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Date: Mon, 29 Sep 2014 16:00:48 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
        "Sylvain 'ythier' Hitier" <sylvain.hitier@gmail.com>,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Vince Weaver <vincent.weaver@maine.edu>
Subject: Re: [PATCH] fork.c: copy_process(): fix cleanup WRT
 perf_event_free_task()
Message-ID: <20140929140048.GK5430@worktop>
References: <20140926210652.GA27199@erable>
 <20140927180725.GA15594@redhat.com>
 <20140929101201.GE5430@worktop>
 <20140929120722.GA11943@gmail.com>
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On Mon, Sep 29, 2014 at 02:07:22PM +0200, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@infradead.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@redhat.com>
> > Reported-by: Oleg Nesterov <oleg@redhat.com>
> > Reported-by: Sylvain 'ythier' Hitier <sylvain.hitier@gmail.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.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.