Add support for mount propagation

Properly handle propagation options for root and mounts. Now usage of
mount options shared, rshared, and noexec cause error to start. shared/
rshared breaks sandbox=>host isolation. slave however can be supported
because changes propagate from host to sandbox.

Root FS setup moved inside the gofer. Apart from simplifying the code,
it keeps all mounts inside the namespace. And they are torn down when
the namespace is destroyed (DestroyFS is no longer needed).

PiperOrigin-RevId: 239037661
Change-Id: I8b5ee4d50da33c042ea34fa68e56514ebe20e6e0

1 files changed, 139 insertions, 0 deletions

diff --git a/runsc/specutils/fs.go b/runsc/specutils/fs.go
new file mode 100644
index 000000000..b812a5fbd
--- /dev/null
+++ b/runsc/specutils/fs.go
@@ -0,0 +1,139 @@
+// Copyright 2018 Google LLC
+//
+// 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 specutils
+
+import (
+	"fmt"
+	"path"
+	"syscall"
+
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+)
+
+type mapping struct {
+	set bool
+	val uint32
+}
+
+// optionsMap maps mount propagation-related OCI filesystem options to mount(2)
+// syscall flags.
+var optionsMap = map[string]mapping{
+	"acl":           {set: true, val: syscall.MS_POSIXACL},
+	"async":         {set: false, val: syscall.MS_SYNCHRONOUS},
+	"atime":         {set: false, val: syscall.MS_NOATIME},
+	"bind":          {set: true, val: syscall.MS_BIND},
+	"defaults":      {set: true, val: 0},
+	"dev":           {set: false, val: syscall.MS_NODEV},
+	"diratime":      {set: false, val: syscall.MS_NODIRATIME},
+	"dirsync":       {set: true, val: syscall.MS_DIRSYNC},
+	"exec":          {set: false, val: syscall.MS_NOEXEC},
+	"iversion":      {set: true, val: syscall.MS_I_VERSION},
+	"loud":          {set: false, val: syscall.MS_SILENT},
+	"mand":          {set: true, val: syscall.MS_MANDLOCK},
+	"noacl":         {set: false, val: syscall.MS_POSIXACL},
+	"noatime":       {set: true, val: syscall.MS_NOATIME},
+	"nodev":         {set: true, val: syscall.MS_NODEV},
+	"nodiratime":    {set: true, val: syscall.MS_NODIRATIME},
+	"noiversion":    {set: false, val: syscall.MS_I_VERSION},
+	"nomand":        {set: false, val: syscall.MS_MANDLOCK},
+	"norelatime":    {set: false, val: syscall.MS_RELATIME},
+	"nostrictatime": {set: false, val: syscall.MS_STRICTATIME},
+	"nosuid":        {set: true, val: syscall.MS_NOSUID},
+	"rbind":         {set: true, val: syscall.MS_BIND | syscall.MS_REC},
+	"relatime":      {set: true, val: syscall.MS_RELATIME},
+	"remount":       {set: true, val: syscall.MS_REMOUNT},
+	"ro":            {set: true, val: syscall.MS_RDONLY},
+	"rw":            {set: false, val: syscall.MS_RDONLY},
+	"silent":        {set: true, val: syscall.MS_SILENT},
+	"strictatime":   {set: true, val: syscall.MS_STRICTATIME},
+	"suid":          {set: false, val: syscall.MS_NOSUID},
+	"sync":          {set: true, val: syscall.MS_SYNCHRONOUS},
+}
+
+// propOptionsMap is similar to optionsMap, but it lists propagation options
+// that cannot be used together with other flags.
+var propOptionsMap = map[string]mapping{
+	"private":     {set: true, val: syscall.MS_PRIVATE},
+	"rprivate":    {set: true, val: syscall.MS_PRIVATE | syscall.MS_REC},
+	"slave":       {set: true, val: syscall.MS_SLAVE},
+	"rslave":      {set: true, val: syscall.MS_SLAVE | syscall.MS_REC},
+	"unbindable":  {set: true, val: syscall.MS_UNBINDABLE},
+	"runbindable": {set: true, val: syscall.MS_UNBINDABLE | syscall.MS_REC},
+}
+
+// invalidOptions list options not allowed.
+//   - shared: sandbox must be isolated from the host. Propagating mount changes
+//     from the sandbox to the host breaks the isolation.
+//   - noexec: not yet supported. Don't ignore it since it could break
+//     in-sandbox security.
+var invalidOptions = []string{"shared", "rshared", "noexec"}
+
+// OptionsToFlags converts mount options to syscall flags.
+func OptionsToFlags(opts []string) uint32 {
+	return optionsToFlags(opts, optionsMap)
+}
+
+// PropOptionsToFlags converts propagation mount options to syscall flags.
+// Propagation options cannot be set other with other options and must be
+// handled separatedly.
+func PropOptionsToFlags(opts []string) uint32 {
+	return optionsToFlags(opts, propOptionsMap)
+}
+
+func optionsToFlags(opts []string, source map[string]mapping) uint32 {
+	var rv uint32
+	for _, opt := range opts {
+		if m, ok := source[opt]; ok {
+			if m.set {
+				rv |= m.val
+			} else {
+				rv ^= m.val
+			}
+		}
+	}
+	return rv
+}
+
+// ValidateMount validates that spec mounts are correct.
+func validateMount(mnt *specs.Mount) error {
+	if !path.IsAbs(mnt.Destination) {
+		return fmt.Errorf("Mount.Destination must be an absolute path: %v", mnt)
+	}
+
+	if mnt.Type == "bind" {
+		for _, o := range mnt.Options {
+			if ContainsStr(invalidOptions, o) {
+				return fmt.Errorf("mount option %q is not supported: %v", o, mnt)
+			}
+			_, ok1 := optionsMap[o]
+			_, ok2 := propOptionsMap[o]
+			if !ok1 && !ok2 {
+				log.Warningf("Ignoring unknown mount option %q", o)
+			}
+		}
+	}
+	return nil
+}
+
+// ValidateRootfsPropagation validates that rootfs propagation options are
+// correct.
+func validateRootfsPropagation(opt string) error {
+	flags := PropOptionsToFlags([]string{opt})
+	if flags&(syscall.MS_SLAVE|syscall.MS_PRIVATE) == 0 {
+		return fmt.Errorf("root mount propagation option must specify private or slave: %q", opt)
+	}
+	return nil
+}