ethtool: don't open-code memdup_user()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

net/core/ethtool.c

@@ -2322,16 +2322,12 @@ static int ethtool_set_tunable(struct net_device *dev, void __user *useraddr)
 	ret = ethtool_tunable_valid(&tuna);
 	if (ret)
 		return ret;
-	data = kmalloc(tuna.len, GFP_USER);
-	if (!data)
-		return -ENOMEM;
 	useraddr += sizeof(tuna);
-	ret = -EFAULT;
-	if (copy_from_user(data, useraddr, tuna.len))
-		goto out;
+	data = memdup_user(useraddr, tuna.len);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
 	ret = ops->set_tunable(dev, &tuna, data);
 
-out:
 	kfree(data);
 	return ret;
 }
@@ -2507,18 +2503,14 @@ static int set_phy_tunable(struct net_device *dev, void __user *useraddr)
 	ret = ethtool_phy_tunable_valid(&tuna);
 	if (ret)
 		return ret;
-	data = kmalloc(tuna.len, GFP_USER);
-	if (!data)
-		return -ENOMEM;
 	useraddr += sizeof(tuna);
-	ret = -EFAULT;
-	if (copy_from_user(data, useraddr, tuna.len))
-		goto out;
+	data = memdup_user(useraddr, tuna.len);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
 	mutex_lock(&phydev->lock);
 	ret = phydev->drv->set_tunable(phydev, &tuna, data);
 	mutex_unlock(&phydev->lock);
 
-out:
 	kfree(data);
 	return ret;
 }