Re: [PATCH 07/12] perf_events: add LBR software filter support forIntel X86

From: Masami Hiramatsu
Date: Fri Oct 07 2011 - 03:06:56 EST

(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.


Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
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