Re: [PATCH] Bluetooth: Fix use after free in l2cap_chan_timeout

[Harish Jenny Kandiga Nagaraj <harish_kandiga@mentor.com>]

On Thursday 19 March 2015 01:55 PM, Johan Hedberg wrote:
> Hi,
>
> On Thu, Mar 19, 2015, Harish Jenny K N wrote:
>> There is a potential use after free in bt_sock_poll when a
>> socket gets killed without getting unlinked from accept_q.
>> Hence added code to unlink from accpept_q by calling teardown
>> before freeing the socket for channel type L2CAP_CHAN_CONN_ORIENTED.
>>
>> Signed-off-by: Harish Jenny K N <harish_kandiga@mentor.com>
>> ---
>>  net/bluetooth/l2cap_core.c |    5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
>> index 6ba33f9..c6955fb 100644
>> --- a/net/bluetooth/l2cap_core.c
>> +++ b/net/bluetooth/l2cap_core.c
>> @@ -415,6 +415,11 @@ static void l2cap_chan_timeout(struct work_struct *work)
>>  
>>  	l2cap_chan_close(chan, reason);
>>  
>> +	if ((chan->state == BT_CONNECTED || chan->state == BT_CONFIG) &&
>> +	    chan->chan_type == L2CAP_CHAN_CONN_ORIENTED) {
>> +		chan->ops->teardown(chan, 0);
>> +	}
> Looks quite ok to me, except for a minor issue: we generally don't use
> {} for single-line branches.
>
> Do you have some simple way to reproduce this? It'd be nice if we could
> add a test case for it to our user space l2cap-tester tool.
>
> Johan

There is a potential use after free in bt_sock_poll when a
socket gets killed without getting unlinked from accept_q.
Hence added code to unlink from accpept_q by calling teardown
before freeing the socket for channel type L2CAP_CHAN_CONN_ORIENTED.

Signed-off-by: Harish Jenny K N <harish_kandiga@mentor.com>
---
 net/bluetooth/l2cap_core.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 6ba33f9..3e273e6 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -415,6 +415,10 @@ static void l2cap_chan_timeout(struct work_struct *work)
 
 	l2cap_chan_close(chan, reason);
 
+	if ((chan->state == BT_CONNECTED || chan->state == BT_CONFIG) &&
+	    chan->chan_type == L2CAP_CHAN_CONN_ORIENTED)
+		chan->ops->teardown(chan, 0);
+
 	l2cap_chan_unlock(chan);
 
 	chan->ops->close(chan);