From 8c79f0ea5d6087645ed5ed5d638c338962052766 Mon Sep 17 00:00:00 2001 From: Vinicius Costa Gomes Date: Mon, 29 Apr 2019 15:48:30 -0700 Subject: [PATCH] taprio: Fix potencial use of invalid memory during dequeue() Right now, this isn't a problem, but the next commit allows schedules to be added during runtime. When a new schedule transitions from the inactive to the active state ("admin" -> "oper") the previous one can be freed, if it's freed just after the RCU read lock is released, we may access an invalid entry. So, we should take care to protect the dequeue() flow, so all the places that access the entries are protected by the RCU read lock. Signed-off-by: Vinicius Costa Gomes Signed-off-by: David S. Miller --- net/sched/sch_taprio.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index 09563c245473..f827caa73862 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -136,8 +136,8 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch) { struct taprio_sched *q = qdisc_priv(sch); struct net_device *dev = qdisc_dev(sch); + struct sk_buff *skb = NULL; struct sched_entry *entry; - struct sk_buff *skb; u32 gate_mask; int i; @@ -154,10 +154,9 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch) * "AdminGateSates" */ gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN; - rcu_read_unlock(); if (!gate_mask) - return NULL; + goto done; for (i = 0; i < dev->num_tx_queues; i++) { struct Qdisc *child = q->qdiscs[i]; @@ -197,16 +196,19 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch) skb = child->ops->dequeue(child); if (unlikely(!skb)) - return NULL; + goto done; qdisc_bstats_update(sch, skb); qdisc_qstats_backlog_dec(sch, skb); sch->q.qlen--; - return skb; + goto done; } - return NULL; +done: + rcu_read_unlock(); + + return skb; } static enum hrtimer_restart advance_sched(struct hrtimer *timer) -- 2.30.2