CVE-2022-48814

Summary

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 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 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 device_links_unbind_consumers() 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 mdiobus_unregister and mdiobus_free calls, but it has an external dependency upon mscc_miim_setup() from mdio-mscc-miim.c, which calls devm_mdiobus_alloc_size() on its behalf. So rather than restructuring that, and exporting yet one more symbol mscc_miim_teardown(), let's work with devres and replace of_mdiobus_register 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).

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxac3a68d56651c3dad2c12c7afce065fe15267f44 < 1d13e7221035947c62800c9d3d99b4ed570e27e7affected
LinuxLinuxac3a68d56651c3dad2c12c7afce065fe15267f44 < 0e816362d823cd46c666e64d8bffe329ee22f4ccaffected
LinuxLinuxac3a68d56651c3dad2c12c7afce065fe15267f44 < bd488afc3b39e045ba71aab472233f2a78726e7baffected
LinuxLinux5.9affected
LinuxLinux0 < 5.9unaffected
LinuxLinux5.15.27 <= 5.15.*unaffected
LinuxLinux5.16.10 <= 5.16.*unaffected
LinuxLinux5.17 <= *unaffected

Weaknesses

ADP Enrichment

CVE Program Container

Additional References

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References