination,
 		}
 
 		// If configured, add overlay to all writable mounts.
-		useOverlay = conf.Overlay && !mountFlags(m.Options).ReadOnly
+		useOverlay = conf.Overlay && !mountFlags(m.mount.Options).ReadOnly
 
 	case cgroupfs.Name:
 		var err error
-		data, err = parseAndFilterOptions(m.Options, cgroupfs.SupportedMountOptions...)
+		data, err = parseAndFilterOptions(m.mount.Options, cgroupfs.SupportedMountOptions...)
 		if err != nil {
 			return "", nil, false, err
 		}
 
 	default:
-		log.Warningf("ignoring unknown filesystem type %q", m.Type)
+		log.Warningf("ignoring unknown filesystem type %q", m.mount.Type)
 		return "", nil, false, nil
 	}
 
 	opts := &vfs.MountOptions{
 		GetFilesystemOptions: vfs.GetFilesystemOptions{
 			Data:         strings.Join(data, ","),
-			InternalData: iopts,
+			InternalData: internalData,
 		},
 		InternalMount: true,
 	}
 
-	for _, o := range m.Options {
+	for _, o := range m.mount.Options {
 		switch o {
 		case "rw":
 			opts.ReadOnly = false
@@ -549,13 +555,15 @@ func (c *containerMounter) getMountNameAndOptionsVFS2(conf *config.Config, m *mo
 			opts.Flags.NoATime = true
 		case "noexec":
 			opts.Flags.NoExec = true
+		case "bind", "rbind":
+			// These are the same as a mount with type="bind".
 		default:
 			log.Warningf("ignoring unknown mount option %q", o)
 		}
 	}
 
 	if verityRequested {
-		verityData = verityData + "root_name=" + path.Base(m.Mount.Destination)
+		verityData = verityData + "root_name=" + path.Base(m.mount.Destination)
 		verityOpts.LowerName = fsName
 		verityOpts.LowerGetFSOptions = opts.GetFilesystemOptions
 		fsName = verity.Name
@@ -684,7 +692,7 @@ func (c *containerMounter) mountTmpVFS2(ctx context.Context, conf *config.Config
 			// another user. This is normally done for /tmp.
 			Options: []string{"mode=01777"},
 		}
-		_, err := c.mountSubmountVFS2(ctx, conf, mns, creds, &mountAndFD{Mount: tmpMount})
+		_, err := c.mountSubmountVFS2(ctx, conf, mns, creds, &mountAndFD{mount: &tmpMount})
 		return err
 
 	case syserror.ENOTDIR:
@@ -723,7 +731,7 @@ func (c *containerMounter) processHintsVFS2(conf *config.Config, creds *auth.Cre
 func (c *containerMounter) mountSharedMasterVFS2(ctx context.Context, conf *config.Config, hint *mountHint, creds *auth.Credentials) (*vfs.Mount, error) {
 	// Map mount type to filesystem name, and parse out the options that we are
 	// capable of dealing with.
-	mntFD := &mountAndFD{Mount: hint.mount}
+	mntFD := &mountAndFD{mount: &hint.mount}
 	fsName, opts, useOverlay, err := c.getMountNameAndOptionsVFS2(conf, mntFD)
 	if err != nil {
 		return nil, err
@@ -733,11 +741,11 @@ func (c *containerMounter) mountSharedMasterVFS2(ctx context.Context, conf *conf
 	}
 
 	if useOverlay {
-		log.Infof("Adding overlay on top of shared mount %q", mntFD.Destination)
+		log.Infof("Adding overlay on top of shared mount %q", mntFD.mount.Destination)
 		var cleanup func()
 		opts, cleanup, err = c.configureOverlay(ctx, creds, opts, fsName)
 		if err != nil {
-			return nil, fmt.Errorf("mounting shared volume with overlay at %q: %w", mntFD.Destination, err)
+			return nil, fmt.Errorf("mounting shared volume with overlay at %q: %w", mntFD.mount.Destination, err)
 		}
 		defer cleanup()
 		fsName = overlay.Name
@@ -748,14 +756,14 @@ func (c *containerMounter) mountSharedMasterVFS2(ctx context.Context, conf *conf
 
 // mountSharedSubmount binds mount to a previously mounted volume that is shared
 // among containers in the same pod.
-func (c *containerMounter) mountSharedSubmountVFS2(ctx context.Context, conf *config.Config, mns *vfs.MountNamespace, creds *auth.Credentials, mount specs.Mount, source *mountHint) (*vfs.Mount, error) {
+func (c *containerMounter) mountSharedSubmountVFS2(ctx context.Context, conf *config.Config, mns *vfs.MountNamespace, creds *auth.Credentials, mount *specs.Mount, source *mountHint) (*vfs.Mount, error) {
 	if err := source.checkCompatible(mount); err != nil {
 		return nil, err
 	}
 
 	// Ignore data and useOverlay because these were already applied to
 	// the master mount.
-	_, opts, _, err := c.getMountNameAndOptionsVFS2(conf, &mountAndFD{Mount: mount})
+	_, opts, _, err := c.getMountNameAndOptionsVFS2(conf, &mountAndFD{mount: mount})
 	if err != nil {
 		return nil, err
 	}
@@ -808,7 +816,7 @@ func (c *containerMounter) makeMountPoint(ctx context.Context, creds *auth.Crede
 
 // configureRestore returns an updated context.Context including filesystem
 // state used by restore defined by conf.
-func (c *containerMounter) configureRestore(ctx context.Context, conf *config.Config) (context.Context, error) {
+func (c *containerMounter) configureRestore(ctx context.Context) (context.Context, error) {
 	fdmap := make(map[string]int)
 	fdmap["/"] = c.fds.remove()
 	mounts, err := c.prepareMountsVFS2()
@@ -818,7 +826,7 @@ func (c *containerMounter) configureRestore(ctx context.Context, conf *config.Co
 	for i := range c.mounts {
 		submount := &mounts[i]
 		if submount.fd >= 0 {
-			fdmap[submount.Destination] = submount.fd
+			fdmap[submount.mount.Destination] = submount.fd
 		}
 	}
 	return context.WithValue(ctx, gofer.CtxRestoreServerFDMap, fdmap), nil