net: mdio_bus: validate "addr" for mdiobus_is_registered_device()

mdiobus_is_registered_device() doesn't checking that "addr" was valid
before dereferencing bus->mdio_map[]. Extract the code that checks
this from mdiobus_get_phy(), and use it here as well.

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

drivers/net/phy/mdio_bus.c

···
 }
 EXPORT_SYMBOL(mdiobus_unregister_device);
 
-struct phy_device *mdiobus_get_phy(struct mii_bus *bus, int addr)
+static struct mdio_device *mdiobus_find_device(struct mii_bus *bus, int addr)
 {
 	bool addr_valid = addr >= 0 && addr < ARRAY_SIZE(bus->mdio_map);
-	struct mdio_device *mdiodev;
 
 	if (WARN_ONCE(!addr_valid, "addr %d out of range\n", addr))
 		return NULL;
 
-	mdiodev = bus->mdio_map[addr];
+	return bus->mdio_map[addr];
+}
 
+struct phy_device *mdiobus_get_phy(struct mii_bus *bus, int addr)
+{
+	struct mdio_device *mdiodev;
+
+	mdiodev = mdiobus_find_device(bus, addr);
 	if (!mdiodev)
 		return NULL;
 
···
 
 bool mdiobus_is_registered_device(struct mii_bus *bus, int addr)
 {
-	return bus->mdio_map[addr];
+	return mdiobus_find_device(bus, addr) != NULL;
 }
 EXPORT_SYMBOL(mdiobus_is_registered_device);