[PATCH v2 0/3] KVM: x86: Out-of-bounds access in kvm_recalculate_phys_map()

From: Sean Christopherson
Date: Fri May 26 2023 - 19:51:00 EST

v2 of Michal's fix for a TOCTOU bug in kvm_recalculate_phys_map(). Not
fully tested (will do that next week), though I did confirm the reworked
selftest can hit the bug. Posting a bit prematurely as I have a long weekend
and I don't want Michal to do any duplicate work.

In Michal's words...

kvm_recalculate_apic_map() creates the APIC map iterating over the list of
vCPUs twice. First to find the max APIC ID and allocate a max-sized buffer,
then again, calling kvm_recalculate_phys_map() for each vCPU. This opens a
race window: value of max APIC ID can increase _after_ the buffer was

Michal Luczaj (1):
KVM: selftests: Add test for race in kvm_recalculate_apic_map()

Sean Christopherson (2):
KVM: x86: Bail from kvm_recalculate_phys_map() if x2APIC ID is
KVM: x86: Retry APIC optimized map recalc if vCPU is added/enabled

arch/x86/kvm/lapic.c | 49 ++++++++++--
tools/testing/selftests/kvm/Makefile | 1 +
.../kvm/x86_64/recalc_apic_map_race.c | 76 +++++++++++++++++++
3 files changed, 120 insertions(+), 6 deletions(-)
create mode 100644 tools/testing/selftests/kvm/x86_64/recalc_apic_map_race.c

base-commit: 39428f6ea9eace95011681628717062ff7f5eb5f