[PATCH 3.13 006/187] tcp: Fix integer-overflows in TCP veno

Kamal Mostafa
2014-09-15T23:22:38Z

From: Christoph Paasch <christoph.paasch@uclouvain.be>

[ 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 <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
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 326475a..603ad49 100644
--- a/net/ipv4/tcp_veno.c
+++ b/net/ipv4/tcp_veno.c
@@ -145,7 +145,7 @@ static void tcp_veno_cong_avoid(struct sock *sk, u32 ack, u32 acked,

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);

--
1.9.1