netdev - [PATCH net] tcp: Fix integer-overflows in TCP vegas

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Date:	Tue, 22 Jul 2014 23:36:57 +0200
From:	Christoph Paasch <christoph.paasch@...ouvain.be>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org,
	Christoph Paasch <christoph.paasch@...ouvain.be>,
	Doug Leith <doug.leith@...m.ie>
Subject: [PATCH net] tcp: Fix integer-overflows in TCP vegas

In vegas we do a multiplication of the cwnd and the rtt. This
may overflow and thus their result is stored in a u64. However, we first
need to cast the cwnd so that actually 64-bit arithmetic is done.

Cc: Doug Leith <doug.leith@...m.ie>
Fixes: 8d3a564da34e (tcp: tcp_vegas cong avoid fix)
Signed-off-by: Christoph Paasch <christoph.paasch@...ouvain.be>
---
 net/ipv4/tcp_vegas.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c
index 9a5e05f27f4f..6a4bdea2a0fb 100644
--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -218,7 +218,7 @@ static void tcp_vegas_cong_avoid(struct sock *sk, u32 ack, u32 acked)
 			 * This is:
 			 *     (actual rate in segments) * baseRTT
 			 */
-			target_cwnd = tp->snd_cwnd * vegas->baseRTT / rtt;
+			target_cwnd = (u64)tp->snd_cwnd * vegas->baseRTT / rtt;
 
 			/* Calculate the difference between the window we had,
 			 * and the window we would like to have. This quantity
-- 
1.9.3

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