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

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Date:	Mon, 5 May 2014 14:47:32 -0400 (EDT)
From:	Vince Weaver <vincent.weaver@...ne.edu>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [perf] more perf_fuzzer memory corruption

On Mon, 5 May 2014, Peter Zijlstra wrote:

> Cute.. does the below cure?
> 
> 
> ---
> Subject: perf: Fix perf_event_init_context()
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Mon May  5 19:12:20 CEST 2014
> 
> perf_pin_task_context() can return NULL but perf_event_init_context()
> assumes it will not, correct this.

It makes the oops go away, but it does make the fuzzer become unkillable 
while using 100% CPU.

It looks like it is stuck repeating this forever:
	perf_fuzzer-5256  [000]   275.943049: kmalloc:              (T.1262+0xe) call_site=ffffffff810d022f ptr=0xffff8800cb028400 bytes_req=216 bytes_alloc=256 gfp_flags=GFP_KERNEL|GFP_ZERO
	perf_fuzzer-5256  [000]   275.943057: function:             perf_lock_task_context
	perf_fuzzer-5256  [000]   275.943057: function:             alloc_perf_context
and memory is slowly leaking away.


Meanwhile the haswell and AMD machines have been fuzzing away without 
issue, I don't know why the core2 machine is always the trouble maker.

Vince

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