[PATCH 5.15 236/277] perf/core: Inherit event_caps

[Greg Kroah-Hartman]

From: Namhyung Kim <namhyung@xxxxxxxxxx>

commit e3265a4386428d3d157d9565bb520aabff8b4bf0 upstream.

It was reported that some perf event setup can make fork failed on
ARM64.  It was the case of a group of mixed hw and sw events and it
failed in perf_event_init_task() due to armpmu_event_init().

The ARM PMU code checks if all the events in a group belong to the
same PMU except for software events.  But it didn't set the event_caps
of inherited events and no longer identify them as software events.
Therefore the test failed in a child process.

A simple reproducer is:

  $ perf stat -e '{cycles,cs,instructions}' perf bench sched messaging
  # Running 'sched/messaging' benchmark:
  perf: fork(): Invalid argument

The perf stat was fine but the perf bench failed in fork().  Let's
inherit the event caps from the parent.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20220328200112.457740-1-namhyung@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 kernel/events/core.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11596,6 +11596,9 @@ perf_event_alloc(struct perf_event_attr
 
 	event->state		= PERF_EVENT_STATE_INACTIVE;
 
+	if (parent_event)
+		event->event_caps = parent_event->event_caps;
+
 	if (event->attr.sigtrap)
 		atomic_set(&event->event_limit, 1);