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=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 AA06FC433E7 for ; Fri, 9 Oct 2020 07:05:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50B1D21D41 for ; Fri, 9 Oct 2020 07:05:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731100AbgJIHFc (ORCPT ); Fri, 9 Oct 2020 03:05:32 -0400 Received: from szxga05-in.huawei.com ([45.249.212.191]:15197 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725908AbgJIHFc (ORCPT ); Fri, 9 Oct 2020 03:05:32 -0400 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 6CBE07F916D97EDA2CB9; Fri, 9 Oct 2020 15:05:29 +0800 (CST) Received: from [10.136.114.67] (10.136.114.67) by smtp.huawei.com (10.3.19.207) with Microsoft SMTP Server (TLS) id 14.3.487.0; Fri, 9 Oct 2020 15:05:25 +0800 Subject: Re: [f2fs-dev] [f2fs bug] infinite loop in f2fs_get_meta_page_nofail() To: CC: Eric Biggers , , , , References: <000000000000432c5405b1113296@google.com> <20201007213253.GD1530638@gmail.com> <20201007215305.GA714500@google.com> <20201009015015.GA1931838@google.com> <8fa4f9fe-5ca5-f3a3-c8f4-e800373c1e46@huawei.com> <20201009043237.GB1973455@google.com> From: Chao Yu Message-ID: Date: Fri, 9 Oct 2020 15:05:25 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20201009043237.GB1973455@google.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.136.114.67] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/10/9 12:32, jaegeuk@kernel.org wrote: > On 10/09, Chao Yu wrote: >> On 2020/10/9 9:50, jaegeuk@kernel.org wrote: >>> On 10/09, Chao Yu wrote: >>>> On 2020/10/8 5:53, jaegeuk@kernel.org wrote: >>>>> On 10/07, Eric Biggers wrote: >>>>>> [moved linux-fsdevel to Bcc] >>>>>> >>>>>> On Wed, Oct 07, 2020 at 02:18:19AM -0700, syzbot wrote: >>>>>>> Hello, >>>>>>> >>>>>>> syzbot found the following issue on: >>>>>>> >>>>>>> HEAD commit: a804ab08 Add linux-next specific files for 20201006 >>>>>>> git tree: linux-next >>>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=17fe30bf900000 >>>>>>> kernel config: https://syzkaller.appspot.com/x/.config?x=26c1b4cc4a62ccb >>>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=ee250ac8137be41d7b13 >>>>>>> compiler: gcc (GCC) 10.1.0-syz 20200507 >>>>>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1336413b900000 >>>>>>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f7392b900000 >>>>>>> >>>>>>> The issue was bisected to: >>>>>>> >>>>>>> commit eede846af512572b1f30b34f9889d7df64c017d4 >>>>>>> Author: Jaegeuk Kim >>>>>>> Date: Fri Oct 2 21:17:35 2020 +0000 >>>>>>> >>>>>>> f2fs: f2fs_get_meta_page_nofail should not be failed >>>>>>> >>>>>> >>>>>> Jaegeuk, it looks like the loop you added in the above commit doesn't terminate >>>>>> if the requested page is beyond the end of the device. >>>>> >>>>> Yes, that will go infinite loop. Otherwise, it will trigger a panic during >>>>> the device reboot. Let me think how to avoid that before trying to get the >>>>> wrong lba access. >>>> >>>> Delivering f2fs_get_sum_page()'s return value needs a lot of codes change, I think >>>> we can just zeroing sum_page in error case, as we have already shutdown f2fs via >>>> calling f2fs_stop_checkpoint(), then f2fs_cp_error() will stop all updates to >>>> filesystem data including summary pages. >>> >>> That sounds like one solution tho, I'm afraid of getting another panic by >>> wrong zero'ed summary page. >> >> What case do you mean? maybe I missed some corner cases? > > I sent v2 to fix syzbot issue, which fixes wrong use of > f2fs_get_meta_page_nofail. I agreed to fix that case, however we may encounter deadloop in other places where we call f2fs_get_meta_page_nofail()? like the case that filesystem will always see EIO after we shutdown device via dmflakey? Thanks, > >> >> Thanks, >> >>> >>>> >>>> Thoughts? >>>> >>>> Thanks, >>>> >>>>> >>>>>> >>>>>> - Eric >>>>> >>>>> >>>>> _______________________________________________ >>>>> Linux-f2fs-devel mailing list >>>>> Linux-f2fs-devel@lists.sourceforge.net >>>>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel >>>>> . >>>>> >>> . >>> > . >