linux-kernel - Re: BUG_ON drivers/char/random.c:986 (Was: perf: use after free in perf_remove_from

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Date:	Sat, 17 May 2014 19:00:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Theodore Ts'o <tytso@....edu>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, acme@...stprotocols.net,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dave Jones <davej@...hat.com>, price@....edu
Subject: Re: BUG_ON drivers/char/random.c:986 (Was: perf: use after free in
 perf_remove_from_context)

On Sat, May 17, 2014 at 12:24:32PM -0400, Sasha Levin wrote:
> On 05/16/2014 10:18 PM, Theodore Ts'o wrote:
> > On Fri, May 16, 2014 at 05:46:22PM -0700, Hannes Frederic Sowa wrote:
> >> > This should do the trick:
> >> > dd if=/dev/urandom of=/dev/zero bs=67108707
> >> > 
> >> > I suspect ee1de406ba6eb1 ("random: simplify accounting logic") as the
> >> > culprit.
> > Yep, that it's it.  Thanks for noticing this so quickly!  I'll push
> > the following patch to Linus.
> 
> Peter, could you describe the infrastructure you're running on? I don't
> think Dave or myself have ever hit this issue, and I wonder what made you
> stumble on it.

I'm running it on a WSP-EP, 2 nodes, 6 cores per node, 2 threads per
core for a total of 24 cpus.

I'm running trinity as user, and using:

  MALLOC_CHECK_=0 ./trinity -xinit_module -xreboot -xshutdown -xunshare -xnfsservctl -xclock_nanosleep -xuselib -xumount -xmount -m --quiet -C 400 -l off -xmremap

to run it.

I'm currently also running with syscall and a few other trace bits
enabled, but I suppose that shouldn't affect things too much.

The machine is running Debian wheezy with a few choice testing bits.

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