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,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 A6D53C3F2CD for ; Fri, 28 Feb 2020 13:33:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79F062469D for ; Fri, 28 Feb 2020 13:33:50 +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="i4RC3P4A" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726810AbgB1Ndt (ORCPT ); Fri, 28 Feb 2020 08:33:49 -0500 Received: from gateway36.websitewelcome.com ([192.185.201.2]:11788 "EHLO gateway36.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726388AbgB1Ndt (ORCPT ); Fri, 28 Feb 2020 08:33:49 -0500 Received: from cm13.websitewelcome.com (cm13.websitewelcome.com [100.42.49.6]) by gateway36.websitewelcome.com (Postfix) with ESMTP id AACF8408F1F9F for ; Fri, 28 Feb 2020 06:48:43 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 7flzjIVrKRP4z7flzjguyj; Fri, 28 Feb 2020 07:33:47 -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=aSkfaOdswRAcwEgvUUD/jHq/wDo0j5Z3Rpp7rEjxwzs=; b=i4RC3P4Avjr5/G58F/ZCoUScku V2MZjVGzvtC0nv8YdtVWvd9isNstfUIr57yO9H29QcPyRMmclXVrL0z+IjE6h7dTTir/qus4H/0zU YubdgMsnax0gy0nwo8M7D3Sw/c3JBl1QPxZmaBvLC3DGwKh1oU7CCHp+oQOOEKPHMeFEU76+u2Qta O/gMwWzNhBKAlR85ODVU55wHW1VyxB5Ki7RSLqzUH7oUKDTeC1Vp4oA+hMn3mvqMSmayCu6basPBs UeerteqSSs7bKV2sibVhqFCUsIm5q50vG4ClBWWhUddW5LMWf2e9S5CdseXJ/r8XLQlpDkDw9icTE 46rqtnjw==; Received: from [201.162.240.44] (port=20057 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j7flx-001O1V-J7; Fri, 28 Feb 2020 07:33:46 -0600 Date: Fri, 28 Feb 2020 07:36:41 -0600 From: "Gustavo A. R. Silva" To: Steffen Klassert , Herbert Xu , "David S. Miller" , Alexey Kuznetsov , Hideaki YOSHIFUJI , Jakub Kicinski Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] ipv6: Replace zero-length array with flexible-array member Message-ID: <20200228133641.GA27169@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: 201.162.240.44 X-Source-L: No X-Exim-ID: 1j7flx-001O1V-J7 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.240.44]:20057 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 40 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 --- net/ipv6/ah6.c | 2 +- net/ipv6/seg6_iptunnel.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c index 95835e8d99aa..871d6e52ec67 100644 --- a/net/ipv6/ah6.c +++ b/net/ipv6/ah6.c @@ -36,7 +36,7 @@ struct tmp_ext { struct in6_addr saddr; #endif struct in6_addr daddr; - char hdrs[0]; + char hdrs[]; }; struct ah_skb_cb { diff --git a/net/ipv6/seg6_iptunnel.c b/net/ipv6/seg6_iptunnel.c index ab7f124ff5d7..d8afe7290de8 100644 --- a/net/ipv6/seg6_iptunnel.c +++ b/net/ipv6/seg6_iptunnel.c @@ -29,7 +29,7 @@ struct seg6_lwt { struct dst_cache cache; - struct seg6_iptunnel_encap tuninfo[0]; + struct seg6_iptunnel_encap tuninfo[]; }; static inline struct seg6_lwt *seg6_lwt_lwtunnel(struct lwtunnel_state *lwt) -- 2.25.0