[PATCH] net/sched: sch_dualpi2: Add missing skb check

[Manas <ghandatmanas@gmail.com>]

A packed is dequeued using the function `dequeue_packet()` but there is
no check to see if a packet is dequeued. The assignment is always
considered as true resulting in null-ptr-deref

Fixes: 8f9516daedd6 ("sched: Add enqueue/dequeue of dualpi2 qdisc")
Reported-by: Manas <ghandatmanas@gmail.com>
Reported-by: Rakshit Awasthi <rakshitawasthi17@gmail.com>
Signed-off-by: Manas <ghandatmanas@gmail.com>
---
 net/sched/sch_dualpi2.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_dualpi2.c b/net/sched/sch_dualpi2.c
index 241e6a46bd00..e360bf16d617 100644
--- a/net/sched/sch_dualpi2.c
+++ b/net/sched/sch_dualpi2.c
@@ -588,7 +588,7 @@ static struct sk_buff *dualpi2_qdisc_dequeue(struct Qdisc *sch)
 
 	now = ktime_get_ns();
 
-	while ((skb = dequeue_packet(sch, q, &credit_change, now))) {
+	while ((skb = dequeue_packet(sch, q, &credit_change, now)) && skb) {
 		if (!q->drop_early && must_drop(sch, q, skb)) {
 			drop_and_retry(q, skb, sch, QDISC_DROP_CONGESTED);
 			continue;
-- 
2.43.0