net_sched: Bug in netem reordering

[ Upstream commit eb101924 ]

Not now, but it looks you are correct. q->qdisc is NULL until another
additional qdisc is attached (beside tfifo). See 50612537.
The following patch should work.

From: Hagen Paul Pfeifer <hagen@jauu.net>

netem: catch NULL pointer by updating the real qdisc statistic
Reported-by: Vijay Subramanian <subramanian.vijay@gmail.com>
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/sched/sch_netem.c

@@ -381,8 +381,8 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 		q->counter = 0;
 
 		__skb_queue_head(&q->qdisc->q, skb);
-		q->qdisc->qstats.backlog += qdisc_pkt_len(skb);
-		q->qdisc->qstats.requeues++;
+		sch->qstats.backlog += qdisc_pkt_len(skb);
+		sch->qstats.requeues++;
 		ret = NET_XMIT_SUCCESS;
 	}