net: phy: prevent stale pointer dereference in phy_init()

mdio_bus_init() and phy_driver_register() both have error paths, and if
those are ever hit, ethtool will have a stale pointer to the
phy_ethtool_phy_ops stub structure, which references memory from a
module that failed to load (phylib).

It is probably hard to force an error in this code path even manually,
but the error teardown path of phy_init() should be the same as
phy_exit(), which is now simply not the case.

Fixes: 55d8f053ce1b ("net: phy: Register ethtool PHY operations")
Link: https://lore.kernel.org/netdev/ZLaiJ4G6TaJYGJyU@shell.armlinux.org.uk/
Suggested-by: Russell King (Oracle) <linux@armlinux.org.uk>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://lore.kernel.org/r/20230720000231.1939689-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 0c2014a..61921d4 100644 (file)
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -3451,23 +3451,30 @@ static int __init phy_init(void)
 {
        int rc;
 
+       ethtool_set_ethtool_phy_ops(&phy_ethtool_phy_ops);
+
        rc = mdio_bus_init();
        if (rc)
-               return rc;
+               goto err_ethtool_phy_ops;
 
-       ethtool_set_ethtool_phy_ops(&phy_ethtool_phy_ops);
        features_init();
 
        rc = phy_driver_register(&genphy_c45_driver, THIS_MODULE);
        if (rc)
-               goto err_c45;
+               goto err_mdio_bus;
 
        rc = phy_driver_register(&genphy_driver, THIS_MODULE);
-       if (rc) {
-               phy_driver_unregister(&genphy_c45_driver);
+       if (rc)
+               goto err_c45;
+
+       return 0;
+
 err_c45:
-               mdio_bus_exit();
-       }
+       phy_driver_unregister(&genphy_c45_driver);
+err_mdio_bus:
+       mdio_bus_exit();
+err_ethtool_phy_ops:
+       ethtool_set_ethtool_phy_ops(NULL);
 
        return rc;
 }