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 D243AC10F27 for ; Mon, 9 Mar 2020 15:53:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A98FC208C3 for ; Mon, 9 Mar 2020 15:53:00 +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="zlBTN05m" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727269AbgCIPw7 (ORCPT ); Mon, 9 Mar 2020 11:52:59 -0400 Received: from gateway22.websitewelcome.com ([192.185.46.152]:20685 "EHLO gateway22.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726703AbgCIPw6 (ORCPT ); Mon, 9 Mar 2020 11:52:58 -0400 Received: from cm13.websitewelcome.com (cm13.websitewelcome.com [100.42.49.6]) by gateway22.websitewelcome.com (Postfix) with ESMTP id 9558F23661 for ; Mon, 9 Mar 2020 10:52:57 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id BKi9jO1DmRP4zBKi9jkWhj; Mon, 09 Mar 2020 10:52:57 -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=0JMHXTq/G0YoEBdhsaZPfnkbHay+4mmZgJTTUG0Tcqk=; b=zlBTN05mgAOfMHn+HaCObwNdic u1VY7Z26OOm0w8w9O0mso6XzIBKwBuD1g055X9zHi9zpTBOnoJIj9ydI79sxTvik1oHAsU2VApGxu HgkIBGuGMzN3ybE13N+5GrxXqhgQKk275fdEHPr/x3qi2aI6JLh2Bvc5US9n93SvHwzxNYpUrY0yf XhqNaWpKWBlXr8DzbX1F1WaViPjgOdWtnge3KIYqtOris9Q77gLBUY7OOt+pAOUupJzPtInTPFblF ARwPXCpko1RVaoXUs3N25jCl5Ryc1VODvgywnNKx/1UH0a18OYXOLkf9wL2CpeKnuwa/32M+tztaB rXnaBYVQ==; Received: from [201.162.240.150] (port=28052 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jBKi7-00302e-Nn; Mon, 09 Mar 2020 10:52:56 -0500 Date: Mon, 9 Mar 2020 10:56:08 -0500 From: "Gustavo A. R. Silva" To: Christine Caulfield , David Teigland Cc: cluster-devel@redhat.com, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] dlm: dlm_internal: Replace zero-length array with flexible-array member Message-ID: <20200309155608.GA31883@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: 1jBKi7-00302e-Nn X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.240.150]:28052 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 12 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/dlm/dlm_internal.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h index 416d9de35679..d231ae5d2c65 100644 --- a/fs/dlm/dlm_internal.h +++ b/fs/dlm/dlm_internal.h @@ -421,7 +421,7 @@ struct dlm_message { int m_bastmode; int m_asts; int m_result; /* 0 or -EXXX */ - char m_extra[0]; /* name or lvb */ + char m_extra[]; /* name or lvb */ }; @@ -450,7 +450,7 @@ struct dlm_rcom { uint64_t rc_id; /* match reply with request */ uint64_t rc_seq; /* sender's ls_recover_seq */ uint64_t rc_seq_reply; /* remote ls_recover_seq */ - char rc_buf[0]; + char rc_buf[]; }; union dlm_packet { @@ -506,7 +506,7 @@ struct rcom_lock { __le16 rl_wait_type; __le16 rl_namelen; char rl_name[DLM_RESNAME_MAXLEN]; - char rl_lvb[0]; + char rl_lvb[]; }; /* -- 2.25.0