[kvm-unit-tests patch v6 07/18] x86: pmu: Fix potential out of bound access for fixed events

Dapeng Mi
2024-09-14T07:01:27Z

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

So limit validated fixed counters number to
MIN(pmu.nr_fixed_counters, ARRAY_SIZE(fixed_events)) and print message
to warn that KUT/pmu tests need to be updated if fixed counters number
exceeds defined fixed events number.

Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
---
x86/pmu.c | 27 +++++++++++++++++++++------
1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/x86/pmu.c b/x86/pmu.c
index 53bb7ec0..cc940a61 100644
--- a/x86/pmu.c
+++ b/x86/pmu.c
@@ -54,6 +54,7 @@ char *buf;

static struct pmu_event *gp_events;
static unsigned int gp_events_size;
+static unsigned int fixed_counters_num;

static inline void loop(void)
{
@@ -113,8 +114,12 @@ 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 {
+ unsigned int idx = cnt->ctr - MSR_CORE_PERF_FIXED_CTR0;
+
+ if (idx < ARRAY_SIZE(fixed_events))
+ return &fixed_events[idx];
+ }

return (void*)0;
}
@@ -204,8 +209,12 @@ static noinline void __measure(pmu_counter_t *evt, uint64_t count)

static bool verify_event(uint64_t count, struct pmu_event *e)
{
- bool pass = count >= e->min && count <= e->max;
+ bool pass;

+ if (!e)
+ return false;
+
+ pass = count >= e->min && count <= e->max;
if (!pass)
printf("FAIL: %d <= %"PRId64" <= %d\n", e->min, count, e->max);

@@ -250,7 +259,7 @@ static void check_fixed_counters(void)
};
int i;

- for (i = 0; i < pmu.nr_fixed_counters; i++) {
+ for (i = 0; i < fixed_counters_num; i++) {
cnt.ctr = fixed_events[i].unit_sel;
measure_one(&cnt);
report(verify_event(cnt.count, &fixed_events[i]), "fixed-%d", i);
@@ -271,7 +280,7 @@ static void check_counters_many(void)
gp_events[i % gp_events_size].unit_sel;
n++;
}
- for (i = 0; i < pmu.nr_fixed_counters; i++) {
+ for (i = 0; i < fixed_counters_num; i++) {
cnt[n].ctr = fixed_events[i].unit_sel;
cnt[n].config = EVNTSEL_OS | EVNTSEL_USR;
n++;
@@ -419,7 +428,7 @@ static void check_rdpmc(void)
else
report(cnt.count == (u32)val, "fast-%d", i);
}
- for (i = 0; i < pmu.nr_fixed_counters; i++) {
+ for (i = 0; i < fixed_counters_num; i++) {
uint64_t x = val & ((1ull << pmu.fixed_counter_width) - 1);
pmu_counter_t cnt = {
.ctr = MSR_CORE_PERF_FIXED_CTR0 + i,
@@ -744,6 +753,12 @@ int main(int ac, char **av)
printf("Fixed counters: %d\n", pmu.nr_fixed_counters);
printf("Fixed counter width: %d\n", pmu.fixed_counter_width);

+ fixed_counters_num = MIN(pmu.nr_fixed_counters, ARRAY_SIZE(fixed_events));
+ if (pmu.nr_fixed_counters > ARRAY_SIZE(fixed_events))
+ report_info("Fixed counters number %d > defined fixed events %ld. "
+ "Please update test case.", pmu.nr_fixed_counters,
+ ARRAY_SIZE(fixed_events));
+
apic_write(APIC_LVTPC, PMI_VECTOR);

check_counters();
--
2.40.1