[$] A firewall for device drivers
Device drivers, along with the hardware they control, have long been
considered to be a trusted part of the system. This faith has been under
assault for some time, though, and it fails entirely in some situations,
including virtual machines that do not trust the host system they are
running under. The recently covered virtio-hardening work is one response to this
situation, but that only addresses a small portion of the drivers built
into a typical kernel. What is to be done about the rest? The driver-filter
patch from Kuppuswamy Sathyanarayanan demonstrates one possible
approach: disable them altogether.