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=-13.3 required=3.0 tests=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 3C142C43331 for ; Tue, 24 Mar 2020 16:13:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 195E4208E0 for ; Tue, 24 Mar 2020 16:13:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727773AbgCXQNw (ORCPT ); Tue, 24 Mar 2020 12:13:52 -0400 Received: from mga18.intel.com ([134.134.136.126]:58638 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727681AbgCXQNw (ORCPT ); Tue, 24 Mar 2020 12:13:52 -0400 IronPort-SDR: GKb0EOgvfEjWC88/8TiHNeaUZSlGp7SN06JnaH7RcCAywxmQjb3RL/MRmlNzthNknsvdtj0GMm raX7HMSzG3bA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2020 09:13:51 -0700 IronPort-SDR: W8SciJsflDt7I1KWp22n6eTJA7U0Ua/WogD7R+qVo6jLLLwyy64NWdjac5turEh7gfGs2gJwPy ixWURD/+G7gA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,301,1580803200"; d="scan'208";a="393330458" Received: from rjwysock-mobl1.ger.corp.intel.com (HELO [10.249.142.176]) ([10.249.142.176]) by orsmga004.jf.intel.com with ESMTP; 24 Mar 2020 09:13:50 -0700 Subject: Re: [PATCH][next] pnpbios: pnpbios.h: Replace zero-length array with flexible-array member To: "Gustavo A. R. Silva" Cc: linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org References: <20200320231827.GA21969@embeddedor.com> From: "Rafael J. Wysocki" Organization: Intel Technology Poland Sp. z o. o., KRS 101882, ul. Slowackiego 173, 80-298 Gdansk Message-ID: Date: Tue, 24 Mar 2020 17:13:50 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200320231827.GA21969@embeddedor.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On 3/21/2020 12:18 AM, Gustavo A. R. Silva wrote: > 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 > --- > drivers/pnp/pnpbios/pnpbios.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pnp/pnpbios/pnpbios.h b/drivers/pnp/pnpbios/pnpbios.h > index 37acb8378f39..2ce739ff9c1a 100644 > --- a/drivers/pnp/pnpbios/pnpbios.h > +++ b/drivers/pnp/pnpbios/pnpbios.h > @@ -107,7 +107,7 @@ struct pnp_bios_node { > __u32 eisa_id; > __u8 type_code[3]; > __u16 flags; > - __u8 data[0]; > + __u8 data[]; > }; > #pragma pack() > Please resend this with a CC to linux-acpi, thanks!