A flaw was found in the way KVM hypervisor handled x2APIC Machine Specific Rregister (MSR) access with nested(1) virtualization enabled. In that, L1 guest could access L0's APIC register values via L2 guest, when 'virtualize x2APIC mode' is enabled. A guest could use this flaw to potentially crash the host kernel resulting in DoS issue. Kernel versions from 4.16 and newer are vulnerable to this issue.
Publication date: Wed, 03 Nov 2021 01:18:00 +0000