Date:   Tue, 3 Oct 2017 08:27:32 +0100
From:   James Chapman <jchapman@...alix.com>
To:     SviMik <svimik@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: Fw: [Bug 197099] New: Kernel panic in interrupt [l2tp_ppp]

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.

> http://svimik.com/hdmmsk2kp2.png
> http://svimik.com/hdmmsk2kp3.png
These are both the same crash as the oops of this bug report.

> http://svimik.com/hdmmsk2kp4.png
> http://svimik.com/hdmmsk2kp5.png
These are truncated oops.

> http://svimik.com/hdmmsk7kp1.png
Same crash as hdmmsk1kp1.png

> Screenshots are from three different machines, kernels from 4.8.13 to 4.13.4.

For capturing complete oops messages, have you tried setting up
netconsole? You might also find the full text in the syslog on reboot.

> 2017-10-02 16:56 GMT+03:00 Eric Dumazet <eric.dumazet@...il.com>:
>> CC svimik@...il.com so that he is aware of this netdev thread.
>>
>> On Mon, 2017-10-02 at 14:32 +0100, James Chapman wrote:
>>> This seems to be a NULL pointer exception caused by tunnel->sock being
>>> NULL at the call to bh_lock_sock() in l2tp_xmit_skb() at
>>> l2tp_core.c:1135.
>>>
>>> tunnel->sock is set NULL in l2tp_core's tunnel socket destructor.
>>>
>>> At the moment, I don't understand how this happens because
>>> pppol2tp_xmit() does a sock_hold() on the tunnel socket before
>>> l2tp_xmit_skb() is called. I'm still looking at this.
>>>
>>> Has this problem only recently started happening?
>>>
>>>
>>>
>>>
>>>
>>> On 1 October 2017 at 18:21, Stephen Hemminger
>>> <stephen@...workplumber.org> wrote:
>>> >
>>> >
>>> > Begin forwarded message:
>>> >
>>> > Date: Sun, 01 Oct 2017 16:22:33 +0000
>>> > From: bugzilla-daemon@...zilla.kernel.org
>>> > To: stephen@...workplumber.org
>>> > Subject: [Bug 197099] New: Kernel panic in interrupt [l2tp_ppp]
>>> >
>>> >
>>> > https://bugzilla.kernel.org/show_bug.cgi?id=197099
>>> >
>>> >             Bug ID: 197099
>>> >            Summary: Kernel panic in interrupt [l2tp_ppp]
>>> >            Product: Networking
>>> >            Version: 2.5
>>> >     Kernel Version: 4.8.13-1.el6.elrepo.x86_64
>>> >           Hardware: x86-64
>>> >                 OS: Linux
>>> >               Tree: Mainline
>>> >             Status: NEW
>>> >           Severity: normal
>>> >           Priority: P1
>>> >          Component: Other
>>> >           Assignee: stephen@...workplumber.org
>>> >           Reporter: svimik@...il.com
>>> >         Regression: No
>>> >
>>> > Created attachment 258685
>>> >   --> https://bugzilla.kernel.org/attachment.cgi?id=258685&action=edit
>>> > stacktrace screenshot
>>> >
>>> > Hello!
>>> >
>>> > Getting kernel panics on multiple servers. Since it mentions l2tp_core,
>>> > l2tp_ppp and ppp_generic, I decided to report it to Networking (correct me if
>>> > I'm wrong).
>>> >
>>> > Unfortunately I'm still struggling with making kdump work, so the trace
>>> > screenshot is all I have at this moment. The only hope is that this stacktrace
>>> > means something to the guys that wrote the code.
>>> >
>>> > --
>>> > You are receiving this mail because:
>>> > You are the assignee for the bug.
>>
>>

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