ethtool: ensure channel counts are within bounds during SCHANNELS

Add a sanity check to ensure that all requested channel sizes are within
bounds, which should reduce errors in driver implementation.
Signed-off-by: NJacob Keller <jacob.e.keller@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/ethtool.c

@@ -1274,15 +1274,24 @@ static noinline_for_stack int ethtool_get_channels(struct net_device *dev,
 static noinline_for_stack int ethtool_set_channels(struct net_device *dev,
 						   void __user *useraddr)
 {
-	struct ethtool_channels channels;
+	struct ethtool_channels channels, max;
 	u32 max_rx_in_use = 0;
 
-	if (!dev->ethtool_ops->set_channels)
+	if (!dev->ethtool_ops->set_channels || !dev->ethtool_ops->get_channels)
 		return -EOPNOTSUPP;
 
 	if (copy_from_user(&channels, useraddr, sizeof(channels)))
 		return -EFAULT;
 
+	dev->ethtool_ops->get_channels(dev, &max);
+
+	/* ensure new counts are within the maximums */
+	if ((channels.rx_count > max.max_rx) ||
+	    (channels.tx_count > max.max_tx) ||
+	    (channels.combined_count > max.max_combined) ||
+	    (channels.other_count > max.max_other))
+		return -EINVAL;
+
 	/* ensure the new Rx count fits within the configured Rx flow
 	 * indirection table settings */
 	if (netif_is_rxfh_configured(dev) &&