mirror of
https://github.com/opencontainers/runc.git
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c0ad40c5e6
When we launch a container in a new user namespace, we cannot create devices, so we bind mount the host's devices into place instead. If we are running in a user namespace (i.e. nested in a container), then we need to do the same thing. Add a function to detect that and check for it before doing mknod. Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com> --- Changelog - add a comment clarifying what's going on with the uidmap file.
115 lines
2.2 KiB
Go
115 lines
2.2 KiB
Go
// +build linux
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package system
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import (
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"bufio"
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"fmt"
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"os"
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"os/exec"
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"syscall"
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"unsafe"
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)
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type ParentDeathSignal int
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func (p ParentDeathSignal) Restore() error {
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if p == 0 {
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return nil
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}
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current, err := GetParentDeathSignal()
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if err != nil {
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return err
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}
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if p == current {
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return nil
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}
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return p.Set()
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}
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func (p ParentDeathSignal) Set() error {
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return SetParentDeathSignal(uintptr(p))
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}
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func Execv(cmd string, args []string, env []string) error {
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name, err := exec.LookPath(cmd)
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if err != nil {
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return err
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}
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return syscall.Exec(name, args, env)
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}
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func SetParentDeathSignal(sig uintptr) error {
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if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_PDEATHSIG, sig, 0); err != 0 {
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return err
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}
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return nil
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}
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func GetParentDeathSignal() (ParentDeathSignal, error) {
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var sig int
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_, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_GET_PDEATHSIG, uintptr(unsafe.Pointer(&sig)), 0)
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if err != 0 {
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return -1, err
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}
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return ParentDeathSignal(sig), nil
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}
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func SetKeepCaps() error {
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if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_KEEPCAPS, 1, 0); err != 0 {
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return err
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}
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return nil
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}
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func ClearKeepCaps() error {
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if _, _, err := syscall.RawSyscall(syscall.SYS_PRCTL, syscall.PR_SET_KEEPCAPS, 0, 0); err != 0 {
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return err
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}
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return nil
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}
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func Setctty() error {
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if _, _, err := syscall.RawSyscall(syscall.SYS_IOCTL, 0, uintptr(syscall.TIOCSCTTY), 0); err != 0 {
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return err
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}
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return nil
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}
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/*
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* Detect whether we are currently running in a user namespace.
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* Copied from github.com/lxc/lxd/shared/util.go
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*/
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func RunningInUserNS() bool {
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file, err := os.Open("/proc/self/uid_map")
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if err != nil {
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/*
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* This kernel-provided file only exists if user namespaces are
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* supported
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*/
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return false
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}
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defer file.Close()
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buf := bufio.NewReader(file)
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l, _, err := buf.ReadLine()
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if err != nil {
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return false
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}
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line := string(l)
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var a, b, c int64
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fmt.Sscanf(line, "%d %d %d", &a, &b, &c)
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/*
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* We assume we are in the initial user namespace if we have a full
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* range - 4294967295 uids starting at uid 0.
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*/
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if a == 0 && b == 0 && c == 4294967295 {
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return false
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}
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return true
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}
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