Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753985Ab3JBM7i (ORCPT ); Wed, 2 Oct 2013 08:59:38 -0400 Received: from mail-qe0-f43.google.com ([209.85.128.43]:50113 "EHLO mail-qe0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753495Ab3JBM7e (ORCPT ); Wed, 2 Oct 2013 08:59:34 -0400 MIME-Version: 1.0 In-Reply-To: <20131002124610.GD28601@twins.programming.kicks-ass.net> References: <20130930161546.GG3081@twins.programming.kicks-ass.net> <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> Date: Wed, 2 Oct 2013 14:59:32 +0200 Message-ID: Subject: Re: [RFC] perf: mmap2 not covering VM_CLONE regions From: Stephane Eranian To: Peter Zijlstra 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 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1244 Lines: 26 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: $ perf record -e cycles ...... In per-thread mode and collect kernel level addresses. -- 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/