From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 1/2] xfs: rewrite getbmap using the xfs_iext_* helpers
Date: Thu, 21 Sep 2017 08:35:05 -0700 [thread overview]
Message-ID: <20170921153505.GF7112@magnolia> (raw)
In-Reply-To: <20170921133610.GD13541@lst.de>
On Thu, Sep 21, 2017 at 03:36:10PM +0200, Christoph Hellwig wrote:
> On Wed, Sep 20, 2017 at 04:08:24PM -0700, Darrick J. Wong wrote:
> > > I'm still wondering why we allocate a potentially large getbmapx buffer,
> > > fill it out, and only then format the results to userspace? I think
> > > getbmap (the ioctl) is now the only user of these functions, so can't
> > > we just call the formatter directly from _getbmap_report_one and
> > > _getbmap_report_hole, like what getfsmap does?
> > >
> > > (I also feel like I've asked this before, so apologies if I'm merely
> > > forgetting the answer.)
> >
> > Oh right, it's because we have the inode locked, and copying things to
> > userspace could incur a page fault, which we can't risk with the inode
> > locked because some malicious person could create a fragmented file with
> > a bmap request header at the start of the file, mmap the file, and call
> > bmap on the fragmented file with the pointer being the mmap region.
>
> Yes.
>
> Can I get a Reviewed-by: tag now? :)
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
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next prev parent reply other threads:[~2017-09-21 15:35 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-18 15:26 getbmap refactor V2 Christoph Hellwig
2017-09-18 15:26 ` [PATCH 1/2] xfs: rewrite getbmap using the xfs_iext_* helpers Christoph Hellwig
2017-09-20 13:23 ` Brian Foster
2017-09-20 14:41 ` Christoph Hellwig
2017-09-20 17:03 ` Darrick J. Wong
2017-09-20 23:00 ` Darrick J. Wong
2017-09-20 23:08 ` Darrick J. Wong
2017-09-21 13:36 ` Christoph Hellwig
2017-09-21 15:35 ` Darrick J. Wong [this message]
2017-09-21 13:35 ` Christoph Hellwig
2017-09-21 15:40 ` Darrick J. Wong
2017-09-18 15:26 ` [PATCH 2/2] xfs: simplify the xfs_getbmap interface Christoph Hellwig
2017-09-20 23:08 ` Darrick J. Wong
-- strict thread matches above, loose matches on Subject: below --
2017-09-03 15:51 [PATCH 1/2] xfs: rewrite getbmap using the xfs_iext_* helpers Christoph Hellwig
2017-09-11 15:49 ` Brian Foster
2017-09-17 21:44 ` Christoph Hellwig
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