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 1143DC10F25 for ; Mon, 9 Mar 2020 20:17:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D9EB020873 for ; Mon, 9 Mar 2020 20:17:11 +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="WkouEh14" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726608AbgCIURK (ORCPT ); Mon, 9 Mar 2020 16:17:10 -0400 Received: from gateway31.websitewelcome.com ([192.185.144.28]:46929 "EHLO gateway31.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726106AbgCIURK (ORCPT ); Mon, 9 Mar 2020 16:17:10 -0400 Received: from cm12.websitewelcome.com (cm12.websitewelcome.com [100.42.49.8]) by gateway31.websitewelcome.com (Postfix) with ESMTP id 076D426FC8 for ; Mon, 9 Mar 2020 15:17:10 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id BOppjUfDbvBMdBOpqjO9uu; Mon, 09 Mar 2020 15:17:10 -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=ulbAlsTZmPkWr06VQww9fMcwzBjA45yLahK8oOBRTqA=; b=WkouEh146JrjLOdxwg8CkJw2/I JooWwxJJLkWEq7tFIjtFtBn9tjCLMejsqmxno22TB+EKguj6lt/Xq89zpcSeGjTwtAgKDmEKwMaUn 1oaNdNH4VBX00sv1HZdcXHttB8PAw5FmOuUFgDl63DXHEEz7zxinIOqBxaPFDAXvhoRUqBWYD8Cxq iI7/7U+cLFXaHW+cA4hwZ6LcFNkERE1oGnUpjSsl68VOJ2NY7gvVsHABTZO3PxYT+5Dhn5ghliYLK RNd0CxdwVU5V6AxzhEN9gqNcRkTHm4H6fcj5gOysDTfS9ZjSiZaz1iLoapG7uCzBn7SlnitPrIZDI jjLk9OQw==; Received: from [201.162.168.201] (port=27171 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jBOpl-000x4o-N4; Mon, 09 Mar 2020 15:17:08 -0500 Date: Mon, 9 Mar 2020 15:20:16 -0500 From: "Gustavo A. R. Silva" To: Mark Fasheh , Joel Becker , Joseph Qi Cc: ocfs2-devel@oss.oracle.com, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] ocfs2: dlm: Replace zero-length array with flexible-array member Message-ID: <20200309202016.GA8210@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: 201.162.168.201 X-Source-L: No X-Exim-ID: 1jBOpl-000x4o-N4 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.168.201]:27171 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 10 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/ocfs2/dlm/dlmcommon.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h index 0463dce65bb2..c8a444622faa 100644 --- a/fs/ocfs2/dlm/dlmcommon.h +++ b/fs/ocfs2/dlm/dlmcommon.h @@ -564,7 +564,7 @@ struct dlm_migratable_lockres // 48 bytes u8 lvb[DLM_LVB_LEN]; // 112 bytes - struct dlm_migratable_lock ml[0]; // 16 bytes each, begins at byte 112 + struct dlm_migratable_lock ml[]; // 16 bytes each, begins at byte 112 }; #define DLM_MIG_LOCKRES_MAX_LEN \ (sizeof(struct dlm_migratable_lockres) + \ @@ -601,7 +601,7 @@ struct dlm_convert_lock u8 name[O2NM_MAX_NAME_LEN]; - s8 lvb[0]; + s8 lvb[]; }; #define DLM_CONVERT_LOCK_MAX_LEN (sizeof(struct dlm_convert_lock)+DLM_LVB_LEN) @@ -616,7 +616,7 @@ struct dlm_unlock_lock u8 name[O2NM_MAX_NAME_LEN]; - s8 lvb[0]; + s8 lvb[]; }; #define DLM_UNLOCK_LOCK_MAX_LEN (sizeof(struct dlm_unlock_lock)+DLM_LVB_LEN) @@ -632,7 +632,7 @@ struct dlm_proxy_ast u8 name[O2NM_MAX_NAME_LEN]; - s8 lvb[0]; + s8 lvb[]; }; #define DLM_PROXY_AST_MAX_LEN (sizeof(struct dlm_proxy_ast)+DLM_LVB_LEN) -- 2.25.0 From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gustavo A. R. Silva Date: Mon, 9 Mar 2020 15:20:16 -0500 Subject: [Ocfs2-devel] [PATCH][next] ocfs2: dlm: Replace zero-length array with flexible-array member Message-ID: <20200309202016.GA8210@embeddedor> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Mark Fasheh , Joel Becker , Joseph Qi Cc: ocfs2-devel@oss.oracle.com, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" 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://urldefense.com/v3/__https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html__;!!GqivPVa7Brio!OVOYL_CouISa5L1Lw-20EEFQntw6cKMx-j8UdY4z78uYgzKBUFcfpn50GaurvbV5v7YiUA$ [2] https://urldefense.com/v3/__https://github.com/KSPP/linux/issues/21__;!!GqivPVa7Brio!OVOYL_CouISa5L1Lw-20EEFQntw6cKMx-j8UdY4z78uYgzKBUFcfpn50GaurvbXs8Eh8eg$ [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva --- fs/ocfs2/dlm/dlmcommon.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/ocfs2/dlm/dlmcommon.h b/fs/ocfs2/dlm/dlmcommon.h index 0463dce65bb2..c8a444622faa 100644 --- a/fs/ocfs2/dlm/dlmcommon.h +++ b/fs/ocfs2/dlm/dlmcommon.h @@ -564,7 +564,7 @@ struct dlm_migratable_lockres // 48 bytes u8 lvb[DLM_LVB_LEN]; // 112 bytes - struct dlm_migratable_lock ml[0]; // 16 bytes each, begins at byte 112 + struct dlm_migratable_lock ml[]; // 16 bytes each, begins at byte 112 }; #define DLM_MIG_LOCKRES_MAX_LEN \ (sizeof(struct dlm_migratable_lockres) + \ @@ -601,7 +601,7 @@ struct dlm_convert_lock u8 name[O2NM_MAX_NAME_LEN]; - s8 lvb[0]; + s8 lvb[]; }; #define DLM_CONVERT_LOCK_MAX_LEN (sizeof(struct dlm_convert_lock)+DLM_LVB_LEN) @@ -616,7 +616,7 @@ struct dlm_unlock_lock u8 name[O2NM_MAX_NAME_LEN]; - s8 lvb[0]; + s8 lvb[]; }; #define DLM_UNLOCK_LOCK_MAX_LEN (sizeof(struct dlm_unlock_lock)+DLM_LVB_LEN) @@ -632,7 +632,7 @@ struct dlm_proxy_ast u8 name[O2NM_MAX_NAME_LEN]; - s8 lvb[0]; + s8 lvb[]; }; #define DLM_PROXY_AST_MAX_LEN (sizeof(struct dlm_proxy_ast)+DLM_LVB_LEN) -- 2.25.0