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Fix docker --init with /dev bind mount

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In case a user wants to have a child reaper inside a container
(i.e. run "docker --init") AND a bind-mounted /dev, the following
error occurs:

> docker run -d -v /dev:/dev --init busybox top
> 088c96808c683077f04c4cc2711fddefe1f5970afc085d59e0baae779745a7cf
> docker: Error response from daemon: OCI runtime create failed: container_linux.go:296: starting container process caused "exec: "/dev/init": stat /dev/init: no such file or directory": unknown.

This happens because if a user-suppled /dev is provided, all the
built-in /dev/xxx mounts are filtered out.

To solve, let's move in-container init to /sbin, as the chance that
/sbin will be bind-mounted to a container is smaller than that for /dev.
While at it, let's give it more unique name (docker-init).

NOTE it still won't work for the case of bind-mounted /sbin.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
This commit is contained in:
Kir Kolyshkin 2018-08-22 13:05:12 -07:00
parent 0c5f8d2b9b
commit bcacbf523b
1 changed files with 8 additions and 7 deletions
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15
daemon/oci_linux.go
View file

@ -27,6 +27,10 @@ import (
"golang.org/x/sys/unix"
)
const (
inContainerInitPath = "/sbin/" + daemonconfig.DefaultInitBinary
)
func setResources(s *specs.Spec, r containertypes.Resources) error {
weightDevices, err := getBlkioWeightDevices(r)
if err != nil {
@ -657,19 +661,16 @@ func (daemon *Daemon) populateCommonSpec(s *specs.Spec, c *container.Container)
if c.HostConfig.PidMode.IsPrivate() {
if (c.HostConfig.Init != nil && *c.HostConfig.Init) ||
(c.HostConfig.Init == nil && daemon.configStore.Init) {
s.Process.Args = append([]string{"/dev/init", "--", c.Path}, c.Args...)
var path string
if daemon.configStore.InitPath == "" {
s.Process.Args = append([]string{inContainerInitPath, "--", c.Path}, c.Args...)
path := daemon.configStore.InitPath
if path == "" {
path, err = exec.LookPath(daemonconfig.DefaultInitBinary)
if err != nil {
return err
}
}
if daemon.configStore.InitPath != "" {
path = daemon.configStore.InitPath
}
s.Mounts = append(s.Mounts, specs.Mount{
Destination: "/dev/init",
Destination: inContainerInitPath,
Type: "bind",
Source: path,
Options: []string{"bind", "ro"},