From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Date: Wed, 1 Nov 2017 16:32:15 +0300
Subject: tcp_nv: fix division by zero in tcpnv_acked()
Git-commit: 4eebff27ca4182bbf5f039dd60d79e2d7c0a707e
Patch-mainline: v4.14-rc8
References: networking-stable-17_11_20

Average RTT could become zero. This happened in real life at least twice.
This patch treats zero as 1us.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Lawrence Brakmo <Brakmo@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 net/ipv4/tcp_nv.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp_nv.c
+++ b/net/ipv4/tcp_nv.c
@@ -263,7 +263,7 @@ static void tcpnv_acked(struct sock *sk,
 
 	/* rate in 100's bits per second */
 	rate64 = ((u64)sample->in_flight) * 8000000;
-	rate = (u32)div64_u64(rate64, (u64)(avg_rtt * 100));
+	rate = (u32)div64_u64(rate64, (u64)(avg_rtt ?: 1) * 100);
 
 	/* Remember the maximum rate seen during this RTT
 	 * Note: It may be more than one RTT. This function should be