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 ED0DBC433FE for ; Wed, 6 Oct 2021 16:34:25 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 89C776112D for ; Wed, 6 Oct 2021 16:34:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 89C776112D 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 2941C940007; Wed, 6 Oct 2021 12:34:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 243376B0071; Wed, 6 Oct 2021 12:34:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1326E940007; Wed, 6 Oct 2021 12:34:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0139.hostedemail.com [216.40.44.139]) by kanga.kvack.org (Postfix) with ESMTP id 04E196B006C for ; Wed, 6 Oct 2021 12:34:25 -0400 (EDT) Received: from smtpin02.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id A515F8249980 for ; Wed, 6 Oct 2021 16:34:24 +0000 (UTC) X-FDA: 78666560448.02.4AAFD97 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf23.hostedemail.com (Postfix) with ESMTP id 4E7BB900107E for ; Wed, 6 Oct 2021 16:34:24 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 622A9610E5; Wed, 6 Oct 2021 16:34:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633538063; bh=ctlyh/MM/ZO1vAziMpXnSjbXLCBHhorGWU3Y4W6Lq/Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RkNXjzbdX5MCmCfXVkHWaWb2gGEEnzx2z8pkKs/2PZ4y3s2bPvSbF2h8KpdKmLJ4W UUNUavhpVkKqZT7phW5nnNaBJ/vCNyikpZ9oY1Aiuooj/j23c4JLXYP5MtmiUTpY+i jFHtPAJmCZUsJoT4wdzEIaRrXpmKG+4Sp1U8AWT8W8FdiRMPZo9SE2JVqMgFVmX7De AfwzYccfPCXKRQUprMR1UZYU1qJzR4PlF/HKHzD5IFD8hmArQdGd7tefjG9WoC+RJt Zqx+CUv9YYa8Hhy9FjPpwEZ2uOXrivJ7VzlyV17aEWTir3IxFq8GTkJ9Z6y+QdyAAf C1jMib4pXElyw== Date: Wed, 6 Oct 2021 09:34:23 -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: <20211006163423.GB24266@magnolia> References: <2b5ca6d3-fa7b-5e2f-c353-f07dcff993c1@gmail.com> <16c7a433-6e58-4213-bc00-5f6196fe22f5@gmail.com> <20210930175957.GA10573@magnolia> <20211004165432.GA24266@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20211004165432.GA24266@magnolia> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 4E7BB900107E X-Stat-Signature: fuzeeqwndpumo45kehnuaki8upcorggb Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=RkNXjzbd; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf23.hostedemail.com: domain of djwong@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=djwong@kernel.org X-HE-Tag: 1633538064-210325 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 Mon, Oct 04, 2021 at 09:54:32AM -0700, Darrick J. Wong wrote: > 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 = hours 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 WIF= I/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= 00 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= an absolute > > > address) is quite distinct, and is consistent across all three cras= hes. I'm pretty > > > sure the issue is that page_is_secretmem() doesn't check for a null= page->mapping, > > > e.g. if the page is truncated, which IIUC can happen in parallel si= nce 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 = *page) > > > 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(!)... >=20 > ...which they did, 30 minutes after I sent this email. :( >=20 > I'll hopefully be able to report back to the list in a day or two. Looks like everything went smoothly with the mass fuzz fstesting. I'll let you know if I see any further failures, but for now: Tested-by: Darrick J. Wong --D > --D >=20 > >=20 > > --D > >=20 > > > return false; > > >=20 > > > return mapping->a_ops =3D=3D &secretmem_aops;