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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C81EC433F5 for ; Mon, 4 Oct 2021 16:54:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7ED3C613D5 for ; Mon, 4 Oct 2021 16:54:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 7ED3C613D5 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 86EC0940060; Mon, 4 Oct 2021 12:54:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 81DD194000B; Mon, 4 Oct 2021 12:54:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6E508940060; Mon, 4 Oct 2021 12:54:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0169.hostedemail.com [216.40.44.169]) by kanga.kvack.org (Postfix) with ESMTP id 5CF6094000B for ; Mon, 4 Oct 2021 12:54:34 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 1418232617 for ; Mon, 4 Oct 2021 16:54:34 +0000 (UTC) X-FDA: 78659353668.03.6BCCA2C Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf18.hostedemail.com (Postfix) with ESMTP id AEDC54002805 for ; Mon, 4 Oct 2021 16:54:33 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 9F74161381; Mon, 4 Oct 2021 16:54:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633366472; bh=TvvpjQdHQdhLT/lXbu5+Haobdd8e9Zwi1ru4E+zI7wI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QQZNB2sOslZIecnGF+eD4IyTpxYTRbfRMbD/U+SeJqOti2xoV+DA9fdiH85bcAKH8 csiv9beEQIu/f491XDdtQY997mWjReJ+R3fljw63ThoJv9akyTW8La2NTc6DBr73RM 2HxaJBPuMr6CohDFSI82HV+kLgfqz/WEoiQHcC/4JRFmgt5CBh9Q4fUuPmI41IIwzI /cYLvWNP8ONCt7I6nuip/mx4BNtptQN8LC6REzXgRcG0Jhvt+pp3hz2qU+1/C3mW/Q E00wf2b8E+hgVsreo78g1LWRXUm3Z2VOd+7cH2K2mhAWCzfd+CpyolrB+nr9r4Hg18 eQTfUVg0BSBuA== Date: Mon, 4 Oct 2021 09:54:32 -0700 From: "Darrick J. Wong" To: Sean Christopherson Cc: Stephen , kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: kvm crash in 5.14.1? Message-ID: <20211004165432.GA24266@magnolia> References: <2b5ca6d3-fa7b-5e2f-c353-f07dcff993c1@gmail.com> <16c7a433-6e58-4213-bc00-5f6196fe22f5@gmail.com> <20210930175957.GA10573@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20210930175957.GA10573@magnolia> Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=QQZNB2sO; spf=pass (imf18.hostedemail.com: domain of djwong@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=djwong@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: AEDC54002805 X-Stat-Signature: 3o3a5aajs9uitu9mybbrxazg9ijz8b3f X-HE-Tag: 1633366473-243708 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 Thu, Sep 30, 2021 at 10:59:57AM -0700, Darrick J. Wong wrote: > On Wed, Sep 29, 2021 at 03:21:09PM +0000, Sean Christopherson wrote: > > On Tue, Sep 28, 2021, Stephen wrote: > > > Hello, > > >=20 > > > I got this crash again on 5.14.7 in the early morning of the 27th. > > > Things hung up shortly after I'd gone to bed. Uptime was 1 day 9 ho= urs 9 > > > minutes. > >=20 > > ... > >=20 > > > BUG: kernel NULL pointer dereference, address: 0000000000000068 > > > #PF: supervisor read access in kernel mode > > > #PF: error_code(0x0000) - not-present page > > > PGD 0 P4D 0 > > > Oops: 0000 [#1] SMP NOPTI > > > CPU: 21 PID: 8494 Comm: CPU 7/KVM Tainted: G=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0 E=A0=A0=A0=A0 5.14.7 #32 > > > Hardware name: Gigabyte Technology Co., Ltd. X570 AORUS ELITE WIFI/= X570 > > > AORUS ELITE WIFI, BIOS F35 07/08/2021 > > > RIP: 0010:internal_get_user_pages_fast+0x738/0xda0 > > > Code: 84 24 a0 00 00 00 65 48 2b 04 25 28 00 00 00 0f 85 54 06 00 0= 0 48 > > > 81 c4 a8 00 00 00 44 89 e0 5b 5d 41 5c 41 5d 41 5e 41 5f c3 <48> 81= 78 > > > 68 a0 a3 > > >=20 > > I haven't reproduced the crash, but the code signature (CMP against a= n absolute > > address) is quite distinct, and is consistent across all three crashe= s. I'm pretty > > sure the issue is that page_is_secretmem() doesn't check for a null p= age->mapping, > > e.g. if the page is truncated, which IIUC can happen in parallel sinc= e gup() doesn't > > hold the lock. > >=20 > > I think this should fix the problems? > >=20 > > diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h > > index 21c3771e6a56..988528b5da43 100644 > > --- a/include/linux/secretmem.h > > +++ b/include/linux/secretmem.h > > @@ -23,7 +23,7 @@ static inline bool page_is_secretmem(struct page *p= age) > > mapping =3D (struct address_space *) > > ((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS); > >=20 > > - if (mapping !=3D page->mapping) > > + if (!mapping || mapping !=3D page->mapping) >=20 > I'll roll this out on my vm host and try to re-run the mass fuzztest > overnight, though IT claims they're going to kill power to the whole > datacenter until Monday(!)... ...which they did, 30 minutes after I sent this email. :( I'll hopefully be able to report back to the list in a day or two. --D >=20 > --D >=20 > > return false; > >=20 > > return mapping->a_ops =3D=3D &secretmem_aops;