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