From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Date: Wed, 05 Apr 2017 14:22:05 +0000
Subject: Re: net/sctp: list double add warning in sctp_endpoint_add_asoc
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To: Andrey Konovalov <andreyknvl@google.com>
Cc: Xin Long <lucien.xin@gmail.com>, Vlad Yasevich <vyasevich@gmail.com>, Neil Horman <nhorman@tuxdriver.com>, "David S. Miller" <davem@davemloft.net>, linux-sctp@vger.kernel.org, netdev <netdev@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, Dmitry Vyukov <dvyukov@google.com>, Eric Dumazet <edumazet@google.com>, Kostya Serebryany <kcc@google.com>, syzkaller <syzkaller@googlegroups.com>

On Wed, Apr 05, 2017 at 04:02:44PM +0200, Andrey Konovalov wrote:
> On Tue, Apr 4, 2017 at 11:14 PM, Marcelo Ricardo Leitner
> <marcelo.leitner@gmail.com> wrote:
> > On Wed, Apr 05, 2017 at 01:29:19AM +0800, Xin Long wrote:
> >> On Tue, Apr 4, 2017 at 9:28 PM, Andrey Konovalov <andreyknvl@google.com> wrote:
> >> > Hi,
> >> >
> >> > I've got the following error report while fuzzing the kernel with syzkaller.
> >> >
> >> > On commit a71c9a1c779f2499fb2afc0553e543f18aff6edf (4.11-rc5).
> >> >
> >> > A reproducer and .config are attached.
> >> The script is pretty hard to reproduce the issue in my env.
> >
> > I didn't try running it but I also found the reproducer very complicated
> > to follow. Do you have any plans on having some PoC optimizer, so we can
> > have a more readable code?
> > strace is handy for filtering the noise, yes, but sometimes it doesn't
> > cut it.
> 
> We do have some plans (like to remote all those unnecessary helper
> functions), but it's probably not going to become much better.
> 
> You mostly only need to look at the thr() function to understand
> what's going on.

Okay.

> 
> What I sometimes do is run each of the switch cases under strace
> separately to understand what each of them do.
> 
> I've also attached a program in syzkaller format.
> You can take a look at it, if you find it useful, I can start
> attaching them for subsequent reports.

Comparing it to thr() they look very close, at least for this one.
But when you cannot extract a reproducer, it will certainly help.

Thanks,
Marcelo