runtime: fsGroup support for direct-assigned volume

The fsGroup will be specified by the fsGroup key in
the direct-assign mountinfo metadate field.
This will be set when invoking the kata-runtime
binary and providing the key, value pair in the metadata
field. Similarly, the fsGroupChangePolicy will also
be provided in the mountinfo metadate field.

Adding an extra fields FsGroup and FSGroupChangePolicy
in the Mount construct for container mount which will
be populated when creating block devices by parsing
out the mountInfo.json.

And in handleDeviceBlockVolume of the kata-agent client,
it checks if the mount FSGroup is not nil, which
indicates that fsGroup change is required in the guest,
and will provide the FSGroup field in the protobuf to
pass the value to the agent.

Fixes #4018

Signed-off-by: Yibo Zhuang <yibzhuang@gmail.com>

src/runtime/pkg/direct-volume/utils.go

@@ -17,6 +17,25 @@ import (
 
 const (
 	mountInfoFileName = "mountInfo.json"
+
+	FSGroupMetadataKey             = "fsGroup"
+	FSGroupChangePolicyMetadataKey = "fsGroupChangePolicy"
+)
+
+// FSGroupChangePolicy holds policies that will be used for applying fsGroup to a volume.
+// This type and the allowed values are tracking the PodFSGroupChangePolicy defined in
+// https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/api/core/v1/types.go
+// It is up to the client using the direct-assigned volume feature (e.g. CSI drivers) to determine
+// the optimal setting for this change policy (i.e. from Pod spec or assuming volume ownership
+// based on the storage offering).
+type FSGroupChangePolicy string
+
+const (
+	// FSGroupChangeAlways indicates that volume's ownership should always be changed.
+	FSGroupChangeAlways FSGroupChangePolicy = "Always"
+	// FSGroupChangeOnRootMismatch indicates that volume's ownership will be changed
+	// only when ownership of root directory does not match with the desired group id.
+	FSGroupChangeOnRootMismatch FSGroupChangePolicy = "OnRootMismatch"
 )
 
 var kataDirectVolumeRootPath = "/run/kata-containers/shared/direct-volumes"

src/runtime/pkg/direct-volume/utils_test.go

@@ -25,6 +25,10 @@ func TestAdd(t *testing.T) {
 		VolumeType: "block",
 		Device:     "/dev/sda",
 		FsType:     "ext4",
+		Metadata: map[string]string{
+			FSGroupMetadataKey:             "3000",
+			FSGroupChangePolicyMetadataKey: string(FSGroupChangeOnRootMismatch),
+		},
 		Options: []string{"journal_dev", "noload"},
 	}
 	buf, err := json.Marshal(actual)
@@ -39,6 +43,7 @@ func TestAdd(t *testing.T) {
 	assert.Equal(t, expected.Device, actual.Device)
 	assert.Equal(t, expected.FsType, actual.FsType)
 	assert.Equal(t, expected.Options, actual.Options)
+	assert.Equal(t, expected.Metadata, actual.Metadata)
 
 	// Remove the file
 	err = Remove(volumePath)

src/runtime/virtcontainers/container.go

@@ -639,6 +639,26 @@ func (c *Container) createBlockDevices(ctx context.Context) error {
 			c.mounts[i].Type = mntInfo.FsType
 			c.mounts[i].Options = mntInfo.Options
 			c.mounts[i].ReadOnly = readonly
+
+			for key, value := range mntInfo.Metadata {
+				switch key {
+				case volume.FSGroupMetadataKey:
+					gid, err := strconv.Atoi(value)
+					if err != nil {
+						c.Logger().WithError(err).Errorf("invalid group id value %s provided for key %s", value, volume.FSGroupMetadataKey)
+						continue
+					}
+					c.mounts[i].FSGroup = &gid
+				case volume.FSGroupChangePolicyMetadataKey:
+					if _, exists := mntInfo.Metadata[volume.FSGroupMetadataKey]; !exists {
+						c.Logger().Errorf("%s specified without provding the group id with key %s", volume.FSGroupChangePolicyMetadataKey, volume.FSGroupMetadataKey)
+						continue
+					}
+					c.mounts[i].FSGroupChangePolicy = volume.FSGroupChangePolicy(value)
+				default:
+					c.Logger().Warnf("Ignoring unsupported direct-assignd volume metadata key: %s, value: %s", key, value)
+				}
+			}
 		}
 
 		var stat unix.Stat_t

src/runtime/virtcontainers/kata_agent.go

@@ -19,6 +19,7 @@ import (
 	"time"
 
 	"github.com/docker/go-units"
+	volume "github.com/kata-containers/kata-containers/src/runtime/pkg/direct-volume"
 	"github.com/kata-containers/kata-containers/src/runtime/pkg/katautils/katatrace"
 	resCtrl "github.com/kata-containers/kata-containers/src/runtime/pkg/resourcecontrol"
 	"github.com/kata-containers/kata-containers/src/runtime/pkg/uuid"
@@ -167,6 +168,15 @@ func getPagesizeFromOpt(fsOpts []string) string {
 	return ""
 }
 
+func getFSGroupChangePolicy(policy volume.FSGroupChangePolicy) pbTypes.FSGroupChangePolicy {
+	switch policy {
+	case volume.FSGroupChangeOnRootMismatch:
+		return pbTypes.FSGroupChangePolicy_OnRootMismatch
+	default:
+		return pbTypes.FSGroupChangePolicy_Always
+	}
+}
+
 // Shared path handling:
 // 1. create three directories for each sandbox:
 // -. /run/kata-containers/shared/sandboxes/$sbx_id/mounts/, a directory to hold all host/guest shared mounts
@@ -1468,6 +1478,12 @@ func (k *kataAgent) handleDeviceBlockVolume(c *Container, m Mount, device api.De
 	if len(vol.Options) == 0 {
 		vol.Options = m.Options
 	}
+	if m.FSGroup != nil {
+		vol.FsGroup = &grpc.FSGroup{
+			GroupId:           uint32(*m.FSGroup),
+			GroupChangePolicy: getFSGroupChangePolicy(m.FSGroupChangePolicy),
+		}
+	}
 
 	return vol, nil
 }

src/runtime/virtcontainers/kata_agent_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/stretchr/testify/assert"
 
 	"code.cloudfoundry.org/bytefmt"
+	volume "github.com/kata-containers/kata-containers/src/runtime/pkg/direct-volume"
 	"github.com/kata-containers/kata-containers/src/runtime/virtcontainers/device/api"
 	"github.com/kata-containers/kata-containers/src/runtime/virtcontainers/device/config"
 	"github.com/kata-containers/kata-containers/src/runtime/virtcontainers/device/drivers"
@@ -234,6 +235,7 @@ func TestHandleLocalStorage(t *testing.T) {
 }
 
 func TestHandleDeviceBlockVolume(t *testing.T) {
+	var gid = 2000
 	k := kataAgent{}
 
 	// nolint: govet
@@ -315,6 +317,27 @@ func TestHandleDeviceBlockVolume(t *testing.T) {
 				Source: testSCSIAddr,
 			},
 		},
+		{
+			BlockDeviceDriver: config.VirtioBlock,
+			inputMount: Mount{
+				FSGroup:             &gid,
+				FSGroupChangePolicy: volume.FSGroupChangeOnRootMismatch,
+			},
+			inputDev: &drivers.BlockDevice{
+				BlockDrive: &config.BlockDrive{
+					PCIPath:  testPCIPath,
+					VirtPath: testVirtPath,
+				},
+			},
+			resultVol: &pb.Storage{
+				Driver: kataBlkDevType,
+				Source: testPCIPath.String(),
+				FsGroup: &pb.FSGroup{
+					GroupId:           uint32(gid),
+					GroupChangePolicy: pbTypes.FSGroupChangePolicy_OnRootMismatch,
+				},
+			},
+		},
 	}
 
 	for _, test := range tests {

src/runtime/virtcontainers/mount.go

@@ -14,6 +14,7 @@ import (
 	"syscall"
 
 	merr "github.com/hashicorp/go-multierror"
+	volume "github.com/kata-containers/kata-containers/src/runtime/pkg/direct-volume"
 	"github.com/kata-containers/kata-containers/src/runtime/pkg/katautils/katatrace"
 	"github.com/kata-containers/kata-containers/src/runtime/virtcontainers/utils"
 	"github.com/pkg/errors"
@@ -325,6 +326,7 @@ func bindMountContainerRootfs(ctx context.Context, shareDir, cid, cRootFs string
 }
 
 // Mount describes a container mount.
+// nolint: govet
 type Mount struct {
 	// Source is the source of the mount.
 	Source string
@@ -352,6 +354,14 @@ type Mount struct {
 
 	// ReadOnly specifies if the mount should be read only or not
 	ReadOnly bool
+
+	// FSGroup a group ID that the group ownership of the files for the mounted volume
+	// will need to be changed when set.
+	FSGroup *int
+
+	// FSGroupChangePolicy specifies the policy that will be used when applying
+	// group id ownership change for a volume.
+	FSGroupChangePolicy volume.FSGroupChangePolicy
 }
 
 func isSymlink(path string) bool {