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=-2.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 26BEAC4360C for ; Thu, 26 Sep 2019 12:14:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F07C4208C3 for ; Thu, 26 Sep 2019 12:14:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=rasmusvillemoes.dk header.i=@rasmusvillemoes.dk header.b="Z3tMSPBQ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726410AbfIZMOQ (ORCPT ); Thu, 26 Sep 2019 08:14:16 -0400 Received: from mail-lf1-f65.google.com ([209.85.167.65]:39162 "EHLO mail-lf1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725836AbfIZMOP (ORCPT ); Thu, 26 Sep 2019 08:14:15 -0400 Received: by mail-lf1-f65.google.com with SMTP id 72so1519729lfh.6 for ; Thu, 26 Sep 2019 05:14:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rasmusvillemoes.dk; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=HxmJw9dmwOmUpSMCqEkLBVzIwTXQ9sN0mqmrf5PISjc=; b=Z3tMSPBQpthOduFIpYEw/QsUGEuPp4hvaijkNHmYcUB/NhsHBXmVU1k8CIoVjZuZT2 DrP9E551AmwNzhFR1KFUGPM1Ddg2VjBFaz8/d0M6BKjaGb4hZvfnSoao0llkUc8TxG1/ KvWoPWBhqcuz9/E3N0iU7UPoDxFCOV/60Nhc8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=HxmJw9dmwOmUpSMCqEkLBVzIwTXQ9sN0mqmrf5PISjc=; b=UgJZUSPm/tfR9c1fHtQBB6/YTFwOG1XntGb6MbR0ZRYUfbYhQGl7jWUsWUTPFIDzHw SdjIdxJMIuWPodyKwLPYoroWfPNsIGEIrpLNhzzRpIMjFxwJwO+m6TgFH6xziBjKew2O chKEg02LDd+afsnC7bK27IdipjuvRgYJaSvkfhM2nUUmMK0WJr3pFthGoYxalvTzGUN+ XV3dkdnSCMHGMnQJ2FMILdHLtibSgbaqHccUtcfSHFH0QxvZP+Ik4xEyIww4ibCJxTYZ xl8H5W2yISpqNwgx4dOT0Q484YFDzlfMtx+5PmNmXoGGUnQLgfPh3erbTWO9aadYV8xi xbxQ== X-Gm-Message-State: APjAAAWTEfD1IbrZJzv+vF1Wx+VLb5TOvkIQRsXGjMB1I9dk8hpZa5Zk U3NL+1hbEaSOyrVeGE4FTfF7OrziIA1HI0BP X-Google-Smtp-Source: APXvYqxj08u1D9pH/PR1ybjpV0jEmy0AvvI4NI6cTqKsv0ckuKm+9vFi/zeXe7qtlQx59r/lIqNlJw== X-Received: by 2002:a19:c002:: with SMTP id q2mr1113325lff.62.1569500051593; Thu, 26 Sep 2019 05:14:11 -0700 (PDT) Received: from [172.16.11.28] ([81.216.59.226]) by smtp.gmail.com with ESMTPSA id g27sm473044lja.33.2019.09.26.05.14.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 26 Sep 2019 05:14:10 -0700 (PDT) Subject: Re: [PATCH][next] io_uring: ensure variable ret is initialized to zero To: Jens Axboe , Dan Carpenter Cc: Colin King , Alexander Viro , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190926095012.31826-1-colin.king@canonical.com> <3aa821ea-3041-fb56-2458-ec643963c511@kernel.dk> <20190926113329.GE27389@kadam> <04262621-68fd-a4bb-ab0c-83954c03fbb0@kernel.dk> From: Rasmus Villemoes Message-ID: <2de0eb45-3abc-3ccd-f3d3-346d899ba50d@rasmusvillemoes.dk> Date: Thu, 26 Sep 2019 14:14:09 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <04262621-68fd-a4bb-ab0c-83954c03fbb0@kernel.dk> Content-Type: text/plain; charset=utf-8 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 On 26/09/2019 13.42, Jens Axboe wrote: > On 9/26/19 1:33 PM, Dan Carpenter wrote: >> On Thu, Sep 26, 2019 at 11:56:30AM +0200, Jens Axboe wrote: >>> On 9/26/19 11:50 AM, Colin King wrote: >>>> From: Colin Ian King >>>> >>>> In the case where sig is NULL the error variable ret is not initialized >>>> and may contain a garbage value on the final checks to see if ret is >>>> -ERESTARTSYS. Best to initialize ret to zero before the do loop to >>>> ensure the ret does not accidentially contain -ERESTARTSYS before the >>>> loop. >>> >>> Oops, weird it didn't complain. I've folded in this fix, as that commit >>> isn't upstream yet. Thanks! >> >> There is a bug in GCC where at certain optimization levels, instead of >> complaining, it initializes it to zero. > > That's awfully nice of it ;-) > > Tried with -O0 and still didn't complain for me. > > $ gcc --version > gcc (Ubuntu 9.1.0-2ubuntu2~18.04) 9.1.0 > > Tried gcc 5/6/7/8 as well. Might have to go look at what code it's > generating. > I think it's essentially the same as https://lore.kernel.org/lkml/CAHk-=whP-9yPAWuJDwA6+rQ-9owuYZgmrMA9AqO3EGJVefe8vg@mail.gmail.com/ (thread "tmpfs: fix uninitialized return value in shmem_link"). Rasmus