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=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 83875C3402A for ; Mon, 17 Feb 2020 22:02:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5A3A620801 for ; Mon, 17 Feb 2020 22:02:43 +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="fQRsoHfi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726298AbgBQWCm (ORCPT ); Mon, 17 Feb 2020 17:02:42 -0500 Received: from gateway23.websitewelcome.com ([192.185.48.104]:14870 "EHLO gateway23.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726010AbgBQWCj (ORCPT ); Mon, 17 Feb 2020 17:02:39 -0500 Received: from cm13.websitewelcome.com (cm13.websitewelcome.com [100.42.49.6]) by gateway23.websitewelcome.com (Postfix) with ESMTP id 26E6D4D33 for ; Mon, 17 Feb 2020 15:40:20 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 3o7ojqPi3RP4z3o7ojH0hP; Mon, 17 Feb 2020 15:40:20 -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=Up3NXkZ9MtOum0S7bVKL3huOyiNJmhlgLtMxveQ6vXs=; b=fQRsoHfiS305ia7mB6Tk7BCDh/ zu8WsjITjAx40ENo5SGDIPWQAysvcReMoY1px5no4omSD8BUVo+NaTDaafIhYlocD9N2uhjf129cn q0LrXgtBRbkzJYjXJ5febzafT1u6lqfyUVKdIkDfNQaGdjCGxWnwYObZn+SMeBVTO+xO5+UsOgntB SUD4DLY8MuqHtf5wrhfWuTpdfgHWmUnDQ8/voYHayRkfOjtIKD4VOmLHOsm1sDkVCxG/hxiIk1r7b 1ZsQSv8vO8GDPS5aWRsW0yXwDR4pHyPBTbPq6F4TZltM4pCR5sOSQ6mLRLRAqxOxlL3kIdTOAInYL nPOEal+w==; Received: from [200.68.140.26] (port=16142 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j3o7m-001GXx-EB; Mon, 17 Feb 2020 15:40:18 -0600 Date: Mon, 17 Feb 2020 15:43:00 -0600 From: "Gustavo A. R. Silva" To: Marek Lindner , Simon Wunderlich , Antonio Quartulli , Sven Eckelmann , "David S. Miller" , Jakub Kicinski Cc: b.a.t.m.a.n@lists.open-mesh.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] batman-adv: Replace zero-length array with flexible-array member Message-ID: <20200217214300.GA14129@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: 200.68.140.26 X-Source-L: No X-Exim-ID: 1j3o7m-001GXx-EB X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.140.26]:16142 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 9 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 --- net/batman-adv/distributed-arp-table.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c index 3d21dd83f8cc..b85da4b7a77b 100644 --- a/net/batman-adv/distributed-arp-table.c +++ b/net/batman-adv/distributed-arp-table.c @@ -88,7 +88,7 @@ struct batadv_dhcp_packet { __u8 sname[64]; __u8 file[128]; __be32 magic; - __u8 options[0]; + __u8 options[]; }; #define BATADV_DHCP_YIADDR_LEN sizeof(((struct batadv_dhcp_packet *)0)->yiaddr) -- 2.25.0