From patchwork Mon Mar 9 18:13:29 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: 11427963 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4861D14BC for ; Mon, 9 Mar 2020 20:19:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2832D20873 for ; Mon, 9 Mar 2020 20:19:39 +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="zjAn8OAc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726106AbgCIUTi (ORCPT ); Mon, 9 Mar 2020 16:19:38 -0400 Received: from gateway21.websitewelcome.com ([192.185.45.154]:47259 "EHLO gateway21.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725992AbgCIUTi (ORCPT ); Mon, 9 Mar 2020 16:19:38 -0400 X-Greylist: delayed 3633 seconds by postgrey-1.27 at vger.kernel.org; Mon, 09 Mar 2020 16:19:37 EDT Received: from cm10.websitewelcome.com (cm10.websitewelcome.com [100.42.49.4]) by gateway21.websitewelcome.com (Postfix) with ESMTP id 756174036C7EE for ; Mon, 9 Mar 2020 13:10:19 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id BMr5jyIJREfyqBMr5j0w2A; Mon, 09 Mar 2020 13:10:19 -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: To:From:Date:Sender:Reply-To:Cc: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=RyR+AnHFtg8ENe4FqD1p4qkHhSuKpxiB0Z6NTI7dKPk=; b=zjAn8OAcZerZeuOTAPs7yu0wq7 NZ0gyMiRZ1hSKI0AlWbcWHF8HOurzuz1D7KN3dy7B1Jj2EETPYetwmXZnrhofciakuRqq3HL0AD/c EmoGKNvhqjhAfb9ein4ilFbJlf+BWgzra1OAEuSzRisBFB28h3z7KcpbeeD2zdIyUBtOTRmmdXzaK LZIcBwBr1eeBshrSI2Zp8dz3bitl4AnNZHrs1q5adc5Bcl0xo8edyiE6ydF3FmGmvnMHg9wpdQD0K Ywk2bl4gThm55+yR7X0MpC9Hmb/SxSA4JSpfbkyI9NlcZFCO5Uun5iTsrhLYFiVE+rc0z5Ad9BeuI 4gM/I0YQ==; Received: from [201.162.240.150] (port=7181 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jBMr3-004FeC-G9; Mon, 09 Mar 2020 13:10:17 -0500 Date: Mon, 9 Mar 2020 13:13:29 -0500 From: "Gustavo A. R. Silva" To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] hfsplus: hfsplus_fs.h: Replace zero-length array with flexible-array member Message-ID: <20200309181329.GA3925@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: 1jBMr3-004FeC-G9 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.240.150]:7181 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 14 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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/hfsplus/hfsplus_fs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h index 3b03fff68543..a92de5199ec3 100644 --- a/fs/hfsplus/hfsplus_fs.h +++ b/fs/hfsplus/hfsplus_fs.h @@ -117,7 +117,7 @@ struct hfs_bnode { wait_queue_head_t lock_wq; atomic_t refcnt; unsigned int page_offset; - struct page *page[0]; + struct page *page[]; }; #define HFS_BNODE_LOCK 0