linux-kernel - Re: OOPS in perf_mmap

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Message-ID: <20130529074433.GB12193@twins.programming.kicks-ass.net>
Date:	Wed, 29 May 2013 09:44:33 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	trinity@...r.kernel.org
Subject: Re: OOPS in perf_mmap_close()

On Tue, May 28, 2013 at 02:22:11PM -0400, Vince Weaver wrote:
> On Tue, 28 May 2013, Vince Weaver wrote:
> 
> > It looks like this is already in tip, but I can confirm that this 
> > patch seems to fix things on my machine and holds up against longer 
> > fuzzing runs.
> 
> OK, I take it back.  Even with the new patch applied, my fuzzer can still 
> make the kernel leak user->locked_vm
> 
> I assume that the locked_vm value should go back to 0 once a process that 
> has a bunch of mmap'd perf_events opened exits?

Yep.

> I admit this is sort of an obscure corner case, but it does mean that a 
> user can leak user->locked_vm to the point that "perf record" no longer 
> works.

Hurm.. I don't suppose you have an easy reproducer handy eh? I'll go
stare at it. At least the current state is better than before, but
clearly we're not quite there yet.
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