2 files changed, 24 insertions, 3 deletions
diff --git a/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go b/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go
index e03a0c665..142ee53b0 100644
--- a/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go
+++ b/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go
@@ -28,6 +28,9 @@ import (
 	"gvisor.dev/gvisor/pkg/sync"
 )
 
+// Name is the default filesystem name.
+const Name = "devtmpfs"
+
 // FilesystemType implements vfs.FilesystemType.
 type FilesystemType struct {
 	initOnce sync.Once
@@ -39,6 +42,11 @@ type FilesystemType struct {
 	root *vfs.Dentry
 }
 
+// Name implements vfs.FilesystemType.Name.
+func (*FilesystemType) Name() string {
+	return Name
+}
+
 // GetFilesystem implements vfs.FilesystemType.GetFilesystem.
 func (fst *FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
 	fst.initOnce.Do(func() {
@@ -107,6 +115,7 @@ func (a *Accessor) wrapContext(ctx context.Context) *accessorContext {
 func (ac *accessorContext) Value(key interface{}) interface{} {
 	switch key {
 	case vfs.CtxMountNamespace:
+		ac.a.mntns.IncRef()
 		return ac.a.mntns
 	case vfs.CtxRoot:
 		ac.a.root.IncRef()
@@ -154,16 +163,25 @@ func (a *Accessor) CreateDeviceFile(ctx context.Context, pathname string, kind v
 func (a *Accessor) UserspaceInit(ctx context.Context) error {
 	actx := a.wrapContext(ctx)
 
-	// systemd: src/shared/dev-setup.c:dev_setup()
+	// Initialize symlinks.
 	for _, symlink := range []struct {
 		source string
 		target string
 	}{
-		// /proc/kcore is not implemented.
+		// systemd: src/shared/dev-setup.c:dev_setup()
 		{source: "fd", target: "/proc/self/fd"},
 		{source: "stdin", target: "/proc/self/fd/0"},
 		{source: "stdout", target: "/proc/self/fd/1"},
 		{source: "stderr", target: "/proc/self/fd/2"},
+		// /proc/kcore is not implemented.
+
+		// Linux implements /dev/ptmx as a device node, but advises
+		// container implementations to create /dev/ptmx as a symlink
+		// to pts/ptmx (Documentation/filesystems/devpts.txt). Systemd
+		// follows this advice (src/nspawn/nspawn.c:setup_pts()), while
+		// LXC tries to create a bind mount and falls back to a symlink
+		// (src/lxc/conf.c:lxc_setup_devpts()).
+		{source: "ptmx", target: "pts/ptmx"},
 	} {
 		if err := a.vfsObj.SymlinkAt(actx, a.creds, a.pathOperationAt(symlink.source), symlink.target); err != nil {
 			return fmt.Errorf("failed to create symlink %q => %q: %v", symlink.source, symlink.target, err)
diff --git a/pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go b/pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go
index 73308a2b5..b6d52c015 100644
--- a/pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go
+++ b/pkg/sentry/fsimpl/devtmpfs/devtmpfs_test.go
@@ -29,7 +29,10 @@ func TestDevtmpfs(t *testing.T) {
 	ctx := contexttest.Context(t)
 	creds := auth.CredentialsFromContext(ctx)
 
-	vfsObj := vfs.New()
+	vfsObj := &vfs.VirtualFilesystem{}
+	if err := vfsObj.Init(); err != nil {
+		t.Fatalf("VFS init: %v", err)
+	}
 	// Register tmpfs just so that we can have a root filesystem that isn't
 	// devtmpfs.
 	vfsObj.MustRegisterFilesystemType("tmpfs", tmpfs.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{