archive: add human-readable hint to Lchown error

AkihiroSuda · AkihiroSuda · commit f67de000dc26 · 2022-05-25T19:17:38.000+09:00
Before: ``` $ nerdctl pull gcr.io/kubeflow-images-public/tensorflow-1.14.0-notebook-cpu:v0.7.0 FATA[0026] failed to extract layer sha256:f8a604834d388fd3d04c26e4ed832b36b617ea8a4e0b1665b9199bd10cfcb171: mount callback failed on /var/lib/containerd/tmpmounts/containerd-mount1818823128: lchown /var/lib/containerd/tmpmounts/containerd-mount1818823128/usr/local/bin/docker-credential-gcr: invalid argument: unknown ``` After: ``` $ nerdctl pull gcr.io/kubeflow-images-public/tensorflow-1.14.0-notebook-cpu:v0.7.0 FATA[0027] failed to extract layer sha256:f8a604834d388fd3d04c26e4ed832b36b617ea8a4e0b1665b9199bd10cfcb171: mount callback failed on /var/lib/containerd/tmpmounts/containerd-mount3521205359: failed to Lchown "/var/lib/containerd/tmpmounts/containerd-mount3521205359/usr/local/bin/docker-credential-gcr" for UID 205001, GID 5000: lchown /var/lib/containerd/tmpmounts/containerd-mount3521205359/usr/local/bin/docker-credential-gcr: invalid argument (Hint: try increasing the number of subordinate IDs in /etc/subuid and /etc/subgid): unknown ``` Related to moby/moby issue 43576 but for containerd Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp> (cherry picked from commit d2f3015) Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
diff --git a/archive/tar.go b/archive/tar.go
@@ -19,6 +19,7 @@ package archive
 import (
 	"archive/tar"
 	"context"
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
@@ -29,6 +30,7 @@ import (
 	"time"
 
 	"github.com/containerd/containerd/log"
+	"github.com/containerd/containerd/pkg/userns"
 	"github.com/containerd/continuity/fs"
 	"github.com/pkg/errors"
 )
@@ -376,6 +378,10 @@ func createTarFile(ctx context.Context, path, extractDir string, hdr *tar.Header
 	// Lchown is not supported on Windows.
 	if runtime.GOOS != "windows" {
 		if err := os.Lchown(path, hdr.Uid, hdr.Gid); err != nil {
+			err = fmt.Errorf("failed to Lchown %q for UID %d, GID %d: %w", path, hdr.Uid, hdr.Gid, err)
+			if errors.Is(err, syscall.EINVAL) && userns.RunningInUserNS() {
+				err = fmt.Errorf("%w (Hint: try increasing the number of subordinate IDs in /etc/subuid and /etc/subgid)", err)
+			}
 			return err
 		}
 	}
