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SubjectRe: [PATCH v1] net/ethtool/ioctl: ensure that we have phy ops before using them
On Mon, 14 Nov 2022 11:15:32 +0300 Daniil Tatianin wrote:
> + if (!(phydev && phy_ops && phy_ops->get_stats) &&
> + !ops->get_ethtool_phy_stats)

This condition is still complicated.

> + return -EOPNOTSUPP;

The only way this crash can happen is if driver incorrectly returns
non-zero stats count but doesn't have a callback to read the stats.
So WARN_ON() would be in order here.

> if (!phydev && (!ops->get_ethtool_phy_stats || !ops->get_sset_count))
> return -EOPNOTSUPP;
>
> @@ -2063,13 +2066,12 @@ static int ethtool_get_phy_stats(struct net_device *dev, void __user *useraddr)
> if (!data)
> return -ENOMEM;
>
> - if (dev->phydev && !ops->get_ethtool_phy_stats &&
> - phy_ops && phy_ops->get_stats) {
> - ret = phy_ops->get_stats(dev->phydev, &stats, data);
> + if (ops->get_ethtool_phy_stats) {
> + ops->get_ethtool_phy_stats(dev, &stats, data);
> + } else {
> + ret = phy_ops->get_stats(phydev, &stats, data);
> if (ret < 0)
> goto out;
> - } else {
> - ops->get_ethtool_phy_stats(dev, &stats, data);
> }

We can also clean up the pointless indentation of this code while at it.

How about something along these lines (completely untested, please
review, test and make your own):

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 99272a67525c..ee04c388f4c9 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2105,23 +2105,28 @@ static int ethtool_get_phy_stats(struct net_device *dev, void __user *useraddr)

stats.n_stats = n_stats;

- if (n_stats) {
- data = vzalloc(array_size(n_stats, sizeof(u64)));
- if (!data)
- return -ENOMEM;
+ if (!n_stats) {
+ data = NULL;
+ goto copy_back;
+ }

- 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);
- }
+ data = vzalloc(array_size(n_stats, sizeof(u64)));
+ if (!data)
+ return -ENOMEM;
+
+ if (ops->get_ethtool_phy_stats) {
+ ops->get_ethtool_phy_stats(dev, &stats, data);
+ } else if (phydev && phy_ops && phy_ops->get_stats) {
+ ret = phy_ops->get_stats(phydev, &stats, data);
+ if (ret < 0)
+ goto out;
} else {
- data = NULL;
+ WARN_ON_ONCE(1);
+ n_stats = 0;
+ stats.n_stats = 0;
}

+copy_back:
ret = -EFAULT;
if (copy_to_user(useraddr, &stats, sizeof(stats)))
goto out;
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