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// 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 specutils
import (
"fmt"
"math/bits"
"path"
specs "github.com/opencontainers/runtime-spec/specs-go"
"golang.org/x/sys/unix"
)
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: unix.MS_POSIXACL},
"async": {set: false, val: unix.MS_SYNCHRONOUS},
"atime": {set: false, val: unix.MS_NOATIME},
"bind": {set: true, val: unix.MS_BIND},
"defaults": {set: true, val: 0},
"dev": {set: false, val: unix.MS_NODEV},
"diratime": {set: false, val: unix.MS_NODIRATIME},
"dirsync": {set: true, val: unix.MS_DIRSYNC},
"exec": {set: false, val: unix.MS_NOEXEC},
"noexec": {set: true, val: unix.MS_NOEXEC},
"iversion": {set: true, val: unix.MS_I_VERSION},
"loud": {set: false, val: unix.MS_SILENT},
"mand": {set: true, val: unix.MS_MANDLOCK},
"noacl": {set: false, val: unix.MS_POSIXACL},
"noatime": {set: true, val: unix.MS_NOATIME},
"nodev": {set: true, val: unix.MS_NODEV},
"nodiratime": {set: true, val: unix.MS_NODIRATIME},
"noiversion": {set: false, val: unix.MS_I_VERSION},
"nomand": {set: false, val: unix.MS_MANDLOCK},
"norelatime": {set: false, val: unix.MS_RELATIME},
"nostrictatime": {set: false, val: unix.MS_STRICTATIME},
"nosuid": {set: true, val: unix.MS_NOSUID},
"rbind": {set: true, val: unix.MS_BIND | unix.MS_REC},
"relatime": {set: true, val: unix.MS_RELATIME},
"remount": {set: true, val: unix.MS_REMOUNT},
"ro": {set: true, val: unix.MS_RDONLY},
"rw": {set: false, val: unix.MS_RDONLY},
"silent": {set: true, val: unix.MS_SILENT},
"strictatime": {set: true, val: unix.MS_STRICTATIME},
"suid": {set: false, val: unix.MS_NOSUID},
"sync": {set: true, val: unix.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: unix.MS_PRIVATE},
"rprivate": {set: true, val: unix.MS_PRIVATE | unix.MS_REC},
"slave": {set: true, val: unix.MS_SLAVE},
"rslave": {set: true, val: unix.MS_SLAVE | unix.MS_REC},
"unbindable": {set: true, val: unix.MS_UNBINDABLE},
"runbindable": {set: true, val: unix.MS_UNBINDABLE | unix.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.
var invalidOptions = []string{"shared", "rshared"}
// 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 separately.
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" {
return ValidateMountOptions(mnt.Options)
}
return nil
}
// ValidateMountOptions validates that mount options are correct.
func ValidateMountOptions(opts []string) error {
for _, o := range opts {
if ContainsStr(invalidOptions, o) {
return fmt.Errorf("mount option %q is not supported", o)
}
_, ok1 := optionsMap[o]
_, ok2 := propOptionsMap[o]
if !ok1 && !ok2 {
return fmt.Errorf("unknown mount option %q", o)
}
if err := validatePropagation(o); err != nil {
return err
}
}
return nil
}
// ValidateRootfsPropagation validates that rootfs propagation options are
// correct.
func validateRootfsPropagation(opt string) error {
flags := PropOptionsToFlags([]string{opt})
if flags&(unix.MS_SLAVE|unix.MS_PRIVATE) == 0 {
return fmt.Errorf("root mount propagation option must specify private or slave: %q", opt)
}
return validatePropagation(opt)
}
func validatePropagation(opt string) error {
flags := PropOptionsToFlags([]string{opt})
exclusive := flags & (unix.MS_SLAVE | unix.MS_PRIVATE | unix.MS_SHARED | unix.MS_UNBINDABLE)
if bits.OnesCount32(exclusive) > 1 {
return fmt.Errorf("mount propagation options are mutually exclusive: %q", opt)
}
return nil
}
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