net: phy: Fix PHY module checks and NULL deref in phy_attach_direct()

The Generic PHY drivers gets assigned after we checked that the current
PHY driver is NULL, so we need to check a few things before we can
safely dereference d->driver. This would be causing a NULL deference to
occur when a system binds to the Generic PHY driver. Update
phy_attach_direct() to do the following:

- grab the driver module reference after we have assigned the Generic
  PHY drivers accordingly, and remember we came from the generic PHY
  path

- update the error path to clean up the module reference in case the
  Generic PHY probe function fails

- split the error path involving phy_detacht() to avoid double free/put
  since phy_detach() does all the clean up

- finally, have phy_detach() drop the module reference count before we
  call device_release_driver() for the Generic PHY driver case

Fixes: cafe8df8b9bc ("net: phy: Fix lack of reference count on PHY driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 0d8f4d3847f668d9bf8176e679cc26d9487f59d8..8c8e15b8739dec0ae96d72b514045a99eb1ed7e1 100644 (file)
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -908,6 +908,7 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
        struct module *ndev_owner = dev->dev.parent->driver->owner;
        struct mii_bus *bus = phydev->mdio.bus;
        struct device *d = &phydev->mdio.dev;
+       bool using_genphy = false;
        int err;
 
        /* For Ethernet device drivers that register their own MDIO bus, we
@@ -920,11 +921,6 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
                return -EIO;
        }
 
-       if (!try_module_get(d->driver->owner)) {
-               dev_err(&dev->dev, "failed to get the device driver module\n");
-               return -EIO;
-       }
-
        get_device(d);
 
        /* Assume that if there is no driver, that it doesn't
@@ -938,12 +934,22 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
                        d->driver =
                                &genphy_driver[GENPHY_DRV_1G].mdiodrv.driver;
 
+               using_genphy = true;
+       }
+
+       if (!try_module_get(d->driver->owner)) {
+               dev_err(&dev->dev, "failed to get the device driver module\n");
+               err = -EIO;
+               goto error_put_device;
+       }
+
+       if (using_genphy) {
                err = d->driver->probe(d);
                if (err >= 0)
                        err = device_bind_driver(d);
 
                if (err)
-                       goto error;
+                       goto error_module_put;
        }
 
        if (phydev->attached_dev) {
@@ -980,9 +986,14 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
        return err;
 
 error:
+       /* phy_detach() does all of the cleanup below */
        phy_detach(phydev);
-       put_device(d);
+       return err;
+
+error_module_put:
        module_put(d->driver->owner);
+error_put_device:
+       put_device(d);
        if (ndev_owner != bus->owner)
                module_put(bus->owner);
        return err;
@@ -1045,6 +1056,8 @@ void phy_detach(struct phy_device *phydev)
 
        phy_led_triggers_unregister(phydev);
 
+       module_put(phydev->mdio.dev.driver->owner);
+
        /* If the device had no specific driver before (i.e. - it
         * was using the generic driver), we unbind the device
         * from the generic driver so that there's a chance a
@@ -1065,7 +1078,6 @@ void phy_detach(struct phy_device *phydev)
        bus = phydev->mdio.bus;
 
        put_device(&phydev->mdio.dev);
-       module_put(phydev->mdio.dev.driver->owner);
        if (ndev_owner != bus->owner)
                module_put(bus->owner);
 }