net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net: mdio: fix unbalanced fwnode reference count in mdio_device_release() There is warning report about of_node refcount leak while probing mdio device: OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /spi/soc@0/mdio@710700c0/ethernet@4 In of_mdiobus_register_device(), we increase fwnode refcount by fwnode_handle_get() before associating the of_node with mdio device, but it has never been decreased in normal path. Since that, in mdio_device_release(), it needs to call fwnode_handle_put() in addition instead of calling kfree() directly. After above, just calling mdio_device_free() in the error handle path of of_mdiobus_register_device() is enough to keep the refcount balanced.

References

• https://git.kernel.org/stable/c/16854177745a5648f8ec322353b432e18460f43a
• https://git.kernel.org/stable/c/a5c6de1a6656b8cc6bce7cb3d9874dd7df4968c3
• https://git.kernel.org/stable/c/cb37617687f2bfa5b675df7779f869147c9002bd