Add TTY support on VFS2 to runsc

Updates #1623, #1487

PiperOrigin-RevId: 309777922

4 files changed, 150 insertions, 207 deletions

diff --git a/runsc/boot/BUILD b/runsc/boot/BUILD
index abcaf4206..0e71e800b 100644
--- a/runsc/boot/BUILD
+++ b/runsc/boot/BUILD
@@ -12,7 +12,6 @@ go_library(
         "controller.go",
         "debug.go",
         "events.go",
-        "fds.go",
         "fs.go",
         "limits.go",
         "loader.go",
@@ -43,6 +42,7 @@ go_library(
         "//pkg/sentry/arch:registers_go_proto",
         "//pkg/sentry/control",
         "//pkg/sentry/devices/memdev",
+        "//pkg/sentry/fdimport",
         "//pkg/sentry/fs",
         "//pkg/sentry/fs/dev",
         "//pkg/sentry/fs/gofer",
@@ -53,6 +53,7 @@ go_library(
         "//pkg/sentry/fs/tmpfs",
         "//pkg/sentry/fs/tty",
         "//pkg/sentry/fs/user",
+        "//pkg/sentry/fsimpl/devpts",
         "//pkg/sentry/fsimpl/devtmpfs",
         "//pkg/sentry/fsimpl/gofer",
         "//pkg/sentry/fsimpl/host",
diff --git a/runsc/boot/fds.go b/runsc/boot/fds.go
deleted file mode 100644
index 7e7a31fbd..000000000
--- a/runsc/boot/fds.go
+++ /dev/null
@@ -1,108 +0,0 @@
-// Copyright 2018 The gVisor Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package boot
-
-import (
-	"fmt"
-
-	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
-	"gvisor.dev/gvisor/pkg/sentry/fs/host"
-	vfshost "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-)
-
-// createFDTable creates an FD table that contains stdin, stdout, and stderr.
-// If console is true, then ioctl calls will be passed through to the host FD.
-// Upon success, createFDMap dups then closes stdioFDs.
-func createFDTable(ctx context.Context, console bool, stdioFDs []int) (*kernel.FDTable, error) {
-	if len(stdioFDs) != 3 {
-		return nil, fmt.Errorf("stdioFDs should contain exactly 3 FDs (stdin, stdout, and stderr), but %d FDs received", len(stdioFDs))
-	}
-
-	if kernel.VFS2Enabled {
-		return createFDTableVFS2(ctx, console, stdioFDs)
-	}
-
-	k := kernel.KernelFromContext(ctx)
-	fdTable := k.NewFDTable()
-	defer fdTable.DecRef()
-
-	var ttyFile *fs.File
-	for appFD, hostFD := range stdioFDs {
-		var appFile *fs.File
-
-		if console && appFD < 3 {
-			// Import the file as a host TTY file.
-			if ttyFile == nil {
-				var err error
-				appFile, err = host.ImportFile(ctx, hostFD, true /* isTTY */)
-				if err != nil {
-					return nil, err
-				}
-				defer appFile.DecRef()
-
-				// Remember this in the TTY file, as we will
-				// use it for the other stdio FDs.
-				ttyFile = appFile
-			} else {
-				// Re-use the existing TTY file, as all three
-				// stdio FDs must point to the same fs.File in
-				// order to share TTY state, specifically the
-				// foreground process group id.
-				appFile = ttyFile
-			}
-		} else {
-			// Import the file as a regular host file.
-			var err error
-			appFile, err = host.ImportFile(ctx, hostFD, false /* isTTY */)
-			if err != nil {
-				return nil, err
-			}
-			defer appFile.DecRef()
-		}
-
-		// Add the file to the FD map.
-		if err := fdTable.NewFDAt(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
-			return nil, err
-		}
-	}
-
-	fdTable.IncRef()
-	return fdTable, nil
-}
-
-func createFDTableVFS2(ctx context.Context, console bool, stdioFDs []int) (*kernel.FDTable, error) {
-	k := kernel.KernelFromContext(ctx)
-	fdTable := k.NewFDTable()
-	defer fdTable.DecRef()
-
-	for appFD, hostFD := range stdioFDs {
-		// TODO(gvisor.dev/issue/1482): Add TTY support.
-		appFile, err := vfshost.ImportFD(ctx, k.HostMount(), hostFD, false)
-		if err != nil {
-			return nil, err
-		}
-
-		if err := fdTable.NewFDAtVFS2(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
-			appFile.DecRef()
-			return nil, err
-		}
-		appFile.DecRef()
-	}
-
-	fdTable.IncRef()
-	return fdTable, nil
-}
diff --git a/runsc/boot/loader.go b/runsc/boot/loader.go
index f6ea4c102..79ef3a880 100644
--- a/runsc/boot/loader.go
+++ b/runsc/boot/loader.go
@@ -27,16 +27,18 @@ import (
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"golang.org/x/sys/unix"
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/cpuid"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/memutil"
 	"gvisor.dev/gvisor/pkg/rand"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/control"
+	"gvisor.dev/gvisor/pkg/sentry/fdimport"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/host"
 	"gvisor.dev/gvisor/pkg/sentry/fs/user"
-	vfs2host "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
+	hostvfs2 "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
@@ -143,6 +145,9 @@ type execProcess struct {
 	// tty will be nil if the process is not attached to a terminal.
 	tty *host.TTYFileOperations
 
+	// tty will be nil if the process is not attached to a terminal.
+	ttyVFS2 *hostvfs2.TTYFileDescription
+
 	// pidnsPath is the pid namespace path in spec
 	pidnsPath string
 }
@@ -333,7 +338,7 @@ func New(args Args) (*Loader, error) {
 
 	if kernel.VFS2Enabled {
 		// Set up host mount that will be used for imported fds.
-		hostFilesystem := vfs2host.NewFilesystem(k.VFS())
+		hostFilesystem := hostvfs2.NewFilesystem(k.VFS())
 		defer hostFilesystem.DecRef()
 		hostMount, err := k.VFS().NewDisconnectedMount(hostFilesystem, nil, &vfs.MountOptions{})
 		if err != nil {
@@ -528,6 +533,8 @@ func (l *Loader) run() error {
 
 	// If we are restoring, we do not want to create a process.
 	// l.restore is set by the container manager when a restore call is made.
+	var ttyFile *host.TTYFileOperations
+	var ttyFileVFS2 *hostvfs2.TTYFileDescription
 	if !l.restore {
 		if l.conf.ProfileEnable {
 			pprof.Initialize()
@@ -542,13 +549,14 @@ func (l *Loader) run() error {
 		// Create the FD map, which will set stdin, stdout, and stderr.  If console
 		// is true, then ioctl calls will be passed through to the host fd.
 		ctx := l.rootProcArgs.NewContext(l.k)
-		fdTable, err := createFDTable(ctx, l.console, l.stdioFDs)
+		var err error
+
+		// CreateProcess takes a reference on FDMap if successful. We won't need
+		// ours either way.
+		l.rootProcArgs.FDTable, ttyFile, ttyFileVFS2, err = createFDTable(ctx, l.console, l.stdioFDs)
 		if err != nil {
 			return fmt.Errorf("importing fds: %v", err)
 		}
-		// CreateProcess takes a reference on FDMap if successful. We won't need
-		// ours either way.
-		l.rootProcArgs.FDTable = fdTable
 
 		// Setup the root container file system.
 		l.startGoferMonitor(l.sandboxID, l.goferFDs)
@@ -591,14 +599,16 @@ func (l *Loader) run() error {
 		ep.pidnsPath = ns.Path
 	}
 	if l.console {
-		ttyFile, _ := l.rootProcArgs.FDTable.Get(0)
-		defer ttyFile.DecRef()
-		ep.tty = ttyFile.FileOperations.(*host.TTYFileOperations)
-
-		// Set the foreground process group on the TTY to the global
-		// init process group, since that is what we are about to
-		// start running.
-		ep.tty.InitForegroundProcessGroup(ep.tg.ProcessGroup())
+		// Set the foreground process group on the TTY to the global init process
+		// group, since that is what we are about to start running.
+		switch {
+		case ttyFileVFS2 != nil:
+			ep.ttyVFS2 = ttyFileVFS2
+			ttyFileVFS2.InitForegroundProcessGroup(ep.tg.ProcessGroup())
+		case ttyFile != nil:
+			ep.tty = ttyFile
+			ttyFile.InitForegroundProcessGroup(ep.tg.ProcessGroup())
+		}
 	}
 
 	// Handle signals by forwarding them to the root container process
@@ -719,7 +729,7 @@ func (l *Loader) startContainer(spec *specs.Spec, conf *Config, cid string, file
 
 	// Create the FD map, which will set stdin, stdout, and stderr.
 	ctx := procArgs.NewContext(l.k)
-	fdTable, err := createFDTable(ctx, false, stdioFDs)
+	fdTable, _, _, err := createFDTable(ctx, false, stdioFDs)
 	if err != nil {
 		return fmt.Errorf("importing fds: %v", err)
 	}
@@ -804,14 +814,14 @@ func (l *Loader) destroyContainer(cid string) error {
 	l.mu.Lock()
 	defer l.mu.Unlock()
 
-	_, _, started, err := l.threadGroupFromIDLocked(execID{cid: cid})
+	tg, err := l.tryThreadGroupFromIDLocked(execID{cid: cid})
 	if err != nil {
 		// Container doesn't exist.
 		return err
 	}
 
-	// The container exists, has it been started?
-	if started {
+	// The container exists, but has it been started?
+	if tg != nil {
 		if err := l.signalAllProcesses(cid, int32(linux.SIGKILL)); err != nil {
 			return fmt.Errorf("sending SIGKILL to all container processes: %v", err)
 		}
@@ -853,48 +863,65 @@ func (l *Loader) executeAsync(args *control.ExecArgs) (kernel.ThreadID, error) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
 
-	tg, _, started, err := l.threadGroupFromIDLocked(execID{cid: args.ContainerID})
+	tg, err := l.tryThreadGroupFromIDLocked(execID{cid: args.ContainerID})
 	if err != nil {
 		return 0, err
 	}
-	if !started {
+	if tg == nil {
 		return 0, fmt.Errorf("container %q not started", args.ContainerID)
 	}
 
-	// TODO(gvisor.dev/issue/1623): Add VFS2 support
-
 	// Get the container MountNamespace from the Task.
-	tg.Leader().WithMuLocked(func(t *kernel.Task) {
+	if kernel.VFS2Enabled {
 		// task.MountNamespace() does not take a ref, so we must do so ourselves.
-		args.MountNamespace = t.MountNamespace()
-		args.MountNamespace.IncRef()
-	})
-	if args.MountNamespace != nil {
-		defer args.MountNamespace.DecRef()
+		args.MountNamespaceVFS2 = tg.Leader().MountNamespaceVFS2()
+		args.MountNamespaceVFS2.IncRef()
+	} else {
+		tg.Leader().WithMuLocked(func(t *kernel.Task) {
+			// task.MountNamespace() does not take a ref, so we must do so ourselves.
+			args.MountNamespace = t.MountNamespace()
+			args.MountNamespace.IncRef()
+		})
 	}
 
 	// Add the HOME environment variable if it is not already set.
-	root := args.MountNamespace.Root()
-	defer root.DecRef()
-	ctx := fs.WithRoot(l.k.SupervisorContext(), root)
-	envv, err := user.MaybeAddExecUserHome(ctx, args.MountNamespace, args.KUID, args.Envv)
-	if err != nil {
-		return 0, err
+	if kernel.VFS2Enabled {
+		defer args.MountNamespaceVFS2.DecRef()
+
+		root := args.MountNamespaceVFS2.Root()
+		defer root.DecRef()
+		ctx := vfs.WithRoot(l.k.SupervisorContext(), root)
+		envv, err := user.MaybeAddExecUserHomeVFS2(ctx, args.MountNamespaceVFS2, args.KUID, args.Envv)
+		if err != nil {
+			return 0, err
+		}
+		args.Envv = envv
+	} else {
+		defer args.MountNamespace.DecRef()
+
+		root := args.MountNamespace.Root()
+		defer root.DecRef()
+		ctx := fs.WithRoot(l.k.SupervisorContext(), root)
+		envv, err := user.MaybeAddExecUserHome(ctx, args.MountNamespace, args.KUID, args.Envv)
+		if err != nil {
+			return 0, err
+		}
+		args.Envv = envv
 	}
-	args.Envv = envv
 
 	// Start the process.
 	proc := control.Proc{Kernel: l.k}
 	args.PIDNamespace = tg.PIDNamespace()
-	newTG, tgid, ttyFile, err := control.ExecAsync(&proc, args)
+	newTG, tgid, ttyFile, ttyFileVFS2, err := control.ExecAsync(&proc, args)
 	if err != nil {
 		return 0, err
 	}
 
 	eid := execID{cid: args.ContainerID, pid: tgid}
 	l.processes[eid] = &execProcess{
-		tg:  newTG,
-		tty: ttyFile,
+		tg:      newTG,
+		tty:     ttyFile,
+		ttyVFS2: ttyFileVFS2,
 	}
 	log.Debugf("updated processes: %v", l.processes)
 
@@ -905,7 +932,7 @@ func (l *Loader) executeAsync(args *control.ExecArgs) (kernel.ThreadID, error) {
 func (l *Loader) waitContainer(cid string, waitStatus *uint32) error {
 	// Don't defer unlock, as doing so would make it impossible for
 	// multiple clients to wait on the same container.
-	tg, _, err := l.threadGroupFromID(execID{cid: cid})
+	tg, err := l.threadGroupFromID(execID{cid: cid})
 	if err != nil {
 		return fmt.Errorf("can't wait for container %q: %v", cid, err)
 	}
@@ -924,7 +951,7 @@ func (l *Loader) waitPID(tgid kernel.ThreadID, cid string, waitStatus *uint32) e
 
 	// Try to find a process that was exec'd
 	eid := execID{cid: cid, pid: tgid}
-	execTG, _, err := l.threadGroupFromID(eid)
+	execTG, err := l.threadGroupFromID(eid)
 	if err == nil {
 		ws := l.wait(execTG)
 		*waitStatus = ws
@@ -938,7 +965,7 @@ func (l *Loader) waitPID(tgid kernel.ThreadID, cid string, waitStatus *uint32) e
 
 	// The caller may be waiting on a process not started directly via exec.
 	// In this case, find the process in the container's PID namespace.
-	initTG, _, err := l.threadGroupFromID(execID{cid: cid})
+	initTG, err := l.threadGroupFromID(execID{cid: cid})
 	if err != nil {
 		return fmt.Errorf("waiting for PID %d: %v", tgid, err)
 	}
@@ -1089,8 +1116,7 @@ func (l *Loader) signal(cid string, pid, signo int32, mode SignalDeliveryMode) e
 			return fmt.Errorf("PID (%d) cannot be set when signaling all processes", pid)
 		}
 		// Check that the container has actually started before signaling it.
-		_, _, err := l.threadGroupFromID(execID{cid: cid})
-		if err != nil {
+		if _, err := l.threadGroupFromID(execID{cid: cid}); err != nil {
 			return err
 		}
 		if err := l.signalAllProcesses(cid, signo); err != nil {
@@ -1104,7 +1130,7 @@ func (l *Loader) signal(cid string, pid, signo int32, mode SignalDeliveryMode) e
 }
 
 func (l *Loader) signalProcess(cid string, tgid kernel.ThreadID, signo int32) error {
-	execTG, _, err := l.threadGroupFromID(execID{cid: cid, pid: tgid})
+	execTG, err := l.threadGroupFromID(execID{cid: cid, pid: tgid})
 	if err == nil {
 		// Send signal directly to the identified process.
 		return l.k.SendExternalSignalThreadGroup(execTG, &arch.SignalInfo{Signo: signo})
@@ -1113,7 +1139,7 @@ func (l *Loader) signalProcess(cid string, tgid kernel.ThreadID, signo int32) er
 	// The caller may be signaling a process not started directly via exec.
 	// In this case, find the process in the container's PID namespace and
 	// signal it.
-	initTG, _, err := l.threadGroupFromID(execID{cid: cid})
+	initTG, err := l.threadGroupFromID(execID{cid: cid})
 	if err != nil {
 		return fmt.Errorf("no thread group found: %v", err)
 	}
@@ -1127,17 +1153,35 @@ func (l *Loader) signalProcess(cid string, tgid kernel.ThreadID, signo int32) er
 	return l.k.SendExternalSignalThreadGroup(tg, &arch.SignalInfo{Signo: signo})
 }
 
+// signalForegrondProcessGroup looks up foreground process group from the TTY
+// for the given "tgid" inside container "cid", and send the signal to it.
 func (l *Loader) signalForegrondProcessGroup(cid string, tgid kernel.ThreadID, signo int32) error {
-	// Lookup foreground process group from the TTY for the given process,
-	// and send the signal to it.
-	tg, tty, err := l.threadGroupFromID(execID{cid: cid, pid: tgid})
+	l.mu.Lock()
+	tg, err := l.tryThreadGroupFromIDLocked(execID{cid: cid, pid: tgid})
 	if err != nil {
+		l.mu.Unlock()
 		return fmt.Errorf("no thread group found: %v", err)
 	}
-	if tty == nil {
+	if tg == nil {
+		l.mu.Unlock()
+		return fmt.Errorf("container %q not started", cid)
+	}
+
+	tty, ttyVFS2, err := l.ttyFromIDLocked(execID{cid: cid, pid: tgid})
+	l.mu.Unlock()
+	if err != nil {
+		return fmt.Errorf("no thread group found: %v", err)
+	}
+
+	var pg *kernel.ProcessGroup
+	switch {
+	case ttyVFS2 != nil:
+		pg = ttyVFS2.ForegroundProcessGroup()
+	case tty != nil:
+		pg = tty.ForegroundProcessGroup()
+	default:
 		return fmt.Errorf("no TTY attached")
 	}
-	pg := tty.ForegroundProcessGroup()
 	if pg == nil {
 		// No foreground process group has been set. Signal the
 		// original thread group.
@@ -1168,33 +1212,57 @@ func (l *Loader) signalAllProcesses(cid string, signo int32) error {
 	return l.k.SendContainerSignal(cid, &arch.SignalInfo{Signo: signo})
 }
 
-// threadGroupFromID same as threadGroupFromIDLocked except that it acquires
-// mutex before calling it.
-func (l *Loader) threadGroupFromID(key execID) (*kernel.ThreadGroup, *host.TTYFileOperations, error) {
+// threadGroupFromID is similar to tryThreadGroupFromIDLocked except that it
+// acquires mutex before calling it and fails in case container hasn't started
+// yet.
+func (l *Loader) threadGroupFromID(key execID) (*kernel.ThreadGroup, error) {
 	l.mu.Lock()
 	defer l.mu.Unlock()
-	tg, tty, ok, err := l.threadGroupFromIDLocked(key)
+	tg, err := l.tryThreadGroupFromIDLocked(key)
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
-	if !ok {
-		return nil, nil, fmt.Errorf("container %q not started", key.cid)
+	if tg == nil {
+		return nil, fmt.Errorf("container %q not started", key.cid)
 	}
-	return tg, tty, nil
+	return tg, nil
 }
 
-// threadGroupFromIDLocked returns the thread group and TTY for the given
-// execution ID. TTY may be nil if the process is not attached to a terminal.
-// Also returns a boolean indicating whether the container has already started.
-// Returns error if execution ID is invalid or if the container cannot be
-// found (maybe it has been deleted). Caller must hold 'mu'.
-func (l *Loader) threadGroupFromIDLocked(key execID) (*kernel.ThreadGroup, *host.TTYFileOperations, bool, error) {
+// tryThreadGroupFromIDLocked returns the thread group for the given execution
+// ID. It may return nil in case the container has not started yet. Returns
+// error if execution ID is invalid or if the container cannot be found (maybe
+// it has been deleted). Caller must hold 'mu'.
+func (l *Loader) tryThreadGroupFromIDLocked(key execID) (*kernel.ThreadGroup, error) {
 	ep := l.processes[key]
 	if ep == nil {
-		return nil, nil, false, fmt.Errorf("container %q not found", key.cid)
+		return nil, fmt.Errorf("container %q not found", key.cid)
 	}
-	if ep.tg == nil {
-		return nil, nil, false, nil
+	return ep.tg, nil
+}
+
+// ttyFromIDLocked returns the TTY files for the given execution ID. It may
+// return nil in case the container has not started yet. Returns error if
+// execution ID is invalid or if the container cannot be found (maybe it has
+// been deleted). Caller must hold 'mu'.
+func (l *Loader) ttyFromIDLocked(key execID) (*host.TTYFileOperations, *hostvfs2.TTYFileDescription, error) {
+	ep := l.processes[key]
+	if ep == nil {
+		return nil, nil, fmt.Errorf("container %q not found", key.cid)
+	}
+	return ep.tty, ep.ttyVFS2, nil
+}
+
+func createFDTable(ctx context.Context, console bool, stdioFDs []int) (*kernel.FDTable, *host.TTYFileOperations, *hostvfs2.TTYFileDescription, error) {
+	if len(stdioFDs) != 3 {
+		return nil, nil, nil, fmt.Errorf("stdioFDs should contain exactly 3 FDs (stdin, stdout, and stderr), but %d FDs received", len(stdioFDs))
+	}
+
+	k := kernel.KernelFromContext(ctx)
+	fdTable := k.NewFDTable()
+	ttyFile, ttyFileVFS2, err := fdimport.Import(ctx, fdTable, console, stdioFDs)
+	if err != nil {
+		fdTable.DecRef()
+		return nil, nil, nil, err
 	}
-	return ep.tg, ep.tty, true, nil
+	return fdTable, ttyFile, ttyFileVFS2, nil
 }
diff --git a/runsc/boot/vfs.go b/runsc/boot/vfs.go
index 0b9b0b436..448fc4459 100644
--- a/runsc/boot/vfs.go
+++ b/runsc/boot/vfs.go
@@ -26,6 +26,7 @@ import (
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/devices/memdev"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	devpts2 "gvisor.dev/gvisor/pkg/sentry/fsimpl/devpts"
 	devtmpfsimpl "gvisor.dev/gvisor/pkg/sentry/fsimpl/devtmpfs"
 	goferimpl "gvisor.dev/gvisor/pkg/sentry/fsimpl/gofer"
 	procimpl "gvisor.dev/gvisor/pkg/sentry/fsimpl/proc"
@@ -41,37 +42,28 @@ import (
 )
 
 func registerFilesystems(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials) error {
-
-	vfsObj.MustRegisterFilesystemType(rootFsName, &goferimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
-		AllowUserList: true,
-	})
-
-	vfsObj.MustRegisterFilesystemType(bind, &goferimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
+	vfsObj.MustRegisterFilesystemType(devpts2.Name, &devpts2.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
 		AllowUserList: true,
+		// TODO(b/29356795): Users may mount this once the terminals are in a
+		//  usable state.
+		AllowUserMount: false,
 	})
-
-	vfsObj.MustRegisterFilesystemType(devpts, &devtmpfsimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
+	vfsObj.MustRegisterFilesystemType(devtmpfsimpl.Name, &devtmpfsimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
 		AllowUserMount: true,
 		AllowUserList:  true,
 	})
-
-	vfsObj.MustRegisterFilesystemType(devtmpfs, &devtmpfsimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
-		AllowUserMount: true,
-		AllowUserList:  true,
-	})
-	vfsObj.MustRegisterFilesystemType(proc, &procimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
-		AllowUserMount: true,
-		AllowUserList:  true,
+	vfsObj.MustRegisterFilesystemType(goferimpl.Name, &goferimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
+		AllowUserList: true,
 	})
-	vfsObj.MustRegisterFilesystemType(sysfs, &sysimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
+	vfsObj.MustRegisterFilesystemType(procimpl.Name, &procimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
 		AllowUserMount: true,
 		AllowUserList:  true,
 	})
-	vfsObj.MustRegisterFilesystemType(tmpfs, &tmpfsimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
+	vfsObj.MustRegisterFilesystemType(sysimpl.Name, &sysimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
 		AllowUserMount: true,
 		AllowUserList:  true,
 	})
-	vfsObj.MustRegisterFilesystemType(nonefs, &sysimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
+	vfsObj.MustRegisterFilesystemType(tmpfsimpl.Name, &tmpfsimpl.FilesystemType{}, &vfs.RegisterFilesystemTypeOptions{
 		AllowUserMount: true,
 		AllowUserList:  true,
 	})
@@ -108,7 +100,6 @@ func setupContainerVFS2(ctx context.Context, conf *Config, mntr *containerMounte
 }
 
 func setExecutablePathVFS2(ctx context.Context, procArgs *kernel.CreateProcessArgs) error {
-
 	exe := procArgs.Argv[0]
 
 	// Absolute paths can be used directly.
@@ -120,11 +111,9 @@ func setExecutablePathVFS2(ctx context.Context, procArgs *kernel.CreateProcessAr
 	// Paths with '/' in them should be joined to the working directory, or
 	// to the root if working directory is not set.
 	if strings.IndexByte(exe, '/') > 0 {
-
 		if !path.IsAbs(procArgs.WorkingDirectory) {
 			return fmt.Errorf("working directory %q must be absolute", procArgs.WorkingDirectory)
 		}
-
 		procArgs.Filename = path.Join(procArgs.WorkingDirectory, exe)
 		return nil
 	}
@@ -144,21 +133,17 @@ func setExecutablePathVFS2(ctx context.Context, procArgs *kernel.CreateProcessAr
 	creds := procArgs.Credentials
 
 	for _, p := range paths {
-
 		binPath := path.Join(p, exe)
-
 		pop := &vfs.PathOperation{
 			Root:               root,
 			Start:              root,
 			Path:               fspath.Parse(binPath),
 			FollowFinalSymlink: true,
 		}
-
 		opts := &vfs.OpenOptions{
 			FileExec: true,
 			Flags:    linux.O_RDONLY,
 		}
-
 		dentry, err := root.Mount().Filesystem().VirtualFilesystem().OpenAt(ctx, creds, pop, opts)
 		if err == syserror.ENOENT || err == syserror.EACCES {
 			// Didn't find it here.
@@ -209,7 +194,6 @@ func (c *containerMounter) setupVFS2(ctx context.Context, conf *Config, procArgs
 }
 
 func (c *containerMounter) createMountNamespaceVFS2(ctx context.Context, conf *Config, creds *auth.Credentials) (*vfs.MountNamespace, error) {
-
 	fd := c.fds.remove()
 	opts := strings.Join(p9MountOptionsVFS2(fd, conf.FileAccess), ",")
 
@@ -222,7 +206,6 @@ func (c *containerMounter) createMountNamespaceVFS2(ctx context.Context, conf *C
 }
 
 func (c *containerMounter) mountSubmountsVFS2(ctx context.Context, conf *Config, mns *vfs.MountNamespace, creds *auth.Credentials) error {
-
 	c.prepareMountsVFS2()
 
 	for _, submount := range c.mounts {
@@ -256,7 +239,6 @@ func (c *containerMounter) mountSubmountVFS2(ctx context.Context, conf *Config,
 	if err != nil {
 		return fmt.Errorf("mountOptions failed: %w", err)
 	}
-
 	if fsName == "" {
 		// Filesystem is not supported (e.g. cgroup), just skip it.
 		return nil
@@ -277,7 +259,7 @@ func (c *containerMounter) mountSubmountVFS2(ctx context.Context, conf *Config,
 	// All writes go to upper, be paranoid and make lower readonly.
 	opts.ReadOnly = useOverlay
 
-	if err := c.k.VFS().MountAt(ctx, creds, "", target, submount.Type, opts); err != nil {
+	if err := c.k.VFS().MountAt(ctx, creds, "", target, fsName, opts); err != nil {
 		return fmt.Errorf("failed to mount %q (type: %s): %w, opts: %v", submount.Destination, submount.Type, err, opts)
 	}
 	log.Infof("Mounted %q to %q type: %s, internal-options: %q", submount.Source, submount.Destination, submount.Type, opts)