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=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 2F78AC11D3D for ; Thu, 27 Feb 2020 20:20:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EF3F32469C for ; Thu, 27 Feb 2020 20:20:44 +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="UorAoA/b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729714AbgB0UUn (ORCPT ); Thu, 27 Feb 2020 15:20:43 -0500 Received: from gateway31.websitewelcome.com ([192.185.144.218]:33158 "EHLO gateway31.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726758AbgB0UUn (ORCPT ); Thu, 27 Feb 2020 15:20:43 -0500 Received: from cm13.websitewelcome.com (cm13.websitewelcome.com [100.42.49.6]) by gateway31.websitewelcome.com (Postfix) with ESMTP id 7A8094C593B for ; Thu, 27 Feb 2020 14:20:42 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 7PeEj0239RP4z7PeEjOZp8; Thu, 27 Feb 2020 14:20:42 -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=uf8a9vBAJSYVV5Wk+v1AR61ZSb+YDaIsUBmlQZO8jm8=; b=UorAoA/beGmNp854mZM6EhCWQJ Wff6qCXV1quzre04qY8DTcR/JJUSLrQBjm5DYFEfnsRnIR6aZMWZsqeAuz4K+AEn+W+Sr6OCdMVJs HlUDttPh2a6lKQImcyMasvc0zBxQTJbtdm06fY0LimHxusfcLSnFPVVXI/1Nu6HsIy+6hSYrzGTe7 D5uKJBoVsOKHXmIt5Vy8WV1TexJmHM0ufOpYBb7tPvTBOa5rbAOt+F4MwaFsPxSWlCOEHCcOQerzT fHS48Y9zpNPqpCXhfZKJkz6/ZtEnOD2FecYQMvpLrWqM/QfOmd+xZyWVHuFKy7eEkaYvQ0+u97dK4 o/f/1cmA==; Received: from [201.162.169.69] (port=6534 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j7PeC-000TA7-FV; Thu, 27 Feb 2020 14:20:40 -0600 Date: Thu, 27 Feb 2020 14:23:32 -0600 From: "Gustavo A. R. Silva" To: Evgeniy Polyakov Cc: linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] w1_netlink.h: Replace zero-length array with flexible-array member Message-ID: <20200227202332.GA15501@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: 201.162.169.69 X-Source-L: No X-Exim-ID: 1j7PeC-000TA7-FV X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.169.69]:6534 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 11 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 --- drivers/w1/w1_netlink.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/w1/w1_netlink.h b/drivers/w1/w1_netlink.h index 3041092e84b3..449680a61569 100644 --- a/drivers/w1/w1_netlink.h +++ b/drivers/w1/w1_netlink.h @@ -73,7 +73,7 @@ struct w1_netlink_msg __u32 res; } mst; } id; - __u8 data[0]; + __u8 data[]; }; /** @@ -122,7 +122,7 @@ struct w1_netlink_cmd __u8 cmd; __u8 res; __u16 len; - __u8 data[0]; + __u8 data[]; }; #ifdef __KERNEL__ -- 2.25.0