platform/chrome: cros_ec_proto: handle empty payload in getting wake mask

cros_ec_get_host_event_wake_mask() expects to receive
sizeof(struct ec_response_host_event_mask) from send_command().  The
payload is valid only if the return value is positive.

Return -EPROTO if send_command() returns 0 in
cros_ec_get_host_event_wake_mask().
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220609084957.3684698-22-tzungbi@kernel.org

drivers/platform/chrome/cros_ec_proto.c

@@ -256,19 +256,23 @@ static int cros_ec_get_host_event_wake_mask(struct cros_ec_device *ec_dev, uint3
 	msg->insize = sizeof(*r);
 
 	ret = send_command(ec_dev, msg);
-	if (ret >= 0) {
-		mapped = cros_ec_map_error(msg->result);
-		if (mapped) {
-			ret = mapped;
-			goto exit;
-		}
+	if (ret < 0)
+		goto exit;
+
+	mapped = cros_ec_map_error(msg->result);
+	if (mapped) {
+		ret = mapped;
+		goto exit;
 	}
-	if (ret > 0) {
-		r = (struct ec_response_host_event_mask *)msg->data;
-		*mask = r->mask;
-		ret = 0;
+
+	if (ret == 0) {
+		ret = -EPROTO;
+		goto exit;
 	}
 
+	r = (struct ec_response_host_event_mask *)msg->data;
+	*mask = r->mask;
+	ret = 0;
 exit:
 	kfree(msg);
 	return ret;