drivers/perf: hisi: hns3: Fix out-of-bound access when valid event group

The perf tool allows users to create event groups through following
cmd [1], but the driver does not check whether the array index is out
of bounds when writing data to the event_group array. If the number of
events in an event_group is greater than HNS3_PMU_MAX_HW_EVENTS, the
memory write overflow of event_group array occurs.

Add array index check to fix the possible array out of bounds violation,
and return directly when write new events are written to array bounds.

There are 9 different events in an event_group.
[1] perf stat -e '{pmu/event1/, ... ,pmu/event9/}

Fixes: 66637ab ("drivers/perf: hisi: add driver for HNS3 PMU")
Signed-off-by: Junhao He <[email protected]>
Signed-off-by: Hao Chen <[email protected]>
Acked-by: Jonathan Cameron <[email protected]>
Reviewed-by: Jijie Shao <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>

Author: Junhao He

drivers/perf/hisilicon/hns3_pmu.c

@@ -1085,15 +1085,27 @@ static bool hns3_pmu_validate_event_group(struct perf_event *event)
 			return false;
 
 		for (num = 0; num < counters; num++) {
+			/*
+			 * If we find a related event, then it's a valid group
+			 * since we don't need to allocate a new counter for it.
+			 */
 			if (hns3_pmu_cmp_event(event_group[num], sibling))
 				break;
 		}
 
+		/*
+		 * Otherwise it's a new event but if there's no available counter,
+		 * fail the check since we cannot schedule all the events in
+		 * the group simultaneously.
+		 */
+		if (num == HNS3_PMU_MAX_HW_EVENTS)
+			return false;
+
 		if (num == counters)
 			event_group[counters++] = sibling;
 	}
 
-	return counters <= HNS3_PMU_MAX_HW_EVENTS;
+	return true;
 }
 
 static u32 hns3_pmu_get_filter_condition(struct perf_event *event)