[kvm-unit-tests Patch v2 5/5] x86: pmu: Add asserts to warn inconsistent fixed events and counters

[Dapeng Mi]

Current PMU code doesn't check whether the number of fixed counters is
larger than pre-defined fixed events. If so, it would cause out of range
memory access.

So add asserts to warn this invalid case.

Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
---
 x86/pmu.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/x86/pmu.c b/x86/pmu.c
index 404dc7b62ac2..3ce05f0a1d38 100644
--- a/x86/pmu.c
+++ b/x86/pmu.c
@@ -117,8 +117,12 @@ static struct pmu_event* get_counter_event(pmu_counter_t *cnt)
 		for (i = 0; i < gp_events_size; i++)
 			if (gp_events[i].unit_sel == (cnt->config & 0xffff))
 				return &gp_events[i];
-	} else
-		return &fixed_events[cnt->ctr - MSR_CORE_PERF_FIXED_CTR0];
+	} else {
+		int idx = cnt->ctr - MSR_CORE_PERF_FIXED_CTR0;
+
+		assert(idx < ARRAY_SIZE(fixed_events));
+		return &fixed_events[idx];
+	}
 
 	return (void*)0;
 }
@@ -251,6 +255,7 @@ static void check_fixed_counters(void)
 	};
 	int i;
 
+	assert(pmu.nr_fixed_counters <= ARRAY_SIZE(fixed_events));
 	for (i = 0; i < pmu.nr_fixed_counters; i++) {
 		cnt.ctr = fixed_events[i].unit_sel;
 		measure_one(&cnt);
@@ -272,6 +277,7 @@ static void check_counters_many(void)
 			gp_events[i % gp_events_size].unit_sel;
 		n++;
 	}
+	assert(pmu.nr_fixed_counters <= ARRAY_SIZE(fixed_events));
 	for (i = 0; i < pmu.nr_fixed_counters; i++) {
 		cnt[n].ctr = fixed_events[i].unit_sel;
 		cnt[n].config = EVNTSEL_OS | EVNTSEL_USR;
-- 
2.34.1