[PATCH v2] tracing: Add NULL pointer check to trigger_data_free()

[Guenter Roeck <linux@roeck-us.net>]

If trigger_data_alloc() fails and returns NULL, event_hist_trigger_parse()
jumps to the out_free error path. While kfree() safely handles a NULL
pointer, trigger_data_free() does not. This causes a NULL pointer
dereference in trigger_data_free() when evaluating
data->cmd_ops->set_filter.

Fix the problem by adding a NULL pointer check to trigger_data_free().

The problem was found by an experimental code review agent based on
gemini-3.1-pro while reviewing backports into v6.18.y.

Assisted-by: Gemini:gemini-3.1-pro
Cc: Miaoqian Lin <linmq006@gmail.com>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Fixes: 0550069cc25f ("tracing: Properly process error handling in event_hist_trigger_parse()")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
v2: Add NULL pointer check to trigger_data_free() to make it more robust
    instead of changing the calling code.
    Note: Changed patch description to reflect new functionality.

 kernel/trace/trace_events_trigger.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index fecbd679d432..d5230b759a2d 100644
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -50,6 +50,9 @@ static int trigger_kthread_fn(void *ignore)
 
 void trigger_data_free(struct event_trigger_data *data)
 {
+	if (!data)
+		return;
+
 	if (data->cmd_ops->set_filter)
 		data->cmd_ops->set_filter(NULL, data, NULL);
 
-- 
2.45.2