Commit efb55222 authored Aug 30, 2019 by Vladimir Oltean Committed by David S. Miller Aug 31, 2019

taprio: Fix kernel panic in taprio_destroy



taprio_init may fail earlier than this line:

	list_add(&q->taprio_list, &taprio_list);

i.e. due to the net device not being multi queue.

Attempting to remove q from the global taprio_list when it is not part
of it will result in a kernel panic.

Fix it by matching list_add and list_del better to one another in the
order of operations. This way we can keep the deletion unconditional
and with lower complexity - O(1).

Cc: Leandro Dorileo <leandro.maciel.dorileo@intel.com>
Fixes: 7b9eba7b ("net/sched: taprio: fix picos_per_byte 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>

parent 5f81d545

net/sched/sch_taprio.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -1249,6 +1249,10 @@ static int taprio_init(struct Qdisc sch, struct nlattr opt,
		*/
		q->clockid = -1;

		spin_lock(&taprio_list_lock);
		list_add(&q->taprio_list, &taprio_list);
		spin_unlock(&taprio_list_lock);

		if (sch->parent != TC_H_ROOT)
		return -EOPNOTSUPP;

		@@ -1266,10 +1270,6 @@ static int taprio_init(struct Qdisc sch, struct nlattr opt,
		if (!opt)
		return -EINVAL;

		spin_lock(&taprio_list_lock);
		list_add(&q->taprio_list, &taprio_list);
		spin_unlock(&taprio_list_lock);

		for (i = 0; i < dev->num_tx_queues; i++) {
		struct netdev_queue *dev_queue;
		struct Qdisc *qdisc;

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