linux-kernel - Re: DRAM unreliable under specific access patern

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Date:	Wed, 24 Dec 2014 18:25:06 +0100
From:	Pavel Machek <pavel@....cz>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: DRAM unreliable under specific access patern

On Wed 2014-12-24 09:13:32, Andy Lutomirski wrote:
> On Wed, Dec 24, 2014 at 8:38 AM, Pavel Machek <pavel@....cz> wrote:
> > Hi!
> >
> > It seems that it is easy to induce DRAM bit errors by doing repeated
> > reads from adjacent memory cells on common hw. Details are at
> >
> > https://www.ece.cmu.edu/~safari/pubs/kim-isca14.pdf
> >
> > . Older memory modules seem to work better, and ECC should detect
> > this. Paper has inner loop that should trigger this.
> >
> > Workarounds seem to be at hardware level, and tricky, too.
> 
> One mostly-effective solution would be to stop buying computers
> without ECC.  Unfortunately, no one seems to sell non-server chips
> that can do ECC.

Or keep using old computers :-).

> > Does anyone have implementation of detector? Any ideas how to work
> > around it in software?
> >
> 
> Platform-dependent page coloring with very strict, and impossible to
> implement fully correctly, page allocation constraints?

This seems to be at cacheline level, not at page level, if I
understand it correctly.

So the problem would is: I have something mapped read-only, and I can
still cause bitflips in it.

Hmm. So it is pretty obviously a security problem, no need for
java. Just do some bit flips in binary root is going to run, and it
will crash for him. You can map binaries read-only, so you have enough
access.

As far as I understand it, attached program could reproduce it on
affected machines?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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