surface: check buffer size is compatible with scale

This relies on [1].

[1]: 8d5fadad47

types/wlr_surface.c

@@ -145,17 +145,22 @@ static void surface_set_input_region(struct wl_client *client,
  * rectangle) but before applying the viewport scaling (via the viewport's
  * destination rectangle).
  */
-static void surface_state_viewport_src_size(struct wlr_surface_state *state,
+static bool surface_state_viewport_src_size(struct wlr_surface_state *state,
 		int *out_width, int *out_height) {
 	if (state->buffer_width == 0 && state->buffer_height == 0) {
 		*out_width = *out_height = 0;
-		return;
+		return true;
 	}
 
 	if (state->viewport.has_src) {
 		*out_width = state->viewport.src.width;
 		*out_height = state->viewport.src.height;
 	} else {
+		if (state->buffer_width % state->scale != 0 ||
+				state->buffer_height % state->scale != 0) {
+			return false;
+		}
+
 		int width = state->buffer_width / state->scale;
 		int height = state->buffer_height / state->scale;
 		if ((state->transform & WL_OUTPUT_TRANSFORM_90) != 0) {
@@ -166,9 +171,11 @@ static void surface_state_viewport_src_size(struct wlr_surface_state *state,
 		*out_width = width;
 		*out_height = height;
 	}
+
+	return true;
 }
 
-static void surface_state_finalize(struct wlr_surface *surface,
+static bool surface_state_finalize(struct wlr_surface *surface,
 		struct wlr_surface_state *state) {
 	if ((state->committed & WLR_SURFACE_STATE_BUFFER)) {
 		if (state->buffer_resource != NULL) {
@@ -187,8 +194,13 @@ static void surface_state_finalize(struct wlr_surface *surface,
 			state->height = state->viewport.dst_height;
 		}
 	} else {
-		surface_state_viewport_src_size(state,
-			&state->width, &state->height);
+		if (!surface_state_viewport_src_size(state,
+				&state->width, &state->height)) {
+			wl_resource_post_error(surface->resource,
+				WL_SURFACE_ERROR_INVALID_SIZE,
+				"Buffer size not divisible by scale");
+			return false;
+		}
 	}
 
 	pixman_region32_intersect_rect(&state->surface_damage,
@@ -197,6 +209,8 @@ static void surface_state_finalize(struct wlr_surface *surface,
 	pixman_region32_intersect_rect(&state->buffer_damage,
 		&state->buffer_damage, 0, 0, state->buffer_width,
 		state->buffer_height);
+
+	return true;
 }
 
 static void surface_update_damage(pixman_region32_t *buffer_damage,
@@ -388,7 +402,9 @@ static void surface_update_input_region(struct wlr_surface *surface) {
 }
 
 static void surface_commit_pending(struct wlr_surface *surface) {
-	surface_state_finalize(surface, &surface->pending);
+	if (!surface_state_finalize(surface, &surface->pending)) {
+		return;
+	}
 
 	if (surface->role && surface->role->precommit) {
 		surface->role->precommit(surface);