drm: Reject bad property flag combinations

Pimp drm_property_type_valid() to check for more fails with the
property flags. Also make the check before adding the property,
and bail out if things look bad.

Since we're now chekcing for more than the type let's also
change the function name to drm_property_flags_valid().
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180306164849.2862-6-ville.syrjala@linux.intel.comReviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_property.c

@@ -50,11 +50,27 @@
  * IOCTL and in the get/set property IOCTL.
  */
 
-static bool drm_property_type_valid(struct drm_property *property)
+static bool drm_property_flags_valid(u32 flags)
 {
-	if (property->flags & DRM_MODE_PROP_EXTENDED_TYPE)
-		return !(property->flags & DRM_MODE_PROP_LEGACY_TYPE);
-	return !!(property->flags & DRM_MODE_PROP_LEGACY_TYPE);
+	u32 legacy_type = flags & DRM_MODE_PROP_LEGACY_TYPE;
+	u32 ext_type = flags & DRM_MODE_PROP_EXTENDED_TYPE;
+
+	/* Reject undefined/deprecated flags */
+	if (flags & ~(DRM_MODE_PROP_LEGACY_TYPE |
+		      DRM_MODE_PROP_EXTENDED_TYPE |
+		      DRM_MODE_PROP_IMMUTABLE |
+		      DRM_MODE_PROP_ATOMIC))
+		return false;
+
+	/* We want either a legacy type or an extended type, but not both */
+	if (!legacy_type == !ext_type)
+		return false;
+
+	/* Only one legacy type at a time please */
+	if (legacy_type && !is_power_of_2(legacy_type))
+		return false;
+
+	return true;
 }
 
 /**
@@ -79,6 +95,9 @@ struct drm_property *drm_property_create(struct drm_device *dev,
 	struct drm_property *property = NULL;
 	int ret;
 
+	if (WARN_ON(!drm_property_flags_valid(flags)))
+		return NULL;
+
 	if (WARN_ON(strlen(name) >= DRM_PROP_NAME_LEN))
 		return NULL;
 
@@ -108,8 +127,6 @@ struct drm_property *drm_property_create(struct drm_device *dev,
 
 	list_add_tail(&property->head, &dev->mode_config.property_list);
 
-	WARN_ON(!drm_property_type_valid(property));
-
 	return property;
 fail:
 	kfree(property->values);