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>
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 567b585..b85e390 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -625,8 +625,13 @@
 
 		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 @@
 
 			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;