TCP: tcp_hybla: Fix integer overflow in slow start increment

For large values of rtt, 2^rho operation may overflow u32. Clamp down the increment to 2^16.
Signed-off-by: NDaniele Lacamera <root@danielinux.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/tcp_hybla.c

@@ -126,8 +126,8 @@ static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 in_flight)
 		 * calculate 2^fract in a <<7 value.
 		 */
 		is_slowstart = 1;
-		increment = ((1 << ca->rho) * hybla_fraction(rho_fractions))
-			- 128;
+		increment = ((1 << min(ca->rho, 16U)) *
+			hybla_fraction(rho_fractions)) - 128;
 	} else {
 		/*
 		 * congestion avoidance