Merge 216da0b7 (automated)

7 files changed, 663 insertions, 0 deletions

diff --git a/pkg/sentry/fs/dev/dev.go b/pkg/sentry/fs/dev/dev.go
new file mode 100644
index 000000000..34ac01173
--- /dev/null
+++ b/pkg/sentry/fs/dev/dev.go
@@ -0,0 +1,146 @@
+// 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 dev provides a filesystem with simple devices.
+package dev
+
+import (
+	"math"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ashmem"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/binder"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/tmpfs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// Memory device numbers are from Linux's drivers/char/mem.c
+const (
+	// Mem device major.
+	memDevMajor uint16 = 1
+
+	// Mem device minors.
+	nullDevMinor    uint32 = 3
+	zeroDevMinor    uint32 = 5
+	fullDevMinor    uint32 = 7
+	randomDevMinor  uint32 = 8
+	urandomDevMinor uint32 = 9
+)
+
+func newCharacterDevice(iops fs.InodeOperations, msrc *fs.MountSource) *fs.Inode {
+	return fs.NewInode(iops, msrc, fs.StableAttr{
+		DeviceID:  devDevice.DeviceID(),
+		InodeID:   devDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.CharacterDevice,
+	})
+}
+
+func newMemDevice(iops fs.InodeOperations, msrc *fs.MountSource, minor uint32) *fs.Inode {
+	return fs.NewInode(iops, msrc, fs.StableAttr{
+		DeviceID:        devDevice.DeviceID(),
+		InodeID:         devDevice.NextIno(),
+		BlockSize:       usermem.PageSize,
+		Type:            fs.CharacterDevice,
+		DeviceFileMajor: memDevMajor,
+		DeviceFileMinor: minor,
+	})
+}
+
+func newDirectory(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	iops := ramfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0555))
+	return fs.NewInode(iops, msrc, fs.StableAttr{
+		DeviceID:  devDevice.DeviceID(),
+		InodeID:   devDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.Directory,
+	})
+}
+
+func newSymlink(ctx context.Context, target string, msrc *fs.MountSource) *fs.Inode {
+	iops := ramfs.NewSymlink(ctx, fs.RootOwner, target)
+	return fs.NewInode(iops, msrc, fs.StableAttr{
+		DeviceID:  devDevice.DeviceID(),
+		InodeID:   devDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.Symlink,
+	})
+}
+
+// New returns the root node of a device filesystem.
+func New(ctx context.Context, msrc *fs.MountSource, binderEnabled bool, ashmemEnabled bool) *fs.Inode {
+	contents := map[string]*fs.Inode{
+		"fd":     newSymlink(ctx, "/proc/self/fd", msrc),
+		"stdin":  newSymlink(ctx, "/proc/self/fd/0", msrc),
+		"stdout": newSymlink(ctx, "/proc/self/fd/1", msrc),
+		"stderr": newSymlink(ctx, "/proc/self/fd/2", msrc),
+
+		"null": newMemDevice(newNullDevice(ctx, fs.RootOwner, 0666), msrc, nullDevMinor),
+		"zero": newMemDevice(newZeroDevice(ctx, fs.RootOwner, 0666), msrc, zeroDevMinor),
+		"full": newMemDevice(newFullDevice(ctx, fs.RootOwner, 0666), msrc, fullDevMinor),
+
+		// This is not as good as /dev/random in linux because go
+		// runtime uses sys_random and /dev/urandom internally.
+		// According to 'man 4 random', this will be sufficient unless
+		// application uses this to generate long-lived GPG/SSL/SSH
+		// keys.
+		"random":  newMemDevice(newRandomDevice(ctx, fs.RootOwner, 0444), msrc, randomDevMinor),
+		"urandom": newMemDevice(newRandomDevice(ctx, fs.RootOwner, 0444), msrc, urandomDevMinor),
+
+		"shm": tmpfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0777), msrc),
+
+		// A devpts is typically mounted at /dev/pts to provide
+		// pseudoterminal support. Place an empty directory there for
+		// the devpts to be mounted over.
+		"pts": newDirectory(ctx, msrc),
+		// Similarly, applications expect a ptmx device at /dev/ptmx
+		// connected to the terminals provided by /dev/pts/. Rather
+		// than creating a device directly (which requires a hairy
+		// lookup on open to determine if a devpts exists), just create
+		// a symlink to the ptmx provided by devpts. (The Linux devpts
+		// documentation recommends this).
+		//
+		// If no devpts is mounted, this will simply be a dangling
+		// symlink, which is fine.
+		"ptmx": newSymlink(ctx, "pts/ptmx", msrc),
+	}
+
+	if binderEnabled {
+		binder := binder.NewDevice(ctx, fs.RootOwner, fs.FilePermsFromMode(0666))
+		contents["binder"] = newCharacterDevice(binder, msrc)
+	}
+
+	if ashmemEnabled {
+		ashmem := ashmem.NewDevice(ctx, fs.RootOwner, fs.FilePermsFromMode(0666))
+		contents["ashmem"] = newCharacterDevice(ashmem, msrc)
+	}
+
+	iops := ramfs.NewDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
+	return fs.NewInode(iops, msrc, fs.StableAttr{
+		DeviceID:  devDevice.DeviceID(),
+		InodeID:   devDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.Directory,
+	})
+}
+
+// readZeros implements fs.FileOperations.Read with infinite null bytes.
+type readZeros struct{}
+
+// Read implements fs.FileOperations.Read.
+func (*readZeros) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
+	return dst.ZeroOut(ctx, math.MaxInt64)
+}
diff --git a/pkg/sentry/fs/dev/dev_state_autogen.go b/pkg/sentry/fs/dev/dev_state_autogen.go
new file mode 100755
index 000000000..afe94ff86
--- /dev/null
+++ b/pkg/sentry/fs/dev/dev_state_autogen.go
@@ -0,0 +1,108 @@
+// automatically generated by stateify.
+
+package dev
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/state"
+)
+
+func (x *filesystem) beforeSave() {}
+func (x *filesystem) save(m state.Map) {
+	x.beforeSave()
+}
+
+func (x *filesystem) afterLoad() {}
+func (x *filesystem) load(m state.Map) {
+}
+
+func (x *fullDevice) beforeSave() {}
+func (x *fullDevice) save(m state.Map) {
+	x.beforeSave()
+	m.Save("InodeSimpleAttributes", &x.InodeSimpleAttributes)
+}
+
+func (x *fullDevice) afterLoad() {}
+func (x *fullDevice) load(m state.Map) {
+	m.Load("InodeSimpleAttributes", &x.InodeSimpleAttributes)
+}
+
+func (x *fullFileOperations) beforeSave() {}
+func (x *fullFileOperations) save(m state.Map) {
+	x.beforeSave()
+}
+
+func (x *fullFileOperations) afterLoad() {}
+func (x *fullFileOperations) load(m state.Map) {
+}
+
+func (x *nullDevice) beforeSave() {}
+func (x *nullDevice) save(m state.Map) {
+	x.beforeSave()
+	m.Save("InodeSimpleAttributes", &x.InodeSimpleAttributes)
+}
+
+func (x *nullDevice) afterLoad() {}
+func (x *nullDevice) load(m state.Map) {
+	m.Load("InodeSimpleAttributes", &x.InodeSimpleAttributes)
+}
+
+func (x *nullFileOperations) beforeSave() {}
+func (x *nullFileOperations) save(m state.Map) {
+	x.beforeSave()
+}
+
+func (x *nullFileOperations) afterLoad() {}
+func (x *nullFileOperations) load(m state.Map) {
+}
+
+func (x *zeroDevice) beforeSave() {}
+func (x *zeroDevice) save(m state.Map) {
+	x.beforeSave()
+	m.Save("nullDevice", &x.nullDevice)
+}
+
+func (x *zeroDevice) afterLoad() {}
+func (x *zeroDevice) load(m state.Map) {
+	m.Load("nullDevice", &x.nullDevice)
+}
+
+func (x *zeroFileOperations) beforeSave() {}
+func (x *zeroFileOperations) save(m state.Map) {
+	x.beforeSave()
+}
+
+func (x *zeroFileOperations) afterLoad() {}
+func (x *zeroFileOperations) load(m state.Map) {
+}
+
+func (x *randomDevice) beforeSave() {}
+func (x *randomDevice) save(m state.Map) {
+	x.beforeSave()
+	m.Save("InodeSimpleAttributes", &x.InodeSimpleAttributes)
+}
+
+func (x *randomDevice) afterLoad() {}
+func (x *randomDevice) load(m state.Map) {
+	m.Load("InodeSimpleAttributes", &x.InodeSimpleAttributes)
+}
+
+func (x *randomFileOperations) beforeSave() {}
+func (x *randomFileOperations) save(m state.Map) {
+	x.beforeSave()
+}
+
+func (x *randomFileOperations) afterLoad() {}
+func (x *randomFileOperations) load(m state.Map) {
+}
+
+func init() {
+	state.Register("dev.filesystem", (*filesystem)(nil), state.Fns{Save: (*filesystem).save, Load: (*filesystem).load})
+	state.Register("dev.fullDevice", (*fullDevice)(nil), state.Fns{Save: (*fullDevice).save, Load: (*fullDevice).load})
+	state.Register("dev.fullFileOperations", (*fullFileOperations)(nil), state.Fns{Save: (*fullFileOperations).save, Load: (*fullFileOperations).load})
+	state.Register("dev.nullDevice", (*nullDevice)(nil), state.Fns{Save: (*nullDevice).save, Load: (*nullDevice).load})
+	state.Register("dev.nullFileOperations", (*nullFileOperations)(nil), state.Fns{Save: (*nullFileOperations).save, Load: (*nullFileOperations).load})
+	state.Register("dev.zeroDevice", (*zeroDevice)(nil), state.Fns{Save: (*zeroDevice).save, Load: (*zeroDevice).load})
+	state.Register("dev.zeroFileOperations", (*zeroFileOperations)(nil), state.Fns{Save: (*zeroFileOperations).save, Load: (*zeroFileOperations).load})
+	state.Register("dev.randomDevice", (*randomDevice)(nil), state.Fns{Save: (*randomDevice).save, Load: (*randomDevice).load})
+	state.Register("dev.randomFileOperations", (*randomFileOperations)(nil), state.Fns{Save: (*randomFileOperations).save, Load: (*randomFileOperations).load})
+}
diff --git a/pkg/sentry/fs/dev/device.go b/pkg/sentry/fs/dev/device.go
new file mode 100644
index 000000000..9f4e41fc9
--- /dev/null
+++ b/pkg/sentry/fs/dev/device.go
@@ -0,0 +1,20 @@
+// 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 dev
+
+import "gvisor.googlesource.com/gvisor/pkg/sentry/device"
+
+// devDevice is the pseudo-filesystem device.
+var devDevice = device.NewAnonDevice()
diff --git a/pkg/sentry/fs/dev/fs.go b/pkg/sentry/fs/dev/fs.go
new file mode 100644
index 000000000..6096a40f8
--- /dev/null
+++ b/pkg/sentry/fs/dev/fs.go
@@ -0,0 +1,99 @@
+// 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 dev
+
+import (
+	"strconv"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// Optional key containing boolean flag which specifies if Android Binder IPC should be enabled.
+const binderEnabledKey = "binder_enabled"
+
+// Optional key containing boolean flag which specifies if Android ashmem should be enabled.
+const ashmemEnabledKey = "ashmem_enabled"
+
+// filesystem is a devtmpfs.
+//
+// +stateify savable
+type filesystem struct{}
+
+var _ fs.Filesystem = (*filesystem)(nil)
+
+func init() {
+	fs.RegisterFilesystem(&filesystem{})
+}
+
+// FilesystemName is the name underwhich the filesystem is registered.
+// Name matches drivers/base/devtmpfs.c:dev_fs_type.name.
+const FilesystemName = "devtmpfs"
+
+// Name is the name of the file system.
+func (*filesystem) Name() string {
+	return FilesystemName
+}
+
+// AllowUserMount allows users to mount(2) this file system.
+func (*filesystem) AllowUserMount() bool {
+	return true
+}
+
+// AllowUserList allows this filesystem to be listed in /proc/filesystems.
+func (*filesystem) AllowUserList() bool {
+	return true
+}
+
+// Flags returns that there is nothing special about this file system.
+//
+// In Linux, devtmpfs does the same thing.
+func (*filesystem) Flags() fs.FilesystemFlags {
+	return 0
+}
+
+// Mount returns a devtmpfs root that can be positioned in the vfs.
+func (f *filesystem) Mount(ctx context.Context, device string, flags fs.MountSourceFlags, data string, _ interface{}) (*fs.Inode, error) {
+	// device is always ignored.
+	// devtmpfs backed by ramfs ignores bad options. See fs/ramfs/inode.c:ramfs_parse_options.
+	//  -> we should consider parsing the mode and backing devtmpfs by this.
+
+	// Parse generic comma-separated key=value options.
+	options := fs.GenericMountSourceOptions(data)
+
+	// binerEnabledKey is optional and binder is disabled by default.
+	binderEnabled := false
+	if beStr, exists := options[binderEnabledKey]; exists {
+		var err error
+		binderEnabled, err = strconv.ParseBool(beStr)
+		if err != nil {
+			return nil, syserror.EINVAL
+		}
+	}
+
+	// ashmemEnabledKey is optional and ashmem is disabled by default.
+	ashmemEnabled := false
+	if aeStr, exists := options[ashmemEnabledKey]; exists {
+		var err error
+		ashmemEnabled, err = strconv.ParseBool(aeStr)
+		if err != nil {
+			return nil, syserror.EINVAL
+		}
+	}
+
+	// Construct the devtmpfs root.
+	return New(ctx, fs.NewNonCachingMountSource(f, flags), binderEnabled, ashmemEnabled), nil
+}
diff --git a/pkg/sentry/fs/dev/full.go b/pkg/sentry/fs/dev/full.go
new file mode 100644
index 000000000..8f6c6da2d
--- /dev/null
+++ b/pkg/sentry/fs/dev/full.go
@@ -0,0 +1,81 @@
+// 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 dev
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// fullDevice is used to implement /dev/full.
+//
+// +stateify savable
+type fullDevice struct {
+	fsutil.InodeGenericChecker       `state:"nosave"`
+	fsutil.InodeNoExtendedAttributes `state:"nosave"`
+	fsutil.InodeNoopAllocate         `state:"nosave"`
+	fsutil.InodeNoopRelease          `state:"nosave"`
+	fsutil.InodeNoopTruncate         `state:"nosave"`
+	fsutil.InodeNoopWriteOut         `state:"nosave"`
+	fsutil.InodeNotDirectory         `state:"nosave"`
+	fsutil.InodeNotMappable          `state:"nosave"`
+	fsutil.InodeNotSocket            `state:"nosave"`
+	fsutil.InodeNotSymlink           `state:"nosave"`
+	fsutil.InodeVirtual              `state:"nosave"`
+
+	fsutil.InodeSimpleAttributes
+}
+
+var _ fs.InodeOperations = (*fullDevice)(nil)
+
+func newFullDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *fullDevice {
+	f := &fullDevice{
+		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fs.FilePermsFromMode(mode), linux.TMPFS_MAGIC),
+	}
+	return f
+}
+
+// GetFile implements fs.InodeOperations.GetFile.
+func (f *fullDevice) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	flags.Pread = true
+	return fs.NewFile(ctx, dirent, flags, &fullFileOperations{}), nil
+}
+
+// +stateify savable
+type fullFileOperations struct {
+	waiter.AlwaysReady              `state:"nosave"`
+	fsutil.FileGenericSeek          `state:"nosave"`
+	fsutil.FileNoIoctl              `state:"nosave"`
+	fsutil.FileNoMMap               `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileNoopFsync            `state:"nosave"`
+	fsutil.FileNoopRelease          `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	readZeros                       `state:"nosave"`
+}
+
+var _ fs.FileOperations = (*fullFileOperations)(nil)
+
+// Write implements FileOperations.Write.
+func (*fullFileOperations) Write(context.Context, *fs.File, usermem.IOSequence, int64) (int64, error) {
+	return 0, syserror.ENOSPC
+}
diff --git a/pkg/sentry/fs/dev/null.go b/pkg/sentry/fs/dev/null.go
new file mode 100644
index 000000000..3f1accef8
--- /dev/null
+++ b/pkg/sentry/fs/dev/null.go
@@ -0,0 +1,130 @@
+// 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 dev
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/pgalloc"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// +stateify savable
+type nullDevice struct {
+	fsutil.InodeGenericChecker       `state:"nosave"`
+	fsutil.InodeNoExtendedAttributes `state:"nosave"`
+	fsutil.InodeNoopAllocate         `state:"nosave"`
+	fsutil.InodeNoopRelease          `state:"nosave"`
+	fsutil.InodeNoopTruncate         `state:"nosave"`
+	fsutil.InodeNoopWriteOut         `state:"nosave"`
+	fsutil.InodeNotDirectory         `state:"nosave"`
+	fsutil.InodeNotMappable          `state:"nosave"`
+	fsutil.InodeNotSocket            `state:"nosave"`
+	fsutil.InodeNotSymlink           `state:"nosave"`
+	fsutil.InodeVirtual              `state:"nosave"`
+
+	fsutil.InodeSimpleAttributes
+}
+
+var _ fs.InodeOperations = (*nullDevice)(nil)
+
+func newNullDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *nullDevice {
+	n := &nullDevice{
+		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fs.FilePermsFromMode(mode), linux.TMPFS_MAGIC),
+	}
+	return n
+}
+
+// GetFile implements fs.FileOperations.GetFile.
+func (n *nullDevice) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	flags.Pread = true
+	flags.Pwrite = true
+
+	return fs.NewFile(ctx, dirent, flags, &nullFileOperations{}), nil
+}
+
+// +stateify savable
+type nullFileOperations struct {
+	fsutil.FileGenericSeek          `state:"nosave"`
+	fsutil.FileNoIoctl              `state:"nosave"`
+	fsutil.FileNoMMap               `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileNoopFsync            `state:"nosave"`
+	fsutil.FileNoopRead             `state:"nosave"`
+	fsutil.FileNoopRelease          `state:"nosave"`
+	fsutil.FileNoopWrite            `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+	waiter.AlwaysReady              `state:"nosave"`
+}
+
+var _ fs.FileOperations = (*nullFileOperations)(nil)
+
+// +stateify savable
+type zeroDevice struct {
+	nullDevice
+}
+
+var _ fs.InodeOperations = (*zeroDevice)(nil)
+
+func newZeroDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *zeroDevice {
+	zd := &zeroDevice{
+		nullDevice: nullDevice{
+			InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fs.FilePermsFromMode(mode), linux.TMPFS_MAGIC),
+		},
+	}
+	return zd
+}
+
+// GetFile implements fs.FileOperations.GetFile.
+func (zd *zeroDevice) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	flags.Pread = true
+	flags.Pwrite = true
+
+	return fs.NewFile(ctx, dirent, flags, &zeroFileOperations{}), nil
+}
+
+// +stateify savable
+type zeroFileOperations struct {
+	fsutil.FileGenericSeek          `state:"nosave"`
+	fsutil.FileNoIoctl              `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileNoopFsync            `state:"nosave"`
+	fsutil.FileNoopRelease          `state:"nosave"`
+	fsutil.FileNoopWrite            `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+	waiter.AlwaysReady              `state:"nosave"`
+	readZeros                       `state:"nosave"`
+}
+
+var _ fs.FileOperations = (*zeroFileOperations)(nil)
+
+// ConfigureMMap implements fs.FileOperations.ConfigureMMap.
+func (*zeroFileOperations) ConfigureMMap(ctx context.Context, file *fs.File, opts *memmap.MMapOpts) error {
+	m, err := mm.NewSharedAnonMappable(opts.Length, pgalloc.MemoryFileProviderFromContext(ctx))
+	if err != nil {
+		return err
+	}
+	opts.MappingIdentity = m
+	opts.Mappable = m
+	return nil
+}
diff --git a/pkg/sentry/fs/dev/random.go b/pkg/sentry/fs/dev/random.go
new file mode 100644
index 000000000..e5a01a906
--- /dev/null
+++ b/pkg/sentry/fs/dev/random.go
@@ -0,0 +1,79 @@
+// 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 dev
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/rand"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// +stateify savable
+type randomDevice struct {
+	fsutil.InodeGenericChecker       `state:"nosave"`
+	fsutil.InodeNoExtendedAttributes `state:"nosave"`
+	fsutil.InodeNoopAllocate         `state:"nosave"`
+	fsutil.InodeNoopRelease          `state:"nosave"`
+	fsutil.InodeNoopTruncate         `state:"nosave"`
+	fsutil.InodeNoopWriteOut         `state:"nosave"`
+	fsutil.InodeNotDirectory         `state:"nosave"`
+	fsutil.InodeNotMappable          `state:"nosave"`
+	fsutil.InodeNotSocket            `state:"nosave"`
+	fsutil.InodeNotSymlink           `state:"nosave"`
+	fsutil.InodeVirtual              `state:"nosave"`
+
+	fsutil.InodeSimpleAttributes
+}
+
+var _ fs.InodeOperations = (*randomDevice)(nil)
+
+func newRandomDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *randomDevice {
+	r := &randomDevice{
+		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, owner, fs.FilePermsFromMode(mode), linux.TMPFS_MAGIC),
+	}
+	return r
+}
+
+// GetFile implements fs.InodeOperations.GetFile.
+func (*randomDevice) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	return fs.NewFile(ctx, dirent, flags, &randomFileOperations{}), nil
+}
+
+// +stateify savable
+type randomFileOperations struct {
+	fsutil.FileGenericSeek          `state:"nosave"`
+	fsutil.FileNoIoctl              `state:"nosave"`
+	fsutil.FileNoMMap               `state:"nosave"`
+	fsutil.FileNoSplice             `state:"nosave"`
+	fsutil.FileNoopFlush            `state:"nosave"`
+	fsutil.FileNoopFsync            `state:"nosave"`
+	fsutil.FileNoopRelease          `state:"nosave"`
+	fsutil.FileNoopWrite            `state:"nosave"`
+	fsutil.FileNotDirReaddir        `state:"nosave"`
+	fsutil.FileUseInodeUnstableAttr `state:"nosave"`
+	waiter.AlwaysReady              `state:"nosave"`
+}
+
+var _ fs.FileOperations = (*randomFileOperations)(nil)
+
+// Read implements fs.FileOperations.Read.
+func (*randomFileOperations) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, _ int64) (int64, error) {
+	return dst.CopyOutFrom(ctx, safemem.FromIOReader{rand.Reader})
+}