Commit 006a0f06 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: x86: avoid out of bounds indices for fixed performance counters 



Because IceLake has 4 fixed performance counters but KVM only
supports 3, it is possible for reprogram_fixed_counters to pass
to reprogram_fixed_counter an index that is out of bounds for the
fixed_pmc_events array.

Ultimately intel_find_fixed_event, which is the only place that uses
fixed_pmc_events, handles this correctly because it checks against the
size of fixed_pmc_events anyway.  Every other place operates on the
fixed_counters[] array which is sized according to INTEL_PMC_MAX_FIXED.
However, it is cleaner if the unsupported performance counters are culled
early on in reprogram_fixed_counters.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5b61178c

arch/x86/kvm/vmx/pmu_intel.c

+4 −3
Original line number Diff line number Diff line
@@ -91,7 +91,7 @@ static unsigned intel_find_fixed_event(int idx) 
	u32 event;

	size_t size = ARRAY_SIZE(fixed_pmc_events);



	if (idx >= size)

	if (WARN_ON_ONCE(idx >= size))

		return PERF_COUNT_HW_MAX;



	event = fixed_pmc_events[array_index_nospec(idx, size)];
@@ -500,8 +500,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu) 
		pmu->nr_arch_fixed_counters = 0;

	} else {

		pmu->nr_arch_fixed_counters =

			min_t(int, edx.split.num_counters_fixed,

			      x86_pmu.num_counters_fixed);

			min3(ARRAY_SIZE(fixed_pmc_events),

			     (size_t) edx.split.num_counters_fixed,

			     (size_t) x86_pmu.num_counters_fixed);

		edx.split.bit_width_fixed = min_t(int,

			edx.split.bit_width_fixed, x86_pmu.bit_width_fixed);

		pmu->counter_bitmask[KVM_PMC_FIXED] =