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- Avoid iterating over newly created group leader event's siblings

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because there are none, and thus prevent a lockdep splat
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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
This commit is contained in:
Linus Torvalds 2023-12-17 14:03:11 -08:00
commit 177c2ffe69
1 changed files with 10 additions and 0 deletions
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10
kernel/events/core.c
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@ -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)