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

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Date:	Fri, 07 Oct 2011 16:06:45 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Stephane Eranian <eranian@...gle.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, acme@...hat.com,
	ming.m.lin@...el.com, robert.richter@....com, ravitillo@....gov,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [PATCH 07/12] perf_events: add LBR software filter support for
 Intel X86

(2011/10/07 1:43), 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?
> 
> ISTR Masami telling me they ran fuzzers on it, feeding it bad
> instructions etc. But maybe he can tell more.

I've tested it by decoding userspace libraries and binaries.
It is also easy to test decoding with random binaries too :)
I'll try to do that.

Thanks,

-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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