linux-kernel - Re: [RFC] perf: mmap2 not covering VM

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Message-ID: <20131002130143.GF28601@twins.programming.kicks-ass.net>
Date:	Wed, 2 Oct 2013 15:01:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Kees Cook <keescook@...omium.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC] perf: mmap2 not covering VM_CLONE regions

On Wed, Oct 02, 2013 at 02:59:32PM +0200, Stephane Eranian wrote:
> On Wed, Oct 2, 2013 at 2:46 PM, Peter Zijlstra <peterz@...radead.org> 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.
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