hv_netvsc: disable NAPI before channel close

This makes sure that no CPU is still process packets when
the channel is closed.

Fixes: 76bb5db5 ("netvsc: fix use after free on module removal")
Signed-off-by: NStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc.c

@@ -568,6 +568,10 @@ void netvsc_device_remove(struct hv_device *device)
 
 	RCU_INIT_POINTER(net_device_ctx->nvdev, NULL);
 
+	/* And disassociate NAPI context from device */
+	for (i = 0; i < net_device->num_chn; i++)
+		netif_napi_del(&net_device->chan_table[i].napi);
+
 	/*
 	 * At this point, no one should be accessing net_device
 	 * except in here
@@ -579,10 +583,6 @@ void netvsc_device_remove(struct hv_device *device)
 
 	netvsc_teardown_gpadl(device, net_device);
 
-	/* And dissassociate NAPI context from device */
-	for (i = 0; i < net_device->num_chn; i++)
-		netif_napi_del(&net_device->chan_table[i].napi);
-
 	/* Release all resources */
 	free_netvsc_device_rcu(net_device);
 }