Re: [PATCHv2] Bluetooth: Check l2cap pending status before sending l2cap connect request

[Marcel Holtmann <marcel@holtmann.org>]

Hi Andrei,

> Due to race condition in L2CAP state machine L2CAP Connection Request
> may be sent twice for SDP with the same source channel id. Problems
> reported connecting to Apple products, some carkit, Blackberry phones.
> 
> ...
> 2010-06-07 21:18:03.651031 < ACL data: handle 1 flags 0x02 dlen 12
>     L2CAP(s): Connect req: psm 1 scid 0x0040
> 2010-06-07 21:18:03.653473 > HCI Event: Number of Completed Packets (0x13) plen 5
>     handle 1 packets 1
> 2010-06-07 21:18:03.653808 > HCI Event: Auth Complete (0x06) plen 3
>     status 0x00 handle 1
> 2010-06-07 21:18:03.653869 < ACL data: handle 1 flags 0x02 dlen 12
>     L2CAP(s): Connect req: psm 1 scid 0x0040
> ...
> 
> Patch uses L2CAP_CONF_CONNECT_PEND flag to mark that L2CAP Connection
> Request has been sent already.
> 
> Modified version of Ville Tervo patch.
> 
> Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@nokia.com>
> ---
>  net/bluetooth/l2cap.c |   14 +++++++++++---
>  1 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
> index bb00015..899cca5 100644
> --- a/net/bluetooth/l2cap.c
> +++ b/net/bluetooth/l2cap.c
> @@ -401,6 +401,11 @@ static inline void l2cap_send_rr_or_rnr(struct l2cap_pinfo *pi, u16 control)
>  	l2cap_send_sframe(pi, control);
>  }
>  
> +static inline int l2cap_check_pending(struct sock *sk)
> +{
> +	return l2cap_pi(sk)->conf_state & L2CAP_CONF_CONNECT_PEND;
> +}
> +

I changed my mind about the naming here. It was a bad proposal on my
side. So something like __no_connect_pend (positive check) as a define
is better.

>  static void l2cap_do_start(struct sock *sk)
>  {
>  	struct l2cap_conn *conn = l2cap_pi(sk)->conn;
> @@ -409,12 +414,13 @@ static void l2cap_do_start(struct sock *sk)
>  		if (!(conn->info_state & L2CAP_INFO_FEAT_MASK_REQ_DONE))
>  			return;
>  
> -		if (l2cap_check_security(sk)) {
> +		if (l2cap_check_security(sk) && !l2cap_check_pending(sk)) {
>  			struct l2cap_conn_req req;
>  			req.scid = cpu_to_le16(l2cap_pi(sk)->scid);
>  			req.psm  = l2cap_pi(sk)->psm;
>  
>  			l2cap_pi(sk)->ident = l2cap_get_ident(conn);
> +			l2cap_pi(sk)->conf_state |= L2CAP_CONF_CONNECT_PEND;
>  
>  			l2cap_send_cmd(conn, l2cap_pi(sk)->ident,
>  					L2CAP_CONN_REQ, sizeof(req), &req);
> @@ -464,12 +470,14 @@ static void l2cap_conn_start(struct l2cap_conn *conn)
>  		}
>  
>  		if (sk->sk_state == BT_CONNECT) {
> -			if (l2cap_check_security(sk)) {
> +			if (l2cap_check_security(sk) &&
> +					!l2cap_check_pending(sk)) {
>  				struct l2cap_conn_req req;
>  				req.scid = cpu_to_le16(l2cap_pi(sk)->scid);
>  				req.psm  = l2cap_pi(sk)->psm;
>  
>  				l2cap_pi(sk)->ident = l2cap_get_ident(conn);
> +				l2cap_pi(sk)->conf_state |= L2CAP_CONF_CONNECT_PEND;
>  
>  				l2cap_send_cmd(conn, l2cap_pi(sk)->ident,
>  					L2CAP_CONN_REQ, sizeof(req), &req);
> @@ -2914,7 +2922,6 @@ static inline int l2cap_connect_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hd
>  		l2cap_pi(sk)->ident = 0;
>  		l2cap_pi(sk)->dcid = dcid;
>  		l2cap_pi(sk)->conf_state |= L2CAP_CONF_REQ_SENT;
> -
>  		l2cap_pi(sk)->conf_state &= ~L2CAP_CONF_CONNECT_PEND;
>  
>  		l2cap_send_cmd(conn, l2cap_get_ident(conn), L2CAP_CONF_REQ,
> @@ -4406,6 +4413,7 @@ static int l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)
>  				req.psm  = l2cap_pi(sk)->psm;
>  
>  				l2cap_pi(sk)->ident = l2cap_get_ident(conn);
> +				l2cap_pi(sk)->conf_state |= L2CAP_CONF_CONNECT_PEND;
>  
>  				l2cap_send_cmd(conn, l2cap_pi(sk)->ident,
>  					L2CAP_CONN_REQ, sizeof(req), &req);

Rest looks fine to me.

Regards

Marcel