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

------------------

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

[ Upstream commit 1f74e613ded11517db90b2bd57e9464d9e0fb161 ]

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.

Then, we need to do do_div to allow this to be used on 32-bit arches.

Cc: Stephen Hemminger <step...@networkplumber.org>
Cc: Neal Cardwell <ncardw...@google.com>
Cc: Eric Dumazet <eric.duma...@gmail.com>
Cc: David Laight <david.lai...@aculab.com>
Cc: Doug Leith <doug.le...@nuim.ie>
Fixes: 8d3a564da34e (tcp: tcp_vegas cong avoid fix)
Signed-off-by: Christoph Paasch <christoph.paa...@uclouvain.be>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/ipv4/tcp_vegas.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/ipv4/tcp_vegas.c
+++ b/net/ipv4/tcp_vegas.c
@@ -218,7 +218,8 @@ static void tcp_vegas_cong_avoid(struct
                         * This is:
                         *     (actual rate in segments) * baseRTT
                         */
-                       target_cwnd = tp->snd_cwnd * vegas->baseRTT / rtt;
+                       target_cwnd = (u64)tp->snd_cwnd * vegas->baseRTT;
+                       do_div(target_cwnd, rtt);
 
                        /* Calculate the difference between the window we had,
                         * and the window we would like to have. This quantity


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