linux-kernel - Re: [perf] more perf_fuzzer memory corruption

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Message-ID: <20140418171516.GR13658@twins.programming.kicks-ass.net>
Date:	Fri, 18 Apr 2014 19:15:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [perf] more perf_fuzzer memory corruption

On Fri, Apr 18, 2014 at 06:59:58PM +0200, Peter Zijlstra wrote:
> On Fri, Apr 18, 2014 at 05:23:14PM +0200, Peter Zijlstra wrote:
> > OK, that's a good clue. That looks like we're freeing events that still
> > are on the owner list, which would indicate we're freeing events that
> > have a refcount.
> > 
> > I added a WARN in free_event() to check the refcount, along with a
> > number of false positives (through the perf_event_open() fail path) I do
> > appear to be getting actual fails here.
> > 
> > At least I can 'reproduce' this. Earlier attempts, even based on your
> > .config only got me very mysterious lockups -- I suspect the corruption
> > happens on a slightly different spot or so and completely messes up the
> > machine.
> 
> The below should have only made the false positives go away, but my
> machine has magically stopped going all funny on me. Could you give it a
> go?
> 

Hmm the fuzzer task seems stuck in kernel space, can't kill it anymore.

So its likely it just didn't get around to doing enough to wreck the
system or so.

/me goes stab it in the eye.
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