[Bug 52145] kernel freezes when binding bluetooth rfcomm on Ubuntu 5.10

[vanderson.gold]

Public bug reported:

The kernel freezes (due to an Oops) when disconnecting and immediately
reconnecting a bluetooth RFCOMM device.

It's due to a race condition, already fixed in versions 2.6.13 and
above.

The patch below, from Marcell Holtmann (maintainer of the BT stack)
should be enough to fix this bug:

From: http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=dcc365d8f28d6a2332fa37e64d669858a8d017e8
{{{
    [Bluetooth] Revert session reference counting fix

    The fix for the reference counting problem of the signal DLC introduced
    a race condition which leads to an oops. The reason for it is not fully
    understood by now and so revert this fix, because the reference counting
    problem is not crashing the RFCOMM layer and its appearance it rare.

    Signed-off-by: Marcel Holtmann <marcel at holtmann.org>
}}} 

How to reproduce it:

 * Just running rfcomm bind / rfcomm release should trigger the bug, but
   since it's a racing condition, you mileage may vary. The steps below
   should be sufficient to reproduce it:

{{{
  1. remove any cache from application who detects bluetooth
     devices (ex:some-bt-app)
  2. /etc/init.d/bluez-utils start
  3. run some bluetoooth application which uses rfcomm ports
  4. do needed stuff to establish bluetooth connection (ex: check
     if /dev/rfcomm* are ok)
  5. stop your bluetooth application
  6. /etc/init.d/bluez-utils stop
  7. wait a few seconds
  8. Oops, completely freezing the machine
}}}

Just a few seconds later the machine freezes with an oops.

This was originally reported on the Mandriva bugzilla:
http://qa.mandriva.com/show_bug.cgi?id=22566. They've fixed the
problem applying the aforementioned patch, including the fix on
the next kernel update of MDV2006.

Any chances we can have this fixed on one of the next kernel
official updates for Ubuntu 5.10?

** Affects: linux-source-2.6.12 (Ubuntu)
     Importance: Untriaged
         Status: Unconfirmed

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kernel freezes when binding bluetooth rfcomm on Ubuntu 5.10
https://launchpad.net/bugs/52145