net: mdio: ensure the type of mdio devices match mdio drivers

On the MDIO bus, we have PHYLIB devices and drivers, and we have non-
PHYLIB devices and drivers. PHYLIB devices are MDIO devices that are
wrapped with a struct phy_device.

Trying to bind a MDIO device with a PHYLIB driver results in out-of-
bounds accesses as we attempt to access struct phy_device members. So,
let's prevent this by ensuring that the type of the MDIO device
(indicated by the MDIO_DEVICE_FLAG_PHY flag) matches the type of the
MDIO driver (indicated by the MDIO_DEVICE_IS_PHY flag.)

Link: https://lore.kernel.org/r/[e-mail]
Tested-by: Andrew Lunn <[e-mail]>
Reviewed-by: Andrew Lunn <[e-mail]>
Signed-off-by: Russell King (Oracle) <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/mdio_bus.c

···
  */
 static int mdio_bus_match(struct device *dev, struct device_driver *drv)
 {
+	struct mdio_driver *mdiodrv = to_mdio_driver(drv);
 	struct mdio_device *mdio = to_mdio_device(dev);
+
+	/* Both the driver and device must type-match */
+	if (!(mdiodrv->mdiodrv.flags & MDIO_DEVICE_IS_PHY) !=
+	    !(mdio->flags & MDIO_DEVICE_FLAG_PHY))
+		return 0;
 
 	if (of_driver_match_device(dev, drv))
 		return 1;