netdev - [PATCH] net/sched: fix use-after-free in taprio_dev

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Message-ID: <aElUZyKy7x66X3SD@v4bel-B760M-AORUS-ELITE-AX>
Date: Wed, 11 Jun 2025 06:03:19 -0400
From: Hyunwoo Kim <imv4bel@...il.com>
To: vinicius.gomes@...el.com, jhs@...atatu.com, xiyou.wangcong@...il.com,
	jiri@...nulli.us, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org
Cc: netdev@...r.kernel.org, imv4bel@...il.com, v4bel@...ori.io
Subject: [PATCH] net/sched: fix use-after-free in taprio_dev_notifier

Since taprio’s taprio_dev_notifier() isn’t protected by an
RCU read-side critical section, a race with advance_sched()
can lead to a use-after-free.

Adding rcu_read_lock() inside taprio_dev_notifier() prevents this.

Signed-off-by: Hyunwoo Kim <imv4bel@...il.com>
---
 net/sched/sch_taprio.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 14021b812329..bd2b02d1dc63 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1320,6 +1320,7 @@ static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
 	if (event != NETDEV_UP && event != NETDEV_CHANGE)
 		return NOTIFY_DONE;
 
+	rcu_read_lock();
 	list_for_each_entry(q, &taprio_list, taprio_list) {
 		if (dev != qdisc_dev(q->root))
 			continue;
@@ -1328,16 +1329,17 @@ static int taprio_dev_notifier(struct notifier_block *nb, unsigned long event,
 
 		stab = rtnl_dereference(q->root->stab);
 
-		oper = rtnl_dereference(q->oper_sched);
+		oper = rcu_dereference(q->oper_sched);
 		if (oper)
 			taprio_update_queue_max_sdu(q, oper, stab);
 
-		admin = rtnl_dereference(q->admin_sched);
+		admin = rcu_dereference(q->admin_sched);
 		if (admin)
 			taprio_update_queue_max_sdu(q, admin, stab);
 
 		break;
 	}
+	rcu_read_unlock();
 
 	return NOTIFY_DONE;
 }
-- 
2.34.1