tracing: Do not reference event data in post call triggers

Trace event triggers can be called before or after the event has been
committed. If it has been called after the commit, there's a possibility
that the event no longer exists. Currently, the two post callers is the
trigger to disable tracing (traceoff) and the one that will record a stack
dump (stacktrace). Neither of them reference the trace event entry record,
as that would lead to a race condition that could pass in corrupted data.

To prevent any other users of the post data triggers from using the trace
event record, pass in NULL to the post call trigger functions for the event
record, as they should never need to use them in the first place.

This does not fix any bug, but prevents bugs from happening by new post call
trigger users.

Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index 2bde3eff564c..d1c442d9bd85 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -435,8 +435,7 @@ event_triggers_call(struct trace_event_file *file, void *rec,
 		    struct ring_buffer_event *event);
 extern void
 event_triggers_post_call(struct trace_event_file *file,
-			 enum event_trigger_type tt,
-			 void *rec, struct ring_buffer_event *event);
+			 enum event_trigger_type tt);
 
 bool trace_event_ignore_this_pid(struct trace_event_file *trace_file);