netdev - [PATCH net] net/sched: sch_taprio: ensure to reset/destroy all child qdiscs

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Date:   Thu, 17 Dec 2020 22:29:46 +0100
From:   Davide Caratti <dcaratti@...hat.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>,
        Jakub Kicinski <kuba@...nel.org>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc:     netdev@...r.kernel.org
Subject: [PATCH net] net/sched: sch_taprio: ensure to reset/destroy all child qdiscs

taprio_graft() can insert a NULL element in the array of child qdiscs. As
a consquence, taprio_reset() might not reset child qdiscs completely, and
taprio_destroy() might leak resources. Fix it by ensuring that loops that
iterate over q->qdiscs[] don't end when they find the first NULL item.

Fixes: 44d4775ca518 ("net/sched: sch_taprio: reset child qdiscs before freeing them")
Fixes: 5a781ccbd19e ("tc: Add support for configuring the taprio scheduler")
Suggested-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
 net/sched/sch_taprio.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index c74817ec9964..6f775275826a 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1605,8 +1605,9 @@ static void taprio_reset(struct Qdisc *sch)
 
 	hrtimer_cancel(&q->advance_timer);
 	if (q->qdiscs) {
-		for (i = 0; i < dev->num_tx_queues && q->qdiscs[i]; i++)
-			qdisc_reset(q->qdiscs[i]);
+		for (i = 0; i < dev->num_tx_queues; i++)
+			if (q->qdiscs[i])
+				qdisc_reset(q->qdiscs[i]);
 	}
 	sch->qstats.backlog = 0;
 	sch->q.qlen = 0;
@@ -1626,7 +1627,7 @@ static void taprio_destroy(struct Qdisc *sch)
 	taprio_disable_offload(dev, q, NULL);
 
 	if (q->qdiscs) {
-		for (i = 0; i < dev->num_tx_queues && q->qdiscs[i]; i++)
+		for (i = 0; i < dev->num_tx_queues; i++)
 			qdisc_put(q->qdiscs[i]);
 
 		kfree(q->qdiscs);
-- 
2.29.2