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Date: Thu, 1 May 2014 18:31:31 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Vince Weaver <vincent.weaver@maine.edu>
cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>,
        linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [perf] more perf_fuzzer memory corruption
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On Thu, 1 May 2014, Vince Weaver wrote:

> On Thu, 1 May 2014, Peter Zijlstra wrote:
> > 
> > But yes please!
> 
> OK, sorry for the delay, had forgotten to re-enable -pg for perf in the 
> makefile when I applied your patch so had to re-build the kernel.
> 
> The trace is here:
> 	www.eece.maine.edu/~vweaver/junk/pzbug.out.bz2
> 
> No analysis so hopefully it's good, I've got an event to go to in a few 
> minutes.
> 
> The messages:
> 
> [  634.846367] ------------[ cut here ]------------
> [  634.851477] WARNING: CPU: 6 PID: 2915 at kernel/events/core.c:3232 __free_event+0x93/0xa0()

So we are on the right track:

     perf_fuzzer-2915  [006]   634.846280: bprint:               _free_event: freeing with 0 refs; ptr=0x0xffff8800cef05000

> [  634.935276] CPU: 6 PID: 2915 Comm: perf_fuzzer Not tainted 3.15.0-rc1+ #94
> [  634.942754] Hardware name: LENOVO 10AM000AUS/SHARKBAY, BIOS FBKT72AUS 01/26/2014
> [  634.950728]  0000000000000009 ffff8801174b7b78 ffffffff81649bf0 0000000000000000
> [  634.958795]  ffff8801174b7bb0 ffffffff810646ad ffff8800cef05000 0000000000000000

----------------------------------------------------^^^^^^^^^^^^^^^^

> [  634.966855]  ffff8800cd47be10 ffff880036c7b388 ffff8800cef052a0 ffff8801174b7bc0

And the corrupted element:

> [  635.995839] Slab corruption (Tainted: G        W    ): kmalloc-2048 start=ffff8800cef05000, len=2048

The same address.

Heading out now and postponing the chase for tomorrow morning.

Thanks,

	tglx