linux-kernel - Re: perf: use after free in perf_remove_from

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Message-ID: <20140514163535.GS30445@twins.programming.kicks-ass.net>
Date:	Wed, 14 May 2014 18:35:35 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Ingo Molnar <mingo@...nel.org>, acme@...stprotocols.net,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dave Jones <davej@...hat.com>
Subject: Re: perf: use after free in perf_remove_from_context

On Wed, May 14, 2014 at 12:32:26PM -0400, Sasha Levin wrote:
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> On 05/14/2014 12:29 PM, Peter Zijlstra wrote:
> > On Mon, May 12, 2014 at 11:42:33AM -0400, Sasha Levin wrote:
> >> Hi all,
> >> 
> >> While fuzzing with trinity inside a KVM tools guest running the latest -next kernel I've stumbled on the following spew. Maybe related to the very recent change in freeing on task exit?
> >> 
> >> [ 2509.827261] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 2509.830379] Dumping ftrace buffer: [ 2509.830379]    (ftrace buffer empty) [ 2509.830379] Modules linked in: [ 2509.830379] CPU: 47 PID: 43306 Comm: trinity-c126 Tainted: G        W     3.15.0-rc5-next-20140512-sasha-00019-ga20bc00-dirty #456
> > 
> > Any particular trinity setup? And would you happen to have the seed of that run?
> 
> Nothing special about trinity options. 400 threads and blacklisting some of the
> destructive syscalls (umount, reboot, etc).
> 
> I don't have the seed, but that problem did reproduce again tonight so I can test
> out debug code if you have something in mind.

Nah, I drew a pretty big blank, which is why I wanted to see if I could
reproduce. If you could share your trinity cmdline I'd be much obliged.
While I did manage to clone (the repo moved since last time) and build
it, I'm not really that handy with it and want to avoid destroying my
machine if possible ;-)

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