From: Keita Suzuki keitasuzuki.park@sslab.ics.keio.ac.jp

In create_var_ref(), init_var_ref() is called to initialize the fields of variable ref_field, which is allocated in the previous function call to create_hist_field(). Function init_var_ref() allocates the corresponding fields such as ref_field->system, but frees these fields when the function encounters an error. The caller later calls destroy_hist_field() to conduct error handling, which frees the fields and the variable itself. This results in double free of the fields which are already freed in the previous function.

Fix this by storing NULL to the corresponding fields when they are freed in init_var_ref().

Link: https://lkml.kernel.org/r/20220425063739.3859998-1-keitasuzuki.park@sslab.ic...

Fixes: 067fe038e70f ("tracing: Add variable reference handling to hist triggers") CC: stable@vger.kernel.org Reviewed-by: Masami Hiramatsu mhiramat@kernel.org Reviewed-by: Tom Zanussi zanussi@kernel.org Signed-off-by: Keita Suzuki keitasuzuki.park@sslab.ics.keio.ac.jp Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/trace_events_hist.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 038dc591545d..c6a65738feb3 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -2093,8 +2093,11 @@ static int init_var_ref(struct hist_field *ref_field, return err; free: kfree(ref_field->system); + ref_field->system = NULL; kfree(ref_field->event_name); + ref_field->event_name = NULL; kfree(ref_field->name); + ref_field->name = NULL;

goto out; }