From patchwork Mon Mar 9 18:24:42 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: 11427769 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 AA9A092A for ; Mon, 9 Mar 2020 18:43:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8AD21208C3 for ; Mon, 9 Mar 2020 18:43:24 +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="Kbde3Il7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727421AbgCISnY (ORCPT ); Mon, 9 Mar 2020 14:43:24 -0400 Received: from gateway22.websitewelcome.com ([192.185.47.109]:26513 "EHLO gateway22.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727334AbgCISnX (ORCPT ); Mon, 9 Mar 2020 14:43:23 -0400 X-Greylist: delayed 1311 seconds by postgrey-1.27 at vger.kernel.org; Mon, 09 Mar 2020 14:43:23 EDT Received: from cm10.websitewelcome.com (cm10.websitewelcome.com [100.42.49.4]) by gateway22.websitewelcome.com (Postfix) with ESMTP id EE6B6167BB for ; Mon, 9 Mar 2020 13:21:31 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id BN1vjyY2AEfyqBN1vj1BdS; Mon, 09 Mar 2020 13:21:31 -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=94Q67ojJZX0sr3cTE6wQF4GveZtQlKTfPuEaR91kEuo=; b=Kbde3Il7M3zJ70zSOwLiT3SbLZ mOUvlifuwYuxtTck+M1RWB+lkNJJEFU7af6Oq6QHGgq2exvgq0Qq8rsMJrQbcasMUu6p7CRWqyl4N JDRdNpcU6o42jPnrp0T1slNC4mQ8VjPGEakca1J1yXoJtP3IrUFerpTx9g8HvqP+dKLHiC349i5+4 jzYCdYD2ULtSM+xYKiWxxEbhkgcM0vpa7XOKcin3qL/3vXUzy+uLMnNVO+OB2B71He6FmLqwWcyJa CFz2JOxoJ0tKhb/LILTOHHUaW1Zk3uK5PcHwjSPdX9re1qQX/i+3dT7o0mX+VTW7iY7JmdQ1ByONx VUJB7tuA==; Received: from [201.162.240.150] (port=28860 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1jBN1u-004LTL-1r; Mon, 09 Mar 2020 13:21:30 -0500 Date: Mon, 9 Mar 2020 13:24:42 -0500 From: "Gustavo A. R. Silva" To: Trond Myklebust , Anna Schumaker Cc: linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] nfs: Replace zero-length array with flexible-array member Message-ID: <20200309182442.GA5422@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: 1jBN1u-004LTL-1r X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.240.150]:28860 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 30 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@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/nfs/dir.c | 2 +- fs/nfs/nfs4proc.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c index d4b839b6cf89..a551a30047f9 100644 --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -141,7 +141,7 @@ struct nfs_cache_array { int size; int eof_index; u64 last_cookie; - struct nfs_cache_array_entry array[0]; + struct nfs_cache_array_entry array[]; }; typedef int (*decode_dirent_t)(struct xdr_stream *, struct nfs_entry *, bool); diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 69b7ab7a5815..cc0960558284 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -5550,7 +5550,7 @@ static int buf_to_pages_noslab(const void *buf, size_t buflen, struct nfs4_cached_acl { int cached; size_t len; - char data[0]; + char data[]; }; static void nfs4_set_cached_acl(struct inode *inode, struct nfs4_cached_acl *acl)