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tracing: Fix to check event_mutex is held while accessing trigger list

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Since the check_user_trigger() is called outside of RCU
read lock, this list_for_each_entry_rcu() caused a suspicious
RCU usage warning.

 # echo hist:keys=pid > events/sched/sched_stat_runtime/trigger
 # cat events/sched/sched_stat_runtime/trigger
[   43.167032]
[   43.167418] =============================
[   43.167992] WARNING: suspicious RCU usage
[   43.168567] 5.19.0-rc5-00029-g19ebe4651abf #59 Not tainted
[   43.169283] -----------------------------
[   43.169863] kernel/trace/trace_events_trigger.c:145 RCU-list traversed in non-reader section!!
...

However, this file->triggers list is safe when it is accessed
under event_mutex is held.
To fix this warning, adds a lockdep_is_held check to the
list_for_each_entry_rcu().

Link: https://lkml.kernel.org/r/166226474977.223837.1992182913048377113.stgit@devnote2

Cc: stable@vger.kernel.org
Fixes: 7491e2c442 ("tracing: Add a probe that attaches to trace events")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu (Google) 2022-09-04 13:12:29 +09:00 committed by Steven Rostedt (Google)
parent 54c3931957
commit cecf8e128e
1 changed files with 2 additions and 1 deletions
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3
kernel/trace/trace_events_trigger.c
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@ -142,7 +142,8 @@ static bool check_user_trigger(struct trace_event_file *file)
{ {
struct event_trigger_data *data; struct event_trigger_data *data;
list_for_each_entry_rcu(data, &file->triggers, list) { list_for_each_entry_rcu(data, &file->triggers, list,
lockdep_is_held(&event_mutex)) {
if (data->flags & EVENT_TRIGGER_FL_PROBE) if (data->flags & EVENT_TRIGGER_FL_PROBE)
continue; continue;
return true; return true;