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 5598EC10F25 for ; Mon, 9 Mar 2020 20:22:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2FDEE20828 for ; Mon, 9 Mar 2020 20:22:54 +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="g8S7dm5B" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726492AbgCIUWx (ORCPT ); Mon, 9 Mar 2020 16:22:53 -0400 Received: from gateway34.websitewelcome.com ([192.185.149.72]:29439 "EHLO gateway34.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726096AbgCIUWw (ORCPT ); Mon, 9 Mar 2020 16:22:52 -0400 Received: from cm11.websitewelcome.com (cm11.websitewelcome.com [100.42.49.5]) by gateway34.websitewelcome.com (Postfix) with ESMTP id E4CEBEC12 for ; Mon, 9 Mar 2020 15:22:51 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id BOvLj5XlDSl8qBOvLjgmcP; Mon, 09 Mar 2020 15:22:51 -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=jMunP9V0d2u36jTKl+ej5qOp8rIOFeGZYKT65z+gTFU=; b=g8S7dm5B0nbkMWqRAFALSxChfs RqzmZHbK/ljT7/LfvfOZKT8f166SHIXM/44h2aI2ypZXsCqaT3plrohRWk4KXZSl8y9Titmf5D09W fKfF067lg03NkOI3OYfOD0O6bPgRooJGpqbpk+76c6eG1B2L86Nwx8JskhzSKckOKL+xZWGzcmDFy wdj5+4Vgcpmbi8J3+6eczzV5iDRyEG9iZxLpjQnsBXY0oA1S9hbidLRcUGmpI77bXysNSG7XNlxBc xguXuLrjYTOjL0nZiTfgkZiTyLAL4yLqt2R74UYEx1gbycvN5jgR37b4j5/W2KZEu6WXKZqaMvkXR Wd9G8ljw==; Received: from [201.162.168.201] (port=4007 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jBOvJ-0010Ml-SA; Mon, 09 Mar 2020 15:22:50 -0500 Date: Mon, 9 Mar 2020 15:26:02 -0500 From: "Gustavo A. R. Silva" To: Phillip Lougher Cc: linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] squashfs: squashfs_fs.h: Replace zero-length array with flexible-array member Message-ID: <20200309202602.GA9219@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: 1jBOvJ-0010Ml-SA X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.168.201]:4007 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 28 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/squashfs/squashfs_fs.h | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h index 7187bd1a30ea..8d64edb80ebf 100644 --- a/fs/squashfs/squashfs_fs.h +++ b/fs/squashfs/squashfs_fs.h @@ -262,7 +262,7 @@ struct squashfs_dir_index { __le32 index; __le32 start_block; __le32 size; - unsigned char name[0]; + unsigned char name[]; }; struct squashfs_base_inode { @@ -327,7 +327,7 @@ struct squashfs_symlink_inode { __le32 inode_number; __le32 nlink; __le32 symlink_size; - char symlink[0]; + char symlink[]; }; struct squashfs_reg_inode { @@ -341,7 +341,7 @@ struct squashfs_reg_inode { __le32 fragment; __le32 offset; __le32 file_size; - __le16 block_list[0]; + __le16 block_list[]; }; struct squashfs_lreg_inode { @@ -358,7 +358,7 @@ struct squashfs_lreg_inode { __le32 fragment; __le32 offset; __le32 xattr; - __le16 block_list[0]; + __le16 block_list[]; }; struct squashfs_dir_inode { @@ -389,7 +389,7 @@ struct squashfs_ldir_inode { __le16 i_count; __le16 offset; __le32 xattr; - struct squashfs_dir_index index[0]; + struct squashfs_dir_index index[]; }; union squashfs_inode { @@ -410,7 +410,7 @@ struct squashfs_dir_entry { __le16 inode_number; __le16 type; __le16 size; - char name[0]; + char name[]; }; struct squashfs_dir_header { @@ -428,12 +428,12 @@ struct squashfs_fragment_entry { struct squashfs_xattr_entry { __le16 type; __le16 size; - char data[0]; + char data[]; }; struct squashfs_xattr_val { __le32 vsize; - char value[0]; + char value[]; }; struct squashfs_xattr_id { -- 2.25.0