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 832D1C3F2CD for ; Sat, 29 Feb 2020 00:50:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 59AFB24699 for ; Sat, 29 Feb 2020 00:50:20 +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="ADV34/l4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726791AbgB2AuS (ORCPT ); Fri, 28 Feb 2020 19:50:18 -0500 Received: from gateway22.websitewelcome.com ([192.185.47.163]:21406 "EHLO gateway22.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726418AbgB2AuR (ORCPT ); Fri, 28 Feb 2020 19:50:17 -0500 Received: from cm16.websitewelcome.com (cm16.websitewelcome.com [100.42.49.19]) by gateway22.websitewelcome.com (Postfix) with ESMTP id F126965C71 for ; Fri, 28 Feb 2020 18:50:16 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 7qKejRhm88vkB7qKejMOZs; Fri, 28 Feb 2020 18:50:16 -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=f8vhCCp3OOzlAffu+dZicuZhO8OF+Y4bPnu/LSD79Jo=; b=ADV34/l40VcoT5ws8TKqjwodLl jVADoHzrLqvLxNu+pzKpcr9OBUQi/gFuEYxaIl1BzXp1R6k5EP2LkqgSd5J/uWYkWlzBd9sM29FbW EKyzThtDRSpPRU6JFyXvGdHSiREvZkQs0t54pdLJpvA/5psSDGGu+/LuOf1zKvAzffvVTFER1VvsP s/Zp6+PfEU0a51O9xoEVfxAooecit0Y+9+QKp/+2x/uRDzY/JHgiOt2LuPUCqfEX01Wgdf3ES/2bc 01c2Q3pRrVSCCzrABRGWCMz9fMzkEfw6bjFGWDYbpPNKDQhCUXqtS/PPDZpWdaDX3s9t4A7IGn5Xs 7vTj5xxg==; Received: from [200.39.15.57] (port=22066 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j7qKd-002urX-07; Fri, 28 Feb 2020 18:50:15 -0600 Date: Fri, 28 Feb 2020 18:53:11 -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] ndisc: Replace zero-length array with flexible-array member Message-ID: <20200229005311.GA8953@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: 1j7qKd-002urX-07 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.39.15.57]:22066 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 34 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/ndisc.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/net/ndisc.h b/include/net/ndisc.h index b5ebeb3b0de0..1c61aeb3a1c0 100644 --- a/include/net/ndisc.h +++ b/include/net/ndisc.h @@ -80,12 +80,12 @@ extern struct neigh_table nd_tbl; struct nd_msg { struct icmp6hdr icmph; struct in6_addr target; - __u8 opt[0]; + __u8 opt[]; }; struct rs_msg { struct icmp6hdr icmph; - __u8 opt[0]; + __u8 opt[]; }; struct ra_msg { @@ -98,7 +98,7 @@ struct rd_msg { struct icmp6hdr icmph; struct in6_addr target; struct in6_addr dest; - __u8 opt[0]; + __u8 opt[]; }; struct nd_opt_hdr { -- 2.25.0