tracing/probe: trace_probe_primary_from_call(): checked list_first_entry

All callers of trace_probe_primary_from_call() check the return
value to be non NULL. However, the function returns
list_first_entry(&tpe->probes, ...) which can never be NULL.
Additionally, it does not check for the list being possibly empty,
possibly causing a type confusion on empty lists.
Use list_first_entry_or_null() which solves both problems.

Link: https://lore.kernel.org/linux-trace-kernel/20230128-list-entry-null-check-v1-1-8bde6a3da2ef@diag.uniroma1.it/
Fixes: 60d53e2c3b75 ("tracing/probe: Split trace_event related data from trace_probe")
Signed-off-by: Pietro Borrello <borrello@diag.uniroma1.it>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Mukesh Ojha <quic_mojha@quicinc.com>
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index ef8ed3b65d0550bfd87b74c39b4657b7fc5044f4..6a4ecfb1da438743d4b8fc3c0182b22bd135c134 100644 (file)
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -308,7 +308,7 @@ trace_probe_primary_from_call(struct trace_event_call *call)
 {
        struct trace_probe_event *tpe = trace_probe_event_from_call(call);
 
-       return list_first_entry(&tpe->probes, struct trace_probe, list);
+       return list_first_entry_or_null(&tpe->probes, struct trace_probe, list);
 }
 
 static inline struct list_head *trace_probe_probe_list(struct trace_probe *tp)