linux-kernel - [PATCH] net: sched: taprio: Fix potential integer overflow in taprio_set_picos_per

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Message-ID: <20190903010817.GA13595@embeddedor>
Date:   Mon, 2 Sep 2019 20:08:17 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Vladimir Oltean <olteanv@...il.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] net: sched: taprio: Fix potential integer overflow in
 taprio_set_picos_per_byte

Add suffix LL to constant 1000 in order to avoid a potential integer
overflow and give the compiler complete information about the proper
arithmetic to use. Notice that this constant is being used in a context
that expects an expression of type s64, but it's currently evaluated
using 32-bit arithmetic.

Addresses-Coverity-ID: 1453459 ("Unintentional integer overflow")
Fixes: f04b514c0ce2 ("taprio: Set default link speed to 10 Mbps in taprio_set_picos_per_byte")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 net/sched/sch_taprio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 8d8bc2ec5cd6..956f837436ea 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -966,7 +966,7 @@ static void taprio_set_picos_per_byte(struct net_device *dev,
 
 skip:
 	picos_per_byte = div64_s64(NSEC_PER_SEC * 1000LL * 8,
-				   speed * 1000 * 1000);
+				   speed * 1000LL * 1000);
 
 	atomic64_set(&q->picos_per_byte, picos_per_byte);
 	netdev_dbg(dev, "taprio: set %s's picos_per_byte to: %lld, linkspeed: %d\n",
-- 
2.23.0