Merge pull request #6308 from thaJeztah/rootless_devices

OCI: Mount (accessible) host devices in privileged rootless containers

oci/utils_unix.go

@@ -23,6 +23,7 @@ import (
 	"os"
 	"path/filepath"
 
+	"github.com/containerd/containerd/pkg/userns"
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"github.com/pkg/errors"
 	"golang.org/x/sys/unix"
@@ -31,6 +32,13 @@ import (
 // ErrNotADevice denotes that a file is not a valid linux device.
 var ErrNotADevice = errors.New("not a device node")
 
+// Testing dependencies
+var (
+	osReadDir              = os.ReadDir
+	usernsRunningInUserNS  = userns.RunningInUserNS
+	overrideDeviceFromPath func(path string) error
+)
+
 // HostDevices returns all devices that can be found under /dev directory.
 func HostDevices() ([]specs.LinuxDevice, error) {
 	return getDevices("/dev", "")
@@ -53,7 +61,7 @@ func getDevices(path, containerPath string) ([]specs.LinuxDevice, error) {
 		return []specs.LinuxDevice{*dev}, nil
 	}
 
-	files, err := os.ReadDir(path)
+	files, err := osReadDir(path)
 	if err != nil {
 		return nil, err
 	}
@@ -73,6 +81,12 @@ func getDevices(path, containerPath string) ([]specs.LinuxDevice, error) {
 				}
 				sub, err := getDevices(filepath.Join(path, f.Name()), cp)
 				if err != nil {
+					if errors.Is(err, os.ErrPermission) && usernsRunningInUserNS() {
+						// ignore the "permission denied" error if running in userns.
+						// This allows rootless containers to use devices that are
+						// accessible, ignoring devices / subdirectories that are not.
+						continue
+					}
 					return nil, err
 				}
 
@@ -81,7 +95,7 @@ func getDevices(path, containerPath string) ([]specs.LinuxDevice, error) {
 			}
 		case f.Name() == "console":
 			continue
-		}
+		default:
 			device, err := DeviceFromPath(filepath.Join(path, f.Name()))
 			if err != nil {
 				if err == ErrNotADevice {
@@ -90,6 +104,12 @@ func getDevices(path, containerPath string) ([]specs.LinuxDevice, error) {
 				if os.IsNotExist(err) {
 					continue
 				}
+				if errors.Is(err, os.ErrPermission) && usernsRunningInUserNS() {
+					// ignore the "permission denied" error if running in userns.
+					// This allows rootless containers to use devices that are
+					// accessible, ignoring devices that are not.
+					continue
+				}
 				return nil, err
 			}
 			if device.Type == fifoDevice {
@@ -100,6 +120,7 @@ func getDevices(path, containerPath string) ([]specs.LinuxDevice, error) {
 			}
 			out = append(out, *device)
 		}
+	}
 	return out, nil
 }
 
@@ -114,6 +135,12 @@ const (
 // DeviceFromPath takes the path to a device to look up the information about a
 // linux device and returns that information as a LinuxDevice struct.
 func DeviceFromPath(path string) (*specs.LinuxDevice, error) {
+	if overrideDeviceFromPath != nil {
+		if err := overrideDeviceFromPath(path); err != nil {
+			return nil, err
+		}
+	}
+
 	var stat unix.Stat_t
 	if err := unix.Lstat(path, &stat); err != nil {
 		return nil, err

oci/utils_unix_go116_test.go

@@ -0,0 +1,55 @@
+//go:build !go1.17 && !windows && !darwin
+// +build !go1.17,!windows,!darwin
+
+/*
+   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 oci
+
+import "io/fs"
+
+// The following code is adapted from go1.17.1/src/io/fs/readdir.go
+// to compensate for the lack of fs.FileInfoToDirEntry in Go 1.16.
+
+// dirInfo is a DirEntry based on a FileInfo.
+type dirInfo struct {
+	fileInfo fs.FileInfo
+}
+
+func (di dirInfo) IsDir() bool {
+	return di.fileInfo.IsDir()
+}
+
+func (di dirInfo) Type() fs.FileMode {
+	return di.fileInfo.Mode().Type()
+}
+
+func (di dirInfo) Info() (fs.FileInfo, error) {
+	return di.fileInfo, nil
+}
+
+func (di dirInfo) Name() string {
+	return di.fileInfo.Name()
+}
+
+// fileInfoToDirEntry returns a DirEntry that returns information from info.
+// If info is nil, FileInfoToDirEntry returns nil.
+func fileInfoToDirEntry(info fs.FileInfo) fs.DirEntry {
+	if info == nil {
+		return nil
+	}
+	return dirInfo{fileInfo: info}
+}

oci/utils_unix_go117_test.go

@@ -0,0 +1,24 @@
+//go:build go1.17 && !windows && !darwin
+// +build go1.17,!windows,!darwin
+
+/*
+   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 oci
+
+import "io/fs"
+
+var fileInfoToDirEntry = fs.FileInfoToDirEntry

oci/utils_unix_test.go

@@ -19,7 +19,128 @@
 
 package oci
 
-import "testing"
+import (
+	"errors"
+	"fmt"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/containerd/containerd/pkg/userns"
+)
+
+func cleanupTest() {
+	overrideDeviceFromPath = nil
+	osReadDir = os.ReadDir
+	usernsRunningInUserNS = userns.RunningInUserNS
+}
+
+// Based on test from runc:
+// https://github.com/opencontainers/runc/blob/v1.0.0/libcontainer/devices/device_unix_test.go#L34-L47
+func TestHostDevicesOSReadDirFailure(t *testing.T) {
+	testError := fmt.Errorf("test error: %w", os.ErrPermission)
+
+	// Override os.ReadDir to inject error.
+	osReadDir = func(dirname string) ([]os.DirEntry, error) {
+		return nil, testError
+	}
+
+	// Override userns.RunningInUserNS to ensure not running in user namespace.
+	usernsRunningInUserNS = func() bool {
+		return false
+	}
+	defer cleanupTest()
+
+	_, err := HostDevices()
+	if !errors.Is(err, testError) {
+		t.Fatalf("Unexpected error %v, expected %v", err, testError)
+	}
+}
+
+// Based on test from runc:
+// https://github.com/opencontainers/runc/blob/v1.0.0/libcontainer/devices/device_unix_test.go#L34-L47
+func TestHostDevicesOSReadDirFailureInUserNS(t *testing.T) {
+	testError := fmt.Errorf("test error: %w", os.ErrPermission)
+
+	// Override os.ReadDir to inject error.
+	osReadDir = func(dirname string) ([]os.DirEntry, error) {
+		if dirname == "/dev" {
+			fi, err := os.Lstat("/dev/null")
+			if err != nil {
+				t.Fatalf("Unexpected error %v", err)
+			}
+
+			return []os.DirEntry{fileInfoToDirEntry(fi)}, nil
+		}
+		return nil, testError
+	}
+	// Override userns.RunningInUserNS to ensure running in user namespace.
+	usernsRunningInUserNS = func() bool {
+		return true
+	}
+	defer cleanupTest()
+
+	_, err := HostDevices()
+	if !errors.Is(err, nil) {
+		t.Fatalf("Unexpected error %v, expected %v", err, nil)
+	}
+}
+
+// Based on test from runc:
+// https://github.com/opencontainers/runc/blob/v1.0.0/libcontainer/devices/device_unix_test.go#L49-L74
+func TestHostDevicesDeviceFromPathFailure(t *testing.T) {
+	testError := fmt.Errorf("test error: %w", os.ErrPermission)
+
+	// Override DeviceFromPath to produce an os.ErrPermission on /dev/null.
+	overrideDeviceFromPath = func(path string) error {
+		if path == "/dev/null" {
+			return testError
+		}
+		return nil
+	}
+
+	// Override userns.RunningInUserNS to ensure not running in user namespace.
+	usernsRunningInUserNS = func() bool {
+		return false
+	}
+	defer cleanupTest()
+
+	d, err := HostDevices()
+	if !errors.Is(err, testError) {
+		t.Fatalf("Unexpected error %v, expected %v", err, testError)
+	}
+
+	assert.Equal(t, 0, len(d))
+}
+
+// Based on test from runc:
+// https://github.com/opencontainers/runc/blob/v1.0.0/libcontainer/devices/device_unix_test.go#L49-L74
+func TestHostDevicesDeviceFromPathFailureInUserNS(t *testing.T) {
+	testError := fmt.Errorf("test error: %w", os.ErrPermission)
+
+	// Override DeviceFromPath to produce an os.ErrPermission on all devices,
+	// except for /dev/null.
+	overrideDeviceFromPath = func(path string) error {
+		if path == "/dev/null" {
+			return nil
+		}
+		return testError
+	}
+
+	// Override userns.RunningInUserNS to ensure running in user namespace.
+	usernsRunningInUserNS = func() bool {
+		return true
+	}
+	defer cleanupTest()
+
+	d, err := HostDevices()
+	if !errors.Is(err, nil) {
+		t.Fatalf("Unexpected error %v, expected %v", err, nil)
+	}
+	assert.Equal(t, 1, len(d))
+	assert.Equal(t, d[0].Path, "/dev/null")
+}
 
 func TestHostDevicesAllValid(t *testing.T) {
 	devices, err := HostDevices()