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Date: Mon, 31 Oct 2016 09:27:05 +0100
From: Pavel Machek <pavel@....cz>
To: Mark Rutland <mark.rutland@....com>
Cc: Kees Cook <keescook@...omium.org>,
Peter Zijlstra <peterz@...radead.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
kernel list <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...hat.com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: rowhammer protection [was Re: Getting
interrupt every million cache misses]
Hi!
> On Fri, Oct 28, 2016 at 01:21:36PM +0200, Pavel Machek wrote:
> > > Has this been tested on a system vulnerable to rowhammer, and if so, was
> > > it reliable in mitigating the issue?
> > >
> > > Which particular attack codebase was it tested against?
> >
> > I have rowhammer-test here,
> >
> > commit 9824453fff76e0a3f5d1ac8200bc6c447c4fff57
> > Author: Mark Seaborn <mseaborn@...omium.org>
>
> ... from which repo?
>
> > I do not have vulnerable machine near me, so no "real" tests, but
> > I'm pretty sure it will make the error no longer reproducible with the
> > newer version. [Help welcome ;-)]
>
> Even if we hope this works, I think we have to be very careful with that
> kind of assertion. Until we have data is to its efficacy, I don't think
> we should claim that this is an effective mitigation.
Ok, so it turns out I was right. On my vulnerable machine, normally
bug is reproducible in less than 500 iterations:
Iteration 432 (after 1013.31s)
error at 0xda7cf280: got 0xffffffffffffffef
Iteration 446 (after 1102.56s)
error at 0xec21ea00: got 0xffffffefffffffff
Iteration 206 (after 497.50s)
error at 0xd07d1438: got 0xffffffffffffffdf
Iteration 409 (after 1350.96s)
error at 0xbd3b9108: got 0xefffffffffffffff
Iteration 120 (after 326.08s)
error at 0xe398c438: got 0xffffffffffffffdf
With nohammer, I'm at 2300 iterations, and still no faults.
Daniel Gruss <daniel@...ss.cc> claims he has an attack that can do 30
flips a second on modern hardware. I'm not going to buy broken
hardware just for a test. Code is at
https://github.com/IAIK/rowhammerjs/tree/master/native . Would someone
be willing to get it running on vulnerable machine and test kernel
patches?
Thanks,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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