linux-kernel - Re: [PATCH] fork.c: copy_process(): fix cleanup WRT perf_event_free

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Date:	Wed, 1 Oct 2014 15:44:58 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	"Sylvain 'ythier' Hitier" <sylvain.hitier@...il.com>,
	linux-kernel@...r.kernel.org,
	Vince Weaver <vincent.weaver@...ne.edu>
Subject: Re: [PATCH] fork.c: copy_process(): fix cleanup WRT
 perf_event_free_task()

On Mon, 29 Sep 2014 16:00:48 +0200 Peter Zijlstra <peterz@...radead.org> wrote:

> On Mon, Sep 29, 2014 at 02:07:22PM +0200, Ingo Molnar wrote:
> > 
> > * Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > > Subject: perf: Fix perf bug in fork()
> > > 
> > > Oleg noticed that a cleanup by Sylvain actually uncovered a bug; by
> > > calling perf_event_free_task() when failing sched_fork() we will not yet
> > > have done the memset() on ->perf_event_ctxp[] and will therefore try and
> > > 'free' the inherited contexts, which are still in use by the parent
> > > process. This is bad..
> > > 
> > > Suggested-by: Oleg Nesterov <oleg@...hat.com>
> > > Reported-by: Oleg Nesterov <oleg@...hat.com>
> > > Reported-by: Sylvain 'ythier' Hitier <sylvain.hitier@...il.com>
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > 
> > Could this fix a couple of fuzzer triggered perf crashes perhaps?
> 
> It could indeed I suppose.. you never know what paths those fuzzers
> manage to hit.

The patch isn't in linux-next and didn't cc stable.  I think I'll
squirt it Linuswards later this week unless someone stops me..

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