linux-kernel - [PATCH] arm_pmu: Validate single/group leader events

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Message-Id: <20220408203330.4014015-1-robh@kernel.org>
Date:   Fri,  8 Apr 2022 15:33:30 -0500
From:   Rob Herring <robh@...nel.org>
To:     Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>
Cc:     Al Grant <al.grant@....com>, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] arm_pmu: Validate single/group leader events

In the case where there is only a cycle counter available (i.e.
PMCR_EL0.N is 0) and an event other than CPU cycles is opened, the open
should fail as the event can never possibly be scheduled. However, the
event validation when an event is opened is skipped when the group
leader is opened. Fix this by always validating the group leader events.

Reported-by: Al Grant <al.grant@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Signed-off-by: Rob Herring <robh@...nel.org>
---
 drivers/perf/arm_pmu.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 9694370651fa..59d3980b8ca2 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -400,6 +400,9 @@ validate_group(struct perf_event *event)
 	if (!validate_event(event->pmu, &fake_pmu, leader))
 		return -EINVAL;
 
+	if (event == leader)
+		return 0;
+
 	for_each_sibling_event(sibling, leader) {
 		if (!validate_event(event->pmu, &fake_pmu, sibling))
 			return -EINVAL;
@@ -489,12 +492,7 @@ __hw_perf_event_init(struct perf_event *event)
 		local64_set(&hwc->period_left, hwc->sample_period);
 	}
 
-	if (event->group_leader != event) {
-		if (validate_group(event) != 0)
-			return -EINVAL;
-	}
-
-	return 0;
+	return validate_group(event);
 }
 
 static int armpmu_event_init(struct perf_event *event)
-- 
2.32.0