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 EA07EC10F25 for ; Mon, 9 Mar 2020 19:24:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C24A124654 for ; Mon, 9 Mar 2020 19:24:34 +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="elynEZvM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726389AbgCITYd (ORCPT ); Mon, 9 Mar 2020 15:24:33 -0400 Received: from gateway21.websitewelcome.com ([192.185.45.154]:36385 "EHLO gateway21.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726106AbgCITYd (ORCPT ); Mon, 9 Mar 2020 15:24:33 -0400 Received: from cm12.websitewelcome.com (cm12.websitewelcome.com [100.42.49.8]) by gateway21.websitewelcome.com (Postfix) with ESMTP id 2AD73403D535D for ; Mon, 9 Mar 2020 13:15:54 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id BMwUjS119vBMdBMwUjLWgD; Mon, 09 Mar 2020 13:15:54 -0500 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=C0MvE7PDdq001QbWyBr/GhST3oWeMyr56RQn0qh4KTk=; b=elynEZvMG+011WYLVnxAPS+XYV F2MuUQiXYDlm9MKJf3WJCWQ6j+W/x5i0a2BvpscHyBXnQ2c5//1g+XWZEx/Y2rZdaJwzyEUEpA24n fhPst3r6Mj/qD9wmKT5gTqGB4tnYMSpHlUOke0hgX2vXPoAIUvUjoGBqHfLpTuCK+nyKZz6chkECM OJIEFPAPwqHMJ199TXnqrn0bkJHlOCd+jncb65SyG8hZM/xd+dhK+8qk7Xupb15r/gZZQdg6X/Y4/ Y7AwKn9wGNeFz2lqQIs6zFhMevNDVrgVhLd9Q2NJnw9bk5O2URcLp1zri/rANb41owtgNSi/+YyX9 i62/BP+A==; Received: from [201.162.240.150] (port=12425 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jBMwR-004IWa-Nt; Mon, 09 Mar 2020 13:15:52 -0500 Date: Mon, 9 Mar 2020 13:19:04 -0500 From: "Gustavo A. R. Silva" To: David Woodhouse , Richard Weinberger Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] jffs2: summary.h: Replace zero-length array with flexible-array member Message-ID: <20200309181904.GA4669@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: 201.162.240.150 X-Source-L: No X-Exim-ID: 1jBMwR-004IWa-Nt X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.240.150]:12425 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 24 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 --- fs/jffs2/summary.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/jffs2/summary.h b/fs/jffs2/summary.h index 60207a2ae952..e4131cb1f1d4 100644 --- a/fs/jffs2/summary.h +++ b/fs/jffs2/summary.h @@ -61,7 +61,7 @@ struct jffs2_sum_dirent_flash jint32_t ino; /* == zero for unlink */ uint8_t nsize; /* dirent name size */ uint8_t type; /* dirent type */ - uint8_t name[0]; /* dirent name */ + uint8_t name[]; /* dirent name */ } __attribute__((packed)); struct jffs2_sum_xattr_flash @@ -117,7 +117,7 @@ struct jffs2_sum_dirent_mem jint32_t ino; /* == zero for unlink */ uint8_t nsize; /* dirent name size */ uint8_t type; /* dirent type */ - uint8_t name[0]; /* dirent name */ + uint8_t name[]; /* dirent name */ } __attribute__((packed)); struct jffs2_sum_xattr_mem -- 2.25.0