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[209.85.220.65]) by mx.google.com with SMTPS id k192sor3152491ywe.69.2019.07.11.08.29.05 for (Google Transport Security); Thu, 11 Jul 2019 08:29:05 -0700 (PDT) Received-SPF: pass (google.com: domain of amir73il@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=hi9T44Hc; spf=pass (google.com: domain of amir73il@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=amir73il@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5sCdnmzsl1yenTFWhrojlM/D/t4ITTwRJQe377tVKgo=; b=hi9T44Hc/U1WaGxNK3YRIgCTIIMDaPwvl08nParEY8MDt275bPklFMyJJTW43mNamt 1qo4XRN0biXSUMcH2yqLN0HgB5YbXFc56yN1Pf1NMq32lD3W9NrXaBtmcH72iHw7x+L2 vXnEIqXq7MfEny31h8UAFF6rQ4BwQeStOx1fQ38NgYtozQ4mDWEAjHBi+XK998rvhPgQ 5QBNL+gP6hoNbFaLt/tcnUQ47WfNCnoxyNk7RdurbvFgmUsyASqT7WCf2sCofGQ2OfNe Tm9isExHWRfS57q5NgooDQDb9TbkkKP/oorSth2cpRexa+BL+FbpiBsxrNUG18SetE5i dTBA== X-Google-Smtp-Source: APXvYqybRjoMmoZeVATYSR5xajAV3WU3UTAp1AnSQg+8j0SLgEeFQbs8LxY7VQh36U8PWceOifdD0jQhCXZdcPRaZcg= X-Received: by 2002:a81:3c12:: with SMTP id j18mr2694969ywa.294.1562858944848; Thu, 11 Jul 2019 08:29:04 -0700 (PDT) MIME-Version: 1.0 References: <20190711140012.1671-1-jack@suse.cz> <20190711140012.1671-4-jack@suse.cz> In-Reply-To: <20190711140012.1671-4-jack@suse.cz> From: Amir Goldstein Date: Thu, 11 Jul 2019 18:28:54 +0300 Message-ID: Subject: Re: [PATCH 3/3] xfs: Fix stale data exposure when readahead races with hole punch To: Jan Kara Cc: linux-fsdevel , Linux MM , linux-xfs , Boaz Harrosh , stable Content-Type: text/plain; charset="UTF-8" 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, Jul 11, 2019 at 5:00 PM 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 > --- Looks sane. (I'll let xfs developers offer reviewed-by tags) > fs/xfs/xfs_file.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index 76748255f843..88fe3dbb3ba2 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -33,6 +33,7 @@ > #include > #include > #include > +#include > > static const struct vm_operations_struct xfs_file_vm_ops; > > @@ -939,6 +940,24 @@ 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; > + > + /* Readahead needs protection from hole punching and similar ops */ > + if (advice == POSIX_FADV_WILLNEED) > + xfs_ilock(ip, XFS_IOLOCK_SHARED); > + ret = generic_fadvise(file, start, end, advice); > + if (advice == POSIX_FADV_WILLNEED) > + xfs_iunlock(ip, XFS_IOLOCK_SHARED); > + return ret; > +} > > STATIC loff_t > xfs_file_remap_range( > @@ -1235,6 +1254,7 @@ 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 >