Bluetooth: Check the tx_window size on setsockopt

We have to check if the proposed tx_window value is not greater that
maximum value supported.

Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>
Reviewed-by: João Paulo Rechi Vita <jprvita@profusion.mobi>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/bluetooth/l2cap.c b/net/bluetooth/l2cap.c
index f0441b0..6094870 100644
--- a/net/bluetooth/l2cap.c
+++ b/net/bluetooth/l2cap.c
@@ -1912,6 +1912,11 @@
 			break;
 		}
 
+		if (opts.txwin_size > L2CAP_DEFAULT_TX_WINDOW) {
+			err = -EINVAL;
+			break;
+		}
+
 		l2cap_pi(sk)->mode = opts.mode;
 		switch (l2cap_pi(sk)->mode) {
 		case L2CAP_MODE_BASIC: