Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751979AbaLXRio (ORCPT ); Wed, 24 Dec 2014 12:38:44 -0500 Received: from mail-lb0-f181.google.com ([209.85.217.181]:51734 "EHLO mail-lb0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751216AbaLXRin (ORCPT ); Wed, 24 Dec 2014 12:38:43 -0500 MIME-Version: 1.0 In-Reply-To: <20141224172506.GA23683@amd> References: <20141224163823.GA17035@amd> <20141224172506.GA23683@amd> From: Andy Lutomirski Date: Wed, 24 Dec 2014 09:38:22 -0800 Message-ID: Subject: Re: DRAM unreliable under specific access patern To: Pavel Machek Cc: kernel list Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 24, 2014 at 9:25 AM, Pavel Machek wrote: > On Wed 2014-12-24 09:13:32, Andy Lutomirski wrote: >> On Wed, Dec 24, 2014 at 8:38 AM, Pavel Machek 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. Right. So we're mostly screwed. > > As far as I understand it, attached program could reproduce it on > affected machines? I thought that article suggested using addresses 8M (is that 8 megabytes?) apart for the two accesses. --Andy > Pavel > -- > (english) http://www.livejournal.com/~pavelmachek > (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/