[PATCH v2] tracing: Cleanup event_enable_trigger_parse() by using __free()

From: Steven Rostedt <[email protected]>

The enable_data variable gets freed on most error paths in
event_enable_trigger_parse(). Use free() to free it and just before
returning normally, call retain_and_null_ptr(enable_data) just before a
successful exit to keep it from being freed. On success, the enable_data
is assigned to the trigger_data->private_data field.

Also add a comment to why event_trigger_free(trigger_data) is being called
before a successful exit.

Reviewed-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
---
Changes since v1: https://patch.msgid.link/[email protected]

- Updated the comment about why the trigger_data was freed.
  Apparently, Sashiko reads comments too ;-)

 kernel/trace/trace_events_trigger.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index ad83419cb420..149300cc5e8a 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1753,7 +1753,7 @@ int event_enable_trigger_parse(struct event_command *cmd_ops,
 			       char *glob, char *cmd, char *param_and_filter)
 {
 	struct trace_event_file *event_enable_file;
-	struct enable_trigger_data *enable_data;
+	struct enable_trigger_data *enable_data __free(kfree) = NULL;
 	struct event_trigger_data *trigger_data;
 	struct trace_array *tr = file->tr;
 	char *param, *filter;
@@ -1803,17 +1803,13 @@ int event_enable_trigger_parse(struct event_command *cmd_ops,
 	enable_data->file = event_enable_file;
 
 	trigger_data = trigger_data_alloc(cmd_ops, cmd, param, enable_data);
-	if (!trigger_data) {
-		kfree(enable_data);
+	if (!trigger_data)
 		return ret;
-	}
 
 	if (remove) {
 		event_trigger_unregister(cmd_ops, file, glob+1, trigger_data);
 		kfree(trigger_data);
-		kfree(enable_data);
-		ret = 0;
-		return ret;
+		return 0;
 	}
 
 	/* Up the trigger_data count to make sure nothing frees it on failure */
@@ -1842,7 +1838,12 @@ int event_enable_trigger_parse(struct event_command *cmd_ops,
 	if (ret)
 		goto out_disable;
 
+	/* It's now safe to free the reference taken earlier */
 	event_trigger_free(trigger_data);
+
+	/* The enabled_data is assigned to trigger_data->private_data */
+	retain_and_null_ptr(enable_data);
+
 	return ret;
  out_disable:
 	trace_event_enable_disable(event_enable_file, 0, 1);
@@ -1851,7 +1852,6 @@ int event_enable_trigger_parse(struct event_command *cmd_ops,
  out_free:
 	event_trigger_reset_filter(cmd_ops, trigger_data);
 	event_trigger_free(trigger_data);
-	kfree(enable_data);
 
 	return ret;
 }
-- 
2.53.0