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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Vladimir Oltean <olteanv@gmail.com>,
        Vinicius Costa Gomes <vinicius.gomes@intel.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.2 024/137] net: sched: cbs: Avoid division by zero when calculating the port rate
Date:   Sun,  6 Oct 2019 19:20:08 +0200
Message-Id: <20191006171211.243512149@linuxfoundation.org>
In-Reply-To: <20191006171209.403038733@linuxfoundation.org>
References: <20191006171209.403038733@linuxfoundation.org>
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From: Vladimir Oltean <olteanv@gmail.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@gmail.com>
Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sched/sch_cbs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_cbs.c
+++ b/net/sched/sch_cbs.c
@@ -306,7 +306,7 @@ static void cbs_set_port_rate(struct net
 	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: