linux-kernel - [PATCH] TCP: tcp_hybla: Fix integer overflow in slow start increment

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Date:	Wed,  2 Jun 2010 14:02:04 +0200
From:	Daniele Lacamera <root@...ielinux.net>
To:	netdev@...r.kernel.org
Cc:	davem@...emloft.net, kuznet@....inr.ac.ru, root@...ielinux.net,
	linux-kernel@...r.kernel.org
Subject: [PATCH] TCP: tcp_hybla: Fix integer overflow in slow start increment

From: root <root@...chen.(none)>

For large values of rtt, 2^rho operation may overflow u32. Clamp down the increment to 2^16.
Signed-off-by: Daniele Lacamera <root@...ielinux.net>
---
 net/ipv4/tcp_hybla.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_hybla.c b/net/ipv4/tcp_hybla.c
index c209e05..8db01d4 100644
--- a/net/ipv4/tcp_hybla.c
+++ b/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
-- 
1.5.6.5

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