From patchwork Mon Mar 9 18:04:41 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. Silva" X-Patchwork-Id: 1251757 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=embeddedor.com Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=embeddedor.com header.i=@embeddedor.com header.a=rsa-sha256 header.s=default header.b=WkO42XKT; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 48bnLN5j2Fz9sPF for ; Tue, 10 Mar 2020 05:48:44 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727431AbgCISso (ORCPT ); Mon, 9 Mar 2020 14:48:44 -0400 Received: from gateway36.websitewelcome.com ([192.185.196.23]:31791 "EHLO gateway36.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727334AbgCISso (ORCPT ); Mon, 9 Mar 2020 14:48:44 -0400 X-Greylist: delayed 1501 seconds by postgrey-1.27 at vger.kernel.org; Mon, 09 Mar 2020 14:48:43 EDT Received: from cm13.websitewelcome.com (cm13.websitewelcome.com [100.42.49.6]) by gateway36.websitewelcome.com (Postfix) with ESMTP id 2E150400CA8C6 for ; Mon, 9 Mar 2020 12:17:00 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id BMiYjQrX9RP4zBMiYjnLza; Mon, 09 Mar 2020 13:01:30 -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=SVIZ6aSCvoUYSnrHD4goqt9sqbglq/pYjhmAtIcFfaQ=; b=WkO42XKTXRVsEmWdlFbqQyrgSR UrfmbY32ut+eoh2k7q/LHBEWv9GlZ0qZ8W4hJLgZLXXKqTCrTW4Ld91Eij0kLASucsseUKc1mg5qg /8sp2IndDgYPBMrTy9CVA8Jqsxb5vOHp5guQ5tXce6GOAiwVphWX0hpGTP8hotE7fbNtAMIuQFb4B eQTWo6M5J5QMYQqn2BLmnPJzXxHcus2oY2TBZDX6/aBLBZmet3IvsUMIUWlpCqXTwEHhWfgVrIuRq gyCPBmpI/ei2f3SRT2sKAxD2zCF6TERTIlL6TpqlF4CFmgvvQI+gnBsSUC/tvLcVcblMBf6jCP4/X wUR/yjvw==; Received: from [201.162.240.150] (port=16235 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jBMiW-004BFk-Dm; Mon, 09 Mar 2020 13:01:28 -0500 Date: Mon, 9 Mar 2020 13:04:41 -0500 From: "Gustavo A. R. Silva" To: Jan Kara Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] ext2: xattr.h: Replace zero-length array with flexible-array member Message-ID: <20200309180441.GA2992@embeddedor> MIME-Version: 1.0 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: 1jBMiW-004BFk-Dm X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.240.150]:16235 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 2 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@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/ext2/xattr.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext2/xattr.h b/fs/ext2/xattr.h index cee888cdc235..16272e6ddcf4 100644 --- a/fs/ext2/xattr.h +++ b/fs/ext2/xattr.h @@ -39,7 +39,7 @@ struct ext2_xattr_entry { __le32 e_value_block; /* disk block attribute is stored on (n/i) */ __le32 e_value_size; /* size of attribute value */ __le32 e_hash; /* hash value of name and value */ - char e_name[0]; /* attribute name */ + char e_name[]; /* attribute name */ }; #define EXT2_XATTR_PAD_BITS 2