Subject: CVE-2022-48813: net: dsa: felix: don't use devres for mdiobus

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

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

net: dsa: felix: don't use devres for mdiobus

As explained in commits:
74b6d7d13307 ("net: dsa: realtek: register the MDIO bus under devres")
5135e96a3dd2 ("net: dsa: don't allocate the slave_mii_bus using devres")

mdiobus_free() will panic when called from devm_mdiobus_free() <-
devres_release_all() <- __device_release_driver(), and that mdiobus was
not previously unregistered.

The Felix VSC9959 switch is a PCI device, so the initial set of
constraints that I thought would cause this (I2C or SPI buses which call
->remove on ->shutdown) do not apply. But there is one more which
applies here.

If the DSA master itself is on a bus that calls ->remove from ->shutdown
(like dpaa2-eth, which is on the fsl-mc bus), there is a device link
between the switch and the DSA master, and device_links_unbind_consumers()
will unbind the felix switch driver on shutdown.

So the same treatment must be applied to all DSA switch drivers, which
is: either use devres for both the mdiobus allocation and registration,
or don't use devres at all.

The felix driver has the code structure in place for orderly mdiobus
removal, so just replace devm_mdiobus_alloc_size() with the non-devres
variant, and add manual free where necessary, to ensure that we don't
let devres free a still-registered bus.

The Linux kernel CVE team has assigned CVE-2022-48813 to this issue.

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

	Issue introduced in 5.9 with commit ac3a68d56651 and fixed in 5.10.101 with commit 95e5402f9430
	Issue introduced in 5.9 with commit ac3a68d56651 and fixed in 5.15.24 with commit 8cda7577a0b4
	Issue introduced in 5.9 with commit ac3a68d56651 and fixed in 5.16.10 with commit 9db6f056efd0
	Issue introduced in 5.9 with commit ac3a68d56651 and fixed in 5.17 with commit 209bdb7ec6a2

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-2022-48813
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/dsa/ocelot/felix_vsc9959.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/95e5402f9430b3c7d885dd3ec4c8c02c17936923
	https://git.kernel.org/stable/c/8cda7577a0b4018572f31e0caadfabd305ea2786
	https://git.kernel.org/stable/c/9db6f056efd089e80d81c774c01b639adf30c097
	https://git.kernel.org/stable/c/209bdb7ec6a28c7cdf580a0a98afbc9fc3b98932