netdev - [PATCH net 1/3] taprio: Fix kernel panic in taprio

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Message-Id: <20190828144829.32570-2-olteanv@gmail.com>
Date:   Wed, 28 Aug 2019 17:48:27 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, vinicius.gomes@...el.com,
        vedang.patel@...el.com, leandro.maciel.dorileo@...el.com
Cc:     netdev@...r.kernel.org, Vladimir Oltean <olteanv@...il.com>
Subject: [PATCH net 1/3] 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 iterating through the list and removing it only if found.

Signed-off-by: Vladimir Oltean <olteanv@...il.com>
---
 net/sched/sch_taprio.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 540bde009ea5..f1eea8c68011 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1199,12 +1199,17 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 
 static void taprio_destroy(struct Qdisc *sch)
 {
-	struct taprio_sched *q = qdisc_priv(sch);
+	struct taprio_sched *p, *q = qdisc_priv(sch);
 	struct net_device *dev = qdisc_dev(sch);
+	struct list_head *pos, *tmp;
 	unsigned int i;
 
 	spin_lock(&taprio_list_lock);
-	list_del(&q->taprio_list);
+	list_for_each_safe(pos, tmp, &taprio_list) {
+		p = list_entry(pos, struct taprio_sched, taprio_list);
+		if (p == q)
+			list_del(&q->taprio_list);
+	}
 	spin_unlock(&taprio_list_lock);
 
 	hrtimer_cancel(&q->advance_timer);
-- 
2.17.1