linux-kernel - Re: System crash with perf

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Date:   Fri, 25 Jan 2019 10:11:28 -0500 (EST)
From:   Vince Weaver <vincent.weaver@...ne.edu>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
cc:     lkml <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-perf-users@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>, eranian@...gle.com,
        vincent.weaver@...ne.edu,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Subject: Re: System crash with perf_fuzzer (kernel: 5.0.0-rc3)

On Fri, 25 Jan 2019, Ravi Bangoria wrote:

> I'm seeing a system crash while running perf_fuzzer with upstream kernel
> on an Intel machine. I hit the crash twice (out of which I don't have log
> of first crash so don't know if the reason is same for both the crashes).
> I've attached my .config with the mail.
>                   type = PERF_TYPE_HARDWARE;

>   ========
> 
> And, I'm running fuzzer in a loop with *root*. (Let me know if running
> as root is harmful ;-) ).

There's a known issue related to Intel BTS events that you can trigger 
with the perf_fuzzer, even as a normal user.  I reported it a few months 
ago but I don't think it ever got resolved.  The traces you get look 
similar to some that you posted.

It's hard to track down as it doesn't seem to be a simple issue, but 
rather it looks like the BTS event handling is stomping over memory it 
shouldn't somehow.

Vince