linux-kernel - Re: [PATCH -v4 00/10] FUTEX_UNLOCK

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Message-ID: <20161218223940.GA67477@f23x64.localdomain>
Date:   Sun, 18 Dec 2016 14:39:40 -0800
From:   Darren Hart <dvhart@...radead.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, mingo@...nel.org, juri.lelli@....com,
        rostedt@...dmis.org, xlpang@...hat.com, bigeasy@...utronix.de,
        linux-kernel@...r.kernel.org, mathieu.desnoyers@...icios.com,
        jdesfossez@...icios.com, bristot@...hat.com
Subject: Re: [PATCH -v4 00/10] FUTEX_UNLOCK_PI wobbles

On Sat, Dec 17, 2016 at 02:52:14PM +0100, Peter Zijlstra wrote:
> On Fri, Dec 16, 2016 at 03:31:40PM -0800, Darren Hart wrote:
> > On Tue, Dec 13, 2016 at 09:36:38AM +0100, Peter Zijlstra wrote:
> > > That way, when we drop hb->lock to wait, futex and rt_mutex wait state is
> > > consistent.
> > > 
> > > 
> > > In any case, it passes our inadequate testing.
> > 
> > It passed my CI tools/testing/selftests/futex/functional/run.sh. Did you also
> > happen to run a fuzz tester?
> 
> I did not. I'm not sure how good trinity is at poking holes in futexes.
> I would love a domain specific fuzzer for futex, but I suspect it would
> end up being me writing it :-(
> 

Trinity had some futex awareness and found several issues in the past, I can't
say how likely it is to find more. I haven't tried ... syzcaller? yet.

I had set out to do this in the futextest suite, which I later merged into
kselftests, but I scrapped the fuzz testing, deferring to trinity. Perhaps that
is a project we should resurrect.

-- 
Darren Hart
Intel Open Source Technology Center