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 46D19C33CAF for ; Thu, 16 Jan 2020 21:57:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0C04D20728 for ; Thu, 16 Jan 2020 21:57:06 +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="vX6fievF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387430AbgAPV5F (ORCPT ); Thu, 16 Jan 2020 16:57:05 -0500 Received: from gateway23.websitewelcome.com ([192.185.50.108]:46962 "EHLO gateway23.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729153AbgAPV5E (ORCPT ); Thu, 16 Jan 2020 16:57:04 -0500 X-Greylist: delayed 1235 seconds by postgrey-1.27 at vger.kernel.org; Thu, 16 Jan 2020 16:57:03 EST Received: from cm13.websitewelcome.com (cm13.websitewelcome.com [100.42.49.6]) by gateway23.websitewelcome.com (Postfix) with ESMTP id A142794C7 for ; Thu, 16 Jan 2020 15:36:27 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id sCoVij1MnHiO0sCoVigbF7; Thu, 16 Jan 2020 15:36:27 -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=eAKpUW4Y8qknkzN4AAowy2Wed9URe9xaFrVdLf7t/EI=; b=vX6fievFaA18QZ1ClygheHbXNM QdTnvyNZ4p1+AAUymuJXsaetAMLpJB8ixy5m3U0VlDqut8iQMCzL8rPbI14J7rDedsJF487gyKOj4 jDyiwHjZrCBdOxcPnTHVCjFDY4vyIlXO2roP85bEE1YXax1uR42+DJx6PiGUom0n52ZJNG4CEJnsd pPp/l7A4aiYhaJTzeSVwfqx93xWolfSwpGYZcZTpe7XhWRY/9EIZVkgHSGNMzNXEsklY8O8DniIkS g31CZl/IUyXR3TQI9/4s+pAPu0Ai0SMgYtHWX11Tkw81aViB9LcTi0RAihyoHqbLD2qskeLuZ/CUN lOLKjSnA==; Received: from 187-162-252-62.static.axtel.net ([187.162.252.62]:43810 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1isCoT-000Pu6-Im; Thu, 16 Jan 2020 15:36:25 -0600 Date: Thu, 16 Jan 2020 15:36:25 -0600 From: "Gustavo A. R. Silva" To: Jamal Hadi Salim , Cong Wang , Jiri Pirko , "David S. Miller" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH net-next] net: sched: cls_u32: Use flexible-array member Message-ID: <20200116213625.GA9294@embeddedor.com> 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: 187.162.252.62 X-Source-L: No X-Exim-ID: 1isCoT-000Pu6-Im X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 187-162-252-62.static.axtel.net (embeddedor) [187.162.252.62]:43810 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 5 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Old code in the kernel uses 1-byte and 0-byte arrays to indicate the presence of a "variable length array": struct something { int length; u8 data[1]; }; struct something *instance; instance = kmalloc(sizeof(*instance) + size, GFP_KERNEL); instance->length = size; memcpy(instance->data, source, size); There is also 0-byte arrays. Both cases pose confusion for things like sizeof(), CONFIG_FORTIFY_SOURCE, etc.[1] Instead, the preferred mechanism to declare variable-length types such as the one above is a flexible array member[2] which need to be the last member of a structure and empty-sized: struct something { int stuff; u8 data[]; }; Also, 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 unadvertenly introduced[3] to the codebase from now on. [1] https://github.com/KSPP/linux/issues/21 [2] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva --- net/sched/cls_u32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index a0e6fac613de..5537b5b72ad5 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -79,7 +79,7 @@ struct tc_u_hnode { /* The 'ht' field MUST be the last field in structure to allow for * more entries allocated at end of structure. */ - struct tc_u_knode __rcu *ht[1]; + struct tc_u_knode __rcu *ht[]; }; struct tc_u_common { -- 2.23.0