From: Christoph Paasch <[email protected]>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit 45a07695bc64b3ab5d6d2215f9677e5b8c05a7d0 ]

In veno 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.

A first attempt at fixing 76f1017757aa0 ([TCP]: TCP Veno congestion
control) was made by 159131149c2 (tcp: Overflow bug in Vegas), but it
failed to add the required cast in tcp_veno_cong_avoid().

Fixes: 76f1017757aa0 ([TCP]: TCP Veno congestion control)
Signed-off-by: Christoph Paasch <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
---
 net/ipv4/tcp_veno.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_veno.c b/net/ipv4/tcp_veno.c
index ac43cd747bce..b4d1858be550 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -144,7 +144,7 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, 
u32 in_flight)
 
                rtt = veno->minrtt;
 
-               target_cwnd = (tp->snd_cwnd * veno->basertt);
+               target_cwnd = (u64)tp->snd_cwnd * veno->basertt;
                target_cwnd <<= V_PARAM_SHIFT;
                do_div(target_cwnd, rtt);
 
-- 
2.0.4

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