CVE-2020-29567

An issue was discovered in Xen 4.14.x. When moving IRQs between CPUs to
distribute the load of IRQ handling, IRQ vectors are dynamically allocated
and de-allocated on the relevant CPUs. De-allocation has to happen when
certain constraints are met. If these conditions are not met when first
checked, the checking CPU may send an interrupt to itself, in the
expectation that this IRQ will be delivered only after the condition
preventing the cleanup has cleared. For two specific IRQ vectors, this
expectation was violated, resulting in a continuous stream of
self-interrupts, which renders the CPU effectively unusable. A domain with
a passed through PCI device can cause lockup of a physical CPU, resulting
in a Denial of Service (DoS) to the entire host. Only x86 systems are
vulnerable. Arm systems are not vulnerable. Only guests with physical PCI
devices passed through to them can exploit the vulnerability.

Notes