Merge tag 'perf_urgent_for_v6.7_rc6' of git://git.kernel.org/pub/scm/…

…linux/kernel/git/tip/tip

Pull perf fix from Borislav Petkov:

 - Avoid iterating over newly created group leader event's siblings
   because there are none, and thus prevent a lockdep splat

* tag 'perf_urgent_for_v6.7_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf: Fix perf_event_validate_size() lockdep splat

kernel/events/core.c

@@ -1947,6 +1947,16 @@ static bool perf_event_validate_size(struct perf_event *event)
 				   group_leader->nr_siblings + 1) > 16*1024)
 		return false;
 
+	/*
+	 * When creating a new group leader, group_leader->ctx is initialized
+	 * after the size has been validated, but we cannot safely use
+	 * for_each_sibling_event() until group_leader->ctx is set. A new group
+	 * leader cannot have any siblings yet, so we can safely skip checking
+	 * the non-existent siblings.
+	 */
+	if (event == group_leader)
+		return true;
+
 	for_each_sibling_event(sibling, group_leader) {
 		if (__perf_event_read_size(sibling->attr.read_format,
 					   group_leader->nr_siblings + 1) > 16*1024)