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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 6649DC41514 for ; Fri, 30 Aug 2019 15:24:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 45BEA22CE9 for ; Fri, 30 Aug 2019 15:24:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727884AbfH3PYw (ORCPT ); Fri, 30 Aug 2019 11:24:52 -0400 Received: from mx2.suse.de ([195.135.220.15]:40034 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727135AbfH3PYw (ORCPT ); Fri, 30 Aug 2019 11:24:52 -0400 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 17DFEAD49; Fri, 30 Aug 2019 15:24:50 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 82B441E43A8; Fri, 30 Aug 2019 17:24:49 +0200 (CEST) Date: Fri, 30 Aug 2019 17:24:49 +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: <20190830152449.GA25069@quack2.suse.cz> References: <20190829131034.10563-1-jack@suse.cz> <20190829131034.10563-4-jack@suse.cz> <20190829155204.GD5354@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190829155204.GD5354@magnolia> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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. > Will test it out though... > > Reviewed-by: Darrick J. Wong Thanks. BTW, will you pick up these patches please? Honza > > --D > > > --- > > fs/xfs/xfs_file.c | 26 ++++++++++++++++++++++++++ > > 1 file changed, 26 insertions(+) > > > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > > index 28101bbc0b78..d952d5962e93 100644 > > --- a/fs/xfs/xfs_file.c > > +++ b/fs/xfs/xfs_file.c > > @@ -28,6 +28,7 @@ > > #include > > #include > > #include > > +#include > > > > static const struct vm_operations_struct xfs_file_vm_ops; > > > > @@ -933,6 +934,30 @@ xfs_file_fallocate( > > return error; > > } > > > > +STATIC int > > +xfs_file_fadvise( > > + struct file *file, > > + loff_t start, > > + loff_t end, > > + int advice) > > +{ > > + struct xfs_inode *ip = XFS_I(file_inode(file)); > > + int ret; > > + int lockflags = 0; > > + > > + /* > > + * Operations creating pages in page cache need protection from hole > > + * punching and similar ops > > + */ > > + if (advice == POSIX_FADV_WILLNEED) { > > + lockflags = XFS_IOLOCK_SHARED; > > + xfs_ilock(ip, lockflags); > > + } > > + ret = generic_fadvise(file, start, end, advice); > > + if (lockflags) > > + xfs_iunlock(ip, lockflags); > > + return ret; > > +} > > > > STATIC loff_t > > xfs_file_remap_range( > > @@ -1232,6 +1257,7 @@ const struct file_operations xfs_file_operations = { > > .fsync = xfs_file_fsync, > > .get_unmapped_area = thp_get_unmapped_area, > > .fallocate = xfs_file_fallocate, > > + .fadvise = xfs_file_fadvise, > > .remap_file_range = xfs_file_remap_range, > > }; > > > > -- > > 2.16.4 > > -- Jan Kara SUSE Labs, CR