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

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Date:	Mon, 5 May 2014 21:36:29 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	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, May 05, 2014 at 02:47:32PM -0400, Vince Weaver wrote:
> 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.

Ooh, I know that one. Its what my WSM-EP favours. I'll try and have a
look.

> 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.

Oh, usually when my WSM gets funny like this and I enable the tracer it
just stops being a computer and starts being a brick.

Might be a nice clue though.

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