linux-kernel - [PATCH 4.13 01/35] tcp_nv: fix division by zero in tcpnv

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Message-Id: <20171122101137.854660134@linuxfoundation.org>
Date:   Wed, 22 Nov 2017 11:11:55 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Lawrence Brakmo <Brakmo@...com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.13 01/35] tcp_nv: fix division by zero in tcpnv_acked()

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

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

From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>


[ Upstream commit 4eebff27ca4182bbf5f039dd60d79e2d7c0a707e ]

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@...dex-team.ru>
Acked-by: Lawrence Brakmo <Brakmo@...com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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