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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 AA7ACC4CED0 for ; Wed, 18 Sep 2019 12:31:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 74097205F4 for ; Wed, 18 Sep 2019 12:31:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74097205F4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 0BEC26B0007; Wed, 18 Sep 2019 08:31:17 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 06D2D6B029C; Wed, 18 Sep 2019 08:31:17 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EC5656B029D; Wed, 18 Sep 2019 08:31:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0164.hostedemail.com [216.40.44.164]) by kanga.kvack.org (Postfix) with ESMTP id CB5AD6B0007 for ; Wed, 18 Sep 2019 08:31:16 -0400 (EDT) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 4DADA8243772 for ; Wed, 18 Sep 2019 12:31:16 +0000 (UTC) X-FDA: 75947976552.19.cook52_7f7237bebc01a X-HE-Tag: cook52_7f7237bebc01a X-Filterd-Recvd-Size: 2984 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf43.hostedemail.com (Postfix) with ESMTP for ; Wed, 18 Sep 2019 12:31:15 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id ED106AD2B; Wed, 18 Sep 2019 12:31:13 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 07F751E4201; Wed, 18 Sep 2019 14:31:24 +0200 (CEST) Date: Wed, 18 Sep 2019 14:31:24 +0200 From: Jan Kara To: "Darrick J. Wong" Cc: Jan Kara , linux-xfs@vger.kernel.org, linux-mm@kvack.org, Amir Goldstein , Boaz Harrosh , linux-fsdevel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 3/3] xfs: Fix stale data exposure when readahead races with hole punch Message-ID: <20190918123123.GC31891@quack2.suse.cz> References: <20190829131034.10563-1-jack@suse.cz> <20190829131034.10563-4-jack@suse.cz> <20190829155204.GD5354@magnolia> <20190830152449.GA25069@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190830152449.GA25069@quack2.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Fri 30-08-19 17:24:49, Jan Kara wrote: > On Thu 29-08-19 08:52:04, Darrick J. Wong wrote: > > On Thu, Aug 29, 2019 at 03:10:34PM +0200, Jan Kara wrote: > > > Hole puching currently evicts pages from page cache and then goes on to > > > remove blocks from the inode. This happens under both XFS_IOLOCK_EXCL > > > and XFS_MMAPLOCK_EXCL which provides appropriate serialization with > > > racing reads or page faults. However there is currently nothing that > > > prevents readahead triggered by fadvise() or madvise() from racing with > > > the hole punch and instantiating page cache page after hole punching has > > > evicted page cache in xfs_flush_unmap_range() but before it has removed > > > blocks from the inode. This page cache page will be mapping soon to be > > > freed block and that can lead to returning stale data to userspace or > > > even filesystem corruption. > > > > > > Fix the problem by protecting handling of readahead requests by > > > XFS_IOLOCK_SHARED similarly as we protect reads. > > > > > > CC: stable@vger.kernel.org > > > Link: https://lore.kernel.org/linux-fsdevel/CAOQ4uxjQNmxqmtA_VbYW0Su9rKRk2zobJmahcyeaEVOFKVQ5dw@mail.gmail.com/ > > > Reported-by: Amir Goldstein > > > Signed-off-by: Jan Kara > > > > Is there a test on xfstests to demonstrate this race? > > No, but I can try to create one. I was experimenting with this but I could not reproduce the issue in my test VM without inserting artificial delay at appropriate place... So I don't think there's much point in the fstest for this. Honza -- Jan Kara SUSE Labs, CR