netdev - Re: [PATCH net-next v2] vxlan: Fix kernel crash on rmmod.

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Message-ID: <20130716163156.2374b233@nehalam.linuxnetplumber.net>
Date:	Tue, 16 Jul 2013 16:31:56 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	David Miller <davem@...emloft.net>
Cc:	pshelar@...ira.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2] vxlan: Fix kernel crash on rmmod.

On Thu, 11 Jul 2013 11:46:17 -0700 (PDT)
David Miller <davem@...emloft.net> wrote:

> From: Pravin B Shelar <pshelar@...ira.com>
> Date: Thu, 11 Jul 2013 11:38:06 -0700
> 
> > vxlan exit module unregisters vxlan net and then it unregisters
> > rtnl ops which triggers vxlan_dellink() from __rtnl_kill_links().
> > vxlan_dellink() deletes vxlan-dev from vxlan_list which has
> > list-head in vxlan-net-struct but that is already gone due to
> > net-unregister. That is how we are getting following crash.
> > 
> > Following commit fixes the crash by fixing module exit path.
>  ...
> > Signed-off-by: Pravin B Shelar <pshelar@...ira.com>
> 
> Applied, thanks for fixing the commit message.

This now crashes for me with

# Test 4a new - up - rmmod
ip li add vxlan3 type vxlan id 42 group 239.1.1.1 dev eth0
ip li set dev vxlan3 up
sleep 2
rmmod vxlan

The root cause is that rtnl_kill_links calls dellink even if device is still
UP. Since this a generic problem (several other tunnels will crash or leak
if rmmod when up), I am working on a generic fix.

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