cdi,SPECS.md: allow empty cgroup permissions.

Allow injecting devices with empty cgroup permissions, requested by
the "none" permission string, also defined as pkg/cdi.NoPermissions.

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

Author: klihub

SPEC.md

@@ -139,6 +139,7 @@ The keywords "must", "must not", "required", "shall", "shall not", "should", "sh
                     // * r - allows container to read from the specified device.
                     // * w - allows container to write to the specified device.
                     // * m - allows container to create device files that do not yet exist.
+                    // Omitted or empty permissions default to 'rwm'. 'none' requests empty permissions.
                     "permissions": "<permissions>" (optional),
                     "uid": <int> (optional),
                     "gid": <int> (optional)

pkg/cdi/container-edits.go

@@ -42,6 +42,9 @@ const (
 	PoststartHook = "poststart"
 	// PoststopHook is the name of the OCI "poststop" hook.
 	PoststopHook = "poststop"
+
+	// NoPermissions requests empty cgroup permissions for a device.
+	NoPermissions = "none"
 )
 
 var (
@@ -106,8 +109,11 @@ func (e *ContainerEdits) Apply(spec *oci.Spec) error {
 
 		if dev.Type == "b" || dev.Type == "c" {
 			access := d.Permissions
-			if access == "" {
+			switch access {
+			case "":
 				access = "rwm"
+			case NoPermissions:
+				access = ""
 			}
 			specgen.AddLinuxResourcesDevice(true, dev.Type, &dev.Major, &dev.Minor, access)
 		}
@@ -354,10 +360,12 @@ func (d *DeviceNode) Validate() error {
 	if _, ok := validTypes[d.Type]; !ok {
 		return fmt.Errorf("device %q: invalid type %q", d.Path, d.Type)
 	}
-	for _, bit := range d.Permissions {
-		if bit != 'r' && bit != 'w' && bit != 'm' {
-			return fmt.Errorf("device %q: invalid permissions %q",
-				d.Path, d.Permissions)
+	if d.Permissions != NoPermissions {
+		for _, bit := range d.Permissions {
+			if bit != 'r' && bit != 'w' && bit != 'm' {
+				return fmt.Errorf("device %q: invalid permissions %q",
+					d.Path, d.Permissions)
+			}
 		}
 	}
 	return nil

pkg/cdi/container-edits_test.go

@@ -133,6 +133,18 @@ func TestValidateContainerEdits(t *testing.T) {
 			},
 			invalid: true,
 		},
+		{
+			name: "valid device, with NoPermissions",
+			edits: &cdi.ContainerEdits{
+				DeviceNodes: []*cdi.DeviceNode{
+					{
+						Path:        "/dev/vendorctl",
+						Type:        "b",
+						Permissions: NoPermissions,
+					},
+				},
+			},
+		},
 		{
 			name: "valid mount",
 			edits: &cdi.ContainerEdits{
@@ -420,6 +432,44 @@ func TestApplyContainerEdits(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "empty spec, device with explicitly empty permissions",
+			spec: &oci.Spec{},
+			edits: &cdi.ContainerEdits{
+				DeviceNodes: []*cdi.DeviceNode{
+					{
+						Path:        "/dev/nil",
+						Type:        "c",
+						Major:       1,
+						Minor:       3,
+						Permissions: NoPermissions,
+					},
+				},
+			},
+			result: &oci.Spec{
+				Linux: &oci.Linux{
+					Devices: []oci.LinuxDevice{
+						{
+							Path:  "/dev/nil",
+							Type:  "c",
+							Major: nullDeviceMajor,
+							Minor: nullDeviceMinor,
+						},
+					},
+					Resources: &oci.LinuxResources{
+						Devices: []oci.LinuxDeviceCgroup{
+							{
+								Allow:  true,
+								Type:   "c",
+								Major:  &nullDeviceMajor,
+								Minor:  &nullDeviceMinor,
+								Access: "",
+							},
+						},
+					},
+				},
+			},
+		},
 		{
 			name: "empty spec, device, env var",
 			spec: &oci.Spec{},