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

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
......@@ -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] =
......
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