netvsc: check error return when restoring channels and mtu

If setting new values fails, and the attempt to restore original
settings fails. Then log an error and leave device down.
This should never happen, but if it does don't go down in flames.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/netvsc_drv.c

@@ -845,7 +845,13 @@ static int netvsc_set_channels(struct net_device *net,
 	} else {
 		ret = PTR_ERR(nvdev);
 		device_info.num_chn = orig;
-		rndis_filter_device_add(dev, &device_info);
+		nvdev = rndis_filter_device_add(dev, &device_info);
+
+		if (IS_ERR(nvdev)) {
+			netdev_err(net, "restoring channel setting failed: %ld\n",
+				   PTR_ERR(nvdev));
+			return ret;
+		}
 	}
 
 	if (was_opened)
@@ -953,10 +959,16 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 
 		/* Attempt rollback to original MTU */
 		ndev->mtu = orig_mtu;
-		rndis_filter_device_add(hdev, &device_info);
+		nvdev = rndis_filter_device_add(hdev, &device_info);
 
 		if (vf_netdev)
 			dev_set_mtu(vf_netdev, orig_mtu);
+
+		if (IS_ERR(nvdev)) {
+			netdev_err(ndev, "restoring mtu failed: %ld\n",
+				   PTR_ERR(nvdev));
+			return ret;
+		}
 	}
 
 	if (was_opened)