linux-kernel - Re: perf_fuzzer crash on pentium 4

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Message-ID: <20140508053851.GK8607@moon>
Date:	Thu, 8 May 2014 09:38:51 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: perf_fuzzer crash on pentium 4

On Wed, May 07, 2014 at 10:00:50PM -0400, Don Zickus wrote:
> > 
> > If i'm right (btw it's possible to use addr2line helper?) then hwc->config
> > is corrupted and p4_config_get_bind returned nil simply because proper event
> > was not found. And I don't understand how it could happen because before
> > configuration gets written into hwc->config it's validated once obtained
> > from user-space as a raw event. Weird...
> 
> I think my commit 13beacee817d27a40ffc6f065ea0042685611dd5 explains this
> corruption.  Though I have to admit I haven't looked through the problem
> very closely yet.

nope ;) without the fix above we could (and we did) simply misconfigure
counter but never get access out of array bound. anyway, Vince confirm
the fix from PeterZ healed the problem.

> IOW my lazy fix in that commit doesn't cover fuzzers and the real problem
> in p4_pmu_schedule_events. :-)
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