Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

7 files changed, 489 insertions, 0 deletions

diff --git a/pkg/sentry/fs/dev/BUILD b/pkg/sentry/fs/dev/BUILD
new file mode 100644
index 000000000..42049ecb5
--- /dev/null
+++ b/pkg/sentry/fs/dev/BUILD
@@ -0,0 +1,53 @@
+package(licenses = ["notice"])  # Apache 2.0
+
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("//tools/go_stateify:defs.bzl", "go_stateify")
+
+go_stateify(
+    name = "dev_state",
+    srcs = [
+        "dev.go",
+        "fs.go",
+        "full.go",
+        "null.go",
+        "random.go",
+    ],
+    out = "dev_state.go",
+    package = "dev",
+)
+
+go_library(
+    name = "dev",
+    srcs = [
+        "dev.go",
+        "dev_state.go",
+        "device.go",
+        "fs.go",
+        "full.go",
+        "null.go",
+        "random.go",
+    ],
+    importpath = "gvisor.googlesource.com/gvisor/pkg/sentry/fs/dev",
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/amutex",
+        "//pkg/log",
+        "//pkg/sentry/context",
+        "//pkg/sentry/device",
+        "//pkg/sentry/fs",
+        "//pkg/sentry/fs/ashmem",
+        "//pkg/sentry/fs/binder",
+        "//pkg/sentry/fs/fsutil",
+        "//pkg/sentry/fs/ramfs",
+        "//pkg/sentry/fs/tmpfs",
+        "//pkg/sentry/memmap",
+        "//pkg/sentry/mm",
+        "//pkg/sentry/platform",
+        "//pkg/sentry/safemem",
+        "//pkg/sentry/usage",
+        "//pkg/sentry/usermem",
+        "//pkg/state",
+        "//pkg/syserror",
+    ],
+)
diff --git a/pkg/sentry/fs/dev/dev.go b/pkg/sentry/fs/dev/dev.go
new file mode 100644
index 000000000..36c61bfc2
--- /dev/null
+++ b/pkg/sentry/fs/dev/dev.go
@@ -0,0 +1,122 @@
+// Copyright 2018 Google Inc.
+//
+// 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 (
+	"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/platform"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// Dev is the root node.
+type Dev struct {
+	ramfs.Dir
+}
+
+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 newDirectory(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	iops := &ramfs.Dir{}
+	iops.InitDir(ctx, map[string]*fs.Inode{}, 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.Symlink{}
+	iops.InitSymlink(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 {
+	d := &Dev{}
+
+	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": newCharacterDevice(newNullDevice(ctx, fs.RootOwner, 0666), msrc),
+		"zero": newCharacterDevice(newZeroDevice(ctx, fs.RootOwner, 0666), msrc),
+		"full": newCharacterDevice(newFullDevice(ctx, fs.RootOwner, 0666), msrc),
+
+		// 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":  newCharacterDevice(newRandomDevice(ctx, fs.RootOwner, 0444), msrc),
+		"urandom": newCharacterDevice(newRandomDevice(ctx, fs.RootOwner, 0444), msrc),
+
+		"shm": tmpfs.NewDir(ctx, nil, fs.RootOwner, fs.FilePermsFromMode(0777), msrc, platform.FromContext(ctx)),
+
+		// 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)
+	}
+
+	d.InitDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
+	return fs.NewInode(d, msrc, fs.StableAttr{
+		DeviceID:  devDevice.DeviceID(),
+		InodeID:   devDevice.NextIno(),
+		BlockSize: usermem.PageSize,
+		Type:      fs.Directory,
+	})
+}
diff --git a/pkg/sentry/fs/dev/device.go b/pkg/sentry/fs/dev/device.go
new file mode 100644
index 000000000..9d935e008
--- /dev/null
+++ b/pkg/sentry/fs/dev/device.go
@@ -0,0 +1,20 @@
+// Copyright 2018 Google Inc.
+//
+// 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..4945ac962
--- /dev/null
+++ b/pkg/sentry/fs/dev/fs.go
@@ -0,0 +1,90 @@
+// Copyright 2018 Google Inc.
+//
+// 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.
+type filesystem struct{}
+
+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
+}
+
+// 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) (*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..e13eb6c03
--- /dev/null
+++ b/pkg/sentry/fs/dev/full.go
@@ -0,0 +1,53 @@
+// Copyright 2018 Google Inc.
+//
+// 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 (
+	"math"
+
+	"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/ramfs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// fullDevice is used to implement /dev/full.
+type fullDevice struct {
+	ramfs.Entry
+}
+
+func newFullDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *fullDevice {
+	f := &fullDevice{}
+	f.InitEntry(ctx, owner, fs.FilePermsFromMode(mode))
+	return f
+}
+
+// DeprecatedPwritev implements fs.InodeOperations.DeprecatedPwritev by
+// returining ENOSPC.
+func (f *fullDevice) DeprecatedPwritev(_ context.Context, _ usermem.IOSequence, _ int64) (int64, error) {
+	return 0, syserror.ENOSPC
+}
+
+// DeprecatedPreadv implements fs.InodeOperations.DeprecatedPreadv.
+func (f *fullDevice) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, _ int64) (int64, error) {
+	return dst.ZeroOut(ctx, math.MaxInt64)
+}
+
+// Truncate should be simply ignored for character devices on linux.
+func (f *fullDevice) Truncate(context.Context, *fs.Inode, int64) error {
+	return nil
+}
diff --git a/pkg/sentry/fs/dev/null.go b/pkg/sentry/fs/dev/null.go
new file mode 100644
index 000000000..66b8ba967
--- /dev/null
+++ b/pkg/sentry/fs/dev/null.go
@@ -0,0 +1,96 @@
+// Copyright 2018 Google Inc.
+//
+// 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 (
+	"io"
+	"math"
+
+	"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/fs/ramfs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+type nullDevice struct {
+	ramfs.Entry
+}
+
+func newNullDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *nullDevice {
+	n := &nullDevice{}
+	n.InitEntry(ctx, owner, fs.FilePermsFromMode(mode))
+	return n
+}
+
+// DeprecatedPreadv reads data from the device.
+func (n *nullDevice) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
+	return 0, io.EOF
+}
+
+// DeprecatedPwritev discards writes.
+func (n *nullDevice) DeprecatedPwritev(_ context.Context, src usermem.IOSequence, offset int64) (int64, error) {
+	return src.NumBytes(), nil
+}
+
+// Truncate should be simply ignored for character devices on linux.
+func (n *nullDevice) Truncate(context.Context, *fs.Inode, int64) error {
+	return nil
+}
+
+type zeroDevice struct {
+	nullDevice
+}
+
+func newZeroDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *zeroDevice {
+	zd := &zeroDevice{}
+	zd.InitEntry(ctx, owner, fs.FilePermsFromMode(mode))
+	return zd
+}
+
+// DeprecatedPreadv implements fs.InodeOperations.DeprecatedPreadv.
+func (zd *zeroDevice) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
+	return dst.ZeroOut(ctx, math.MaxInt64)
+}
+
+// GetFile overrides ramfs.Entry.GetFile and returns a zeroFile instead.
+func (zd *zeroDevice) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
+	// Allow pread(2) and pwrite(2) on this file.
+	flags.Pread = true
+	flags.Pwrite = true
+
+	return fs.NewFile(ctx, dirent, flags, &zeroFileOperations{
+		FileOperations: &fsutil.Handle{HandleOperations: dirent.Inode.HandleOps()},
+	}), nil
+}
+
+type zeroFileOperations struct {
+	fs.FileOperations
+}
+
+// ConfigureMMap implements fs.FileOperations.ConfigureMMap.
+func (*zeroFileOperations) ConfigureMMap(ctx context.Context, file *fs.File, opts *memmap.MMapOpts) error {
+	m, err := mm.NewSharedAnonMappable(opts.Length, platform.FromContext(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..0402f9355
--- /dev/null
+++ b/pkg/sentry/fs/dev/random.go
@@ -0,0 +1,55 @@
+// Copyright 2018 Google Inc.
+//
+// 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 (
+	"crypto/rand"
+
+	"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/ramfs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+type randomDevice struct {
+	ramfs.Entry
+}
+
+func newRandomDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *randomDevice {
+	r := &randomDevice{}
+	r.InitEntry(ctx, owner, fs.FilePermsFromMode(mode))
+	return r
+}
+
+// DeprecatedPreadv reads random data.
+func (*randomDevice) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
+	return dst.CopyOutFrom(ctx, safemem.FromIOReader{rand.Reader})
+}
+
+// DeprecatedPwritev implements fs.HandleOperations.DeprecatedPwritev.
+func (*randomDevice) DeprecatedPwritev(ctx context.Context, src usermem.IOSequence, offset int64) (int64, error) {
+	// On Linux, "Writing to /dev/random or /dev/urandom will update the
+	// entropy pool with the data written, but this will not result in a higher
+	// entropy count" - random(4). We don't need to support this, but we do
+	// need to support the write, so just make it a no-op a la /dev/null.
+	return src.NumBytes(), nil
+}
+
+// Truncate should be simply ignored for character devices on linux.
+func (r *randomDevice) Truncate(context.Context, *fs.Inode, int64) error {
+	return nil
+}