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pkg: chrootarchive: chroot_linux: fix mount leak

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When pivot_root fails we need to unmount the bind mounted path we
previously mounted in preparation for pivot_root.

Signed-off-by: Antonio Murdaca <runcom@redhat.com>
This commit is contained in:
Antonio Murdaca 2016-05-10 16:18:16 +02:00
parent 456551a672
commit 7d22887b2c
1 changed files with 14 additions and 6 deletions
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20
pkg/chrootarchive/chroot_linux.go
View file

@ -6,6 +6,8 @@ import (
"os"
"path/filepath"
"syscall"
"github.com/docker/docker/pkg/mount"
)
// chroot on linux uses pivot_root instead of chroot
@ -15,13 +17,12 @@ import (
// Old root is removed after the call to pivot_root so it is no longer available under the new root.
// This is similar to how libcontainer sets up a container's rootfs
func chroot(path string) (err error) {
// Create new mount namespace so mounts don't leak
if err := syscall.Unshare(syscall.CLONE_NEWNS); err != nil {
return fmt.Errorf("Error creating mount namespace before pivot: %v", err)
}
// path must be a different fs for pivot_root, so bind-mount to itself to ensure this
if err := syscall.Mount(path, path, "", syscall.MS_BIND, ""); err != nil {
return fmt.Errorf("Error mounting pivot dir before pivot: %v", err)
if err := mount.MakeRPrivate(path); err != nil {
return err
}
// setup oldRoot for pivot_root
@ -44,17 +45,24 @@ func chroot(path string) (err error) {
errCleanup := os.Remove(pivotDir)
// pivotDir doesn't exist if pivot_root failed and chroot+chdir was successful
// but we already cleaned it up on failed pivot_root
// because we already cleaned it up on failed pivot_root
if errCleanup != nil && !os.IsNotExist(errCleanup) {
errCleanup = fmt.Errorf("Error cleaning up after pivot: %v", errCleanup)
if err == nil {
err = errCleanup
}
}
if errCleanup := syscall.Unmount("/", syscall.MNT_DETACH); errCleanup != nil {
if err == nil {
err = fmt.Errorf("error unmounting root: %v", errCleanup)
}
return
}
}()
if err := syscall.PivotRoot(path, pivotDir); err != nil {
// If pivot fails, fall back to the normal chroot after cleaning up temp dir for pivot_root
// If pivot fails, fall back to the normal chroot after cleaning up temp dir
if err := os.Remove(pivotDir); err != nil {
return fmt.Errorf("Error cleaning up after failed pivot: %v", err)
}