Bluetooth: Fix double L2CAP connection request

If the remote L2CAP server uses authentication pending stage and
encryption is enabled it can happen that a L2CAP connection request is
sent twice due to a race condition in the connection state machine.

When the remote side indicates any kind of connection pending, then
track this state and skip sending of L2CAP commands for this period.
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

include/net/bluetooth/l2cap.h

@@ -259,6 +259,7 @@ struct l2cap_pinfo {
 #define L2CAP_CONF_REQ_SENT	0x01
 #define L2CAP_CONF_INPUT_DONE	0x02
 #define L2CAP_CONF_OUTPUT_DONE	0x04
+#define L2CAP_CONF_CONNECT_PEND	0x80
 
 #define L2CAP_CONF_MAX_RETRIES	2
 

net/bluetooth/l2cap.c

@@ -1946,11 +1946,14 @@ static inline int l2cap_connect_rsp(struct l2cap_conn *conn, struct l2cap_cmd_hd
 		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,
 					l2cap_build_conf_req(sk, req), req);
 		break;
 
 	case L2CAP_CR_PEND:
+		l2cap_pi(sk)->conf_state |= L2CAP_CONF_CONNECT_PEND;
 		break;
 
 	default:
@@ -2478,6 +2481,11 @@ static int l2cap_security_cfm(struct hci_conn *hcon, u8 status, u8 encrypt)
 	for (sk = l->head; sk; sk = l2cap_pi(sk)->next_c) {
 		bh_lock_sock(sk);
 
+		if (l2cap_pi(sk)->conf_state & L2CAP_CONF_CONNECT_PEND) {
+			bh_unlock_sock(sk);
+			continue;
+		}
+
 		if (!status && (sk->sk_state == BT_CONNECTED ||
 						sk->sk_state == BT_CONFIG)) {
 			l2cap_check_encryption(sk, encrypt);