From: Vladimir Oltean <olteanv@gmail.com>
Date: Fri, 30 Aug 2019 01:07:21 +0000 (+0300)
Subject: taprio: Fix kernel panic in taprio_destroy
X-Git-Tag: v5.3-rc7~3^2~6^2~2
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=efb55222d31c8c2af8b4ba42bb56b0b0beedf98e;p=linux.git

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: 7b9eba7ba0c1 ("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>
---

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index e25d414ae12f..8c85f61e98dd 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -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;