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// Copyright (c) 2019-2023, Sylabs Inc. All rights reserved.
// This software is licensed under a 3-clause BSD license. Please consult the
// LICENSE.md file distributed with the sources of this project regarding your
// rights to use or distribute this software.
package tools
import (
"context"
"fmt"
"os"
"path/filepath"
"syscall"
"github.com/sylabs/singularity/v4/internal/pkg/util/fs/overlay"
"github.com/sylabs/singularity/v4/pkg/image"
"github.com/sylabs/singularity/v4/pkg/sylog"
)
// CreateOverlay creates a writable overlay using a directory inside the OCI
// bundle.
func CreateOverlay(ctx context.Context, bundlePath string) error {
oldumask := syscall.Umask(0)
defer syscall.Umask(oldumask)
olDir := filepath.Join(bundlePath, "overlay")
var err error
if err = overlay.EnsureOverlayDir(olDir, true, 0o700); err != nil {
return fmt.Errorf("failed to create %s: %s", olDir, err)
}
// delete overlay directory in case of error
defer func() {
if err != nil {
sylog.Debugf("Encountered error in CreateOverlay; attempting to remove overlay dir %q", olDir)
os.RemoveAll(olDir)
}
}()
olSet := overlay.Set{WritableOverlay: &overlay.Item{
SourcePath: olDir,
Type: image.SANDBOX,
Readonly: false,
}}
return olSet.Mount(ctx, RootFs(bundlePath).Path())
}
// DeleteOverlay deletes an overlay previously created using a directory inside
// the OCI bundle.
func DeleteOverlay(ctx context.Context, bundlePath string) error {
olDir := filepath.Join(bundlePath, "overlay")
rootFsDir := RootFs(bundlePath).Path()
if err := overlay.DetachMount(ctx, rootFsDir); err != nil {
return err
}
return overlay.DetachAndDelete(olDir)
}
// PrepareOverlayTmpfs creates a tmpfs, mounted to the overlay/ directory in the
// bundle, but does not perform an overlay mount using it.
func PrepareOverlayTmpfs(bundlePath string, sizeMiB int, allowSetuid bool) (string, error) {
var err error
oldumask := syscall.Umask(0)
defer syscall.Umask(oldumask)
olDir := filepath.Join(bundlePath, "overlay")
err = overlay.EnsureOverlayDir(olDir, true, 0o700)
if err != nil {
return "", fmt.Errorf("failed to create %s: %s", olDir, err)
}
// delete overlay directory in case of error
defer func() {
if err != nil {
sylog.Debugf("Encountered error in CreateOverlay; attempting to remove overlay dir %q", olDir)
os.RemoveAll(olDir)
}
}()
options := fmt.Sprintf("mode=1777,size=%dm", sizeMiB)
var flags uintptr = syscall.MS_NODEV
if !allowSetuid {
flags |= syscall.MS_NOSUID
}
err = syscall.Mount("tmpfs", olDir, "tmpfs", flags, options)
if err != nil {
return "", fmt.Errorf("failed to bind %s: %s", olDir, err)
}
return olDir, nil
}
// CreateOverlay creates a writable overlay using tmpfs, mounting it over the bundle rootfs.
func CreateOverlayTmpfs(ctx context.Context, bundlePath string, sizeMiB int, allowSetuid bool) (string, error) {
olDir, err := PrepareOverlayTmpfs(bundlePath, sizeMiB, allowSetuid)
if err != nil {
return "", err
}
oi := overlay.Item{
SourcePath: olDir,
Type: image.SANDBOX,
Readonly: false,
}
oi.SetAllowSetuid(allowSetuid)
olSet := overlay.Set{WritableOverlay: &oi}
err = olSet.Mount(ctx, RootFs(bundlePath).Path())
if err != nil {
// best effort to cleanup tmpfs mount
sylog.Debugf("Encountered error in CreateOverlayTmpfs; attempting to detach overlay dir %q", olDir)
syscall.Unmount(olDir, syscall.MNT_DETACH)
return "", err
}
return olDir, nil
}
// DeleteOverlayTmpfs unmounts and deletes a tmpfs backed overlay created with CreateOverlayTmpfs.
func DeleteOverlayTmpfs(ctx context.Context, bundlePath, olDir string) error {
rootFsDir := RootFs(bundlePath).Path()
if err := overlay.DetachMount(ctx, rootFsDir); err != nil {
return err
}
// Because CreateOverlayTmpfs() mounts the tmpfs on olDir, and then
// calls ApplyOverlay(), there needs to be an extra unmount in the this case
if err := overlay.DetachMount(ctx, olDir); err != nil {
return err
}
return overlay.DetachAndDelete(olDir)
}
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