netdev - Re: Fw: [Bug 197099] New: Kernel panic in interrupt [l2tp

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Date:   Mon, 9 Oct 2017 19:15:33 +0200
From:   Guillaume Nault <g.nault@...halink.fr>
To:     James Chapman <jchapman@...alix.com>
Cc:     SviMik <svimik@...il.com>, netdev@...r.kernel.org
Subject: Re: Fw: [Bug 197099] New: Kernel panic in interrupt [l2tp_ppp]

On Tue, Oct 03, 2017 at 08:27:32AM +0100, James Chapman wrote:
> On 2 October 2017 at 19:35, SviMik <svimik@...il.com> wrote:
> > Hi, James!
> >
> > No, I'm suffering from kernel panics since I started using 4.x
> > kernels.
> It's interesting that you are seeing l2tp issues since switching to
> 4.x kernels. Are you able to try earlier kernels to find the latest
> version that works? I'm curious whether things broke at v3.15.
> 
> > See my current collection:
> > http://svimik.com/hdmmsk1kp1.png
> This one is another crash implicating l2tp socket shutdown, this time
> when the session pppol2tp socket is closed. Unfortunately the
> screenshot doesn't show the full oops text. I'll investigate this one
> too if you can get a full oops capture.
> 
For this one too, it looks like tunnel->sock is NULL. This time, it's
l2tp_session_free() that breaks, but the root issue is probably the
same: l2tp_tunnel_destruct() removes the tunnel concurrently, most
likely because the session was created on a closing tunnel (as was
suggested by James in another message). So here too, commit
f3c66d4e144a ("l2tp: prevent creation of sessions on terminated tunnels")
might be a good start.