Re: [PATCH] work around for l2cap NULL dereference inl2cap_conn_start

From: David Fries
Date: Mon Feb 28 2011 - 00:04:17 EST

On Sun, Feb 27, 2011 at 04:15:45PM -0300, Gustavo F. Padovan wrote:
> I pushed the following patch to bluetooth-2.6 tree. It should fix the problem
> by avoiding connections to be accepted before a L2CAP info response comes:

the bluetooth-2.6 tree you mentioned? I don't see your patch there.
As a side note, the inline patch in your e-mail has the tabs replaced by
spaces, once I changed them, it applied cleanly.

I first reverted to the base N900 kernel-power-2.6.28 46 (none of my
changes or debugging), it crashed as expected. I then applied your
patch 743400e0, and it still crashed. I added back the
l2cap_conn_start parent check and some debugging in af_bluetooth.c
dmesg debug output and patches follow.

I haven't at all looked into the bluetooth protocol, but what connect
sequence difference does it make if I power on the bluetooth headset
and press play on the headset before it automatically pairs with the
N900, vs power on bluetooth headset, wait for it to pair then press
play? I ask this partly because I'm curiouse, but mostly how I
trigger the bug. This is with pulse audio running, but no
applications playing audio or responding to a play event from the

[ 443.424560] bt_accept_dequeue, parent cd54ba00 newsock c81f0180, defer_setup && BT_CONNECT2
[ 443.427368] avoided crash in l2cap_conn_start sk c6d3f600 result 1 status 2
[ 443.518463] bt_accept_dequeue, parent cdee9c00 newsock c81f0000, BT_CONNECTED
[ 443.729736] bt_accept_dequeue, parent cd54be00 newsock c81f0000, BT_CONNECTED
[ 443.813537] bt_accept_dequeue, parent cd54b600 newsock c81f0180, defer_setup && BT_CONNECT2