From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3F046C3F2CD for ; Sat, 29 Feb 2020 00:57:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 178172469D for ; Sat, 29 Feb 2020 00:57:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="vSgabok4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726766AbgB2A5s (ORCPT ); Fri, 28 Feb 2020 19:57:48 -0500 Received: from gateway23.websitewelcome.com ([192.185.49.180]:45024 "EHLO gateway23.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726621AbgB2A5q (ORCPT ); Fri, 28 Feb 2020 19:57:46 -0500 Received: from cm17.websitewelcome.com (cm17.websitewelcome.com [100.42.49.20]) by gateway23.websitewelcome.com (Postfix) with ESMTP id 56563FCB5A for ; Fri, 28 Feb 2020 18:57:45 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 7qRtjdL6oAGTX7qRtjmCKN; Fri, 28 Feb 2020 18:57:45 -0600 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Type:MIME-Version:Message-ID:Subject: Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=5zJGKP6eSAdHRVVreVQHGM36vc/G0+uFEcDovAOw10k=; b=vSgabok4xn8RNfrUuKOQZ4yqmr VmOjEEtxyoillPI5x+Gl59KPmauCOPhea93zjwfmBWe+nmrigx7bzu9SPqeCB2QjrQsKgnG4b8lgS clcgerM68QKiY+68JCxAOMySSqboKZjPy1ViqfHpeH8Kvj156DRbMjURKAoDHz5h6sNk/QJAWNDBi Vhto7Bqtjg9sp9GlDItiGS2sY/t2AjfB9kvwGXwOwVElLeNgOlpO1ebbcmPnf+vY5EWhpZmmRYq3H D4SQXSXTYa3lxQARmRHpRG94cU/ReXXwDwMg3CMwi6/KzfhWdwT/fuYv/yOCpETUAEoox4L+woBrQ PniqWdug==; Received: from [200.39.15.57] (port=13359 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j7qRr-002y0f-O0; Fri, 28 Feb 2020 18:57:43 -0600 Date: Fri, 28 Feb 2020 19:00:40 -0600 From: "Gustavo A. R. Silva" To: "David S. Miller" , Jakub Kicinski Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] net: dn_fib: Replace zero-length array with flexible-array member Message-ID: <20200229010040.GA9287@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 200.39.15.57 X-Source-L: No X-Exim-ID: 1j7qRr-002y0f-O0 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.39.15.57]:13359 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 38 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva --- include/net/dn_fib.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/net/dn_fib.h b/include/net/dn_fib.h index 6dd2213c5eb2..ccc6e9df178b 100644 --- a/include/net/dn_fib.h +++ b/include/net/dn_fib.h @@ -90,7 +90,7 @@ struct dn_fib_table { int (*flush)(struct dn_fib_table *t); int (*dump)(struct dn_fib_table *t, struct sk_buff *skb, struct netlink_callback *cb); - unsigned char data[0]; + unsigned char data[]; }; #ifdef CONFIG_DECNET_ROUTER -- 2.25.0