pkt_sched: Fix OOPS on ingress qdisc add.

Bug report from Steven Jan Springl:

	Issuing the following command causes a kernel oops:
		tc qdisc add dev eth0 handle ffff: ingress

The problem mostly stems from all of the special case handling of
ingress qdiscs.

So, to fix this, do the grafting operation the same way we do for TX
qdiscs.  Which means that dev_activate() and dev_deactivate() now do
the "qdisc_sleeping <--> qdisc" transitions on dev->rx_queue too.

Future simplifications are possible now, mainly because it is
impossible for dev_queue->{qdisc,qdisc_sleeping} to be NULL.  There
are NULL checks all over to handle the ingress qdisc special case
that used to exist before this commit.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -2100,7 +2100,7 @@ static int ing_filter(struct sk_buff *skb)
 	rxq = &dev->rx_queue;
 
 	q = rxq->qdisc;
-	if (q) {
+	if (q != &noop_qdisc) {
 		spin_lock(qdisc_lock(q));
 		result = qdisc_enqueue_root(skb, q);
 		spin_unlock(qdisc_lock(q));
@@ -2113,7 +2113,7 @@ static inline struct sk_buff *handle_ing(struct sk_buff *skb,
 					 struct packet_type **pt_prev,
 					 int *ret, struct net_device *orig_dev)
 {
-	if (!skb->dev->rx_queue.qdisc)
+	if (skb->dev->rx_queue.qdisc == &noop_qdisc)
 		goto out;
 
 	if (*pt_prev) {

net/sched/sch_api.c

@@ -572,44 +572,21 @@ static u32 qdisc_alloc_handle(struct net_device *dev)
 static struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
 				     struct Qdisc *qdisc)
 {
+	struct Qdisc *oqdisc = dev_queue->qdisc_sleeping;
 	spinlock_t *root_lock;
-	struct Qdisc *oqdisc;
-	int ingress;
-
-	ingress = 0;
-	if (qdisc && qdisc->flags&TCQ_F_INGRESS)
-		ingress = 1;
-
-	if (ingress) {
-		oqdisc = dev_queue->qdisc;
-	} else {
-		oqdisc = dev_queue->qdisc_sleeping;
-	}
 
 	root_lock = qdisc_root_lock(oqdisc);
 	spin_lock_bh(root_lock);
 
-	if (ingress) {
-		/* Prune old scheduler */
-		if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1) {
-			/* delete */
-			qdisc_reset(oqdisc);
-			dev_queue->qdisc = NULL;
-		} else {  /* new */
-			dev_queue->qdisc = qdisc;
-		}
+	/* Prune old scheduler */
+	if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1)
+		qdisc_reset(oqdisc);
 
-	} else {
-		/* Prune old scheduler */
-		if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1)
-			qdisc_reset(oqdisc);
-
-		/* ... and graft new one */
-		if (qdisc == NULL)
-			qdisc = &noop_qdisc;
-		dev_queue->qdisc_sleeping = qdisc;
-		dev_queue->qdisc = &noop_qdisc;
-	}
+	/* ... and graft new one */
+	if (qdisc == NULL)
+		qdisc = &noop_qdisc;
+	dev_queue->qdisc_sleeping = qdisc;
+	dev_queue->qdisc = &noop_qdisc;
 
 	spin_unlock_bh(root_lock);
 
@@ -678,7 +655,8 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
 
 		ingress = 0;
 		num_q = dev->num_tx_queues;
-		if (q && q->flags & TCQ_F_INGRESS) {
+		if ((q && q->flags & TCQ_F_INGRESS) ||
+		    (new && new->flags & TCQ_F_INGRESS)) {
 			num_q = 1;
 			ingress = 1;
 		}
@@ -692,13 +670,10 @@ static int qdisc_graft(struct net_device *dev, struct Qdisc *parent,
 			if (!ingress)
 				dev_queue = netdev_get_tx_queue(dev, i);
 
-			if (ingress) {
-				old = dev_graft_qdisc(dev_queue, q);
-			} else {
-				old = dev_graft_qdisc(dev_queue, new);
-				if (new && i > 0)
-					atomic_inc(&new->refcnt);
-			}
+			old = dev_graft_qdisc(dev_queue, new);
+			if (new && i > 0)
+				atomic_inc(&new->refcnt);
+
 			notify_and_destroy(skb, n, classid, old, new);
 		}
 
@@ -817,7 +792,7 @@ qdisc_create(struct net_device *dev, struct netdev_queue *dev_queue,
 				goto err_out3;
 			}
 		}
-		if (parent)
+		if (parent && !(sch->flags & TCQ_F_INGRESS))
 			list_add_tail(&sch->list, &dev_queue->qdisc->list);
 
 		return sch;

net/sched/sch_generic.c

@@ -596,7 +596,7 @@ static void transition_one_qdisc(struct net_device *dev,
 	int *need_watchdog_p = _need_watchdog;
 
 	rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
-	if (new_qdisc != &noqueue_qdisc)
+	if (need_watchdog_p && new_qdisc != &noqueue_qdisc)
 		*need_watchdog_p = 1;
 }
 
@@ -619,6 +619,7 @@ void dev_activate(struct net_device *dev)
 
 	need_watchdog = 0;
 	netdev_for_each_tx_queue(dev, transition_one_qdisc, &need_watchdog);
+	transition_one_qdisc(dev, &dev->rx_queue, NULL);
 
 	if (need_watchdog) {
 		dev->trans_start = jiffies;
@@ -677,6 +678,7 @@ void dev_deactivate(struct net_device *dev)
 	bool running;
 
 	netdev_for_each_tx_queue(dev, dev_deactivate_queue, &noop_qdisc);
+	dev_deactivate_queue(dev, &dev->rx_queue, &noop_qdisc);
 
 	dev_watchdog_down(dev);
 
@@ -718,7 +720,7 @@ static void dev_init_scheduler_queue(struct net_device *dev,
 void dev_init_scheduler(struct net_device *dev)
 {
 	netdev_for_each_tx_queue(dev, dev_init_scheduler_queue, &noop_qdisc);
-	dev_init_scheduler_queue(dev, &dev->rx_queue, NULL);
+	dev_init_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);
 
 	setup_timer(&dev->watchdog_timer, dev_watchdog, (unsigned long)dev);
 }
@@ -745,6 +747,6 @@ static void shutdown_scheduler_queue(struct net_device *dev,
 void dev_shutdown(struct net_device *dev)
 {
 	netdev_for_each_tx_queue(dev, shutdown_scheduler_queue, &noop_qdisc);
-	shutdown_scheduler_queue(dev, &dev->rx_queue, NULL);
+	shutdown_scheduler_queue(dev, &dev->rx_queue, &noop_qdisc);
 	WARN_ON(timer_pending(&dev->watchdog_timer));
 }