From patchwork Mon Feb 17 21:44:23 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: 1239626 X-Patchwork-Delegate: pablo@netfilter.org Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.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=netfilter-devel-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=HgN+9rsp; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 48Lyhw3DXdz9sRG for ; Tue, 18 Feb 2020 09:05:20 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726010AbgBQWFS (ORCPT ); Mon, 17 Feb 2020 17:05:18 -0500 Received: from gateway20.websitewelcome.com ([192.185.47.18]:49996 "EHLO gateway20.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726047AbgBQWFS (ORCPT ); Mon, 17 Feb 2020 17:05:18 -0500 X-Greylist: delayed 1401 seconds by postgrey-1.27 at vger.kernel.org; Mon, 17 Feb 2020 17:05:18 EST Received: from cm10.websitewelcome.com (cm10.websitewelcome.com [100.42.49.4]) by gateway20.websitewelcome.com (Postfix) with ESMTP id B3E51400D5C29 for ; Mon, 17 Feb 2020 14:27:50 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 3o99jMJX9Efyq3o99jUbwv; Mon, 17 Feb 2020 15:41:43 -0600 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=8exBLdInKXUzJxq+ZuAOxKExTTscVDb1+bUsC6sGG8g=; b=HgN+9rsp3fFCj0fJUhjufn2/l7 VUbRynRSy0CAxMQY1KjfA6V0LtIYanqWDAcf8yWC0eCA4k6KrY0nHZXuU/xZc13RL7fkTFbpblB9Z oaw0tEO4v2iCjRJSKPg7FVGlJmBpyn54igDPdhEvFipu6bdIypiYf2GXKs6TVHrC6ONCP579pTBsD k6d1SyEurDwqrzaiQ1aIEJb6Ekg+EqhR2woGKuNkFF0iOLmuHVv8PsANnufrSfgeIw47Z2AM++650 z398+1TN/CWW5k09Ld5ZremaZw19BRvbwk+wOE0VJUTDklJDkNpaX6tXERWgdq/NvwlKLQ1s2lOvv y6pqb2rA==; Received: from [200.68.140.26] (port=12036 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j3o97-001HA1-II; Mon, 17 Feb 2020 15:41:41 -0600 Date: Mon, 17 Feb 2020 15:44:23 -0600 From: "Gustavo A. R. Silva" To: Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , Roopa Prabhu , Nikolay Aleksandrov , "David S. Miller" , Jakub Kicinski Cc: netfilter-devel@vger.kernel.org, coreteam@netfilter.org, bridge@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] netfilter: ebtables: Replace zero-length array with flexible-array member Message-ID: <20200217214423.GA15008@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: 200.68.140.26 X-Source-L: No X-Exim-ID: 1j3o97-001HA1-II X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.140.26]:12036 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 18 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@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 --- net/bridge/netfilter/ebtables.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c index e1256e03a9a8..78db58c7aec2 100644 --- a/net/bridge/netfilter/ebtables.c +++ b/net/bridge/netfilter/ebtables.c @@ -1561,7 +1561,7 @@ struct compat_ebt_entry_mwt { compat_uptr_t ptr; } u; compat_uint_t match_size; - compat_uint_t data[0] __attribute__ ((aligned (__alignof__(struct compat_ebt_replace)))); + compat_uint_t data[] __aligned(__alignof__(struct compat_ebt_replace)); }; /* account for possible padding between match_size and ->data */