phy: fix mdiobus module safety

Re-implement the mdiobus module refcounting to ensure that we actually
ensure that the mdiobus module code does not go away while we might call
into it.

The old scheme using bus->dev.driver was buggy, because bus->dev is a
class device which never has a struct device_driver associated with it,
and hence the associated code trying to obtain a refcount did nothing
useful.

Instead, take the approach that other subsystems do: pass the module
when calling mdiobus_register(), and record that in the mii_bus struct.
When we need to increment the module use count in the phy code, use
this stored pointer.  When the phy is deteched, drop the module
refcount, remembering that the phy device might go away at that point.

This doesn't stop the mii_bus going away while there are in-use phys -
it merely stops the underlying code vanishing.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 67553e13bd36..992406624b7c 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -244,7 +244,7 @@ static inline void of_mdiobus_link_phydev(struct mii_bus *mdio,
  *
  * Returns 0 on success or < 0 on error.
  */
-int mdiobus_register(struct mii_bus *bus)
+int __mdiobus_register(struct mii_bus *bus, struct module *owner)
 {
 	int i, err;
 
@@ -255,6 +255,7 @@ int mdiobus_register(struct mii_bus *bus)
 	BUG_ON(bus->state != MDIOBUS_ALLOCATED &&
 	       bus->state != MDIOBUS_UNREGISTERED);
 
+	bus->owner = owner;
 	bus->dev.parent = bus->parent;
 	bus->dev.class = &mdio_bus_class;
 	bus->dev.groups = NULL;
@@ -296,7 +297,7 @@ error:
 	device_del(&bus->dev);
 	return err;
 }
-EXPORT_SYMBOL(mdiobus_register);
+EXPORT_SYMBOL(__mdiobus_register);
 
 void mdiobus_unregister(struct mii_bus *bus)
 {