ethtool: EEPROM dump no longer works for tg3 and natsemi

In the ethtool user-space application, tg3 and natsemi over-ride the
default implementation of dump_eeprom(). In both tg3_dump_eeprom() and
natsemi_dump_eeprom(), there is a magic number check which is not
present in the default implementation.

Commit b131dd5d ("[ETHTOOL]: Add support for large eeproms") snipped
the code which copied the ethtool_eeprom structure back to
user-space. tg3 and natsemi are over-writing the magic number field
and then checking it in user-space. With the ethtool_eeprom copy
removed, the check is failing.

The fix is simple. Add the ethtool_eeprom copy back.
Signed-off-by: NMandeep Singh Baines <msb@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/ethtool.c

@@ -323,6 +323,11 @@ static int ethtool_get_eeprom(struct net_device *dev, void __user *useraddr)
 		bytes_remaining -= eeprom.len;
 	}
 
+	eeprom.len = userbuf - (useraddr + sizeof(eeprom));
+	eeprom.offset -= eeprom.len;
+	if (copy_to_user(useraddr, &eeprom, sizeof(eeprom)))
+		ret = -EFAULT;
+
 	kfree(data);
 	return ret;
 }