From patchwork Sat Feb 29 00:51:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 1246946 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=embeddedor.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=embeddedor.com header.i=@embeddedor.com header.a=rsa-sha256 header.s=default header.b=efrLuhQP; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 48TpKs3MGVz9sRJ for ; Sat, 29 Feb 2020 12:12:33 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726627AbgB2BMa (ORCPT ); Fri, 28 Feb 2020 20:12:30 -0500 Received: from gateway20.websitewelcome.com ([192.185.69.18]:29316 "EHLO gateway20.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726046AbgB2BMa (ORCPT ); Fri, 28 Feb 2020 20:12:30 -0500 Received: from cm14.websitewelcome.com (cm14.websitewelcome.com [100.42.49.7]) by gateway20.websitewelcome.com (Postfix) with ESMTP id 86D61401C96E3 for ; Fri, 28 Feb 2020 17:34:20 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 7qJDjEdg3XVkQ7qJDjZRdw; Fri, 28 Feb 2020 18:48:47 -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=rkgKkwh+Uy7zbmDqvHdqXDUel6G9tCsRpBolNnwM8dI=; b=efrLuhQPWVnz12w0pxW8O9tDfX YgxeX0EVNDJtNTJEb2XROl3trqu3klTXskiynIlVuifHQgq/31YmmcshPBDTuIqEtaGrNuSLvVgoT 2pltiZpQGgZ5PcPW3syE+hy9m3Eq/By106w/TYiT1Rp+I3kBbg3YSFfs1k0iOAEM4kexRv0zKWEZb VXCyEdvvXVlhcIEQNW6LlYEte5wiNiHaTxVD8Nu7L2NyHDWl1Gh1ZqdSktf1QHxN7NuB2Qs/26RY+ D0/ZKWdPjFyiEL+2ZmGsO+XBo2H0MLxx2SbftJizxannL3DmkNgmclUgJSAmBYKV3EXnLugcCmTSX rkZ3wBhA==; Received: from [200.39.15.57] (port=18879 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j7qJB-002uCH-20; Fri, 28 Feb 2020 18:48:45 -0600 Date: Fri, 28 Feb 2020 18:51:41 -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: ipv6: mld: Replace zero-length array with flexible-array member Message-ID: <20200229005141.GA8807@embeddedor> MIME-Version: 1.0 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: 1j7qJB-002uCH-20 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.39.15.57]:18879 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 30 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/mld.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/net/mld.h b/include/net/mld.h index b0f5b3105ef0..496bddb59942 100644 --- a/include/net/mld.h +++ b/include/net/mld.h @@ -24,12 +24,12 @@ struct mld2_grec { __u8 grec_auxwords; __be16 grec_nsrcs; struct in6_addr grec_mca; - struct in6_addr grec_src[0]; + struct in6_addr grec_src[]; }; struct mld2_report { struct icmp6hdr mld2r_hdr; - struct mld2_grec mld2r_grec[0]; + struct mld2_grec mld2r_grec[]; }; #define mld2r_type mld2r_hdr.icmp6_type @@ -55,7 +55,7 @@ struct mld2_query { #endif __u8 mld2q_qqic; __be16 mld2q_nsrcs; - struct in6_addr mld2q_srcs[0]; + struct in6_addr mld2q_srcs[]; }; #define mld2q_type mld2q_hdr.icmp6_type