drm: Check mode object lease status in all master ioctl paths [v4]

Attempts to modify un-leased objects are rejected with an error.
Information returned about unleased objects is modified to make them
appear unusable and/or disconnected.

Changes for v2 as suggested by Daniel Vetter <daniel.vetter@ffwll.ch>:

 * With the change in the __drm_mode_object_find API to pass the
   file_priv along, we can now centralize most of the lease-based
   access checks in that function.

 * A few places skip that API and require in-line checks.

Changes for v3 provided by Dave Airlie <airlied@redhat.com>

 * remove support for leasing encoders.
 * add support for leasing planes.

Changes for v4

 * Only call drm_lease_held if DRIVER_MODESET.

Signed-off-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
index 240a05d..d1599f3 100644
--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -104,6 +104,25 @@ void drm_mode_object_unregister(struct drm_device *dev,
 	mutex_unlock(&dev->mode_config.idr_mutex);
 }
 
+/**
+ * drm_lease_required - check types which must be leased to be used
+ * @type: type of object
+ *
+ * Returns whether the provided type of drm_mode_object must
+ * be owned or leased to be used by a process.
+ */
+static bool drm_lease_required(uint32_t type)
+{
+	switch(type) {
+	case DRM_MODE_OBJECT_CRTC:
+	case DRM_MODE_OBJECT_CONNECTOR:
+	case DRM_MODE_OBJECT_PLANE:
+		return true;
+	default:
+		return false;
+	}
+}
+
 struct drm_mode_object *__drm_mode_object_find(struct drm_device *dev,
 					       struct drm_file *file_priv,
 					       uint32_t id, uint32_t type)
@@ -117,6 +136,9 @@ struct drm_mode_object *__drm_mode_object_find(struct drm_device *dev,
 	if (obj && obj->id != id)
 		obj = NULL;
 
+	if (obj && drm_lease_required(obj->type) && !_drm_lease_held(file_priv, obj->id))
+		obj = NULL;
+
 	if (obj && obj->free_cb) {
 		if (!kref_get_unless_zero(&obj->refcount))
 			obj = NULL;