In the Linux kernel, the following vulnerability has been resolved: net: dsa: seville: register the mdiobus under devres As explained in commits: 74b6d7d13307 ("net: dsa: realtek: register the MDIO bus under devres") 5135e96a3dd2 ("net: dsa: don't allocate the slavemiibus using devres") mdiobusfree() will panic when called from devmmdiobusfree() <- devresreleaseall() <- _devicereleasedriver(), and that mdiobus was not previously unregistered. The Seville VSC9959 switch 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 devicelinksunbindconsumers() will unbind the seville 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 seville driver has a code structure that could accommodate both the mdiobusunregister and mdiobusfree calls, but it has an external dependency upon msccmiimsetup() from mdio-mscc-miim.c, which calls devmmdiobusallocsize() on its behalf. So rather than restructuring that, and exporting yet one more symbol msccmiimteardown(), let's work with devres and replace ofmdiobusregister with the devres variant. When we use all-devres, we can ensure that devres doesn't free a still-registered bus (it either runs both callbacks, or none).
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