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=-13.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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=unavailable 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 7F41BC10F00 for ; Sat, 7 Mar 2020 12:03:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 539062075B for ; Sat, 7 Mar 2020 12:03:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="S2vTzVx4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726259AbgCGMDn (ORCPT ); Sat, 7 Mar 2020 07:03:43 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:50942 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726017AbgCGMDn (ORCPT ); Sat, 7 Mar 2020 07:03:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583582621; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cUukN5YqJY/S454IY2OKTFidd3uQ3MfuvVzq3/Fu8So=; b=S2vTzVx4cTGJ4FwgPRP6hLR/oQDaPcZMHVWUTAA5YwG0sySWF2ovMklqNMw65NdvCI7WQv g4CTbnKz1W5wQgwlrRqluuewdjZM+93v5gHFPLSoiT82d7kNffwa3KOFYH674ZrL7lexhd BlW75y4NTv9vJg1xXuriXd6M4mVKx48= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-460-pQwfmBxmMO-ujxHTSmWIsA-1; Sat, 07 Mar 2020 07:03:37 -0500 X-MC-Unique: pQwfmBxmMO-ujxHTSmWIsA-1 Received: by mail-wr1-f69.google.com with SMTP id n12so2321487wrp.19 for ; Sat, 07 Mar 2020 04:03:36 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=cUukN5YqJY/S454IY2OKTFidd3uQ3MfuvVzq3/Fu8So=; b=bg7ZB8LLUqeRC/a/Z+D3UIRH+zdwdgt1YX0UPYiyO70jiLsPSoPacn3FVYuWJGpmVI +NHT+INchkHaXrEXBGDEGdLHC2ngnIlRX0BBQQY9Sbu/VKdnP0YfCGgzE3BrDGcUxJM8 QVAlcOArDibxJHsXHJ/z5Bx3I++A21NETmivZZOpAmr3YZa3ZkSk2pbGobChpzBV39ft 7vzIFu9FrhDCu5BcS+7J0BgbysaZ+yN3hTsUAOb+7wuMCq4xdBnbscBbDc9uGEA8h4n4 JjRs7A7OsH79ns7W+puTIOntypmjs59S81dLChNd/rIVADmA77q6xqXd5DE/g+0ZO2Vs W+zg== X-Gm-Message-State: ANhLgQ2utLI6N3XspflB8jf6bM1d4nGncKkQXmPQau2uUGKJIThDKYeb Ro2gRwXhNYo4aT/4XRStcux2K/wJdMKNV76fjNDGD3ibBiulp+wdIHjayyuhMkVGNtT/PELOYyn GtaeKKdF6VCFNaul91morH1yQ X-Received: by 2002:adf:f5cb:: with SMTP id k11mr2854992wrp.214.1583582615458; Sat, 07 Mar 2020 04:03:35 -0800 (PST) X-Google-Smtp-Source: ADFU+vtzB8xe/uIZ14rpqcoUTPZsdHikyLwdsuXPODIXDnw8js25x5XEh+do1YNn/zatTaheRRd75g== X-Received: by 2002:adf:f5cb:: with SMTP id k11mr2854975wrp.214.1583582615201; Sat, 07 Mar 2020 04:03:35 -0800 (PST) Received: from x1.localdomain (2001-1c00-0c0c-fe00-fc7e-fd47-85c1-1ab3.cable.dynamic.v6.ziggo.nl. [2001:1c00:c0c:fe00:fc7e:fd47:85c1:1ab3]) by smtp.gmail.com with ESMTPSA id m3sm33958379wrx.9.2020.03.07.04.03.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 Mar 2020 04:03:34 -0800 (PST) Subject: Re: [PATCH][next] drm/vboxvideo/vboxvideo.h: Replace zero-length array with flexible-array member To: "Gustavo A. R. Silva" , David Airlie , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20200305105558.GA19124@embeddedor> <8e2ab9a2-fb47-1d61-d09c-0510ad5ee5ff@redhat.com> <20200306104118.GV2363188@phenom.ffwll.local> From: Hans de Goede Message-ID: <2bc072ea-9e18-2d2c-8427-80a721f8750e@redhat.com> Date: Sat, 7 Mar 2020 13:03:33 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200306104118.GV2363188@phenom.ffwll.local> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 3/6/20 11:41 AM, Daniel Vetter wrote: > On Thu, Mar 05, 2020 at 03:22:38PM +0100, Hans de Goede wrote: >> Hi, >> >> On 3/5/20 11:55 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 >> >> Patch looks good to me: >> >> Reviewed-by: Hans de Goede > > You're also going to push this? r-b by maintainers without any hint to > what's going to happen is always rather confusing. I've pushed this now, sorry for the confusion I will be more clear about my intentions next time. Regards, Hans >>> --- >>> drivers/gpu/drm/vboxvideo/vboxvideo.h | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/gpu/drm/vboxvideo/vboxvideo.h b/drivers/gpu/drm/vboxvideo/vboxvideo.h >>> index 0592004f71aa..a5de40fe1a76 100644 >>> --- a/drivers/gpu/drm/vboxvideo/vboxvideo.h >>> +++ b/drivers/gpu/drm/vboxvideo/vboxvideo.h >>> @@ -138,7 +138,7 @@ struct vbva_buffer { >>> u32 data_len; >>> /* variable size for the rest of the vbva_buffer area in VRAM. */ >>> - u8 data[0]; >>> + u8 data[]; >>> } __packed; >>> #define VBVA_MAX_RECORD_SIZE (128 * 1024 * 1024) >>> >> >