wiphy: Make sure Name attribute is valid utf8

DBus strings must be valid utf8.  The kernel only enforces that the
wiphy name is null terminated string.  It does not validate or otherwise
check the contents in any way.  Thus it is possible to have
non-printable or non-utf8 characters inside.

src/wiphy.c

@@ -720,8 +720,21 @@ static bool wiphy_property_get_name(struct l_dbus *dbus,
 					void *user_data)
 {
 	struct wiphy *wiphy = user_data;
+	char buf[20];
 
-	l_dbus_message_builder_append_basic(builder, 's', wiphy->name);
+	if (l_utf8_validate(wiphy->name, strlen(wiphy->name), NULL)) {
+		l_dbus_message_builder_append_basic(builder, 's', wiphy->name);
+		return true;
+	}
+
+	/*
+	 * In the highly unlikely scenario that the wiphy name is not utf8,
+	 * we simply use the canonical name phy<index>.  The kernel guarantees
+	 * that this name cannot be taken by any other wiphy, so this should
+	 * be safe enough.
+	 */
+	sprintf(buf, "phy%d", wiphy->id);
+	l_dbus_message_builder_append_basic(builder, 's', buf);
 
 	return true;
 }