linux-kernel - [PATCH 4.19 585/639] net: sched: cbs: Avoid division by zero when calculating the port rate

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Message-Id: <20200124093202.761623028@linuxfoundation.org>
Date:   Fri, 24 Jan 2020 10:32:35 +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, Vladimir Oltean <olteanv@...il.com>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 585/639] net: sched: cbs: Avoid division by zero when calculating the port rate

From: Vladimir Oltean <olteanv@...il.com>

[ Upstream commit 83c8c3cf45163f0c823db37be6ab04dfcf8ac751 ]

As explained in the "net: sched: taprio: Avoid division by zero on
invalid link speed" commit, it is legal for the ethtool API to return
zero as a link speed. So guard against it to ensure we don't perform a
division by zero in kernel.

Fixes: e0a7683d30e9 ("net/sched: cbs: fix port_rate miscalculation")
Signed-off-by: Vladimir Oltean <olteanv@...il.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/sched/sch_cbs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_cbs.c b/net/sched/sch_cbs.c
index 289f66b9238d3..940e72d6db185 100644
--- a/net/sched/sch_cbs.c
+++ b/net/sched/sch_cbs.c
@@ -310,7 +310,7 @@ static void cbs_set_port_rate(struct net_device *dev, struct cbs_sched_data *q)
 	if (err < 0)
 		goto skip;
 
-	if (ecmd.base.speed != SPEED_UNKNOWN)
+	if (ecmd.base.speed && ecmd.base.speed != SPEED_UNKNOWN)
 		speed = ecmd.base.speed;
 
 skip:
-- 
2.20.1