Commit 1f74e613 authored Jul 29, 2014 by Christoph Paasch Committed by David S. Miller Jul 30, 2014

tcp: Fix integer-overflow 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.

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

Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Doug Leith <doug.leith@nuim.ie>
Fixes: 8d3a564d (tcp: tcp_vegas cong avoid fix)
Signed-off-by: Christoph Paasch <christoph.paasch@uclouvain.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 45a07695

net/ipv4/tcp_vegas.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -218,7 +218,8 @@ 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;
		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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