linux-kernel - Re: perf: easily crash kernel with rapl event close

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Date:	Thu, 22 Jan 2015 04:39:16 -0800
From:	Stephane Eranian <eranian@...glemail.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: perf: easily crash kernel with rapl event close

On Thu, Jan 22, 2015 at 2:17 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, Jan 21, 2015 at 09:13:11PM -0800, Stephane Eranian wrote:
>> Vince,
>>
>> On Wed, Jan 21, 2015 at 10:55 AM, Vince Weaver <vincent.weaver@...ne.edu> wrote:
>> > Hello
>> >
>> > on my haswell system, running 3.19-rc5, and with
>> >         echo "0" > /proc/sys/kernel/perf_event_paranoid
>> >
>> > I can easily crash my system with the attached test program that simply
>> > opens a RAPL event and then closes it.
>> >
>> > This bug was found by the perf_fuzzer.
>> >
>> > It looks like somehow rapl_pmu gets freed to NULL but the
>> > call in rapl_scale()
>> >         __this_cpu_read(rapl_pmu->hw_unit)
>> > still happens.
>> >
>> I don't see how this can happen.
>>
>> I get some crashes but not with your program on my laptop.
>> But I cannot catch the serial console from my laptop.
>> Will try with another machine tomorrow.
>
> I saw it today as well on an ivb-ep. I disabled rapl for now since I'm
> chasing other things.

I will fix that today.
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