Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754084Ab3JBNiS (ORCPT ); Wed, 2 Oct 2013 09:38:18 -0400 Received: from merlin.infradead.org ([205.233.59.134]:46346 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753703Ab3JBNiP (ORCPT ); Wed, 2 Oct 2013 09:38:15 -0400 Date: Wed, 2 Oct 2013 15:37:59 +0200 From: Peter Zijlstra To: Stephane Eranian Cc: Ingo Molnar , LKML , "mingo@elte.hu" , "ak@linux.intel.com" , Arnaldo Carvalho de Melo , David Ahern , Jiri Olsa , Hugh Dickins , Kees Cook , Linus Torvalds , Andrew Morton Subject: Re: [RFC] perf: mmap2 not covering VM_CLONE regions Message-ID: <20131002133759.GH28601@twins.programming.kicks-ass.net> References: <20130930165420.GI3081@twins.programming.kicks-ass.net> <20131002112316.GP3081@twins.programming.kicks-ass.net> <20131002115826.GM26785@twins.programming.kicks-ass.net> <20131002123953.GB27811@gmail.com> <20131002124610.GD28601@twins.programming.kicks-ass.net> <20131002130143.GF28601@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1776 Lines: 34 On Wed, Oct 02, 2013 at 03:13:16PM +0200, Stephane Eranian wrote: > On Wed, Oct 2, 2013 at 3:01 PM, Peter Zijlstra wrote: > > On Wed, Oct 02, 2013 at 02:59:32PM +0200, Stephane Eranian wrote: > >> On Wed, Oct 2, 2013 at 2:46 PM, Peter Zijlstra wrote: > >> > On Wed, Oct 02, 2013 at 02:39:53PM +0200, Ingo Molnar wrote: > >> >> - then there are timing attacks, and someone having access to a PMU > >> >> context and who can trigger this SHA1 computation arbitrarily in task > >> >> local context can run very accurate and low noise timing attacks... > >> >> > >> >> I don't think the kernel's sha_transform() is hardened against timing > >> >> attacks, it's performance optimized so it has variable execution time > >> >> highly dependent on plaintext input - which leaks information about the > >> >> plaintext. > >> > > >> > Typical user doesn't have enough priv to profile kernel space; once you > >> > do you also have enough priv to see kernel addresses outright (ie. > >> > kallsyms etc..). > >> > > >> I was going to say just that. But that's not the default, paranoid level > >> is at 1 by default and not 2. So I supposedly can still do: > > > > Oh right you are.. so yes that's a very viable avenue. > > You mean simply encoding the vma->vm_mm as the ino number, for instance. Nah.. I think Kees would very much shoot us on the spot for doing that. But with the paranoid level defaulting to 1 the PMU attack on the kernel SHA implenentation is feasible. -- 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/