From patchwork Thu Feb 27 20:58:44 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: 1246106 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming-netdev@ozlabs.org Delivered-To: patchwork-incoming-netdev@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=netdev-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=Oh64htQA; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 48T4hH3HCMz9sRL for ; Fri, 28 Feb 2020 07:55:59 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729757AbgB0Uzz (ORCPT ); Thu, 27 Feb 2020 15:55:55 -0500 Received: from gateway21.websitewelcome.com ([192.185.45.38]:25197 "EHLO gateway21.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729439AbgB0Uzz (ORCPT ); Thu, 27 Feb 2020 15:55:55 -0500 Received: from cm14.websitewelcome.com (cm14.websitewelcome.com [100.42.49.7]) by gateway21.websitewelcome.com (Postfix) with ESMTP id 3EFB1400C9C5A for ; Thu, 27 Feb 2020 14:55:54 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 7QCIjhr1gXVkQ7QCIj2smD; Thu, 27 Feb 2020 14:55:54 -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=MJVDWhNS0EA1OFOvhs7NhRz+ei3OwBXs0MRwTBoRDU4=; b=Oh64htQAJlmzOqavF6aI+lLuQJ yi2B+nKcpQZfFWrZv5idvV/Q/+hXpQZTxNa9KjVtZ+NVIcSPHAkQPeVPoJzgaNpOn8oOBRl/yJpNI 6IXWFhyg0UV2A9SKm3l/FfvLLH5moAfzOnMjkeSkASwzKcWnB2p+LA/n8As+H3cSDp58G1mR6l2tW Y9JPYyCFF8pdl/rM3LkT94GzUsj7XzMd9ecaG/iPC7nK8ZQNZUyhjfKjAnjlGJeeG1AYUgM95vQav Hhiq7LtryQNNXCR0mb0Q1t5pki/ZLmSF6etUd0tNwjKghmm8r5Se+qW+y3X9RO7RsrbBTrlsSNIQ7 C9UM2cNg==; Received: from [201.162.169.69] (port=8222 helo=embeddedor) by gator4166.hostgator.com with esmtpa (Exim 4.92) (envelope-from ) id 1j7QCF-000kyF-UD; Thu, 27 Feb 2020 14:55:52 -0600 Date: Thu, 27 Feb 2020 14:58:44 -0600 From: "Gustavo A. R. Silva" To: Jamal Hadi Salim , Cong Wang , Jiri Pirko , "David S. Miller" , Jakub Kicinski , Stephen Hemminger Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] net: sched: Replace zero-length array with flexible-array member Message-ID: <20200227205844.GA18578@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: 201.162.169.69 X-Source-L: No X-Exim-ID: 1j7QCF-000kyF-UD X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.162.169.69]:8222 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 18 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 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 --- include/net/pkt_sched.h | 2 +- net/sched/em_ipt.c | 2 +- net/sched/em_nbyte.c | 2 +- net/sched/sch_atm.c | 2 +- net/sched/sch_netem.c | 2 +- 5 files changed, 5 insertions(+), 5 deletions(-) diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h index 6a70845bd9ab..20d2c6419612 100644 --- a/include/net/pkt_sched.h +++ b/include/net/pkt_sched.h @@ -181,7 +181,7 @@ struct tc_taprio_qopt_offload { u64 cycle_time_extension; size_t num_entries; - struct tc_taprio_sched_entry entries[0]; + struct tc_taprio_sched_entry entries[]; }; /* Reference counting */ diff --git a/net/sched/em_ipt.c b/net/sched/em_ipt.c index 9fff6480acc6..eecfe072c508 100644 --- a/net/sched/em_ipt.c +++ b/net/sched/em_ipt.c @@ -22,7 +22,7 @@ struct em_ipt_match { const struct xt_match *match; u32 hook; u8 nfproto; - u8 match_data[0] __aligned(8); + u8 match_data[] __aligned(8); }; struct em_ipt_xt_match { diff --git a/net/sched/em_nbyte.c b/net/sched/em_nbyte.c index 88c7ce42df7e..2c1192a2ee5e 100644 --- a/net/sched/em_nbyte.c +++ b/net/sched/em_nbyte.c @@ -16,7 +16,7 @@ struct nbyte_data { struct tcf_em_nbyte hdr; - char pattern[0]; + char pattern[]; }; static int em_nbyte_change(struct net *net, void *data, int data_len, diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c index f4f9b8cdbffb..ee12ca9f55b4 100644 --- a/net/sched/sch_atm.c +++ b/net/sched/sch_atm.c @@ -58,7 +58,7 @@ struct atm_flow_data { struct atm_flow_data *excess; /* flow for excess traffic; NULL to set CLP instead */ int hdr_len; - unsigned char hdr[0]; /* header data; MUST BE LAST */ + unsigned char hdr[]; /* header data; MUST BE LAST */ }; struct atm_qdisc_data { diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 42e557d48e4e..84f82771cdf5 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -66,7 +66,7 @@ struct disttable { u32 size; - s16 table[0]; + s16 table[]; }; struct netem_sched_data {