Bluetooth: Allow L2CAP to increase the security level

Some incomming connections needs to increase the security level by
requesting encryption for example (HID keyboard case). This change allows
the userspace to change it through setsockopt with defer_setup enabled.
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>

net/bluetooth/l2cap_sock.c

@@ -625,8 +625,13 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname, ch
 
 		chan->sec_level = sec.level;
 
+		if (!chan->conn)
+			break;
+
 		conn = chan->conn;
-		if (conn && chan->scid == L2CAP_CID_LE_DATA) {
+
+		/*change security for LE channels */
+		if (chan->scid == L2CAP_CID_LE_DATA) {
 			if (!conn->hcon->out) {
 				err = -EINVAL;
 				break;
@@ -634,9 +639,14 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname, ch
 
 			if (smp_conn_security(conn, sec.level))
 				break;
-
-			err = 0;
 			sk->sk_state = BT_CONFIG;
+
+		/* or for ACL link, under defer_setup time */
+		} else if (sk->sk_state == BT_CONNECT2 &&
+					bt_sk(sk)->defer_setup) {
+			err = l2cap_chan_check_security(chan);
+		} else {
+			err = -EINVAL;
 		}
 		break;