perf/arm-cmn: Fix filter_sel lookup

Carefully considering the bounds of an array is all well and good,
until you forget that that array also contains a NULL sentinel at
the end and dereference it. So close...

Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/bebba768156aa3c0757140457bdd0fec10819388.1652217788.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: rmurphy-arm

drivers/perf/arm-cmn.c

@@ -1514,7 +1514,7 @@ static enum cmn_filter_select arm_cmn_filter_sel(enum cmn_model model,
 	struct arm_cmn_event_attr *e;
 	int i;
 
-	for (i = 0; i < ARRAY_SIZE(arm_cmn_event_attrs); i++) {
+	for (i = 0; i < ARRAY_SIZE(arm_cmn_event_attrs) - 1; i++) {
 		e = container_of(arm_cmn_event_attrs[i], typeof(*e), attr.attr);
 		if (e->model & model && e->type == type && e->eventid == eventid)
 			return e->fsel;