[PATCH 5.10 003/145] net/sched: sch_taprio: ensure to reset/destroy all child qdiscs

[Greg Kroah-Hartman]

From: Davide Caratti <dcara...@redhat.com>

[ Upstream commit 698285da79f5b0b099db15a37ac661ac408c80eb ]

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 <k...@kernel.org>
Signed-off-by: Davide Caratti <dcara...@redhat.com>
Link: 
https://lore.kernel.org/r/13edef6778fef03adc751582562fba4a13e06d6a.1608240532.git.dcara...@redhat.com
Signed-off-by: Jakub Kicinski <k...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 net/sched/sch_taprio.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1604,8 +1604,9 @@ static void taprio_reset(struct Qdisc *s
 
        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;
@@ -1625,7 +1626,7 @@ static void taprio_destroy(struct Qdisc
        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);