mirror of
https://github.com/moby/moby.git
synced 2022-11-09 12:21:53 -05:00
2d39a44c1c
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
(cherry picked from commit a8008f7313)
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
116 lines
3.8 KiB
Go
116 lines
3.8 KiB
Go
// +build linux
|
|
|
|
// Forked from https://github.com/containerd/containerd/blob/9ade247b38b5a685244e1391c86ff41ab109556e/snapshots/overlay/check.go
|
|
/*
|
|
Copyright The containerd 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 overlayutils
|
|
|
|
import (
|
|
"fmt"
|
|
"io/ioutil"
|
|
"os"
|
|
"path/filepath"
|
|
|
|
"github.com/containerd/containerd/mount"
|
|
"github.com/containerd/containerd/sys"
|
|
"github.com/docker/docker/pkg/parsers/kernel"
|
|
"github.com/sirupsen/logrus"
|
|
)
|
|
|
|
// NeedsUserXAttr returns whether overlayfs should be mounted with the "userxattr" mount option.
|
|
//
|
|
// The "userxattr" option is needed for mounting overlayfs inside a user namespace with kernel >= 5.11.
|
|
//
|
|
// The "userxattr" option is NOT needed for the initial user namespace (aka "the host").
|
|
//
|
|
// Also, Ubuntu (since circa 2015) and Debian (since 10) with kernel < 5.11 can mount
|
|
// the overlayfs in a user namespace without the "userxattr" option.
|
|
//
|
|
// The corresponding kernel commit: https://github.com/torvalds/linux/commit/2d2f2d7322ff43e0fe92bf8cccdc0b09449bf2e1
|
|
// > ovl: user xattr
|
|
// >
|
|
// > Optionally allow using "user.overlay." namespace instead of "trusted.overlay."
|
|
// > ...
|
|
// > Disable redirect_dir and metacopy options, because these would allow privilege escalation through direct manipulation of the
|
|
// > "user.overlay.redirect" or "user.overlay.metacopy" xattrs.
|
|
// > ...
|
|
//
|
|
// The "userxattr" support is not exposed in "/sys/module/overlay/parameters".
|
|
func NeedsUserXAttr(d string) (bool, error) {
|
|
if !sys.RunningInUserNS() {
|
|
// we are the real root (i.e., the root in the initial user NS),
|
|
// so we do never need "userxattr" opt.
|
|
return false, nil
|
|
}
|
|
|
|
// Fast path for kernel >= 5.11 .
|
|
//
|
|
// Keep in mind that distro vendors might be going to backport the patch to older kernels.
|
|
// So we can't completely remove the "slow path".
|
|
if kernel.CheckKernelVersion(5, 11, 0) {
|
|
return true, nil
|
|
}
|
|
|
|
tdRoot := filepath.Join(d, "userxattr-check")
|
|
if err := os.RemoveAll(tdRoot); err != nil {
|
|
logrus.WithError(err).Warnf("Failed to remove check directory %v", tdRoot)
|
|
}
|
|
|
|
if err := os.MkdirAll(tdRoot, 0700); err != nil {
|
|
return false, err
|
|
}
|
|
|
|
defer func() {
|
|
if err := os.RemoveAll(tdRoot); err != nil {
|
|
logrus.WithError(err).Warnf("Failed to remove check directory %v", tdRoot)
|
|
}
|
|
}()
|
|
|
|
td, err := ioutil.TempDir(tdRoot, "")
|
|
if err != nil {
|
|
return false, err
|
|
}
|
|
|
|
for _, dir := range []string{"lower1", "lower2", "upper", "work", "merged"} {
|
|
if err := os.Mkdir(filepath.Join(td, dir), 0755); err != nil {
|
|
return false, err
|
|
}
|
|
}
|
|
|
|
opts := []string{
|
|
fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", filepath.Join(td, "lower2"), filepath.Join(td, "lower1"), filepath.Join(td, "upper"), filepath.Join(td, "work")),
|
|
"userxattr",
|
|
}
|
|
|
|
m := mount.Mount{
|
|
Type: "overlay",
|
|
Source: "overlay",
|
|
Options: opts,
|
|
}
|
|
|
|
dest := filepath.Join(td, "merged")
|
|
if err := m.Mount(dest); err != nil {
|
|
// Probably the host is running Ubuntu/Debian kernel (< 5.11) with the userns patch but without the userxattr patch.
|
|
// Return false without error.
|
|
logrus.WithError(err).Debugf("cannot mount overlay with \"userxattr\", probably the kernel does not support userxattr")
|
|
return false, nil
|
|
}
|
|
if err := mount.UnmountAll(dest, 0); err != nil {
|
|
logrus.WithError(err).Warnf("Failed to unmount check directory %v", dest)
|
|
}
|
|
return true, nil
|
|
}
|