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From: Christoph Hellwig <hch@lst.de>
To: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org,
	Goldwyn Rodrigues <rgoldwyn@suse.de>,
	Matthew Bobrowski <mbobrowski@mbobrowski.org>
Subject: Re: [PATCH 2/2] iomap: move the iomap_dio_rw ->end_io callback into a structure
Date: Wed, 4 Sep 2019 14:51:10 +0200	[thread overview]
Message-ID: <20190904125110.GB17285@lst.de> (raw)
In-Reply-To: <20190903161446.GH29434@bombadil.infradead.org>

On Tue, Sep 03, 2019 at 09:14:46AM -0700, Matthew Wilcox wrote:
> On Tue, Sep 03, 2019 at 03:03:27PM +0200, Christoph Hellwig wrote:
> > Add a new iomap_dio_ops structure that for now just contains the end_io
> > handler.  This avoid storing the function pointer in a mutable structure,
> > which is a possible exploit vector for kernel code execution, and prepares
> > for adding a submit_io handler that btrfs needs.
> 
> Is it really a security win?  If I can overwrite dio->end_io, I can as
> well overwrite dio->dops.

Which you'd then need to point to another place where you can stuff
function pointer.  Not impossible, but just another hoop to jump
through.  At least until we add run-time checks that ops structures
are in read-only memory, which sounds more sensible than some of the
other security hardening patches floating around.

  reply	other threads:[~2019-09-04 12:51 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-03 13:03 iomap_dio_rw ->end_io improvements Christoph Hellwig
2019-09-03 13:03 ` [PATCH 1/2] iomap: split size and error for iomap_dio_rw ->end_io Christoph Hellwig
2019-09-03 14:44   ` Darrick J. Wong
2019-09-03 15:24   ` Matthew Wilcox
2019-09-03 13:03 ` [PATCH 2/2] iomap: move the iomap_dio_rw ->end_io callback into a structure Christoph Hellwig
2019-09-03 14:46   ` Darrick J. Wong
2019-09-03 16:14   ` Matthew Wilcox
2019-09-04 12:51     ` Christoph Hellwig [this message]
2019-09-03 21:32 ` iomap_dio_rw ->end_io improvements Matthew Bobrowski
2019-09-03 22:16 ` Darrick J. Wong
2019-09-04  2:19   ` Damien Le Moal
2019-09-04  5:12   ` Christoph Hellwig
2019-09-04 11:46     ` Andreas Gruenbacher
2019-09-04 17:45       ` Darrick J. Wong

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