blob: c5495e4cbb9cf1fd77fe9811c85ce6bd731f9d30 [file] [log] [blame]
// +build linux
package libcontainer
import (
"encoding/json"
"errors"
"fmt"
"io"
"os"
"os/exec"
"path/filepath"
"strconv"
"syscall" // only for Signal
"github.com/opencontainers/runc/libcontainer/cgroups"
"github.com/opencontainers/runc/libcontainer/configs"
"github.com/opencontainers/runc/libcontainer/system"
"github.com/opencontainers/runc/libcontainer/utils"
"golang.org/x/sys/unix"
)
type parentProcess interface {
// pid returns the pid for the running process.
pid() int
// start starts the process execution.
start() error
// send a SIGKILL to the process and wait for the exit.
terminate() error
// wait waits on the process returning the process state.
wait() (*os.ProcessState, error)
// startTime returns the process start time.
startTime() (uint64, error)
signal(os.Signal) error
externalDescriptors() []string
setExternalDescriptors(fds []string)
}
type setnsProcess struct {
cmd *exec.Cmd
parentPipe *os.File
childPipe *os.File
cgroupPaths map[string]string
config *initConfig
fds []string
process *Process
bootstrapData io.Reader
}
func (p *setnsProcess) startTime() (uint64, error) {
stat, err := system.Stat(p.pid())
return stat.StartTime, err
}
func (p *setnsProcess) signal(sig os.Signal) error {
s, ok := sig.(syscall.Signal)
if !ok {
return errors.New("os: unsupported signal type")
}
return unix.Kill(p.pid(), s)
}
func (p *setnsProcess) start() (err error) {
defer p.parentPipe.Close()
err = p.cmd.Start()
p.childPipe.Close()
if err != nil {
return newSystemErrorWithCause(err, "starting setns process")
}
if p.bootstrapData != nil {
if _, err := io.Copy(p.parentPipe, p.bootstrapData); err != nil {
return newSystemErrorWithCause(err, "copying bootstrap data to pipe")
}
}
if err = p.execSetns(); err != nil {
return newSystemErrorWithCause(err, "executing setns process")
}
// We can't join cgroups if we're in a rootless container.
if !p.config.Rootless && len(p.cgroupPaths) > 0 {
if err := cgroups.EnterPid(p.cgroupPaths, p.pid()); err != nil {
return newSystemErrorWithCausef(err, "adding pid %d to cgroups", p.pid())
}
}
// set rlimits, this has to be done here because we lose permissions
// to raise the limits once we enter a user-namespace
if err := setupRlimits(p.config.Rlimits, p.pid()); err != nil {
return newSystemErrorWithCause(err, "setting rlimits for process")
}
if err := utils.WriteJSON(p.parentPipe, p.config); err != nil {
return newSystemErrorWithCause(err, "writing config to pipe")
}
ierr := parseSync(p.parentPipe, func(sync *syncT) error {
switch sync.Type {
case procReady:
// This shouldn't happen.
panic("unexpected procReady in setns")
case procHooks:
// This shouldn't happen.
panic("unexpected procHooks in setns")
default:
return newSystemError(fmt.Errorf("invalid JSON payload from child"))
}
})
if err := unix.Shutdown(int(p.parentPipe.Fd()), unix.SHUT_WR); err != nil {
return newSystemErrorWithCause(err, "calling shutdown on init pipe")
}
// Must be done after Shutdown so the child will exit and we can wait for it.
if ierr != nil {
p.wait()
return ierr
}
return nil
}
// execSetns runs the process that executes C code to perform the setns calls
// because setns support requires the C process to fork off a child and perform the setns
// before the go runtime boots, we wait on the process to die and receive the child's pid
// over the provided pipe.
func (p *setnsProcess) execSetns() error {
status, err := p.cmd.Process.Wait()
if err != nil {
p.cmd.Wait()
return newSystemErrorWithCause(err, "waiting on setns process to finish")
}
if !status.Success() {
p.cmd.Wait()
return newSystemError(&exec.ExitError{ProcessState: status})
}
var pid *pid
if err := json.NewDecoder(p.parentPipe).Decode(&pid); err != nil {
p.cmd.Wait()
return newSystemErrorWithCause(err, "reading pid from init pipe")
}
// Clean up the zombie parent process
firstChildProcess, err := os.FindProcess(pid.PidFirstChild)
if err != nil {
return err
}
// Ignore the error in case the child has already been reaped for any reason
_, _ = firstChildProcess.Wait()
process, err := os.FindProcess(pid.Pid)
if err != nil {
return err
}
p.cmd.Process = process
p.process.ops = p
return nil
}
// terminate sends a SIGKILL to the forked process for the setns routine then waits to
// avoid the process becoming a zombie.
func (p *setnsProcess) terminate() error {
if p.cmd.Process == nil {
return nil
}
err := p.cmd.Process.Kill()
if _, werr := p.wait(); err == nil {
err = werr
}
return err
}
func (p *setnsProcess) wait() (*os.ProcessState, error) {
err := p.cmd.Wait()
// Return actual ProcessState even on Wait error
return p.cmd.ProcessState, err
}
func (p *setnsProcess) pid() int {
return p.cmd.Process.Pid
}
func (p *setnsProcess) externalDescriptors() []string {
return p.fds
}
func (p *setnsProcess) setExternalDescriptors(newFds []string) {
p.fds = newFds
}
type initProcess struct {
cmd *exec.Cmd
parentPipe *os.File
childPipe *os.File
config *initConfig
manager cgroups.Manager
container *linuxContainer
fds []string
process *Process
bootstrapData io.Reader
sharePidns bool
rootDir *os.File
}
func (p *initProcess) pid() int {
return p.cmd.Process.Pid
}
func (p *initProcess) externalDescriptors() []string {
return p.fds
}
// execSetns runs the process that executes C code to perform the setns calls
// because setns support requires the C process to fork off a child and perform the setns
// before the go runtime boots, we wait on the process to die and receive the child's pid
// over the provided pipe.
// This is called by initProcess.start function
func (p *initProcess) execSetns() error {
status, err := p.cmd.Process.Wait()
if err != nil {
p.cmd.Wait()
return err
}
if !status.Success() {
p.cmd.Wait()
return &exec.ExitError{ProcessState: status}
}
var pid *pid
if err := json.NewDecoder(p.parentPipe).Decode(&pid); err != nil {
p.cmd.Wait()
return err
}
// Clean up the zombie parent process
firstChildProcess, err := os.FindProcess(pid.PidFirstChild)
if err != nil {
return err
}
// Ignore the error in case the child has already been reaped for any reason
_, _ = firstChildProcess.Wait()
process, err := os.FindProcess(pid.Pid)
if err != nil {
return err
}
p.cmd.Process = process
p.process.ops = p
return nil
}
func (p *initProcess) start() error {
defer p.parentPipe.Close()
err := p.cmd.Start()
p.process.ops = p
p.childPipe.Close()
p.rootDir.Close()
if err != nil {
p.process.ops = nil
return newSystemErrorWithCause(err, "starting init process command")
}
if _, err := io.Copy(p.parentPipe, p.bootstrapData); err != nil {
return newSystemErrorWithCause(err, "copying bootstrap data to pipe")
}
if err := p.execSetns(); err != nil {
return newSystemErrorWithCause(err, "running exec setns process for init")
}
// Save the standard descriptor names before the container process
// can potentially move them (e.g., via dup2()). If we don't do this now,
// we won't know at checkpoint time which file descriptor to look up.
fds, err := getPipeFds(p.pid())
if err != nil {
return newSystemErrorWithCausef(err, "getting pipe fds for pid %d", p.pid())
}
p.setExternalDescriptors(fds)
// Do this before syncing with child so that no children can escape the
// cgroup. We don't need to worry about not doing this and not being root
// because we'd be using the rootless cgroup manager in that case.
if err := p.manager.Apply(p.pid()); err != nil {
return newSystemErrorWithCause(err, "applying cgroup configuration for process")
}
defer func() {
if err != nil {
// TODO: should not be the responsibility to call here
p.manager.Destroy()
}
}()
if err := p.createNetworkInterfaces(); err != nil {
return newSystemErrorWithCause(err, "creating network interfaces")
}
if err := p.sendConfig(); err != nil {
return newSystemErrorWithCause(err, "sending config to init process")
}
var (
sentRun bool
sentResume bool
)
ierr := parseSync(p.parentPipe, func(sync *syncT) error {
switch sync.Type {
case procReady:
// set rlimits, this has to be done here because we lose permissions
// to raise the limits once we enter a user-namespace
if err := setupRlimits(p.config.Rlimits, p.pid()); err != nil {
return newSystemErrorWithCause(err, "setting rlimits for ready process")
}
// call prestart hooks
if !p.config.Config.Namespaces.Contains(configs.NEWNS) {
// Setup cgroup before prestart hook, so that the prestart hook could apply cgroup permissions.
if err := p.manager.Set(p.config.Config); err != nil {
return newSystemErrorWithCause(err, "setting cgroup config for ready process")
}
if p.config.Config.Hooks != nil {
s := configs.HookState{
Version: p.container.config.Version,
ID: p.container.id,
Pid: p.pid(),
Bundle: utils.SearchLabels(p.config.Config.Labels, "bundle"),
}
for i, hook := range p.config.Config.Hooks.Prestart {
if err := hook.Run(s); err != nil {
return newSystemErrorWithCausef(err, "running prestart hook %d", i)
}
}
}
}
// Sync with child.
if err := writeSync(p.parentPipe, procRun); err != nil {
return newSystemErrorWithCause(err, "writing syncT 'run'")
}
sentRun = true
case procHooks:
// Setup cgroup before prestart hook, so that the prestart hook could apply cgroup permissions.
if err := p.manager.Set(p.config.Config); err != nil {
return newSystemErrorWithCause(err, "setting cgroup config for procHooks process")
}
if p.config.Config.Hooks != nil {
s := configs.HookState{
Version: p.container.config.Version,
ID: p.container.id,
Pid: p.pid(),
Bundle: utils.SearchLabels(p.config.Config.Labels, "bundle"),
}
for i, hook := range p.config.Config.Hooks.Prestart {
if err := hook.Run(s); err != nil {
return newSystemErrorWithCausef(err, "running prestart hook %d", i)
}
}
}
// Sync with child.
if err := writeSync(p.parentPipe, procResume); err != nil {
return newSystemErrorWithCause(err, "writing syncT 'resume'")
}
sentResume = true
default:
return newSystemError(fmt.Errorf("invalid JSON payload from child"))
}
return nil
})
if !sentRun {
return newSystemErrorWithCause(ierr, "container init")
}
if p.config.Config.Namespaces.Contains(configs.NEWNS) && !sentResume {
return newSystemError(fmt.Errorf("could not synchronise after executing prestart hooks with container process"))
}
if err := unix.Shutdown(int(p.parentPipe.Fd()), unix.SHUT_WR); err != nil {
return newSystemErrorWithCause(err, "shutting down init pipe")
}
// Must be done after Shutdown so the child will exit and we can wait for it.
if ierr != nil {
p.wait()
return ierr
}
return nil
}
func (p *initProcess) wait() (*os.ProcessState, error) {
err := p.cmd.Wait()
if err != nil {
return p.cmd.ProcessState, err
}
// we should kill all processes in cgroup when init is died if we use host PID namespace
if p.sharePidns {
signalAllProcesses(p.manager, unix.SIGKILL)
}
return p.cmd.ProcessState, nil
}
func (p *initProcess) terminate() error {
if p.cmd.Process == nil {
return nil
}
err := p.cmd.Process.Kill()
if _, werr := p.wait(); err == nil {
err = werr
}
return err
}
func (p *initProcess) startTime() (uint64, error) {
stat, err := system.Stat(p.pid())
return stat.StartTime, err
}
func (p *initProcess) sendConfig() error {
// send the config to the container's init process, we don't use JSON Encode
// here because there might be a problem in JSON decoder in some cases, see:
// https://github.com/docker/docker/issues/14203#issuecomment-174177790
return utils.WriteJSON(p.parentPipe, p.config)
}
func (p *initProcess) createNetworkInterfaces() error {
for _, config := range p.config.Config.Networks {
strategy, err := getStrategy(config.Type)
if err != nil {
return err
}
n := &network{
Network: *config,
}
if err := strategy.create(n, p.pid()); err != nil {
return err
}
p.config.Networks = append(p.config.Networks, n)
}
return nil
}
func (p *initProcess) signal(sig os.Signal) error {
s, ok := sig.(syscall.Signal)
if !ok {
return errors.New("os: unsupported signal type")
}
return unix.Kill(p.pid(), s)
}
func (p *initProcess) setExternalDescriptors(newFds []string) {
p.fds = newFds
}
func getPipeFds(pid int) ([]string, error) {
fds := make([]string, 3)
dirPath := filepath.Join("/proc", strconv.Itoa(pid), "/fd")
for i := 0; i < 3; i++ {
// XXX: This breaks if the path is not a valid symlink (which can
// happen in certain particularly unlucky mount namespace setups).
f := filepath.Join(dirPath, strconv.Itoa(i))
target, err := os.Readlink(f)
if err != nil {
// Ignore permission errors, for rootless containers and other
// non-dumpable processes. if we can't get the fd for a particular
// file, there's not much we can do.
if os.IsPermission(err) {
continue
}
return fds, err
}
fds[i] = target
}
return fds, nil
}
// InitializeIO creates pipes for use with the process's stdio and returns the
// opposite side for each. Do not use this if you want to have a pseudoterminal
// set up for you by libcontainer (TODO: fix that too).
// TODO: This is mostly unnecessary, and should be handled by clients.
func (p *Process) InitializeIO(rootuid, rootgid int) (i *IO, err error) {
var fds []uintptr
i = &IO{}
// cleanup in case of an error
defer func() {
if err != nil {
for _, fd := range fds {
unix.Close(int(fd))
}
}
}()
// STDIN
r, w, err := os.Pipe()
if err != nil {
return nil, err
}
fds = append(fds, r.Fd(), w.Fd())
p.Stdin, i.Stdin = r, w
// STDOUT
if r, w, err = os.Pipe(); err != nil {
return nil, err
}
fds = append(fds, r.Fd(), w.Fd())
p.Stdout, i.Stdout = w, r
// STDERR
if r, w, err = os.Pipe(); err != nil {
return nil, err
}
fds = append(fds, r.Fd(), w.Fd())
p.Stderr, i.Stderr = w, r
// change ownership of the pipes incase we are in a user namespace
for _, fd := range fds {
if err := unix.Fchown(int(fd), rootuid, rootgid); err != nil {
return nil, err
}
}
return i, nil
}