Merge branch 'ethtool_gert_phy_stats-fixes'

Daniil Tatianin says:

====================
net/ethtool/ioctl: split ethtool_get_phy_stats into multiple helpers

This series fixes a potential NULL dereference in ethtool_get_phy_stats
while also attempting to refactor/split said function into multiple
helpers so that it's easier to reason about what's going on.

I've taken Andrew Lunn's suggestions on the previous version of this
patch and added a bit of my own.

Changes since v1:
- Remove an extra newline in the first patch
- Move WARN_ON_ONCE into the if check as it already returns the
  result of the comparison
- Actually split ethtool_get_phy_stats instead of attempting to
  refactor it
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ethtool/ioctl.c

@@ -2078,58 +2078,91 @@ static int ethtool_get_stats(struct net_device *dev, void __user *useraddr)
 	return ret;
 }
 
-static int ethtool_get_phy_stats(struct net_device *dev, void __user *useraddr)
+static int ethtool_vzalloc_stats_array(int n_stats, u64 **data)
 {
+	if (n_stats < 0)
+		return n_stats;
+	if (n_stats > S32_MAX / sizeof(u64))
+		return -ENOMEM;
+	if (WARN_ON_ONCE(!n_stats))
+		return -EOPNOTSUPP;
+
+	*data = vzalloc(array_size(n_stats, sizeof(u64)));
+	if (!*data)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static int ethtool_get_phy_stats_phydev(struct phy_device *phydev,
+					 struct ethtool_stats *stats,
+					 u64 **data)
+ {
 	const struct ethtool_phy_ops *phy_ops = ethtool_phy_ops;
+	int n_stats, ret;
+
+	if (!phy_ops || !phy_ops->get_sset_count || !phy_ops->get_stats)
+		return -EOPNOTSUPP;
+
+	n_stats = phy_ops->get_sset_count(phydev);
+
+	ret = ethtool_vzalloc_stats_array(n_stats, data);
+	if (ret)
+		return ret;
+
+	stats->n_stats = n_stats;
+	return phy_ops->get_stats(phydev, stats, *data);
+}
+
+static int ethtool_get_phy_stats_ethtool(struct net_device *dev,
+					  struct ethtool_stats *stats,
+					  u64 **data)
+{
 	const struct ethtool_ops *ops = dev->ethtool_ops;
-	struct phy_device *phydev = dev->phydev;
-	struct ethtool_stats stats;
-	u64 *data;
-	int ret, n_stats;
+	int n_stats, ret;
 
-	if (!phydev && (!ops->get_ethtool_phy_stats || !ops->get_sset_count))
+	if (!ops || !ops->get_sset_count || ops->get_ethtool_phy_stats)
 		return -EOPNOTSUPP;
 
-	if (phydev && !ops->get_ethtool_phy_stats &&
-	    phy_ops && phy_ops->get_sset_count)
-		n_stats = phy_ops->get_sset_count(phydev);
-	else
-		n_stats = ops->get_sset_count(dev, ETH_SS_PHY_STATS);
-	if (n_stats < 0)
-		return n_stats;
-	if (n_stats > S32_MAX / sizeof(u64))
-		return -ENOMEM;
-	WARN_ON_ONCE(!n_stats);
+	n_stats = ops->get_sset_count(dev, ETH_SS_PHY_STATS);
+
+	ret = ethtool_vzalloc_stats_array(n_stats, data);
+	if (ret)
+		return ret;
+
+	stats->n_stats = n_stats;
+	ops->get_ethtool_phy_stats(dev, stats, *data);
+
+	return 0;
+}
+
+static int ethtool_get_phy_stats(struct net_device *dev, void __user *useraddr)
+{
+	struct phy_device *phydev = dev->phydev;
+	struct ethtool_stats stats;
+	u64 *data = NULL;
+	int ret = -EOPNOTSUPP;
 
 	if (copy_from_user(&stats, useraddr, sizeof(stats)))
 		return -EFAULT;
 
-	stats.n_stats = n_stats;
+	if (phydev)
+		ret = ethtool_get_phy_stats_phydev(phydev, &stats, &data);
 
-	if (n_stats) {
-		data = vzalloc(array_size(n_stats, sizeof(u64)));
-		if (!data)
-			return -ENOMEM;
+	if (ret == -EOPNOTSUPP)
+		ret = ethtool_get_phy_stats_ethtool(dev, &stats, &data);
 
-		if (phydev && !ops->get_ethtool_phy_stats &&
-		    phy_ops && phy_ops->get_stats) {
-			ret = phy_ops->get_stats(phydev, &stats, data);
-			if (ret < 0)
-				goto out;
-		} else {
-			ops->get_ethtool_phy_stats(dev, &stats, data);
-		}
-	} else {
-		data = NULL;
-	}
+	if (ret)
+		goto out;
 
-	ret = -EFAULT;
-	if (copy_to_user(useraddr, &stats, sizeof(stats)))
+	if (copy_to_user(useraddr, &stats, sizeof(stats))) {
+		ret = -EFAULT;
 		goto out;
+	}
+
 	useraddr += sizeof(stats);
-	if (n_stats && copy_to_user(useraddr, data, array_size(n_stats, sizeof(u64))))
-		goto out;
-	ret = 0;
+	if (copy_to_user(useraddr, data, array_size(stats.n_stats, sizeof(u64))))
+		ret = -EFAULT;
 
  out:
 	vfree(data);