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

net: dsa: bcm_sf2: 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 Starfighter 2 is a platform 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 bcm_sf2 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 bcm_sf2 driver has the code structure in place for orderly mdiobus
removal, so just replace devm_mdiobus_alloc() with the non-devres
variant, and add manual free where necessary, to ensure that we don't
let devres free a still-registered bus.

kernel.org https://git.kernel.org/stable/c/08e1a3554e99a1a5bd2835907381e2383ee85cae [No types assigned]

kernel.org https://git.kernel.org/stable/c/08f1a20822349004bb9cc1b153ecb516e9f2889d [No types assigned]

kernel.org https://git.kernel.org/stable/c/2770b795294ed312375c11ef1d0b810499c66b83 [No types assigned]

kernel.org https://git.kernel.org/stable/c/caabb5f64f5c32fceed93356bb688ef1ec6c5783 [No types assigned]