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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 7C72FC433DB for ; Wed, 31 Mar 2021 06:45:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1E4D7619C1 for ; Wed, 31 Mar 2021 06:45:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1E4D7619C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8177E6B007E; Wed, 31 Mar 2021 02:45:03 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7A05B6B0081; Wed, 31 Mar 2021 02:45:03 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5CB856B0082; Wed, 31 Mar 2021 02:45:03 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0077.hostedemail.com [216.40.44.77]) by kanga.kvack.org (Postfix) with ESMTP id 3C2776B007E for ; Wed, 31 Mar 2021 02:45:03 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id E4B36180AD820 for ; Wed, 31 Mar 2021 06:45:02 +0000 (UTC) X-FDA: 77979232044.25.A41D820 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf16.hostedemail.com (Postfix) with ESMTP id 10D9F80192DA for ; Wed, 31 Mar 2021 06:45:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1617173102; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sOu3IBaGpEdrns18pR1ePpxympivW2akSHdNF3h92OE=; b=gQUCHNd29C4FgTMP3Cr6jrI4Zrf8JdqTDd8y/SpnaQfhtp4ykL9BfnW/BIiD3Ltwi+7qrI ZKXYFUR1/coLyvhKRoOxoE3XypGSzMu39ZqSpHh1IAMKCUioxn5ZTJJjQbzPXcQ1OLsdLi djZHQXD8rM6c1NlngI9OcLpvKPazrZc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-268-T3j-aA0FNWuBocLvx2Mxcg-1; Wed, 31 Mar 2021 02:44:59 -0400 X-MC-Unique: T3j-aA0FNWuBocLvx2Mxcg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8E8F0100960D; Wed, 31 Mar 2021 06:44:57 +0000 (UTC) Received: from [10.36.113.60] (ovpn-113-60.ams2.redhat.com [10.36.113.60]) by smtp.corp.redhat.com (Postfix) with ESMTP id C33E060CE7; Wed, 31 Mar 2021 06:44:54 +0000 (UTC) Subject: Re: [PATCH v5] mm/gup: check page hwposion status for coredump. To: =?UTF-8?B?SE9SSUdVQ0hJIE5BT1lBKOWggOWPoyDnm7TkuZ8p?= , Aili Yao Cc: Matthew Wilcox , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "yangfeng1@kingsoft.com" , "sunhao2@kingsoft.com" , Oscar Salvador , Mike Kravetz References: <20a0d078-f49d-54d6-9f04-f6b41dd51e5f@redhat.com> <20210318044600.GJ3420@casper.infradead.org> <20210318133412.12078eb7@alex-virtual-machine> <20210319104437.6f30e80d@alex-virtual-machine> <20210320003516.GC3420@casper.infradead.org> <20210322193318.377c9ce9@alex-virtual-machine> <20210331015258.GB22060@hori.linux.bs1.fc.nec.co.jp> <20210331104303.145aea53@alex-virtual-machine> <20210331043231.GA26013@hori.linux.bs1.fc.nec.co.jp> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <9f49c415-a75a-1ea3-b80c-5ba512331de6@redhat.com> Date: Wed, 31 Mar 2021 08:44:53 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210331043231.GA26013@hori.linux.bs1.fc.nec.co.jp> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 10D9F80192DA X-Stat-Signature: 8cstbq55d7jwdkcyy7f341ai5ge5b6tj Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf16; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=170.10.133.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617173101-842168 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 31.03.21 06:32, HORIGUCHI NAOYA(=E5=A0=80=E5=8F=A3 =E7=9B=B4=E4=B9=9F)= wrote: > On Wed, Mar 31, 2021 at 10:43:36AM +0800, Aili Yao wrote: >> On Wed, 31 Mar 2021 01:52:59 +0000 HORIGUCHI NAOYA(=E5=A0=80=E5=8F=A3=E3= =80=80=E7=9B=B4=E4=B9=9F) wrote: >>> On Fri, Mar 26, 2021 at 03:22:49PM +0100, David Hildenbrand wrote: >>>> On 26.03.21 15:09, David Hildenbrand wrote: >>>>> On 22.03.21 12:33, Aili Yao wrote: >>>>>> When we do coredump for user process signal, this may be one SIGBU= S signal >>>>>> with BUS_MCEERR_AR or BUS_MCEERR_AO code, which means this signal = is >>>>>> resulted from ECC memory fail like SRAR or SRAO, we expect the mem= ory >>>>>> recovery work is finished correctly, then the get_dump_page() will= not >>>>>> return the error page as its process pte is set invalid by >>>>>> memory_failure(). >>>>>> >>>>>> But memory_failure() may fail, and the process's related pte may n= ot be >>>>>> correctly set invalid, for current code, we will return the poison= page, >>>>>> get it dumped, and then lead to system panic as its in kernel code= . >>>>>> >>>>>> So check the hwpoison status in get_dump_page(), and if TRUE, retu= rn NULL. >>>>>> >>>>>> There maybe other scenario that is also better to check hwposion s= tatus >>>>>> and not to panic, so make a wrapper for this check, Thanks to Davi= d's >>>>>> suggestion(). >>>>>> >>>>>> Link: https://lkml.kernel.org/r/20210319104437.6f30e80d@alex-virtu= al-machine >>>>>> Signed-off-by: Aili Yao >>>>>> Cc: David Hildenbrand >>>>>> Cc: Matthew Wilcox >>>>>> Cc: Naoya Horiguchi >>>>>> Cc: Oscar Salvador >>>>>> Cc: Mike Kravetz >>>>>> Cc: Aili Yao >>>>>> Cc: stable@vger.kernel.org >>>>>> Signed-off-by: Andrew Morton >>>>>> --- >>>>>> mm/gup.c | 4 ++++ >>>>>> mm/internal.h | 20 ++++++++++++++++++++ >>>>>> 2 files changed, 24 insertions(+) >>>>>> >>>>>> diff --git a/mm/gup.c b/mm/gup.c >>>>>> index e4c224c..6f7e1aa 100644 >>>>>> --- a/mm/gup.c >>>>>> +++ b/mm/gup.c >>>>>> @@ -1536,6 +1536,10 @@ struct page *get_dump_page(unsigned long ad= dr) >>>>>> FOLL_FORCE | FOLL_DUMP | FOLL_GET); >>>>>> if (locked) >>>>>> mmap_read_unlock(mm); >>>>> >>>>> Thinking again, wouldn't we get -EFAULT from __get_user_pages_locke= d() >>>>> when stumbling over a hwpoisoned page? >>>>> >>>>> See __get_user_pages_locked()->__get_user_pages()->faultin_page(): >>>>> >>>>> handle_mm_fault()->vm_fault_to_errno(), which translates >>>>> VM_FAULT_HWPOISON to -EFAULT, unless FOLL_HWPOISON is set (-> -EHWP= OISON) >>>>> >>>>> ? >>> >>> We could get -EFAULT, but sometimes not (depends on how memory_failur= e() fails). >>> >>> If we failed to unmap, the page table is not converted to hwpoison en= try, >>> so __get_user_pages_locked() get the hwpoisoned page. >>> >>> If we successfully unmapped but failed in truncate_error_page() for e= xample, >>> the processes mapping the page would get -EFAULT as expected. But ev= en in >>> this case, other processes could reach the error page via page cache = and >>> __get_user_pages_locked() for them could return the hwpoisoned page. >>> >>>> >>>> Or doesn't that happen as you describe "But memory_failure() may fai= l, and >>>> the process's related pte may not be correctly set invalid" -- but w= hy does >>>> that happen? >>> >>> Simply because memory_failure() doesn't handle some page types like k= sm page >>> and zero page. Or maybe shmem thp also belongs to this class. Thanks for that info! >>> >>>> >>>> On a similar thought, should get_user_pages() never return a page th= at has >>>> HWPoison set? E.g., check also for existing PTEs if the page is hwpo= isoned? >>> >>> Make sense to me. Maybe inserting hwpoison check into follow_page_pte= () and >>> follow_huge_pmd() would work well. >> >> I think we should take more care to broadcast the hwpoison check to ot= her cases, >> SIGBUS coredump is such a case that it is supposed to not touch the po= ison page, >> and if we return NULL for this, the coredump process will get a succes= sful finish. >> >> Other cases may also meet the requirements like coredump, but we need = to identify it, >> that's the poison check wrapper's purpose. If not, we may break the in= tegrity of the >> related action, which may be no better than panic. >=20 > If you worry about regression and would like to make this new behavior = conditional, > we could use FOLL_HWPOISON to specify that the caller is hwpoison-aware= so that > any !FOLL_HWPOISON caller ignores the hwpoison check and works as it do= es now. > This approach looks to me helpful because it would encourage developers= touching > gup code to pay attention to FOLL_HWPOISON code. FOLL_HWPOISON might be the right start, indeed. --=20 Thanks, David / dhildenb