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=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 771F9C1975A for ; Wed, 18 Mar 2020 01:09:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B77E206EC for ; Wed, 18 Mar 2020 01:09:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727151AbgCRBJW (ORCPT ); Tue, 17 Mar 2020 21:09:22 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:37612 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726735AbgCRBJW (ORCPT ); Tue, 17 Mar 2020 21:09:22 -0400 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id F08B0236845E1D675B1F; Wed, 18 Mar 2020 09:09:18 +0800 (CST) Received: from [127.0.0.1] (10.133.210.141) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.487.0; Wed, 18 Mar 2020 09:09:14 +0800 Subject: Re: [locks] 6d390e4b5d: will-it-scale.per_process_ops -96.6% regression To: Jeff Layton , Linus Torvalds CC: NeilBrown , kernel test robot , LKML , , Bruce Fields , Al Viro References: <20200308140314.GQ5972@shao2-debian> <0066a9f150a55c13fcc750f6e657deae4ebdef97.camel@kernel.org> <87v9nattul.fsf@notabene.neil.brown.name> <87o8t2tc9s.fsf@notabene.neil.brown.name> <877dznu0pk.fsf@notabene.neil.brown.name> <87pndcsxc6.fsf@notabene.neil.brown.name> <7c8d3752-6573-ab83-d0af-f3dd4fc373f5@huawei.com> <6df79609-90eb-2f59-7e86-3532ac309a7a@huawei.com> <61d6b91e9387969f5dfaba192aee366cc9b310f0.camel@kernel.org> From: yangerkun Message-ID: <79d65a56-5281-502f-8d8f-568e082cacf4@huawei.com> Date: Wed, 18 Mar 2020 09:09:13 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <61d6b91e9387969f5dfaba192aee366cc9b310f0.camel@kernel.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.133.210.141] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/3/18 0:07, Jeff Layton wrote: > On Tue, 2020-03-17 at 22:05 +0800, yangerkun wrote: >> >> On 2020/3/17 9:41, yangerkun wrote: >>> >>> On 2020/3/17 1:26, Linus Torvalds wrote: >>>> On Mon, Mar 16, 2020 at 4:07 AM Jeff Layton wrote: >>>>> >>>>> + /* >>>>> + * If fl_blocker is NULL, it won't be set again as this >>>>> thread "owns" >>>>> + * the lock and is the only one that might try to claim the >>>>> lock. >>>>> + * Because fl_blocker is explicitly set last during a delete, >>>>> it's >>>>> + * safe to locklessly test to see if it's NULL. If it is, >>>>> then we know >>>>> + * that no new locks can be inserted into its >>>>> fl_blocked_requests list, >>>>> + * and we can therefore avoid doing anything further as long >>>>> as that >>>>> + * list is empty. >>>>> + */ >>>>> + if (!smp_load_acquire(&waiter->fl_blocker) && >>>>> + list_empty(&waiter->fl_blocked_requests)) >>>>> + return status; >>>> >>>> Ack. This looks sane to me now. >>>> >>>> yangerkun - how did you find the original problem?\ >>> >>> While try to fix CVE-2019-19769, add some log in __locks_wake_up_blocks >>> help me to rebuild the problem soon. This help me to discern the problem >>> soon. >>> >>>> Would you mind using whatever stress test that caused commit >>>> 6d390e4b5d48 ("locks: fix a potential use-after-free problem when >>>> wakeup a waiter") with this patch? And if you did it analytically, >>>> you're a champ and should look at this patch too! >>> >>> I will try to understand this patch, and if it's looks good to me, will >>> do the performance test! >> >> This patch looks good to me, with this patch, the bug '6d390e4b5d48 >> ("locks: fix a potential use-after-free problem when wakeup a waiter")' >> describes won't happen again. Actually, I find that syzkaller has report >> this bug before[1], and the log of it can help us to reproduce it with >> some latency in __locks_wake_up_blocks! >> >> Also, some ltp testcases describes in [2] pass too with the patch! >> >> For performance test, I have try to understand will-it-scale/lkp, but it >> seem a little complex to me, and may need some more time. So, Rong Chen, >> can you help to do this? Or the results may come a little later... >> >> Thanks, >> ---- >> [1] https://syzkaller.appspot.com/bug?extid=922689db06e57b69c240 >> [2] https://lkml.org/lkml/2020/3/11/578 > > Thanks yangerkun. Let me know if you want to add your Reviewed-by tag. Yeah, you can add: Reviewed-by: yangerkun > > Cheers, >