linux-kernel - Re: [PATCH 07/12] perf_events: add LBR software filter support for Intel X86

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Date:	Mon, 10 Oct 2011 08:08:10 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org, acme@...hat.com,
	ming.m.lin@...el.com, robert.richter@....com, ravitillo@....gov,
	"masami.hiramatsu.pt" <masami.hiramatsu.pt@...achi.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [PATCH 07/12] perf_events: add LBR software filter support for
 Intel X86


* Andi Kleen <andi@...stfloor.org> wrote:

> On Thu, Oct 06, 2011 at 06:43:44PM +0200, Peter Zijlstra wrote:
> > On Thu, 2011-10-06 at 17:32 +0200, Andi Kleen wrote:
> > > > +	kernel_insn_init(&insn, kaddr);
> > > > +	insn_get_opcode(&insn);
> > > 
> > > This makes me uncomfortable. AFAIK that's the first use of the opcode
> > > decoder being used directly for user space. It has a quite large attack
> > > surface. Who says it cannot be exploited?
> > 
> > You mean:
> > arch/x86/kernel/cpu/perf_event_intel_ds.c:intel_pmu_pebs_fixup_ip()
> > doesn't use the opcode decoder on user space code?
> 
> True it does. Ok the second.

That's what matters.

> I know uprobes is planning it too, so the problem has to be handled
> eventually.
> 
> Still it makes me uncomfortable.

FUD is not how we approach these things - you need to say something 
specific.

Thanks,

	Ingo
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