archive: add human-readable hint to Lchown error

AkihiroSuda · AkihiroSuda · commit d2f30150b36e · 2022-05-24T17:57:53.000+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 &lt;akihiro.suda.cz@hco.ntt.co.jp&gt;
diff --git a/archive/tar.go b/archive/tar.go
@@ -31,6 +31,7 @@ import (
 	"time"
 
 	"github.com/containerd/containerd/log"
+	"github.com/containerd/containerd/pkg/userns"
 	"github.com/containerd/continuity/fs"
 )
 
@@ -380,6 +381,10 @@ 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
 		}
 	}

Original file line number	Diff line number	Diff line change
`@@ -31,6 +31,7 @@ import (`
`31`	`31`	`"time"`
`32`	`32`
`33`	`33`	`"github.com/containerd/containerd/log"`
	`34`	`+ "github.com/containerd/containerd/pkg/userns"`
`34`	`35`	`"github.com/containerd/continuity/fs"`
`35`	`36`	`)`
`36`	`37`
`@@ -380,6 +381,10 @@ func createTarFile(ctx context.Context, path, extractDir string, hdr *tar.Header`
`380`	`381`	`// Lchown is not supported on Windows.`
`381`	`382`	`if runtime.GOOS != "windows" {`
`382`	`383`	`if err := os.Lchown(path, hdr.Uid, hdr.Gid); err != nil {`
	`384`	`+ err = fmt.Errorf("failed to Lchown %q for UID %d, GID %d: %w", path, hdr.Uid, hdr.Gid, err)`
	`385`	`+ if errors.Is(err, syscall.EINVAL) && userns.RunningInUserNS() {`
	`386`	`+ err = fmt.Errorf("%w (Hint: try increasing the number of subordinate IDs in /etc/subuid and /etc/subgid)", err)`
	`387`	`+ }`
`383`	`388`	`return err`
`384`	`389`	`}`
`385`	`390`	`}`