diff options
| author | Mark Rutland <mark.rutland@arm.com> | 2023-12-15 11:24:50 +0000 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-12-15 12:33:23 +0100 |
| commit | 7e2c1e4b34f07d9aa8937fab88359d4a0fce468e (patch) | |
| tree | 3fe66c682b97c9107d8e20883053231ad922a0d9 | |
| parent | a39b6ac3781d46ba18193c9dbb2110f31e9bffe9 (diff) | |
perf: Fix perf_event_validate_size() lockdep splat
When lockdep is enabled, the for_each_sibling_event(sibling, event)
macro checks that event->ctx->mutex is held. When creating a new group
leader event, we call perf_event_validate_size() on a partially
initialized event where event->ctx is NULL, and so when
for_each_sibling_event() attempts to check event->ctx->mutex, we get a
splat, as reported by Lucas De Marchi:
WARNING: CPU: 8 PID: 1471 at kernel/events/core.c:1950 __do_sys_perf_event_open+0xf37/0x1080
This only happens for a new event which is its own group_leader, and in
this case there cannot be any sibling events. Thus it's safe to skip the
check for siblings, which avoids having to make invasive and ugly
changes to for_each_sibling_event().
Avoid the splat by bailing out early when the new event is its own
group_leader.
Fixes: 382c27f4ed28f803 ("perf: Fix perf_event_validate_size()")
Closes: https://lore.kernel.org/lkml/20231214000620.3081018-1-lucas.demarchi@intel.com/
Closes: https://lore.kernel.org/lkml/ZXpm6gQ%2Fd59jGsuW@xpf.sh.intel.com/
Reported-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reported-by: Pengfei Xu <pengfei.xu@intel.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20231215112450.3972309-1-mark.rutland@arm.com
| -rw-r--r-- | kernel/events/core.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index c9d123e13b57..9efd0d7775e7 100644 --- a/kernel/events/core.c +++ b/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) |