sch_sfb: Fix missing NULL check

Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=44461

Signed-off-by: Alan Cox <alan@linux.intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_sfb.c

@@ -570,6 +570,8 @@ static int sfb_dump(struct Qdisc *sch, struct sk_buff *skb)
 
 	sch->qstats.backlog = q->qdisc->qstats.backlog;
 	opts = nla_nest_start(skb, TCA_OPTIONS);
+	if (opts == NULL)
+		goto nla_put_failure;
 	if (nla_put(skb, TCA_SFB_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
 	return nla_nest_end(skb, opts);