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 A56D1C3F2D7 for ; Mon, 2 Mar 2020 11:57:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7BA8521739 for ; Mon, 2 Mar 2020 11:57:36 +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="ALZlif2s" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727810AbgCBL5d (ORCPT ); Mon, 2 Mar 2020 06:57:33 -0500 Received: from gateway34.websitewelcome.com ([192.185.148.200]:13605 "EHLO gateway34.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727228AbgCBL5c (ORCPT ); Mon, 2 Mar 2020 06:57:32 -0500 Received: from cm17.websitewelcome.com (cm17.websitewelcome.com [100.42.49.20]) by gateway34.websitewelcome.com (Postfix) with ESMTP id 4788B373769 for ; Mon, 2 Mar 2020 05:57:31 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 8jhTjXT1OAGTX8jhTjftXE; Mon, 02 Mar 2020 05:57:31 -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=LiBSQ0LE0yixdsEF469J2Wh45sDnPKDOgsNU7LNoc5U=; b=ALZlif2ssH12bw2MEJdivRbbvj 2HoUrWDFHhVGOw2DSibJzrgG0p8vAl9jc142h/t6ZbIinBXzRGzviLChmToa1+pZmESfb7DCFyTF9 akN0rcmuhPOxiVhrz7FxJYgY2FXz8s7u6KCa3pgLOGBiRw/kNMIwl6jENlEZc+YXUDGez7er2rzk2 lbdc7mlDXUZCiSP/h6pRLJTHdppK56xSCTyx55CT5V5UOcOXhiwzf/zRGhkwbSHD6h6H1NENlwJNU afKfXt95BFtk/vOj+qZdmPgR5EFq9XFN9Txlsfm5SFRWyL+gWQ2fJE3u3BtnlZ+H4Ki8MXucKS5Pj 8Ha/tzSA==; Received: from [201.166.157.123] (port=42204 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j8jga-003oib-A9; Mon, 02 Mar 2020 05:56:36 -0600 Date: Mon, 2 Mar 2020 05:59:33 -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] netdevice: Replace zero-length array with flexible-array member Message-ID: <20200302115933.GA15346@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: 201.166.157.123 X-Source-L: No X-Exim-ID: 1j8jga-003oib-A9 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.166.157.123]:42204 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 3 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/linux/netdevice.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 6c3f7032e8d9..b6fedd54cd8e 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -664,7 +664,7 @@ static inline void netdev_queue_numa_node_write(struct netdev_queue *q, int node struct rps_map { unsigned int len; struct rcu_head rcu; - u16 cpus[0]; + u16 cpus[]; }; #define RPS_MAP_SIZE(_num) (sizeof(struct rps_map) + ((_num) * sizeof(u16))) @@ -686,7 +686,7 @@ struct rps_dev_flow { struct rps_dev_flow_table { unsigned int mask; struct rcu_head rcu; - struct rps_dev_flow flows[0]; + struct rps_dev_flow flows[]; }; #define RPS_DEV_FLOW_TABLE_SIZE(_num) (sizeof(struct rps_dev_flow_table) + \ ((_num) * sizeof(struct rps_dev_flow))) @@ -704,7 +704,7 @@ struct rps_dev_flow_table { struct rps_sock_flow_table { u32 mask; - u32 ents[0] ____cacheline_aligned_in_smp; + u32 ents[] ____cacheline_aligned_in_smp; }; #define RPS_SOCK_FLOW_TABLE_SIZE(_num) (offsetof(struct rps_sock_flow_table, ents[_num])) @@ -767,7 +767,7 @@ struct xps_map { unsigned int len; unsigned int alloc_len; struct rcu_head rcu; - u16 queues[0]; + u16 queues[]; }; #define XPS_MAP_SIZE(_num) (sizeof(struct xps_map) + ((_num) * sizeof(u16))) #define XPS_MIN_MAP_ALLOC ((L1_CACHE_ALIGN(offsetof(struct xps_map, queues[1])) \ @@ -778,7 +778,7 @@ struct xps_map { */ struct xps_dev_maps { struct rcu_head rcu; - struct xps_map __rcu *attr_map[0]; /* Either CPUs map or RXQs map */ + struct xps_map __rcu *attr_map[]; /* Either CPUs map or RXQs map */ }; #define XPS_CPU_DEV_MAPS_SIZE(_tcs) (sizeof(struct xps_dev_maps) + \ -- 2.25.0