Kernel panic on kernel 3.8.x, 3.9RC6 when closing bluetooth dun connection (regression from 3.7.x)

[Sergio Callegari <sergio.callegari@gmail.com>]

Hi,

I'm following up with a previous email where I was reporting a systematic kernel 
panic/system freeze when closing a bluetooth DUN connection.

I have made a few more tests, all with 64 bit machines:

- Bug happens with all the 3.8.x kernel series, up to the latest 3.8.6
- Bug happens with the 3.9RC6 kernel
- Bug is not present up to 3.7.x, including the latest 3.7.10
- Bug happens on the DELL E6500 laptop that has a Dell Computer Corp. Wireless 
370 Bluetooth Mini-card
- Bug also happens on a desktop that has a Cambridge Silicon Radio, Ltd 
Bluetooth Dongle (HCI mode)

Let me recall that the bug is triggered by connecting to the internet via a 
mobile phone, using bluetooth DUN and then disconnecting. Kernel panics on 
disconnection (the phone I am using is a Samsung Galaxy S Plus)

- Bug does not happen on the same machines when connecting to the internet via 
ppp using a usb gsm/umts dongle and the same provider, so the bug seems to be BT 
related and not common to all internet connections using a Point to Point serial 
protocol.

Unfortunately, I see the bug on a machine that I use for day by day work and
I cannot afford bisecting here.

Nonetheless, the bug seems easy to reproduce (I catched it on two different 
machines with different setups). So I hope this note can help haunting the 
regression anyway.

Thanks for the attention,

Sergio Callegari