netvsc: handle select_queue when device is being removed

Move the send indirection table from the inner device (netvsc)
to the network device context.

It is possible that netvsc_device is not present (remove in progress).
This solves potential use after free issues when packet is being
created during MTU change, shutdown, or queue count changes.

Fixes: d8e18ee0fa ("netvsc: enhance transmit select_queue")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc_drv.c

@@ -206,17 +206,15 @@ static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
 			void *accel_priv, select_queue_fallback_t fallback)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(ndev);
-	struct netvsc_device *nvsc_dev = net_device_ctx->nvdev;
+	unsigned int num_tx_queues = ndev->real_num_tx_queues;
 	struct sock *sk = skb->sk;
 	int q_idx = sk_tx_queue_get(sk);
 
-	if (q_idx < 0 || skb->ooo_okay ||
-	    q_idx >= ndev->real_num_tx_queues) {
+	if (q_idx < 0 || skb->ooo_okay || q_idx >= num_tx_queues) {
 		u16 hash = __skb_tx_hash(ndev, skb, VRSS_SEND_TAB_SIZE);
 		int new_idx;
 
-		new_idx = nvsc_dev->send_table[hash]
-			% nvsc_dev->num_chn;
+		new_idx = net_device_ctx->tx_send_table[hash] % num_tx_queues;
 
 		if (q_idx != new_idx && sk &&
 		    sk_fullsock(sk) && rcu_access_pointer(sk->sk_dst_cache))
@@ -225,9 +223,6 @@ static u16 netvsc_select_queue(struct net_device *ndev, struct sk_buff *skb,
 		q_idx = new_idx;
 	}
 
-	if (unlikely(!nvsc_dev->chan_table[q_idx].channel))
-		q_idx = 0;
-
 	return q_idx;
 }