Commit 162c9e3f authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf/core: Fix event->parent life-time issue 



Due to an oversight in merging:

  da916e96 ("perf: Make perf_pmu_unregister() useable")

on top of:

  56799bc0 ("perf: Fix hang while freeing sigtrap event")

.. it is now possible to hit put_event(EVENT_TOMBSTONE), which makes
the computer sad.

This also means that for the event->parent == EVENT_TOMBSTONE, the
put_event() matching inherit_event() has gone missing.

Previously this was done in perf_event_release_kernel() after calling
perf_remove_from_context(), but with it delegated to put_event(), this
case is now entirely missed, leading to leaks.

Fixes: da916e96 ("perf: Make perf_pmu_unregister() useable")
Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Tested-by: default avatarkernel test robot <oliver.sang@intel.com>
Tested-by: default avatarJames Clark <james.clark@linaro.org>
Tested-by: default avatarVenkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Closes: https://lore.kernel.org/oe-lkp/202504131701.941039cd-lkp@intel.com
Link: https://lkml.kernel.org/r/20250415131446.GN5600@noisy.programming.kicks-ass.net
parent 2839f393

kernel/events/core.c

+2 −1
Original line number Diff line number Diff line
@@ -2343,6 +2343,7 @@ static void perf_child_detach(struct perf_event *event) 
	 * not being a child event. See for example unaccount_event().

	 */

	event->parent = EVENT_TOMBSTONE;

	put_event(parent_event);

}



static bool is_orphaned_event(struct perf_event *event)
@@ -5688,7 +5689,7 @@ static void put_event(struct perf_event *event) 
	_free_event(event);



	/* Matches the refcount bump in inherit_event() */

	if (parent)

	if (parent && parent != EVENT_TOMBSTONE)

		put_event(parent);

}