Merge release-20200211.0-17-g4075de1 (automated)

32 files changed, 1106 insertions, 278 deletions

diff --git a/pkg/sentry/control/proc.go b/pkg/sentry/control/proc.go
index ced51c66c..8973754c8 100644
--- a/pkg/sentry/control/proc.go
+++ b/pkg/sentry/control/proc.go
@@ -18,19 +18,26 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"path"
 	"sort"
 	"strings"
 	"text/tabwriter"
 	"time"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/fspath"
+	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/host"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/urpc"
 )
 
@@ -60,6 +67,12 @@ type ExecArgs struct {
 	// process's MountNamespace.
 	MountNamespace *fs.MountNamespace
 
+	// MountNamespaceVFS2 is the mount namespace to execute the new process in.
+	// A reference on MountNamespace must be held for the lifetime of the
+	// ExecArgs. If MountNamespace is nil, it will default to the init
+	// process's MountNamespace.
+	MountNamespaceVFS2 *vfs.MountNamespace
+
 	// WorkingDirectory defines the working directory for the new process.
 	WorkingDirectory string `json:"wd"`
 
@@ -150,6 +163,7 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI
 		Envv:                    args.Envv,
 		WorkingDirectory:        args.WorkingDirectory,
 		MountNamespace:          args.MountNamespace,
+		MountNamespaceVFS2:      args.MountNamespaceVFS2,
 		Credentials:             creds,
 		FDTable:                 fdTable,
 		Umask:                   0022,
@@ -166,24 +180,53 @@ func (proc *Proc) execAsync(args *ExecArgs) (*kernel.ThreadGroup, kernel.ThreadI
 		// be donated to the new process in CreateProcess.
 		initArgs.MountNamespace.IncRef()
 	}
+	if initArgs.MountNamespaceVFS2 != nil {
+		// initArgs must hold a reference on MountNamespaceVFS2, which will
+		// be donated to the new process in CreateProcess.
+		initArgs.MountNamespaceVFS2.IncRef()
+	}
 	ctx := initArgs.NewContext(proc.Kernel)
 
 	if initArgs.Filename == "" {
-		// Get the full path to the filename from the PATH env variable.
-		paths := fs.GetPath(initArgs.Envv)
-		mns := initArgs.MountNamespace
-		if mns == nil {
-			mns = proc.Kernel.GlobalInit().Leader().MountNamespace()
-		}
-		f, err := mns.ResolveExecutablePath(ctx, initArgs.WorkingDirectory, initArgs.Argv[0], paths)
-		if err != nil {
-			return nil, 0, nil, fmt.Errorf("error finding executable %q in PATH %v: %v", initArgs.Argv[0], paths, err)
+		if kernel.VFS2Enabled {
+			// Get the full path to the filename from the PATH env variable.
+			if initArgs.MountNamespaceVFS2 == nil {
+				// Set initArgs so that 'ctx' returns the namespace.
+				//
+				// MountNamespaceVFS2 adds a reference to the namespace, which is
+				// transferred to the new process.
+				initArgs.MountNamespaceVFS2 = proc.Kernel.GlobalInit().Leader().MountNamespaceVFS2()
+			}
+
+			paths := fs.GetPath(initArgs.Envv)
+			vfsObj := proc.Kernel.VFS
+			file, err := ResolveExecutablePath(ctx, vfsObj, initArgs.WorkingDirectory, initArgs.Argv[0], paths)
+			if err != nil {
+				return nil, 0, nil, fmt.Errorf("error finding executable %q in PATH %v: %v", initArgs.Argv[0], paths, err)
+			}
+			initArgs.File = fsbridge.NewVFSFile(file)
+		} else {
+			// Get the full path to the filename from the PATH env variable.
+			paths := fs.GetPath(initArgs.Envv)
+			if initArgs.MountNamespace == nil {
+				// Set initArgs so that 'ctx' returns the namespace.
+				initArgs.MountNamespace = proc.Kernel.GlobalInit().Leader().MountNamespace()
+
+				// initArgs must hold a reference on MountNamespace, which will
+				// be donated to the new process in CreateProcess.
+				initArgs.MountNamespaceVFS2.IncRef()
+			}
+			f, err := initArgs.MountNamespace.ResolveExecutablePath(ctx, initArgs.WorkingDirectory, initArgs.Argv[0], paths)
+			if err != nil {
+				return nil, 0, nil, fmt.Errorf("error finding executable %q in PATH %v: %v", initArgs.Argv[0], paths, err)
+			}
+			initArgs.Filename = f
 		}
-		initArgs.Filename = f
 	}
 
 	mounter := fs.FileOwnerFromContext(ctx)
 
+	// TODO(gvisor.dev/issue/1623): Use host FD when supported in VFS2.
 	var ttyFile *fs.File
 	for appFD, hostFile := range args.FilePayload.Files {
 		var appFile *fs.File
@@ -411,3 +454,67 @@ func ttyName(tty *kernel.TTY) string {
 	}
 	return fmt.Sprintf("pts/%d", tty.Index)
 }
+
+// ResolveExecutablePath resolves the given executable name given a set of
+// paths that might contain it.
+func ResolveExecutablePath(ctx context.Context, vfsObj *vfs.VirtualFilesystem, wd, name string, paths []string) (*vfs.FileDescription, error) {
+	root := vfs.RootFromContext(ctx)
+	defer root.DecRef()
+	creds := auth.CredentialsFromContext(ctx)
+
+	// Absolute paths can be used directly.
+	if path.IsAbs(name) {
+		return openExecutable(ctx, vfsObj, creds, root, name)
+	}
+
+	// Paths with '/' in them should be joined to the working directory, or
+	// to the root if working directory is not set.
+	if strings.IndexByte(name, '/') > 0 {
+		if len(wd) == 0 {
+			wd = "/"
+		}
+		if !path.IsAbs(wd) {
+			return nil, fmt.Errorf("working directory %q must be absolute", wd)
+		}
+		return openExecutable(ctx, vfsObj, creds, root, path.Join(wd, name))
+	}
+
+	// Otherwise, we must lookup the name in the paths, starting from the
+	// calling context's root directory.
+	for _, p := range paths {
+		if !path.IsAbs(p) {
+			// Relative paths aren't safe, no one should be using them.
+			log.Warningf("Skipping relative path %q in $PATH", p)
+			continue
+		}
+
+		binPath := path.Join(p, name)
+		f, err := openExecutable(ctx, vfsObj, creds, root, binPath)
+		if err != nil {
+			return nil, err
+		}
+		if f == nil {
+			continue // Not found/no access.
+		}
+		return f, nil
+	}
+	return nil, syserror.ENOENT
+}
+
+func openExecutable(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, root vfs.VirtualDentry, path string) (*vfs.FileDescription, error) {
+	pop := vfs.PathOperation{
+		Root:               root,
+		Start:              root, // binPath is absolute, Start can be anything.
+		Path:               fspath.Parse(path),
+		FollowFinalSymlink: true,
+	}
+	opts := &vfs.OpenOptions{
+		Flags:    linux.O_RDONLY,
+		FileExec: true,
+	}
+	f, err := vfsObj.OpenAt(ctx, creds, &pop, opts)
+	if err == syserror.ENOENT || err == syserror.EACCES {
+		return nil, nil
+	}
+	return f, err
+}
diff --git a/pkg/sentry/fs/proc/task.go b/pkg/sentry/fs/proc/task.go
index ca020e11e..8ab8d8a02 100644
--- a/pkg/sentry/fs/proc/task.go
+++ b/pkg/sentry/fs/proc/task.go
@@ -28,6 +28,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/proc/device"
 	"gvisor.dev/gvisor/pkg/sentry/fs/proc/seqfile"
 	"gvisor.dev/gvisor/pkg/sentry/fs/ramfs"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
@@ -249,7 +250,7 @@ func newExe(t *kernel.Task, msrc *fs.MountSource) *fs.Inode {
 	return newProcInode(t, exeSymlink, msrc, fs.Symlink, t)
 }
 
-func (e *exe) executable() (d *fs.Dirent, err error) {
+func (e *exe) executable() (file fsbridge.File, err error) {
 	e.t.WithMuLocked(func(t *kernel.Task) {
 		mm := t.MemoryManager()
 		if mm == nil {
@@ -262,8 +263,8 @@ func (e *exe) executable() (d *fs.Dirent, err error) {
 		// The MemoryManager may be destroyed, in which case
 		// MemoryManager.destroy will simply set the executable to nil
 		// (with locks held).
-		d = mm.Executable()
-		if d == nil {
+		file = mm.Executable()
+		if file == nil {
 			err = syserror.ENOENT
 		}
 	})
@@ -283,15 +284,7 @@ func (e *exe) Readlink(ctx context.Context, inode *fs.Inode) (string, error) {
 	}
 	defer exec.DecRef()
 
-	root := fs.RootFromContext(ctx)
-	if root == nil {
-		// This doesn't correspond to anything in Linux because the vfs is
-		// global there.
-		return "", syserror.EINVAL
-	}
-	defer root.DecRef()
-	n, _ := exec.FullName(root)
-	return n, nil
+	return exec.PathnameWithDeleted(ctx), nil
 }
 
 // namespaceSymlink represents a symlink in the namespacefs, such as the files
diff --git a/pkg/sentry/fsbridge/bridge.go b/pkg/sentry/fsbridge/bridge.go
new file mode 100755
index 000000000..8e7590721
--- /dev/null
+++ b/pkg/sentry/fsbridge/bridge.go
@@ -0,0 +1,54 @@
+// Copyright 2020 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 fsbridge provides common interfaces to bridge between VFS1 and VFS2
+// files.
+package fsbridge
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// File provides a common interface to bridge between VFS1 and VFS2 files.
+type File interface {
+	// PathnameWithDeleted returns an absolute pathname to vd, consistent with
+	// Linux's d_path(). In particular, if vd.Dentry() has been disowned,
+	// PathnameWithDeleted appends " (deleted)" to the returned pathname.
+	PathnameWithDeleted(ctx context.Context) string
+
+	// ReadFull read all contents from the file.
+	ReadFull(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error)
+
+	// ConfigureMMap mutates opts to implement mmap(2) for the file.
+	ConfigureMMap(context.Context, *memmap.MMapOpts) error
+
+	// Type returns the file type, e.g. linux.S_IFREG.
+	Type(context.Context) (linux.FileMode, error)
+
+	// IncRef increments reference.
+	IncRef()
+
+	// DecRef decrements reference.
+	DecRef()
+}
+
+// Lookup provides a common interface to open files.
+type Lookup interface {
+	// OpenPath opens a file.
+	OpenPath(ctx context.Context, path string, opts vfs.OpenOptions, remainingTraversals *uint, resolveFinal bool) (File, error)
+}
diff --git a/pkg/sentry/fsbridge/fs.go b/pkg/sentry/fsbridge/fs.go
new file mode 100755
index 000000000..093ce1fb3
--- /dev/null
+++ b/pkg/sentry/fsbridge/fs.go
@@ -0,0 +1,181 @@
+// Copyright 2020 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 fsbridge
+
+import (
+	"io"
+	"strings"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// fsFile implements File interface over fs.File.
+//
+// +stateify savable
+type fsFile struct {
+	file *fs.File
+}
+
+var _ File = (*fsFile)(nil)
+
+// NewFSFile creates a new File over fs.File.
+func NewFSFile(file *fs.File) File {
+	return &fsFile{file: file}
+}
+
+// PathnameWithDeleted implements File.
+func (f *fsFile) PathnameWithDeleted(ctx context.Context) string {
+	root := fs.RootFromContext(ctx)
+	if root == nil {
+		// This doesn't correspond to anything in Linux because the vfs is
+		// global there.
+		return ""
+	}
+	defer root.DecRef()
+
+	name, _ := f.file.Dirent.FullName(root)
+	return name
+}
+
+// ReadFull implements File.
+func (f *fsFile) ReadFull(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
+	var total int64
+	for dst.NumBytes() > 0 {
+		n, err := f.file.Preadv(ctx, dst, offset+total)
+		total += n
+		if err == io.EOF && total != 0 {
+			return total, io.ErrUnexpectedEOF
+		} else if err != nil {
+			return total, err
+		}
+		dst = dst.DropFirst64(n)
+	}
+	return total, nil
+}
+
+// ConfigureMMap implements File.
+func (f *fsFile) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
+	return f.file.ConfigureMMap(ctx, opts)
+}
+
+// Type implements File.
+func (f *fsFile) Type(context.Context) (linux.FileMode, error) {
+	return linux.FileMode(f.file.Dirent.Inode.StableAttr.Type.LinuxType()), nil
+}
+
+// IncRef implements File.
+func (f *fsFile) IncRef() {
+	f.file.IncRef()
+}
+
+// DecRef implements File.
+func (f *fsFile) DecRef() {
+	f.file.DecRef()
+}
+
+// fsLookup implements Lookup interface using fs.File.
+//
+// +stateify savable
+type fsLookup struct {
+	mntns *fs.MountNamespace
+
+	root       *fs.Dirent
+	workingDir *fs.Dirent
+}
+
+var _ Lookup = (*fsLookup)(nil)
+
+// NewFSLookup creates a new Lookup using VFS1.
+func NewFSLookup(mntns *fs.MountNamespace, root, workingDir *fs.Dirent) Lookup {
+	return &fsLookup{
+		mntns:      mntns,
+		root:       root,
+		workingDir: workingDir,
+	}
+}
+
+// OpenPath implements Lookup.
+func (l *fsLookup) OpenPath(ctx context.Context, path string, opts vfs.OpenOptions, remainingTraversals *uint, resolveFinal bool) (File, error) {
+	var d *fs.Dirent
+	var err error
+	if resolveFinal {
+		d, err = l.mntns.FindInode(ctx, l.root, l.workingDir, path, remainingTraversals)
+	} else {
+		d, err = l.mntns.FindLink(ctx, l.root, l.workingDir, path, remainingTraversals)
+	}
+	if err != nil {
+		return nil, err
+	}
+	defer d.DecRef()
+
+	if !resolveFinal && fs.IsSymlink(d.Inode.StableAttr) {
+		return nil, syserror.ELOOP
+	}
+
+	fsPerm := openOptionsToPermMask(&opts)
+	if err := d.Inode.CheckPermission(ctx, fsPerm); err != nil {
+		return nil, err
+	}
+
+	// If they claim it's a directory, then make sure.
+	if strings.HasSuffix(path, "/") {
+		if d.Inode.StableAttr.Type != fs.Directory {
+			return nil, syserror.ENOTDIR
+		}
+	}
+
+	if opts.FileExec && d.Inode.StableAttr.Type != fs.RegularFile {
+		ctx.Infof("%q is not a regular file: %v", path, d.Inode.StableAttr.Type)
+		return nil, syserror.EACCES
+	}
+
+	f, err := d.Inode.GetFile(ctx, d, flagsToFileFlags(opts.Flags))
+	if err != nil {
+		return nil, err
+	}
+
+	return &fsFile{file: f}, nil
+}
+
+func openOptionsToPermMask(opts *vfs.OpenOptions) fs.PermMask {
+	mode := opts.Flags & linux.O_ACCMODE
+	return fs.PermMask{
+		Read:    mode == linux.O_RDONLY || mode == linux.O_RDWR,
+		Write:   mode == linux.O_WRONLY || mode == linux.O_RDWR,
+		Execute: opts.FileExec,
+	}
+}
+
+func flagsToFileFlags(flags uint32) fs.FileFlags {
+	return fs.FileFlags{
+		Direct:      flags&linux.O_DIRECT != 0,
+		DSync:       flags&(linux.O_DSYNC|linux.O_SYNC) != 0,
+		Sync:        flags&linux.O_SYNC != 0,
+		NonBlocking: flags&linux.O_NONBLOCK != 0,
+		Read:        (flags & linux.O_ACCMODE) != linux.O_WRONLY,
+		Write:       (flags & linux.O_ACCMODE) != linux.O_RDONLY,
+		Append:      flags&linux.O_APPEND != 0,
+		Directory:   flags&linux.O_DIRECTORY != 0,
+		Async:       flags&linux.O_ASYNC != 0,
+		LargeFile:   flags&linux.O_LARGEFILE != 0,
+		Truncate:    flags&linux.O_TRUNC != 0,
+	}
+}
diff --git a/pkg/sentry/fsbridge/fsbridge_state_autogen.go b/pkg/sentry/fsbridge/fsbridge_state_autogen.go
new file mode 100755
index 000000000..51b57d859
--- /dev/null
+++ b/pkg/sentry/fsbridge/fsbridge_state_autogen.go
@@ -0,0 +1,66 @@
+// automatically generated by stateify.
+
+package fsbridge
+
+import (
+	"gvisor.dev/gvisor/pkg/state"
+)
+
+func (x *fsFile) beforeSave() {}
+func (x *fsFile) save(m state.Map) {
+	x.beforeSave()
+	m.Save("file", &x.file)
+}
+
+func (x *fsFile) afterLoad() {}
+func (x *fsFile) load(m state.Map) {
+	m.Load("file", &x.file)
+}
+
+func (x *fsLookup) beforeSave() {}
+func (x *fsLookup) save(m state.Map) {
+	x.beforeSave()
+	m.Save("mntns", &x.mntns)
+	m.Save("root", &x.root)
+	m.Save("workingDir", &x.workingDir)
+}
+
+func (x *fsLookup) afterLoad() {}
+func (x *fsLookup) load(m state.Map) {
+	m.Load("mntns", &x.mntns)
+	m.Load("root", &x.root)
+	m.Load("workingDir", &x.workingDir)
+}
+
+func (x *vfsFile) beforeSave() {}
+func (x *vfsFile) save(m state.Map) {
+	x.beforeSave()
+	m.Save("file", &x.file)
+}
+
+func (x *vfsFile) afterLoad() {}
+func (x *vfsFile) load(m state.Map) {
+	m.Load("file", &x.file)
+}
+
+func (x *vfsLookup) beforeSave() {}
+func (x *vfsLookup) save(m state.Map) {
+	x.beforeSave()
+	m.Save("mntns", &x.mntns)
+	m.Save("root", &x.root)
+	m.Save("workingDir", &x.workingDir)
+}
+
+func (x *vfsLookup) afterLoad() {}
+func (x *vfsLookup) load(m state.Map) {
+	m.Load("mntns", &x.mntns)
+	m.Load("root", &x.root)
+	m.Load("workingDir", &x.workingDir)
+}
+
+func init() {
+	state.Register("pkg/sentry/fsbridge.fsFile", (*fsFile)(nil), state.Fns{Save: (*fsFile).save, Load: (*fsFile).load})
+	state.Register("pkg/sentry/fsbridge.fsLookup", (*fsLookup)(nil), state.Fns{Save: (*fsLookup).save, Load: (*fsLookup).load})
+	state.Register("pkg/sentry/fsbridge.vfsFile", (*vfsFile)(nil), state.Fns{Save: (*vfsFile).save, Load: (*vfsFile).load})
+	state.Register("pkg/sentry/fsbridge.vfsLookup", (*vfsLookup)(nil), state.Fns{Save: (*vfsLookup).save, Load: (*vfsLookup).load})
+}
diff --git a/pkg/sentry/fsbridge/vfs.go b/pkg/sentry/fsbridge/vfs.go
new file mode 100755
index 000000000..e657c39bc
--- /dev/null
+++ b/pkg/sentry/fsbridge/vfs.go
@@ -0,0 +1,134 @@
+// Copyright 2020 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 fsbridge
+
+import (
+	"io"
+
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/fspath"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// fsFile implements File interface over vfs.FileDescription.
+//
+// +stateify savable
+type vfsFile struct {
+	file *vfs.FileDescription
+}
+
+var _ File = (*vfsFile)(nil)
+
+// NewVFSFile creates a new File over fs.File.
+func NewVFSFile(file *vfs.FileDescription) File {
+	return &vfsFile{file: file}
+}
+
+// PathnameWithDeleted implements File.
+func (f *vfsFile) PathnameWithDeleted(ctx context.Context) string {
+	root := vfs.RootFromContext(ctx)
+	defer root.DecRef()
+
+	vfsObj := f.file.VirtualDentry().Mount().Filesystem().VirtualFilesystem()
+	name, _ := vfsObj.PathnameWithDeleted(ctx, root, f.file.VirtualDentry())
+	return name
+}
+
+// ReadFull implements File.
+func (f *vfsFile) ReadFull(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
+	var total int64
+	for dst.NumBytes() > 0 {
+		n, err := f.file.PRead(ctx, dst, offset+total, vfs.ReadOptions{})
+		total += n
+		if err == io.EOF && total != 0 {
+			return total, io.ErrUnexpectedEOF
+		} else if err != nil {
+			return total, err
+		}
+		dst = dst.DropFirst64(n)
+	}
+	return total, nil
+}
+
+// ConfigureMMap implements File.
+func (f *vfsFile) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
+	return f.file.ConfigureMMap(ctx, opts)
+}
+
+// Type implements File.
+func (f *vfsFile) Type(ctx context.Context) (linux.FileMode, error) {
+	stat, err := f.file.Stat(ctx, vfs.StatOptions{})
+	if err != nil {
+		return 0, err
+	}
+	return linux.FileMode(stat.Mode).FileType(), nil
+}
+
+// IncRef implements File.
+func (f *vfsFile) IncRef() {
+	f.file.IncRef()
+}
+
+// DecRef implements File.
+func (f *vfsFile) DecRef() {
+	f.file.DecRef()
+}
+
+// fsLookup implements Lookup interface using fs.File.
+//
+// +stateify savable
+type vfsLookup struct {
+	mntns *vfs.MountNamespace
+
+	root       vfs.VirtualDentry
+	workingDir vfs.VirtualDentry
+}
+
+var _ Lookup = (*vfsLookup)(nil)
+
+// NewVFSLookup creates a new Lookup using VFS2.
+func NewVFSLookup(mntns *vfs.MountNamespace, root, workingDir vfs.VirtualDentry) Lookup {
+	return &vfsLookup{
+		mntns:      mntns,
+		root:       root,
+		workingDir: workingDir,
+	}
+}
+
+// OpenPath implements Lookup.
+//
+// remainingTraversals is not configurable in VFS2, all callers are using the
+// default anyways.
+//
+// TODO(gvisor.dev/issue/1623): Check mount has read and exec permission.
+func (l *vfsLookup) OpenPath(ctx context.Context, path string, opts vfs.OpenOptions, _ *uint, resolveFinal bool) (File, error) {
+	vfsObj := l.mntns.Root().Mount().Filesystem().VirtualFilesystem()
+	creds := auth.CredentialsFromContext(ctx)
+	pop := &vfs.PathOperation{
+		Root:               l.root,
+		Start:              l.root,
+		Path:               fspath.Parse(path),
+		FollowFinalSymlink: resolveFinal,
+	}
+	fd, err := vfsObj.OpenAt(ctx, creds, pop, &opts)
+	if err != nil {
+		return nil, err
+	}
+	return &vfsFile{file: fd}, nil
+}
diff --git a/pkg/sentry/kernel/fs_context.go b/pkg/sentry/kernel/fs_context.go
index 2448c1d99..7218aa24e 100644
--- a/pkg/sentry/kernel/fs_context.go
+++ b/pkg/sentry/kernel/fs_context.go
@@ -19,6 +19,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
 )
 
@@ -37,10 +38,16 @@ type FSContext struct {
 	// destroyed.
 	root *fs.Dirent
 
+	// rootVFS2 is the filesystem root.
+	rootVFS2 vfs.VirtualDentry
+
 	// cwd is the current working directory. Will be nil iff the FSContext
 	// has been destroyed.
 	cwd *fs.Dirent
 
+	// cwdVFS2 is the current working directory.
+	cwdVFS2 vfs.VirtualDentry
+
 	// umask is the current file mode creation mask. When a thread using this
 	// context invokes a syscall that creates a file, bits set in umask are
 	// removed from the permissions that the file is created with.
@@ -60,6 +67,19 @@ func newFSContext(root, cwd *fs.Dirent, umask uint) *FSContext {
 	return &f
 }
 
+// NewFSContextVFS2 returns a new filesystem context.
+func NewFSContextVFS2(root, cwd vfs.VirtualDentry, umask uint) *FSContext {
+	root.IncRef()
+	cwd.IncRef()
+	f := FSContext{
+		rootVFS2: root,
+		cwdVFS2:  cwd,
+		umask:    umask,
+	}
+	f.EnableLeakCheck("kernel.FSContext")
+	return &f
+}
+
 // destroy is the destructor for an FSContext.
 //
 // This will call DecRef on both root and cwd Dirents.  If either call to
@@ -75,11 +95,17 @@ func (f *FSContext) destroy() {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 
-	f.root.DecRef()
-	f.root = nil
-
-	f.cwd.DecRef()
-	f.cwd = nil
+	if VFS2Enabled {
+		f.rootVFS2.DecRef()
+		f.rootVFS2 = vfs.VirtualDentry{}
+		f.cwdVFS2.DecRef()
+		f.cwdVFS2 = vfs.VirtualDentry{}
+	} else {
+		f.root.DecRef()
+		f.root = nil
+		f.cwd.DecRef()
+		f.cwd = nil
+	}
 }
 
 // DecRef implements RefCounter.DecRef with destructor f.destroy.
@@ -93,12 +119,21 @@ func (f *FSContext) DecRef() {
 func (f *FSContext) Fork() *FSContext {
 	f.mu.Lock()
 	defer f.mu.Unlock()
-	f.cwd.IncRef()
-	f.root.IncRef()
+
+	if VFS2Enabled {
+		f.cwdVFS2.IncRef()
+		f.rootVFS2.IncRef()
+	} else {
+		f.cwd.IncRef()
+		f.root.IncRef()
+	}
+
 	return &FSContext{
-		cwd:   f.cwd,
-		root:  f.root,
-		umask: f.umask,
+		cwd:      f.cwd,
+		root:     f.root,
+		cwdVFS2:  f.cwdVFS2,
+		rootVFS2: f.rootVFS2,
+		umask:    f.umask,
 	}
 }
 
@@ -109,12 +144,23 @@ func (f *FSContext) Fork() *FSContext {
 func (f *FSContext) WorkingDirectory() *fs.Dirent {
 	f.mu.Lock()
 	defer f.mu.Unlock()
-	if f.cwd != nil {
-		f.cwd.IncRef()
-	}
+
+	f.cwd.IncRef()
 	return f.cwd
 }
 
+// WorkingDirectoryVFS2 returns the current working directory.
+//
+// This will return nil if called after destroy(), otherwise it will return a
+// Dirent with a reference taken.
+func (f *FSContext) WorkingDirectoryVFS2() vfs.VirtualDentry {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	f.cwdVFS2.IncRef()
+	return f.cwdVFS2
+}
+
 // SetWorkingDirectory sets the current working directory.
 // This will take an extra reference on the Dirent.
 //
@@ -137,6 +183,20 @@ func (f *FSContext) SetWorkingDirectory(d *fs.Dirent) {
 	old.DecRef()
 }
 
+// SetWorkingDirectoryVFS2 sets the current working directory.
+// This will take an extra reference on the VirtualDentry.
+//
+// This is not a valid call after destroy.
+func (f *FSContext) SetWorkingDirectoryVFS2(d vfs.VirtualDentry) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	old := f.cwdVFS2
+	f.cwdVFS2 = d
+	d.IncRef()
+	old.DecRef()
+}
+
 // RootDirectory returns the current filesystem root.
 //
 // This will return nil if called after destroy(), otherwise it will return a
@@ -150,6 +210,18 @@ func (f *FSContext) RootDirectory() *fs.Dirent {
 	return f.root
 }
 
+// RootDirectoryVFS2 returns the current filesystem root.
+//
+// This will return nil if called after destroy(), otherwise it will return a
+// Dirent with a reference taken.
+func (f *FSContext) RootDirectoryVFS2() vfs.VirtualDentry {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	f.rootVFS2.IncRef()
+	return f.rootVFS2
+}
+
 // SetRootDirectory sets the root directory.
 // This will take an extra reference on the Dirent.
 //
diff --git a/pkg/sentry/kernel/kernel.go b/pkg/sentry/kernel/kernel.go
index 3ee760ba2..2665f057c 100644
--- a/pkg/sentry/kernel/kernel.go
+++ b/pkg/sentry/kernel/kernel.go
@@ -43,11 +43,13 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/cpuid"
 	"gvisor.dev/gvisor/pkg/eventchannel"
+	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/refs"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/timerfd"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/hostcpu"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
@@ -71,6 +73,10 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
+// VFS2Enabled is set to true when VFS2 is enabled. Added as a global for allow
+// easy access everywhere. To be removed once VFS2 becomes the default.
+var VFS2Enabled = false
+
 // Kernel represents an emulated Linux kernel. It must be initialized by calling
 // Init() or LoadFrom().
 //
@@ -238,6 +244,9 @@ type Kernel struct {
 
 	// SpecialOpts contains special kernel options.
 	SpecialOpts
+
+	// VFS keeps the filesystem state used across the kernel.
+	VFS *vfs.VirtualFilesystem
 }
 
 // InitKernelArgs holds arguments to Init.
@@ -624,7 +633,7 @@ type CreateProcessArgs struct {
 	// File is a passed host FD pointing to a file to load as the init binary.
 	//
 	// This is checked if and only if Filename is "".
-	File *fs.File
+	File fsbridge.File
 
 	// Argvv is a list of arguments.
 	Argv []string
@@ -673,6 +682,13 @@ type CreateProcessArgs struct {
 	// increment it).
 	MountNamespace *fs.MountNamespace
 
+	// MountNamespaceVFS2 optionally contains the mount namespace for this
+	// process. If nil, the init process's mount namespace is used.
+	//
+	// Anyone setting MountNamespaceVFS2 must donate a reference (i.e.
+	// increment it).
+	MountNamespaceVFS2 *vfs.MountNamespace
+
 	// ContainerID is the container that the process belongs to.
 	ContainerID string
 }
@@ -711,11 +727,22 @@ func (ctx *createProcessContext) Value(key interface{}) interface{} {
 		return ctx.args.Credentials
 	case fs.CtxRoot:
 		if ctx.args.MountNamespace != nil {
-			// MountNamespace.Root() will take a reference on the root
-			// dirent for us.
+			// MountNamespace.Root() will take a reference on the root dirent for us.
 			return ctx.args.MountNamespace.Root()
 		}
 		return nil
+	case vfs.CtxRoot:
+		if ctx.args.MountNamespaceVFS2 == nil {
+			return nil
+		}
+		// MountNamespaceVFS2.Root() takes a reference on the root dirent for us.
+		return ctx.args.MountNamespaceVFS2.Root()
+	case vfs.CtxMountNamespace:
+		if ctx.k.globalInit == nil {
+			return nil
+		}
+		// MountNamespaceVFS2 takes a reference for us.
+		return ctx.k.GlobalInit().Leader().MountNamespaceVFS2()
 	case fs.CtxDirentCacheLimiter:
 		return ctx.k.DirentCacheLimiter
 	case ktime.CtxRealtimeClock:
@@ -757,34 +784,77 @@ func (k *Kernel) CreateProcess(args CreateProcessArgs) (*ThreadGroup, ThreadID,
 	defer k.extMu.Unlock()
 	log.Infof("EXEC: %v", args.Argv)
 
-	// Grab the mount namespace.
-	mounts := args.MountNamespace
-	if mounts == nil {
-		mounts = k.GlobalInit().Leader().MountNamespace()
-		mounts.IncRef()
-	}
-
-	tg := k.NewThreadGroup(mounts, args.PIDNamespace, NewSignalHandlers(), linux.SIGCHLD, args.Limits)
 	ctx := args.NewContext(k)
 
-	// Get the root directory from the MountNamespace.
-	root := mounts.Root()
-	// The call to newFSContext below will take a reference on root, so we
-	// don't need to hold this one.
-	defer root.DecRef()
-
-	// Grab the working directory.
-	remainingTraversals := uint(args.MaxSymlinkTraversals)
-	wd := root // Default.
-	if args.WorkingDirectory != "" {
-		var err error
-		wd, err = mounts.FindInode(ctx, root, nil, args.WorkingDirectory, &remainingTraversals)
-		if err != nil {
-			return nil, 0, fmt.Errorf("failed to find initial working directory %q: %v", args.WorkingDirectory, err)
+	var (
+		opener    fsbridge.Lookup
+		fsContext *FSContext
+		mntns     *fs.MountNamespace
+	)
+
+	if VFS2Enabled {
+		mntnsVFS2 := args.MountNamespaceVFS2
+		if mntnsVFS2 == nil {
+			// MountNamespaceVFS2 adds a reference to the namespace, which is
+			// transferred to the new process.
+			mntnsVFS2 = k.GlobalInit().Leader().MountNamespaceVFS2()
+		}
+		// Get the root directory from the MountNamespace.
+		root := args.MountNamespaceVFS2.Root()
+		// The call to newFSContext below will take a reference on root, so we
+		// don't need to hold this one.
+		defer root.DecRef()
+
+		// Grab the working directory.
+		wd := root // Default.
+		if args.WorkingDirectory != "" {
+			pop := vfs.PathOperation{
+				Root:               root,
+				Start:              wd,
+				Path:               fspath.Parse(args.WorkingDirectory),
+				FollowFinalSymlink: true,
+			}
+			var err error
+			wd, err = k.VFS.GetDentryAt(ctx, args.Credentials, &pop, &vfs.GetDentryOptions{
+				CheckSearchable: true,
+			})
+			if err != nil {
+				return nil, 0, fmt.Errorf("failed to find initial working directory %q: %v", args.WorkingDirectory, err)
+			}
+			defer wd.DecRef()
+		}
+		opener = fsbridge.NewVFSLookup(mntnsVFS2, root, wd)
+		fsContext = NewFSContextVFS2(root, wd, args.Umask)
+
+	} else {
+		mntns = args.MountNamespace
+		if mntns == nil {
+			mntns = k.GlobalInit().Leader().MountNamespace()
+			mntns.IncRef()
 		}
-		defer wd.DecRef()
+		// Get the root directory from the MountNamespace.
+		root := mntns.Root()
+		// The call to newFSContext below will take a reference on root, so we
+		// don't need to hold this one.
+		defer root.DecRef()
+
+		// Grab the working directory.
+		remainingTraversals := args.MaxSymlinkTraversals
+		wd := root // Default.
+		if args.WorkingDirectory != "" {
+			var err error
+			wd, err = mntns.FindInode(ctx, root, nil, args.WorkingDirectory, &remainingTraversals)
+			if err != nil {
+				return nil, 0, fmt.Errorf("failed to find initial working directory %q: %v", args.WorkingDirectory, err)
+			}
+			defer wd.DecRef()
+		}
+		opener = fsbridge.NewFSLookup(mntns, root, wd)
+		fsContext = newFSContext(root, wd, args.Umask)
 	}
 
+	tg := k.NewThreadGroup(mntns, args.PIDNamespace, NewSignalHandlers(), linux.SIGCHLD, args.Limits)
+
 	// Check which file to start from.
 	switch {
 	case args.Filename != "":
@@ -805,11 +875,9 @@ func (k *Kernel) CreateProcess(args CreateProcessArgs) (*ThreadGroup, ThreadID,
 	}
 
 	// Create a fresh task context.
-	remainingTraversals = uint(args.MaxSymlinkTraversals)
+	remainingTraversals := args.MaxSymlinkTraversals
 	loadArgs := loader.LoadArgs{
-		Mounts:              mounts,
-		Root:                root,
-		WorkingDirectory:    wd,
+		Opener:              opener,
 		RemainingTraversals: &remainingTraversals,
 		ResolveFinal:        true,
 		Filename:            args.Filename,
@@ -834,13 +902,14 @@ func (k *Kernel) CreateProcess(args CreateProcessArgs) (*ThreadGroup, ThreadID,
 		Kernel:                  k,
 		ThreadGroup:             tg,
 		TaskContext:             tc,
-		FSContext:               newFSContext(root, wd, args.Umask),
+		FSContext:               fsContext,
 		FDTable:                 args.FDTable,
 		Credentials:             args.Credentials,
 		AllowedCPUMask:          sched.NewFullCPUSet(k.applicationCores),
 		UTSNamespace:            args.UTSNamespace,
 		IPCNamespace:            args.IPCNamespace,
 		AbstractSocketNamespace: args.AbstractSocketNamespace,
+		MountNamespaceVFS2:      args.MountNamespaceVFS2,
 		ContainerID:             args.ContainerID,
 	}
 	t, err := k.tasks.NewTask(config)
@@ -1378,6 +1447,20 @@ func (ctx supervisorContext) Value(key interface{}) interface{} {
 			return ctx.k.globalInit.mounts.Root()
 		}
 		return nil
+	case vfs.CtxRoot:
+		if ctx.k.globalInit == nil {
+			return vfs.VirtualDentry{}
+		}
+		mntns := ctx.k.GlobalInit().Leader().MountNamespaceVFS2()
+		defer mntns.DecRef()
+		// Root() takes a reference on the root dirent for us.
+		return mntns.Root()
+	case vfs.CtxMountNamespace:
+		if ctx.k.globalInit == nil {
+			return nil
+		}
+		// MountNamespaceVFS2() takes a reference for us.
+		return ctx.k.GlobalInit().Leader().MountNamespaceVFS2()
 	case fs.CtxDirentCacheLimiter:
 		return ctx.k.DirentCacheLimiter
 	case ktime.CtxRealtimeClock:
diff --git a/pkg/sentry/kernel/kernel_state_autogen.go b/pkg/sentry/kernel/kernel_state_autogen.go
index a98912420..edbaf9db8 100755
--- a/pkg/sentry/kernel/kernel_state_autogen.go
+++ b/pkg/sentry/kernel/kernel_state_autogen.go
@@ -90,7 +90,9 @@ func (x *FSContext) save(m state.Map) {
 	x.beforeSave()
 	m.Save("AtomicRefCount", &x.AtomicRefCount)
 	m.Save("root", &x.root)
+	m.Save("rootVFS2", &x.rootVFS2)
 	m.Save("cwd", &x.cwd)
+	m.Save("cwdVFS2", &x.cwdVFS2)
 	m.Save("umask", &x.umask)
 }
 
@@ -98,7 +100,9 @@ func (x *FSContext) afterLoad() {}
 func (x *FSContext) load(m state.Map) {
 	m.Load("AtomicRefCount", &x.AtomicRefCount)
 	m.Load("root", &x.root)
+	m.Load("rootVFS2", &x.rootVFS2)
 	m.Load("cwd", &x.cwd)
+	m.Load("cwdVFS2", &x.cwdVFS2)
 	m.Load("umask", &x.umask)
 }
 
@@ -152,6 +156,7 @@ func (x *Kernel) save(m state.Map) {
 	m.Save("nextSocketEntry", &x.nextSocketEntry)
 	m.Save("DirentCacheLimiter", &x.DirentCacheLimiter)
 	m.Save("SpecialOpts", &x.SpecialOpts)
+	m.Save("VFS", &x.VFS)
 }
 
 func (x *Kernel) afterLoad() {}
@@ -184,6 +189,7 @@ func (x *Kernel) load(m state.Map) {
 	m.Load("nextSocketEntry", &x.nextSocketEntry)
 	m.Load("DirentCacheLimiter", &x.DirentCacheLimiter)
 	m.Load("SpecialOpts", &x.SpecialOpts)
+	m.Load("VFS", &x.VFS)
 	m.LoadValue("danglingEndpoints", new([]tcpip.Endpoint), func(y interface{}) { x.loadDanglingEndpoints(y.([]tcpip.Endpoint)) })
 	m.LoadValue("deviceRegistry", new(*device.Registry), func(y interface{}) { x.loadDeviceRegistry(y.(*device.Registry)) })
 }
@@ -573,6 +579,7 @@ func (x *Task) save(m state.Map) {
 	m.Save("utsns", &x.utsns)
 	m.Save("ipcns", &x.ipcns)
 	m.Save("abstractSockets", &x.abstractSockets)
+	m.Save("mountNamespaceVFS2", &x.mountNamespaceVFS2)
 	m.Save("parentDeathSignal", &x.parentDeathSignal)
 	m.Save("cleartid", &x.cleartid)
 	m.Save("allowedCPUMask", &x.allowedCPUMask)
@@ -631,6 +638,7 @@ func (x *Task) load(m state.Map) {
 	m.Load("utsns", &x.utsns)
 	m.Load("ipcns", &x.ipcns)
 	m.Load("abstractSockets", &x.abstractSockets)
+	m.Load("mountNamespaceVFS2", &x.mountNamespaceVFS2)
 	m.Load("parentDeathSignal", &x.parentDeathSignal)
 	m.Load("cleartid", &x.cleartid)
 	m.Load("allowedCPUMask", &x.allowedCPUMask)
diff --git a/pkg/sentry/kernel/task.go b/pkg/sentry/kernel/task.go
index 981e8c7fe..a3443ff21 100644
--- a/pkg/sentry/kernel/task.go
+++ b/pkg/sentry/kernel/task.go
@@ -424,6 +424,11 @@ type Task struct {
 	// abstractSockets is protected by mu.
 	abstractSockets *AbstractSocketNamespace
 
+	// mountNamespaceVFS2 is the task's mount namespace.
+	//
+	// It is protected by mu. It is owned by the task goroutine.
+	mountNamespaceVFS2 *vfs.MountNamespace
+
 	// parentDeathSignal is sent to this task's thread group when its parent exits.
 	//
 	// parentDeathSignal is protected by mu.
@@ -638,6 +643,11 @@ func (t *Task) Value(key interface{}) interface{} {
 		return int32(t.ThreadGroup().ID())
 	case fs.CtxRoot:
 		return t.fsContext.RootDirectory()
+	case vfs.CtxRoot:
+		return t.fsContext.RootDirectoryVFS2()
+	case vfs.CtxMountNamespace:
+		t.mountNamespaceVFS2.IncRef()
+		return t.mountNamespaceVFS2
 	case fs.CtxDirentCacheLimiter:
 		return t.k.DirentCacheLimiter
 	case inet.CtxStack:
@@ -701,6 +711,14 @@ func (t *Task) SyscallRestartBlock() SyscallRestartBlock {
 // Preconditions: The caller must be running on the task goroutine, or t.mu
 // must be locked.
 func (t *Task) IsChrooted() bool {
+	if VFS2Enabled {
+		realRoot := t.mountNamespaceVFS2.Root()
+		defer realRoot.DecRef()
+		root := t.fsContext.RootDirectoryVFS2()
+		defer root.DecRef()
+		return root != realRoot
+	}
+
 	realRoot := t.tg.mounts.Root()
 	defer realRoot.DecRef()
 	root := t.fsContext.RootDirectory()
@@ -796,6 +814,15 @@ func (t *Task) MountNamespace() *fs.MountNamespace {
 	return t.tg.mounts
 }
 
+// MountNamespaceVFS2 returns t's MountNamespace. A reference is taken on the
+// returned mount namespace.
+func (t *Task) MountNamespaceVFS2() *vfs.MountNamespace {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+	t.mountNamespaceVFS2.IncRef()
+	return t.mountNamespaceVFS2
+}
+
 // AbstractSockets returns t's AbstractSocketNamespace.
 func (t *Task) AbstractSockets() *AbstractSocketNamespace {
 	return t.abstractSockets
diff --git a/pkg/sentry/kernel/task_clone.go b/pkg/sentry/kernel/task_clone.go
index 53d4d211b..ba74b4c1c 100644
--- a/pkg/sentry/kernel/task_clone.go
+++ b/pkg/sentry/kernel/task_clone.go
@@ -199,6 +199,12 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
 		ipcns = NewIPCNamespace(userns)
 	}
 
+	// TODO(b/63601033): Implement CLONE_NEWNS.
+	mntnsVFS2 := t.mountNamespaceVFS2
+	if mntnsVFS2 != nil {
+		mntnsVFS2.IncRef()
+	}
+
 	tc, err := t.tc.Fork(t, t.k, !opts.NewAddressSpace)
 	if err != nil {
 		return 0, nil, err
@@ -241,7 +247,9 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
 	rseqAddr := usermem.Addr(0)
 	rseqSignature := uint32(0)
 	if opts.NewThreadGroup {
-		tg.mounts.IncRef()
+		if tg.mounts != nil {
+			tg.mounts.IncRef()
+		}
 		sh := t.tg.signalHandlers
 		if opts.NewSignalHandlers {
 			sh = sh.Fork()
@@ -265,6 +273,7 @@ func (t *Task) Clone(opts *CloneOptions) (ThreadID, *SyscallControl, error) {
 		UTSNamespace:            utsns,
 		IPCNamespace:            ipcns,
 		AbstractSocketNamespace: t.abstractSockets,
+		MountNamespaceVFS2:      mntnsVFS2,
 		RSeqAddr:                rseqAddr,
 		RSeqSignature:           rseqSignature,
 		ContainerID:             t.ContainerID(),
diff --git a/pkg/sentry/kernel/task_context.go b/pkg/sentry/kernel/task_context.go
index 2d6e7733c..2be982684 100644
--- a/pkg/sentry/kernel/task_context.go
+++ b/pkg/sentry/kernel/task_context.go
@@ -136,7 +136,7 @@ func (t *Task) Stack() *arch.Stack {
 func (k *Kernel) LoadTaskImage(ctx context.Context, args loader.LoadArgs) (*TaskContext, *syserr.Error) {
 	// If File is not nil, we should load that instead of resolving Filename.
 	if args.File != nil {
-		args.Filename = args.File.MappedName(ctx)
+		args.Filename = args.File.PathnameWithDeleted(ctx)
 	}
 
 	// Prepare a new user address space to load into.
diff --git a/pkg/sentry/kernel/task_exit.go b/pkg/sentry/kernel/task_exit.go
index 435761e5a..c4ade6e8e 100644
--- a/pkg/sentry/kernel/task_exit.go
+++ b/pkg/sentry/kernel/task_exit.go
@@ -269,6 +269,13 @@ func (*runExitMain) execute(t *Task) taskRunState {
 	t.fsContext.DecRef()
 	t.fdTable.DecRef()
 
+	t.mu.Lock()
+	if t.mountNamespaceVFS2 != nil {
+		t.mountNamespaceVFS2.DecRef()
+		t.mountNamespaceVFS2 = nil
+	}
+	t.mu.Unlock()
+
 	// If this is the last task to exit from the thread group, release the
 	// thread group's resources.
 	if lastExiter {
diff --git a/pkg/sentry/kernel/task_log.go b/pkg/sentry/kernel/task_log.go
index 41259210c..6d737d3e5 100644
--- a/pkg/sentry/kernel/task_log.go
+++ b/pkg/sentry/kernel/task_log.go
@@ -198,18 +198,11 @@ func (t *Task) traceExecEvent(tc *TaskContext) {
 	if !trace.IsEnabled() {
 		return
 	}
-	d := tc.MemoryManager.Executable()
-	if d == nil {
+	file := tc.MemoryManager.Executable()
+	if file == nil {
 		trace.Logf(t.traceContext, traceCategory, "exec: << unknown >>")
 		return
 	}
-	defer d.DecRef()
-	root := t.fsContext.RootDirectory()
-	if root == nil {
-		trace.Logf(t.traceContext, traceCategory, "exec: << no root directory >>")
-		return
-	}
-	defer root.DecRef()
-	n, _ := d.FullName(root)
-	trace.Logf(t.traceContext, traceCategory, "exec: %s", n)
+	defer file.DecRef()
+	trace.Logf(t.traceContext, traceCategory, "exec: %s", file.PathnameWithDeleted(t))
 }
diff --git a/pkg/sentry/kernel/task_start.go b/pkg/sentry/kernel/task_start.go
index de838beef..f9236a842 100644
--- a/pkg/sentry/kernel/task_start.go
+++ b/pkg/sentry/kernel/task_start.go
@@ -21,6 +21,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/futex"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/sched"
 	"gvisor.dev/gvisor/pkg/sentry/usage"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
@@ -80,6 +81,9 @@ type TaskConfig struct {
 	// AbstractSocketNamespace is the AbstractSocketNamespace of the new task.
 	AbstractSocketNamespace *AbstractSocketNamespace
 
+	// MountNamespaceVFS2 is the MountNamespace of the new task.
+	MountNamespaceVFS2 *vfs.MountNamespace
+
 	// RSeqAddr is a pointer to the the userspace linux.RSeq structure.
 	RSeqAddr usermem.Addr
 
@@ -116,28 +120,29 @@ func (ts *TaskSet) newTask(cfg *TaskConfig) (*Task, error) {
 			parent:   cfg.Parent,
 			children: make(map[*Task]struct{}),
 		},
-		runState:        (*runApp)(nil),
-		interruptChan:   make(chan struct{}, 1),
-		signalMask:      cfg.SignalMask,
-		signalStack:     arch.SignalStack{Flags: arch.SignalStackFlagDisable},
-		tc:              *tc,
-		fsContext:       cfg.FSContext,
-		fdTable:         cfg.FDTable,
-		p:               cfg.Kernel.Platform.NewContext(),
-		k:               cfg.Kernel,
-		ptraceTracees:   make(map[*Task]struct{}),
-		allowedCPUMask:  cfg.AllowedCPUMask.Copy(),
-		ioUsage:         &usage.IO{},
-		niceness:        cfg.Niceness,
-		netns:           cfg.NetworkNamespaced,
-		utsns:           cfg.UTSNamespace,
-		ipcns:           cfg.IPCNamespace,
-		abstractSockets: cfg.AbstractSocketNamespace,
-		rseqCPU:         -1,
-		rseqAddr:        cfg.RSeqAddr,
-		rseqSignature:   cfg.RSeqSignature,
-		futexWaiter:     futex.NewWaiter(),
-		containerID:     cfg.ContainerID,
+		runState:           (*runApp)(nil),
+		interruptChan:      make(chan struct{}, 1),
+		signalMask:         cfg.SignalMask,
+		signalStack:        arch.SignalStack{Flags: arch.SignalStackFlagDisable},
+		tc:                 *tc,
+		fsContext:          cfg.FSContext,
+		fdTable:            cfg.FDTable,
+		p:                  cfg.Kernel.Platform.NewContext(),
+		k:                  cfg.Kernel,
+		ptraceTracees:      make(map[*Task]struct{}),
+		allowedCPUMask:     cfg.AllowedCPUMask.Copy(),
+		ioUsage:            &usage.IO{},
+		niceness:           cfg.Niceness,
+		netns:              cfg.NetworkNamespaced,
+		utsns:              cfg.UTSNamespace,
+		ipcns:              cfg.IPCNamespace,
+		abstractSockets:    cfg.AbstractSocketNamespace,
+		mountNamespaceVFS2: cfg.MountNamespaceVFS2,
+		rseqCPU:            -1,
+		rseqAddr:           cfg.RSeqAddr,
+		rseqSignature:      cfg.RSeqSignature,
+		futexWaiter:        futex.NewWaiter(),
+		containerID:        cfg.ContainerID,
 	}
 	t.creds.Store(cfg.Credentials)
 	t.endStopCond.L = &t.tg.signalHandlers.mu
diff --git a/pkg/sentry/kernel/thread_group.go b/pkg/sentry/kernel/thread_group.go
index 768e958d2..268f62e9d 100644
--- a/pkg/sentry/kernel/thread_group.go
+++ b/pkg/sentry/kernel/thread_group.go
@@ -256,7 +256,7 @@ type ThreadGroup struct {
 	tty *TTY
 }
 
-// NewThreadGroup returns a new, empty thread group in PID namespace ns. The
+// NewThreadGroup returns a new, empty thread group in PID namespace pidns. The
 // thread group leader will send its parent terminationSignal when it exits.
 // The new thread group isn't visible to the system until a task has been
 // created inside of it by a successful call to TaskSet.NewTask.
@@ -317,7 +317,9 @@ func (tg *ThreadGroup) release() {
 	for _, it := range its {
 		it.DestroyTimer()
 	}
-	tg.mounts.DecRef()
+	if tg.mounts != nil {
+		tg.mounts.DecRef()
+	}
 }
 
 // forEachChildThreadGroupLocked indicates over all child ThreadGroups.
diff --git a/pkg/sentry/loader/elf.go b/pkg/sentry/loader/elf.go
index 122ed05c2..616fafa2c 100644
--- a/pkg/sentry/loader/elf.go
+++ b/pkg/sentry/loader/elf.go
@@ -27,7 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/cpuid"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/limits"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
@@ -97,11 +97,11 @@ type elfInfo struct {
 // accepts from the ELF, and it doesn't parse unnecessary parts of the file.
 //
 // ctx may be nil if f does not need it.
-func parseHeader(ctx context.Context, f *fs.File) (elfInfo, error) {
+func parseHeader(ctx context.Context, f fsbridge.File) (elfInfo, error) {
 	// Check ident first; it will tell us the endianness of the rest of the
 	// structs.
 	var ident [elf.EI_NIDENT]byte
-	_, err := readFull(ctx, f, usermem.BytesIOSequence(ident[:]), 0)
+	_, err := f.ReadFull(ctx, usermem.BytesIOSequence(ident[:]), 0)
 	if err != nil {
 		log.Infof("Error reading ELF ident: %v", err)
 		// The entire ident array always exists.
@@ -137,7 +137,7 @@ func parseHeader(ctx context.Context, f *fs.File) (elfInfo, error) {
 
 	var hdr elf.Header64
 	hdrBuf := make([]byte, header64Size)
-	_, err = readFull(ctx, f, usermem.BytesIOSequence(hdrBuf), 0)
+	_, err = f.ReadFull(ctx, usermem.BytesIOSequence(hdrBuf), 0)
 	if err != nil {
 		log.Infof("Error reading ELF header: %v", err)
 		// The entire header always exists.
@@ -187,7 +187,7 @@ func parseHeader(ctx context.Context, f *fs.File) (elfInfo, error) {
 	}
 
 	phdrBuf := make([]byte, totalPhdrSize)
-	_, err = readFull(ctx, f, usermem.BytesIOSequence(phdrBuf), int64(hdr.Phoff))
+	_, err = f.ReadFull(ctx, usermem.BytesIOSequence(phdrBuf), int64(hdr.Phoff))
 	if err != nil {
 		log.Infof("Error reading ELF phdrs: %v", err)
 		// If phdrs were specified, they should all exist.
@@ -227,7 +227,7 @@ func parseHeader(ctx context.Context, f *fs.File) (elfInfo, error) {
 
 // mapSegment maps a phdr into the Task. offset is the offset to apply to
 // phdr.Vaddr.
-func mapSegment(ctx context.Context, m *mm.MemoryManager, f *fs.File, phdr *elf.ProgHeader, offset usermem.Addr) error {
+func mapSegment(ctx context.Context, m *mm.MemoryManager, f fsbridge.File, phdr *elf.ProgHeader, offset usermem.Addr) error {
 	// We must make a page-aligned mapping.
 	adjust := usermem.Addr(phdr.Vaddr).PageOffset()
 
@@ -395,7 +395,7 @@ type loadedELF struct {
 //
 // Preconditions:
 //  * f is an ELF file
-func loadParsedELF(ctx context.Context, m *mm.MemoryManager, f *fs.File, info elfInfo, sharedLoadOffset usermem.Addr) (loadedELF, error) {
+func loadParsedELF(ctx context.Context, m *mm.MemoryManager, f fsbridge.File, info elfInfo, sharedLoadOffset usermem.Addr) (loadedELF, error) {
 	first := true
 	var start, end usermem.Addr
 	var interpreter string
@@ -431,7 +431,7 @@ func loadParsedELF(ctx context.Context, m *mm.MemoryManager, f *fs.File, info el
 			}
 
 			path := make([]byte, phdr.Filesz)
-			_, err := readFull(ctx, f, usermem.BytesIOSequence(path), int64(phdr.Off))
+			_, err := f.ReadFull(ctx, usermem.BytesIOSequence(path), int64(phdr.Off))
 			if err != nil {
 				// If an interpreter was specified, it should exist.
 				ctx.Infof("Error reading PT_INTERP path: %v", err)
@@ -564,7 +564,7 @@ func loadParsedELF(ctx context.Context, m *mm.MemoryManager, f *fs.File, info el
 // Preconditions:
 //  * f is an ELF file
 //  * f is the first ELF loaded into m
-func loadInitialELF(ctx context.Context, m *mm.MemoryManager, fs *cpuid.FeatureSet, f *fs.File) (loadedELF, arch.Context, error) {
+func loadInitialELF(ctx context.Context, m *mm.MemoryManager, fs *cpuid.FeatureSet, f fsbridge.File) (loadedELF, arch.Context, error) {
 	info, err := parseHeader(ctx, f)
 	if err != nil {
 		ctx.Infof("Failed to parse initial ELF: %v", err)
@@ -602,7 +602,7 @@ func loadInitialELF(ctx context.Context, m *mm.MemoryManager, fs *cpuid.FeatureS
 //
 // Preconditions:
 //  * f is an ELF file
-func loadInterpreterELF(ctx context.Context, m *mm.MemoryManager, f *fs.File, initial loadedELF) (loadedELF, error) {
+func loadInterpreterELF(ctx context.Context, m *mm.MemoryManager, f fsbridge.File, initial loadedELF) (loadedELF, error) {
 	info, err := parseHeader(ctx, f)
 	if err != nil {
 		if err == syserror.ENOEXEC {
@@ -649,16 +649,14 @@ func loadELF(ctx context.Context, args LoadArgs) (loadedELF, arch.Context, error
 		// Refresh the traversal limit.
 		*args.RemainingTraversals = linux.MaxSymlinkTraversals
 		args.Filename = bin.interpreter
-		d, i, err := openPath(ctx, args)
+		intFile, err := openPath(ctx, args)
 		if err != nil {
 			ctx.Infof("Error opening interpreter %s: %v", bin.interpreter, err)
 			return loadedELF{}, nil, err
 		}
-		defer i.DecRef()
-		// We don't need the Dirent.
-		d.DecRef()
+		defer intFile.DecRef()
 
-		interp, err = loadInterpreterELF(ctx, args.MemoryManager, i, bin)
+		interp, err = loadInterpreterELF(ctx, args.MemoryManager, intFile, bin)
 		if err != nil {
 			ctx.Infof("Error loading interpreter: %v", err)
 			return loadedELF{}, nil, err
diff --git a/pkg/sentry/loader/interpreter.go b/pkg/sentry/loader/interpreter.go
index 098a45d36..3886b4d33 100644
--- a/pkg/sentry/loader/interpreter.go
+++ b/pkg/sentry/loader/interpreter.go
@@ -19,7 +19,7 @@ import (
 	"io"
 
 	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
@@ -37,9 +37,9 @@ const (
 )
 
 // parseInterpreterScript returns the interpreter path and argv.
-func parseInterpreterScript(ctx context.Context, filename string, f *fs.File, argv []string) (newpath string, newargv []string, err error) {
+func parseInterpreterScript(ctx context.Context, filename string, f fsbridge.File, argv []string) (newpath string, newargv []string, err error) {
 	line := make([]byte, interpMaxLineLength)
-	n, err := readFull(ctx, f, usermem.BytesIOSequence(line), 0)
+	n, err := f.ReadFull(ctx, usermem.BytesIOSequence(line), 0)
 	// Short read is OK.
 	if err != nil && err != io.ErrUnexpectedEOF {
 		if err == io.EOF {
diff --git a/pkg/sentry/loader/loader.go b/pkg/sentry/loader/loader.go
index 9a613d6b7..d6675b8f0 100644
--- a/pkg/sentry/loader/loader.go
+++ b/pkg/sentry/loader/loader.go
@@ -20,7 +20,6 @@ import (
 	"fmt"
 	"io"
 	"path"
-	"strings"
 
 	"gvisor.dev/gvisor/pkg/abi"
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -29,8 +28,10 @@ import (
 	"gvisor.dev/gvisor/pkg/rand"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -41,16 +42,6 @@ type LoadArgs struct {
 	// MemoryManager is the memory manager to load the executable into.
 	MemoryManager *mm.MemoryManager
 
-	// Mounts is the mount namespace in which to look up Filename.
-	Mounts *fs.MountNamespace
-
-	// Root is the root directory under which to look up Filename.
-	Root *fs.Dirent
-
-	// WorkingDirectory is the working directory under which to look up
-	// Filename.
-	WorkingDirectory *fs.Dirent
-
 	// RemainingTraversals is the maximum number of symlinks to follow to
 	// resolve Filename. This counter is passed by reference to keep it
 	// updated throughout the call stack.
@@ -65,7 +56,12 @@ type LoadArgs struct {
 
 	// File is an open fs.File object of the executable. If File is not
 	// nil, then File will be loaded and Filename will be ignored.
-	File *fs.File
+	//
+	// The caller is responsible for checking that the user can execute this file.
+	File fsbridge.File
+
+	// Opener is used to open the executable file when 'File' is nil.
+	Opener fsbridge.Lookup
 
 	// CloseOnExec indicates that the executable (or one of its parent
 	// directories) was opened with O_CLOEXEC. If the executable is an
@@ -106,103 +102,32 @@ func readFull(ctx context.Context, f *fs.File, dst usermem.IOSequence, offset in
 // installed in the Task FDTable. The caller takes ownership of both.
 //
 // args.Filename must be a readable, executable, regular file.
-func openPath(ctx context.Context, args LoadArgs) (*fs.Dirent, *fs.File, error) {
+func openPath(ctx context.Context, args LoadArgs) (fsbridge.File, error) {
 	if args.Filename == "" {
 		ctx.Infof("cannot open empty name")
-		return nil, nil, syserror.ENOENT
-	}
-
-	var d *fs.Dirent
-	var err error
-	if args.ResolveFinal {
-		d, err = args.Mounts.FindInode(ctx, args.Root, args.WorkingDirectory, args.Filename, args.RemainingTraversals)
-	} else {
-		d, err = args.Mounts.FindLink(ctx, args.Root, args.WorkingDirectory, args.Filename, args.RemainingTraversals)
-	}
-	if err != nil {
-		return nil, nil, err
-	}
-	// Defer a DecRef for the sake of failure cases.
-	defer d.DecRef()
-
-	if !args.ResolveFinal && fs.IsSymlink(d.Inode.StableAttr) {
-		return nil, nil, syserror.ELOOP
-	}
-
-	if err := checkPermission(ctx, d); err != nil {
-		return nil, nil, err
-	}
-
-	// If they claim it's a directory, then make sure.
-	//
-	// N.B. we reject directories below, but we must first reject
-	// non-directories passed as directories.
-	if strings.HasSuffix(args.Filename, "/") && !fs.IsDir(d.Inode.StableAttr) {
-		return nil, nil, syserror.ENOTDIR
-	}
-
-	if err := checkIsRegularFile(ctx, d, args.Filename); err != nil {
-		return nil, nil, err
-	}
-
-	f, err := d.Inode.GetFile(ctx, d, fs.FileFlags{Read: true})
-	if err != nil {
-		return nil, nil, err
-	}
-	// Defer a DecRef for the sake of failure cases.
-	defer f.DecRef()
-
-	if err := checkPread(ctx, f, args.Filename); err != nil {
-		return nil, nil, err
-	}
-
-	d.IncRef()
-	f.IncRef()
-	return d, f, err
-}
-
-// checkFile performs checks on a file to be executed.
-func checkFile(ctx context.Context, f *fs.File, filename string) error {
-	if err := checkPermission(ctx, f.Dirent); err != nil {
-		return err
-	}
-
-	if err := checkIsRegularFile(ctx, f.Dirent, filename); err != nil {
-		return err
+		return nil, syserror.ENOENT
 	}
 
-	return checkPread(ctx, f, filename)
-}
-
-// checkPermission checks whether the file is readable and executable.
-func checkPermission(ctx context.Context, d *fs.Dirent) error {
-	perms := fs.PermMask{
-		// TODO(gvisor.dev/issue/160): Linux requires only execute
-		// permission, not read. However, our backing filesystems may
-		// prevent us from reading the file without read permission.
-		//
-		// Additionally, a task with a non-readable executable has
-		// additional constraints on access via ptrace and procfs.
-		Read:    true,
-		Execute: true,
+	// TODO(gvisor.dev/issue/160): Linux requires only execute permission,
+	// not read. However, our backing filesystems may prevent us from reading
+	// the file without read permission. Additionally, a task with a
+	// non-readable executable has additional constraints on access via
+	// ptrace and procfs.
+	opts := vfs.OpenOptions{
+		Flags:    linux.O_RDONLY,
+		FileExec: true,
 	}
-	return d.Inode.CheckPermission(ctx, perms)
+	return args.Opener.OpenPath(ctx, args.Filename, opts, args.RemainingTraversals, args.ResolveFinal)
 }
 
 // checkIsRegularFile prevents us from trying to execute a directory, pipe, etc.
-func checkIsRegularFile(ctx context.Context, d *fs.Dirent, filename string) error {
-	attr := d.Inode.StableAttr
-	if !fs.IsRegular(attr) {
-		ctx.Infof("%s is not regular: %v", filename, attr)
-		return syserror.EACCES
+func checkIsRegularFile(ctx context.Context, file fsbridge.File, filename string) error {
+	t, err := file.Type(ctx)
+	if err != nil {
+		return err
 	}
-	return nil
-}
-
-// checkPread checks whether we can read the file at arbitrary offsets.
-func checkPread(ctx context.Context, f *fs.File, filename string) error {
-	if !f.Flags().Pread {
-		ctx.Infof("%s cannot be read at an offset: %+v", filename, f.Flags())
+	if t != linux.ModeRegular {
+		ctx.Infof("%q is not a regular file: %v", filename, t)
 		return syserror.EACCES
 	}
 	return nil
@@ -224,8 +149,10 @@ const (
 	maxLoaderAttempts = 6
 )
 
-// loadExecutable loads an executable that is pointed to by args.File. If nil,
-// the path args.Filename is resolved and loaded. If the executable is an
+// loadExecutable loads an executable that is pointed to by args.File. The
+// caller is responsible for checking that the user can execute this file.
+// If nil, the path args.Filename is resolved and loaded (check that the user
+// can execute this file is done here in this case). If the executable is an
 // interpreter script rather than an ELF, the binary of the corresponding
 // interpreter will be loaded.
 //
@@ -234,37 +161,27 @@ const (
 //  * arch.Context matching the binary arch
 //  * fs.Dirent of the binary file
 //  * Possibly updated args.Argv
-func loadExecutable(ctx context.Context, args LoadArgs) (loadedELF, arch.Context, *fs.Dirent, []string, error) {
+func loadExecutable(ctx context.Context, args LoadArgs) (loadedELF, arch.Context, fsbridge.File, []string, error) {
 	for i := 0; i < maxLoaderAttempts; i++ {
-		var (
-			d   *fs.Dirent
-			err error
-		)
 		if args.File == nil {
-			d, args.File, err = openPath(ctx, args)
-			// We will return d in the successful case, but defer a DecRef for the
-			// sake of intermediate loops and failure cases.
-			if d != nil {
-				defer d.DecRef()
-			}
-			if args.File != nil {
-				defer args.File.DecRef()
+			var err error
+			args.File, err = openPath(ctx, args)
+			if err != nil {
+				ctx.Infof("Error opening %s: %v", args.Filename, err)
+				return loadedELF{}, nil, nil, nil, err
 			}
+			// Ensure file is release in case the code loops or errors out.
+			defer args.File.DecRef()
 		} else {
-			d = args.File.Dirent
-			d.IncRef()
-			defer d.DecRef()
-			err = checkFile(ctx, args.File, args.Filename)
-		}
-		if err != nil {
-			ctx.Infof("Error opening %s: %v", args.Filename, err)
-			return loadedELF{}, nil, nil, nil, err
+			if err := checkIsRegularFile(ctx, args.File, args.Filename); err != nil {
+				return loadedELF{}, nil, nil, nil, err
+			}
 		}
 
 		// Check the header. Is this an ELF or interpreter script?
 		var hdr [4]uint8
 		// N.B. We assume that reading from a regular file cannot block.
-		_, err = readFull(ctx, args.File, usermem.BytesIOSequence(hdr[:]), 0)
+		_, err := args.File.ReadFull(ctx, usermem.BytesIOSequence(hdr[:]), 0)
 		// Allow unexpected EOF, as a valid executable could be only three bytes
 		// (e.g., #!a).
 		if err != nil && err != io.ErrUnexpectedEOF {
@@ -281,9 +198,10 @@ func loadExecutable(ctx context.Context, args LoadArgs) (loadedELF, arch.Context
 				ctx.Infof("Error loading ELF: %v", err)
 				return loadedELF{}, nil, nil, nil, err
 			}
-			// An ELF is always terminal. Hold on to d.
-			d.IncRef()
-			return loaded, ac, d, args.Argv, err
+			// An ELF is always terminal. Hold on to file.
+			args.File.IncRef()
+			return loaded, ac, args.File, args.Argv, err
+
 		case bytes.Equal(hdr[:2], []byte(interpreterScriptMagic)):
 			if args.CloseOnExec {
 				return loadedELF{}, nil, nil, nil, syserror.ENOENT
@@ -295,6 +213,7 @@ func loadExecutable(ctx context.Context, args LoadArgs) (loadedELF, arch.Context
 			}
 			// Refresh the traversal limit for the interpreter.
 			*args.RemainingTraversals = linux.MaxSymlinkTraversals
+
 		default:
 			ctx.Infof("Unknown magic: %v", hdr)
 			return loadedELF{}, nil, nil, nil, syserror.ENOEXEC
@@ -317,11 +236,11 @@ func loadExecutable(ctx context.Context, args LoadArgs) (loadedELF, arch.Context
 //  * Load is called on the Task goroutine.
 func Load(ctx context.Context, args LoadArgs, extraAuxv []arch.AuxEntry, vdso *VDSO) (abi.OS, arch.Context, string, *syserr.Error) {
 	// Load the executable itself.
-	loaded, ac, d, newArgv, err := loadExecutable(ctx, args)
+	loaded, ac, file, newArgv, err := loadExecutable(ctx, args)
 	if err != nil {
 		return 0, nil, "", syserr.NewDynamic(fmt.Sprintf("Failed to load %s: %v", args.Filename, err), syserr.FromError(err).ToLinux())
 	}
-	defer d.DecRef()
+	defer file.DecRef()
 
 	// Load the VDSO.
 	vdsoAddr, err := loadVDSO(ctx, args.MemoryManager, vdso, loaded)
@@ -390,7 +309,7 @@ func Load(ctx context.Context, args LoadArgs, extraAuxv []arch.AuxEntry, vdso *V
 	m.SetEnvvStart(sl.EnvvStart)
 	m.SetEnvvEnd(sl.EnvvEnd)
 	m.SetAuxv(auxv)
-	m.SetExecutable(d)
+	m.SetExecutable(file)
 
 	ac.SetIP(uintptr(loaded.entry))
 	ac.SetStack(uintptr(stack.Bottom))
diff --git a/pkg/sentry/loader/vdso.go b/pkg/sentry/loader/vdso.go
index 52f446ed7..161b28c2c 100644
--- a/pkg/sentry/loader/vdso.go
+++ b/pkg/sentry/loader/vdso.go
@@ -27,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/anon"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
@@ -69,6 +70,8 @@ type byteReader struct {
 var _ fs.FileOperations = (*byteReader)(nil)
 
 // newByteReaderFile creates a fake file to read data from.
+//
+// TODO(gvisor.dev/issue/1623): Convert to VFS2.
 func newByteReaderFile(ctx context.Context, data []byte) *fs.File {
 	// Create a fake inode.
 	inode := fs.NewInode(
@@ -123,7 +126,7 @@ func (b *byteReader) Write(ctx context.Context, file *fs.File, src usermem.IOSeq
 // * PT_LOAD segments don't extend beyond the end of the file.
 //
 // ctx may be nil if f does not need it.
-func validateVDSO(ctx context.Context, f *fs.File, size uint64) (elfInfo, error) {
+func validateVDSO(ctx context.Context, f fsbridge.File, size uint64) (elfInfo, error) {
 	info, err := parseHeader(ctx, f)
 	if err != nil {
 		log.Infof("Unable to parse VDSO header: %v", err)
@@ -221,7 +224,7 @@ type VDSO struct {
 // PrepareVDSO validates the system VDSO and returns a VDSO, containing the
 // param page for updating by the kernel.
 func PrepareVDSO(ctx context.Context, mfp pgalloc.MemoryFileProvider) (*VDSO, error) {
-	vdsoFile := newByteReaderFile(ctx, vdsoBin)
+	vdsoFile := fsbridge.NewFSFile(newByteReaderFile(ctx, vdsoBin))
 
 	// First make sure the VDSO is valid. vdsoFile does not use ctx, so a
 	// nil context can be passed.
diff --git a/pkg/sentry/mm/metadata.go b/pkg/sentry/mm/metadata.go
index f550acae0..6a49334f4 100644
--- a/pkg/sentry/mm/metadata.go
+++ b/pkg/sentry/mm/metadata.go
@@ -16,7 +16,7 @@ package mm
 
 import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -132,7 +132,7 @@ func (mm *MemoryManager) SetAuxv(auxv arch.Auxv) {
 //
 // An additional reference will be taken in the case of a non-nil executable,
 // which must be released by the caller.
-func (mm *MemoryManager) Executable() *fs.Dirent {
+func (mm *MemoryManager) Executable() fsbridge.File {
 	mm.metadataMu.Lock()
 	defer mm.metadataMu.Unlock()
 
@@ -147,15 +147,15 @@ func (mm *MemoryManager) Executable() *fs.Dirent {
 // SetExecutable sets the executable.
 //
 // This takes a reference on d.
-func (mm *MemoryManager) SetExecutable(d *fs.Dirent) {
+func (mm *MemoryManager) SetExecutable(file fsbridge.File) {
 	mm.metadataMu.Lock()
 
 	// Grab a new reference.
-	d.IncRef()
+	file.IncRef()
 
 	// Set the executable.
 	orig := mm.executable
-	mm.executable = d
+	mm.executable = file
 
 	mm.metadataMu.Unlock()
 
diff --git a/pkg/sentry/mm/mm.go b/pkg/sentry/mm/mm.go
index 09e582dd3..637383c7a 100644
--- a/pkg/sentry/mm/mm.go
+++ b/pkg/sentry/mm/mm.go
@@ -37,7 +37,7 @@ package mm
 import (
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
-	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
 	"gvisor.dev/gvisor/pkg/sentry/platform"
@@ -215,7 +215,7 @@ type MemoryManager struct {
 	// is not nil, it holds a reference on the Dirent.
 	//
 	// executable is protected by metadataMu.
-	executable *fs.Dirent
+	executable fsbridge.File
 
 	// dumpability describes if and how this MemoryManager may be dumped to
 	// userspace.
diff --git a/pkg/sentry/strace/strace.go b/pkg/sentry/strace/strace.go
index a796b2396..46cb2a1cc 100644
--- a/pkg/sentry/strace/strace.go
+++ b/pkg/sentry/strace/strace.go
@@ -141,6 +141,10 @@ func path(t *kernel.Task, addr usermem.Addr) string {
 }
 
 func fd(t *kernel.Task, fd int32) string {
+	if kernel.VFS2Enabled {
+		return fdVFS2(t, fd)
+	}
+
 	root := t.FSContext().RootDirectory()
 	if root != nil {
 		defer root.DecRef()
@@ -169,6 +173,30 @@ func fd(t *kernel.Task, fd int32) string {
 	return fmt.Sprintf("%#x %s", fd, name)
 }
 
+func fdVFS2(t *kernel.Task, fd int32) string {
+	root := t.FSContext().RootDirectoryVFS2()
+	defer root.DecRef()
+
+	vfsObj := root.Mount().Filesystem().VirtualFilesystem()
+	if fd == linux.AT_FDCWD {
+		wd := t.FSContext().WorkingDirectoryVFS2()
+		defer wd.DecRef()
+
+		name, _ := vfsObj.PathnameWithDeleted(t, root, wd)
+		return fmt.Sprintf("AT_FDCWD %s", name)
+	}
+
+	file := t.GetFileVFS2(fd)
+	if file == nil {
+		// Cast FD to uint64 to avoid printing negative hex.
+		return fmt.Sprintf("%#x (bad FD)", uint64(fd))
+	}
+	defer file.DecRef()
+
+	name, _ := vfsObj.PathnameWithDeleted(t, root, file.VirtualDentry())
+	return fmt.Sprintf("%#x %s", fd, name)
+}
+
 func fdpair(t *kernel.Task, addr usermem.Addr) string {
 	var fds [2]int32
 	_, err := t.CopyIn(addr, &fds)
diff --git a/pkg/sentry/syscalls/linux/sys_prctl.go b/pkg/sentry/syscalls/linux/sys_prctl.go
index 98db32d77..9c6728530 100644
--- a/pkg/sentry/syscalls/linux/sys_prctl.go
+++ b/pkg/sentry/syscalls/linux/sys_prctl.go
@@ -20,6 +20,7 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/mm"
@@ -135,7 +136,7 @@ func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 			}
 
 			// Set the underlying executable.
-			t.MemoryManager().SetExecutable(file.Dirent)
+			t.MemoryManager().SetExecutable(fsbridge.NewFSFile(file))
 
 		case linux.PR_SET_MM_AUXV,
 			linux.PR_SET_MM_START_CODE,
diff --git a/pkg/sentry/syscalls/linux/sys_thread.go b/pkg/sentry/syscalls/linux/sys_thread.go
index 0c9e2255d..00915fdde 100644
--- a/pkg/sentry/syscalls/linux/sys_thread.go
+++ b/pkg/sentry/syscalls/linux/sys_thread.go
@@ -21,6 +21,7 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/sched"
 	"gvisor.dev/gvisor/pkg/sentry/loader"
@@ -119,7 +120,7 @@ func execveat(t *kernel.Task, dirFD int32, pathnameAddr, argvAddr, envvAddr user
 	defer root.DecRef()
 
 	var wd *fs.Dirent
-	var executable *fs.File
+	var executable fsbridge.File
 	var closeOnExec bool
 	if dirFD == linux.AT_FDCWD || path.IsAbs(pathname) {
 		// Even if the pathname is absolute, we may still need the wd
@@ -136,7 +137,15 @@ func execveat(t *kernel.Task, dirFD int32, pathnameAddr, argvAddr, envvAddr user
 		closeOnExec = fdFlags.CloseOnExec
 
 		if atEmptyPath && len(pathname) == 0 {
-			executable = f
+			// TODO(gvisor.dev/issue/160): Linux requires only execute permission,
+			// not read. However, our backing filesystems may prevent us from reading
+			// the file without read permission. Additionally, a task with a
+			// non-readable executable has additional constraints on access via
+			// ptrace and procfs.
+			if err := f.Dirent.Inode.CheckPermission(t, fs.PermMask{Read: true, Execute: true}); err != nil {
+				return 0, nil, err
+			}
+			executable = fsbridge.NewFSFile(f)
 		} else {
 			wd = f.Dirent
 			wd.IncRef()
@@ -152,9 +161,7 @@ func execveat(t *kernel.Task, dirFD int32, pathnameAddr, argvAddr, envvAddr user
 	// Load the new TaskContext.
 	remainingTraversals := uint(linux.MaxSymlinkTraversals)
 	loadArgs := loader.LoadArgs{
-		Mounts:              t.MountNamespace(),
-		Root:                root,
-		WorkingDirectory:    wd,
+		Opener:              fsbridge.NewFSLookup(t.MountNamespace(), root, wd),
 		RemainingTraversals: &remainingTraversals,
 		ResolveFinal:        resolveFinal,
 		Filename:            pathname,
diff --git a/pkg/sentry/syscalls/linux/vfs2/linux64_override_amd64.go b/pkg/sentry/syscalls/linux/vfs2/linux64_override_amd64.go
index c134714ee..e0ac32b33 100755
--- a/pkg/sentry/syscalls/linux/vfs2/linux64_override_amd64.go
+++ b/pkg/sentry/syscalls/linux/vfs2/linux64_override_amd64.go
@@ -22,4 +22,110 @@ import (
 // Override syscall table to add syscalls implementations from this package.
 func Override(table map[uintptr]kernel.Syscall) {
 	table[0] = syscalls.Supported("read", Read)
+
+	// Remove syscalls that haven't been converted yet. It's better to get ENOSYS
+	// rather than a SIGSEGV deep in the stack.
+	delete(table, 1)   // write
+	delete(table, 2)   // open
+	delete(table, 3)   // close
+	delete(table, 4)   // stat
+	delete(table, 5)   // fstat
+	delete(table, 6)   // lstat
+	delete(table, 7)   // poll
+	delete(table, 8)   // lseek
+	delete(table, 9)   // mmap
+	delete(table, 16)  // ioctl
+	delete(table, 17)  // pread64
+	delete(table, 18)  // pwrite64
+	delete(table, 19)  // readv
+	delete(table, 20)  // writev
+	delete(table, 21)  // access
+	delete(table, 22)  // pipe
+	delete(table, 32)  // dup
+	delete(table, 33)  // dup2
+	delete(table, 40)  // sendfile
+	delete(table, 59)  // execve
+	delete(table, 72)  // fcntl
+	delete(table, 73)  // flock
+	delete(table, 74)  // fsync
+	delete(table, 75)  // fdatasync
+	delete(table, 76)  // truncate
+	delete(table, 77)  // ftruncate
+	delete(table, 78)  // getdents
+	delete(table, 79)  // getcwd
+	delete(table, 80)  // chdir
+	delete(table, 81)  // fchdir
+	delete(table, 82)  // rename
+	delete(table, 83)  // mkdir
+	delete(table, 84)  // rmdir
+	delete(table, 85)  // creat
+	delete(table, 86)  // link
+	delete(table, 87)  // unlink
+	delete(table, 88)  // symlink
+	delete(table, 89)  // readlink
+	delete(table, 90)  // chmod
+	delete(table, 91)  // fchmod
+	delete(table, 92)  // chown
+	delete(table, 93)  // fchown
+	delete(table, 94)  // lchown
+	delete(table, 133) // mknod
+	delete(table, 137) // statfs
+	delete(table, 138) // fstatfs
+	delete(table, 161) // chroot
+	delete(table, 162) // sync
+	delete(table, 165) // mount
+	delete(table, 166) // umount2
+	delete(table, 172) // iopl
+	delete(table, 173) // ioperm
+	delete(table, 187) // readahead
+	delete(table, 188) // setxattr
+	delete(table, 189) // lsetxattr
+	delete(table, 190) // fsetxattr
+	delete(table, 191) // getxattr
+	delete(table, 192) // lgetxattr
+	delete(table, 193) // fgetxattr
+	delete(table, 206) // io_setup
+	delete(table, 207) // io_destroy
+	delete(table, 208) // io_getevents
+	delete(table, 209) // io_submit
+	delete(table, 210) // io_cancel
+	delete(table, 213) // epoll_create
+	delete(table, 214) // epoll_ctl_old
+	delete(table, 215) // epoll_wait_old
+	delete(table, 216) // remap_file_pages
+	delete(table, 217) // getdents64
+	delete(table, 232) // epoll_wait
+	delete(table, 233) // epoll_ctl
+	delete(table, 253) // inotify_init
+	delete(table, 254) // inotify_add_watch
+	delete(table, 255) // inotify_rm_watch
+	delete(table, 257) // openat
+	delete(table, 258) // mkdirat
+	delete(table, 259) // mknodat
+	delete(table, 260) // fchownat
+	delete(table, 261) // futimesat
+	delete(table, 262) // fstatat
+	delete(table, 263) // unlinkat
+	delete(table, 264) // renameat
+	delete(table, 265) // linkat
+	delete(table, 266) // symlinkat
+	delete(table, 267) // readlinkat
+	delete(table, 268) // fchmodat
+	delete(table, 269) // faccessat
+	delete(table, 270) // pselect
+	delete(table, 271) // ppoll
+	delete(table, 285) // fallocate
+	delete(table, 291) // epoll_create1
+	delete(table, 292) // dup3
+	delete(table, 293) // pipe2
+	delete(table, 294) // inotify_init1
+	delete(table, 295) // preadv
+	delete(table, 296) // pwritev
+	delete(table, 306) // syncfs
+	delete(table, 316) // renameat2
+	delete(table, 319) // memfd_create
+	delete(table, 322) // execveat
+	delete(table, 327) // preadv2
+	delete(table, 328) // pwritev2
+	delete(table, 332) // statx
 }
diff --git a/pkg/sentry/vfs/context.go b/pkg/sentry/vfs/context.go
index d97362b9a..82781e6d3 100755
--- a/pkg/sentry/vfs/context.go
+++ b/pkg/sentry/vfs/context.go
@@ -29,9 +29,10 @@ const (
 	CtxRoot
 )
 
-// MountNamespaceFromContext returns the MountNamespace used by ctx. It does
-// not take a reference on the returned MountNamespace. If ctx is not
-// associated with a MountNamespace, MountNamespaceFromContext returns nil.
+// MountNamespaceFromContext returns the MountNamespace used by ctx. If ctx is
+// not associated with a MountNamespace, MountNamespaceFromContext returns nil.
+//
+// A reference is taken on the returned MountNamespace.
 func MountNamespaceFromContext(ctx context.Context) *MountNamespace {
 	if v := ctx.Value(CtxMountNamespace); v != nil {
 		return v.(*MountNamespace)
diff --git a/pkg/sentry/vfs/mount.go b/pkg/sentry/vfs/mount.go
index 1fbb420f9..ad2c9fcf4 100755
--- a/pkg/sentry/vfs/mount.go
+++ b/pkg/sentry/vfs/mount.go
@@ -114,6 +114,7 @@ type MountNamespace struct {
 func (vfs *VirtualFilesystem) NewMountNamespace(ctx context.Context, creds *auth.Credentials, source, fsTypeName string, opts *GetFilesystemOptions) (*MountNamespace, error) {
 	rft := vfs.getFilesystemType(fsTypeName)
 	if rft == nil {
+		ctx.Warningf("Unknown filesystem: %s", fsTypeName)
 		return nil, syserror.ENODEV
 	}
 	fs, root, err := rft.fsType.GetFilesystem(ctx, vfs, creds, source, *opts)
@@ -231,9 +232,12 @@ func (vfs *VirtualFilesystem) UmountAt(ctx context.Context, creds *auth.Credenti
 		return syserror.EINVAL
 	}
 	vfs.mountMu.Lock()
-	if mntns := MountNamespaceFromContext(ctx); mntns != nil && mntns != vd.mount.ns {
-		vfs.mountMu.Unlock()
-		return syserror.EINVAL
+	if mntns := MountNamespaceFromContext(ctx); mntns != nil {
+		defer mntns.DecRef()
+		if mntns != vd.mount.ns {
+			vfs.mountMu.Unlock()
+			return syserror.EINVAL
+		}
 	}
 
 	// TODO(jamieliu): Linux special-cases umount of the caller's root, which
diff --git a/pkg/sentry/vfs/options.go b/pkg/sentry/vfs/options.go
index fdf8be157..6af7fdac1 100755
--- a/pkg/sentry/vfs/options.go
+++ b/pkg/sentry/vfs/options.go
@@ -61,7 +61,7 @@ type MountOptions struct {
 type OpenOptions struct {
 	// Flags contains access mode and flags as specified for open(2).
 	//
-	// FilesystemImpls is reponsible for implementing the following flags:
+	// FilesystemImpls are responsible for implementing the following flags:
 	// O_RDONLY, O_WRONLY, O_RDWR, O_APPEND, O_CREAT, O_DIRECT, O_DSYNC,
 	// O_EXCL, O_NOATIME, O_NOCTTY, O_NONBLOCK, O_PATH, O_SYNC, O_TMPFILE, and
 	// O_TRUNC. VFS is responsible for handling O_DIRECTORY, O_LARGEFILE, and
diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go
index 9629afee9..51deae313 100755
--- a/pkg/sentry/vfs/vfs.go
+++ b/pkg/sentry/vfs/vfs.go
@@ -393,7 +393,8 @@ func (vfs *VirtualFilesystem) OpenAt(ctx context.Context, creds *auth.Credential
 					// be executed.
 					return nil, syserror.EACCES
 				}
-				if linux.FileMode(stat.Mode).FileType() != linux.ModeRegular {
+				if t := linux.FileMode(stat.Mode).FileType(); t != linux.ModeRegular {
+					ctx.Infof("%q is not a regular file: %v", pop.Path, t)
 					return nil, syserror.EACCES
 				}
 			}
@@ -743,6 +744,8 @@ func (vfs *VirtualFilesystem) SyncAllFilesystems(ctx context.Context) error {
 // VirtualDentry methods require that a reference is held on the VirtualDentry.
 //
 // VirtualDentry is analogous to Linux's struct path.
+//
+// +stateify savable
 type VirtualDentry struct {
 	mount  *Mount
 	dentry *Dentry
diff --git a/pkg/sentry/vfs/vfs_state_autogen.go b/pkg/sentry/vfs/vfs_state_autogen.go
index ffcd2b90e..3f14d460c 100755
--- a/pkg/sentry/vfs/vfs_state_autogen.go
+++ b/pkg/sentry/vfs/vfs_state_autogen.go
@@ -35,7 +35,21 @@ func (x *epollInterestEntry) load(m state.Map) {
 	m.Load("prev", &x.prev)
 }
 
+func (x *VirtualDentry) beforeSave() {}
+func (x *VirtualDentry) save(m state.Map) {
+	x.beforeSave()
+	m.Save("mount", &x.mount)
+	m.Save("dentry", &x.dentry)
+}
+
+func (x *VirtualDentry) afterLoad() {}
+func (x *VirtualDentry) load(m state.Map) {
+	m.Load("mount", &x.mount)
+	m.Load("dentry", &x.dentry)
+}
+
 func init() {
 	state.Register("pkg/sentry/vfs.epollInterestList", (*epollInterestList)(nil), state.Fns{Save: (*epollInterestList).save, Load: (*epollInterestList).load})
 	state.Register("pkg/sentry/vfs.epollInterestEntry", (*epollInterestEntry)(nil), state.Fns{Save: (*epollInterestEntry).save, Load: (*epollInterestEntry).load})
+	state.Register("pkg/sentry/vfs.VirtualDentry", (*VirtualDentry)(nil), state.Fns{Save: (*VirtualDentry).save, Load: (*VirtualDentry).load})
 }
diff --git a/runsc/boot/loader.go b/runsc/boot/loader.go
index 9f0d5d7af..239ca5302 100644
--- a/runsc/boot/loader.go
+++ b/runsc/boot/loader.go
@@ -795,16 +795,19 @@ func (l *Loader) executeAsync(args *control.ExecArgs) (kernel.ThreadID, error) {
 		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) {
-		// task.MountNamespace() does not take a ref, so we must do so
-		// ourselves.
+		// task.MountNamespace() does not take a ref, so we must do so ourselves.
 		args.MountNamespace = t.MountNamespace()
 		args.MountNamespace.IncRef()
 	})
-	defer args.MountNamespace.DecRef()
+	if args.MountNamespace != nil {
+		defer args.MountNamespace.DecRef()
+	}
 
-	// Add the HOME enviroment varible if it is not already set.
+	// 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)