kernel-packages team mailing list archive

[Sergio Callegari <sergio.callegari@xxxxxxxxx>]

Fixed the bug title (so that the window of affected kernels is clear and
it is clear that this is an issue both for raring and for saucy.

Also marked as confirmed, since the incomplete label was a bit weird at
this point.

If I understand correctly the situation now is this

1) All kernels from 3.8.0 to 3.11.x are affected. 3.12 will most likely be fixed, unless something really unexpected happens with the 3.12 RC kernels and the fix eventually needs to be reverted.
2) The fix that is going into 3.12 RC1 would also apply cleanly to 3.11.x (and probably back to 3.8.x, possibly with very minor changes)
3) In spite of the fixing patches only touching rfcomm (that is anyway completely broken in 3.8.x to 3.11.x), they are considered too 'fat' for inclusion in the kernel stabilization series for 3.10.x and 3.11.x (I think that the kernel stabilization series for 3.9.x is terminated, so that 3.9 will not be fixed in anyway, and the kernel stabilization series for 3.8.x is in ubuntu's hands).
4) To provide a fix to 3.8.x to 3.11.x those who indicated the 3.12 fix as too fat for the stabilization series suggested a much 'thinner' approach based on BUG_ON. Unfortunately, when tried that approach proved not to fix the issue.

Now I wonder if the declaration of the proper fix as too fat for the
stabilization series was in some way influenced by the wrong expectation
to be able to count on a thinner fix.

At this point, either 
- a proper 'thin' fix comes out soon suitable for the stabilization series and ubuntu imports it in raring and saucy's kernels
- ubuntu applies the proper 'fat' fix to its kernels even if it does not go to the stabilization series since in any case they only touch a subsystem that is currently utterly broken and to dangerous to use
- the bug remains unfixed in raring and saucy

In the last case, who is unaware may end up trying bluetooth DUN and
experience a 'delayed' crash and data loss. The others will probably
build a 3.8.x with the 'fat' fix on ppa and live happy.

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https://bugs.launchpad.net/bugs/1165433

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

Status in “linux” package in Ubuntu:
  Confirmed

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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