Subject: CVE-2022-48961: net: mdio: fix unbalanced fwnode reference count in mdio_device_release()

From: Greg Kroah-Hartman <[email-masked]>

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.

The Linux kernel CVE team has assigned CVE-2022-48961 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 4.5 with commit a9049e0c513c and fixed in 5.15.83 with commit 16854177745a
	Issue introduced in 4.5 with commit a9049e0c513c and fixed in 6.0.13 with commit a5c6de1a6656
	Issue introduced in 4.5 with commit a9049e0c513c and fixed in 6.1 with commit cb37617687f2

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-48961
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/net/mdio/of_mdio.c
	drivers/net/phy/mdio_device.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/16854177745a5648f8ec322353b432e18460f43a
	https://git.kernel.org/stable/c/a5c6de1a6656b8cc6bce7cb3d9874dd7df4968c3
	https://git.kernel.org/stable/c/cb37617687f2bfa5b675df7779f869147c9002bd