[PATCH] tracing: Do not call trigger_data_free with NULL data pointer

[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 new goto label and jumping to it if
trigger_data_alloc() returns NULL.

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>
---
 kernel/trace/trace_events_hist.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 73ea180cad55..a2abdfe19281 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -6874,7 +6874,7 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops,
 	trigger_data = trigger_data_alloc(cmd_ops, cmd, param, hist_data);
 	if (!trigger_data) {
 		ret = -ENOMEM;
-		goto out_free;
+		goto out_destroy;
 	}
 
 	ret = event_trigger_set_filter(cmd_ops, file, filter, trigger_data);
@@ -6942,7 +6942,7 @@ static int event_hist_trigger_parse(struct event_command *cmd_ops,
 	remove_hist_vars(hist_data);
 
 	trigger_data_free(trigger_data);
-
+out_destroy:
 	destroy_hist_data(hist_data);
 	goto out;
 }
-- 
2.45.2