From 68ce6688a5baefde30914fc07fc27292dbbe8320 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Sun, 29 Sep 2019 02:01:39 +0300 Subject: [PATCH] net: sched: taprio: Fix potential integer overflow in taprio_set_picos_per_byte The speed divisor is used in a context expecting an s64, but it is evaluated using 32-bit arithmetic. To avoid that happening, instead of multiplying by 1,000,000 in the first place, simplify the fraction and do a standard 32 bit division instead. Fixes: f04b514c0ce2 ("taprio: Set default link speed to 10 Mbps in taprio_set_picos_per_byte") Reported-by: Gustavo A. R. Silva Suggested-by: Eric Dumazet Signed-off-by: Vladimir Oltean Acked-by: Vinicius Costa Gomes Signed-off-by: David S. Miller --- net/sched/sch_taprio.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index 2f7b34205c82..2aab46ada94f 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -1048,8 +1048,7 @@ static void taprio_set_picos_per_byte(struct net_device *dev, speed = ecmd.base.speed; skip: - picos_per_byte = div64_s64(NSEC_PER_SEC * 1000LL * 8, - speed * 1000 * 1000); + picos_per_byte = (USEC_PER_SEC * 8) / speed; atomic64_set(&q->picos_per_byte, picos_per_byte); netdev_dbg(dev, "taprio: set %s's picos_per_byte to: %lld, linkspeed: %d\n",