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[Bug 1165433] Re: Kernels from 3.8.x to 3.11.x panic on bluetooth DUN disconnect


Anyone running into this bug on Ubuntu, please test Linux kernel
3.12-release or newer, if you can compile it (or if there is a package
available...)  This kernel should have the BT DUN fixes.

I really cannot say anything in these forums as I am not running Ubuntu
(I have the same bug posted on Gentoo's bugtracker,
https://bugs.gentoo.org/show_bug.cgi?id=474432 ) but there are not
enough Gentoo users using BT DUN/NetworkManager for me to collaborate
with...  My observations is that with the 3.12 vanilla kernel the crash
goes away if I manually set up an rfcomm link and detach it, but
NetworkManager no longer finds BT DUN as a valid dialup device.
Reverting back to 3.5.7 or 3.6.11 restores operation with the same

** Bug watch added: Gentoo Bugzilla #474432

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  Kernels from 3.8.x to 3.11.x panic on bluetooth DUN disconnect

Status in “linux” package in Ubuntu:

Bug description:
  Issue is obviously in the kernel that should not panic in any circumnstances.
  This bug is seen on quantal using the kernel from PPA mainline. Tested with 3.8.0 to 3.8.6.
  Since 3.8.x is going to be the raring kernel I believe that this should definitely be fixed before raring is shipped.

  Seen on:

  DELL E6500 with kubuntu quantal 12.10 64 bit and as said, kernel 3.8.6 from the mainline ppa.
  The machine has a Dell Computer Corp. Wireless 370 Bluetooth Mini-card (connected via an internal usb connection).

  The issue is shown when connecting to the internet via a Samsung Galaxy S plus phone, using a bluetooth DUN connection.
  It is reproducible every time.

  How to reproduce:

  1) Use the bluetooth applet to discover the phone and associate to it.
  2) Use network manager to setup a DUN connection with the phone through your APN
  3) Connect to the internet via bluetooth DUN (connection works perfectly)
  4) Disconnect from the network manager.

  At the same time you disconnect, the GUI session is terminated and the
  kernel panics, briefly showing a panic log on the screen.

  Note that:

  a) The issue is not present using the standard ubuntu quantal kernel
  b) The issue is not present using kernels from the mainline ppa before 3.8 (e.g., 3.7.x is fine for all x)
  c) The issue is not present when connecting to the internet using a USB mobile dongle (e.g. Huawei usb key)

  This looks pretty serious to me: kernel does not sync when panicing
  and there is a serious risk of data loss; connecting to the internet
  via a smart phone using bluetooth DUN seems to be something that one
  should take for granted on any modern OS. Furthermore, points a) and
  b) above show that this is a *regression* over previous kernels.

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