2010-02-04 00:18:36

by Nick Pelly

Subject: [PATCH] Bluetooth: Do not call rfcomm_session_put() due to RFCOMM UA on closed socket.

Processing a RFCOMM UA frame when the socket is closed and we were not the
RFCOMM initiator would cause rfcomm_session_put() to be called twice during
rfcomm_process_rx(). This would cause a kernel panic in rfcomm_session_close.

This could be easily reproduced during disconnect with devices such as
Motorola H270 that send RFCOMM UA followed quickly by L2CAP disconnect request.
This hcidump for this looks like:

2009-09-21 17:22:37.788895 < ACL data: handle 1 flags 0x02 dlen 8
L2CAP(d): cid 0x0041 len 4 [psm 3]
RFCOMM(s): DISC: cr 0 dlci 20 pf 1 ilen 0 fcs 0x7d
2009-09-21 17:22:37.906204 > HCI Event: Number of Completed Packets (0x13)
plen 5
handle 1 packets 1
2009-09-21 17:22:37.933090 > ACL data: handle 1 flags 0x02 dlen 8
L2CAP(d): cid 0x0040 len 4 [psm 3]
RFCOMM(s): UA: cr 0 dlci 20 pf 1 ilen 0 fcs 0x57
2009-09-21 17:22:38.636764 < ACL data: handle 1 flags 0x02 dlen 8
L2CAP(d): cid 0x0041 len 4 [psm 3]
RFCOMM(s): DISC: cr 0 dlci 0 pf 1 ilen 0 fcs 0x9c
2009-09-21 17:22:38.744125 > HCI Event: Number of Completed Packets (0x13)
plen 5
handle 1 packets 1
2009-09-21 17:22:38.763687 > ACL data: handle 1 flags 0x02 dlen 8
L2CAP(d): cid 0x0040 len 4 [psm 3]
RFCOMM(s): UA: cr 0 dlci 0 pf 1 ilen 0 fcs 0xb6
2009-09-21 17:22:38.783554 > ACL data: handle 1 flags 0x02 dlen 12
L2CAP(s): Disconn req: dcid 0x0040 scid 0x0041

Avoid calling rfcomm_session_put() twice by skipping this call
in rfcomm_recv_ua() if the socket is closed.

Signed-off-by: Nick Pelly <[email protected]>
---
net/bluetooth/rfcomm/core.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c
index 25692bc..950d95c 100644
--- a/net/bluetooth/rfcomm/core.c
+++ b/net/bluetooth/rfcomm/core.c
@@ -1148,7 +1148,11 @@ static int rfcomm_recv_ua(struct rfcomm_session *s, u8 dlci)
break;

case BT_DISCONN:
- rfcomm_session_put(s);
+ /* When socket is closed and we are not RFCOMM
+ * initiator rfcomm_process_rx already calls
+ * rfcomm_session_put() */
+ if (s->sock->sk->sk_state != BT_CLOSED)
+ rfcomm_session_put(s);
break;
}
}
--
1.6.5.3

2010-02-04 00:33:03

by Marcel Holtmann

Subject: Re: [PATCH] Bluetooth: Do not call rfcomm_session_put() due to RFCOMM UA on closed socket.

Hi Nick,

> Processing a RFCOMM UA frame when the socket is closed and we were not the
> RFCOMM initiator would cause rfcomm_session_put() to be called twice during
> rfcomm_process_rx(). This would cause a kernel panic in rfcomm_session_close.
>
> This could be easily reproduced during disconnect with devices such as
> Motorola H270 that send RFCOMM UA followed quickly by L2CAP disconnect request.
> This hcidump for this looks like:
>
> 2009-09-21 17:22:37.788895 < ACL data: handle 1 flags 0x02 dlen 8
> L2CAP(d): cid 0x0041 len 4 [psm 3]
> RFCOMM(s): DISC: cr 0 dlci 20 pf 1 ilen 0 fcs 0x7d
> 2009-09-21 17:22:37.906204 > HCI Event: Number of Completed Packets (0x13)
> plen 5
> handle 1 packets 1
> 2009-09-21 17:22:37.933090 > ACL data: handle 1 flags 0x02 dlen 8
> L2CAP(d): cid 0x0040 len 4 [psm 3]
> RFCOMM(s): UA: cr 0 dlci 20 pf 1 ilen 0 fcs 0x57
> 2009-09-21 17:22:38.636764 < ACL data: handle 1 flags 0x02 dlen 8
> L2CAP(d): cid 0x0041 len 4 [psm 3]
> RFCOMM(s): DISC: cr 0 dlci 0 pf 1 ilen 0 fcs 0x9c
> 2009-09-21 17:22:38.744125 > HCI Event: Number of Completed Packets (0x13)
> plen 5
> handle 1 packets 1
> 2009-09-21 17:22:38.763687 > ACL data: handle 1 flags 0x02 dlen 8
> L2CAP(d): cid 0x0040 len 4 [psm 3]
> RFCOMM(s): UA: cr 0 dlci 0 pf 1 ilen 0 fcs 0xb6
> 2009-09-21 17:22:38.783554 > ACL data: handle 1 flags 0x02 dlen 12
> L2CAP(s): Disconn req: dcid 0x0040 scid 0x0041
>
> Avoid calling rfcomm_session_put() twice by skipping this call
> in rfcomm_recv_ua() if the socket is closed.

patch has been applied. Thanks.

Regards

Marcel