[PKT_SCHED]: Fix slab corruption in cbq_destroy

Fixes slab corruption in cbq_destroy. cbq_destroy_filters and
qdisc_put_rtab(q->link.R_tab) are already called in cbq_destroy_class.
The latter lead to a slab corruption due to repeated freeing of
q->link.R_tab because q->link is part of q->classes. Problem introduced
in 1.21.
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_cbq.c

@@ -1770,10 +1770,6 @@ cbq_destroy(struct Qdisc* sch)
 #ifdef CONFIG_NET_CLS_POLICE
 	q->rx_class = NULL;
 #endif
-	for (h = 0; h < 16; h++) {
-		for (cl = q->classes[h]; cl; cl = cl->next)
-			cbq_destroy_filters(cl);
-	}
 
 	for (h = 0; h < 16; h++) {
 		struct cbq_class *next;
@@ -1783,8 +1779,6 @@ cbq_destroy(struct Qdisc* sch)
 			cbq_destroy_class(sch, cl);
 		}
 	}
-
-	qdisc_put_rtab(q->link.R_tab);
 }
 
 static void cbq_put(struct Qdisc *sch, unsigned long arg)