ethtool: ioctl: improve error checking for set_wol

The netlink version of set_wol checks for not supported wolopts and avoids
setting wol when the correct wolopt is already set. If we do the same with
the ioctl version then we can remove these checks from the driver layer.

Reviewed-by: Simon Horman <[e-mail]>
Signed-off-by: Justin Chen <[e-mail]>
Reviewed-by: Florian Fainelli <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/ethtool/ioctl.c

···
 
 static int ethtool_set_wol(struct net_device *dev, char __user *useraddr)
 {
-	struct ethtool_wolinfo wol;
+	struct ethtool_wolinfo wol, cur_wol;
 	int ret;
 
-	if (!dev->ethtool_ops->set_wol)
+	if (!dev->ethtool_ops->get_wol || !dev->ethtool_ops->set_wol)
 		return -EOPNOTSUPP;
+
+	memset(&cur_wol, 0, sizeof(struct ethtool_wolinfo));
+	cur_wol.cmd = ETHTOOL_GWOL;
+	dev->ethtool_ops->get_wol(dev, &cur_wol);
 
 	if (copy_from_user(&wol, useraddr, sizeof(wol)))
 		return -EFAULT;
+
+	if (wol.wolopts & ~cur_wol.supported)
+		return -EINVAL;
+
+	if (wol.wolopts == cur_wol.wolopts)
+		return 0;
 
 	ret = dev->ethtool_ops->set_wol(dev, &wol);
 	if (ret)