linux-kernel - [PATCH] tracing/probe: trace_probe_primary_from_call(): checked list_first

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Message-Id: <20230128-list-entry-null-check-v1-1-8bde6a3da2ef@diag.uniroma1.it>
Date:   Sat, 28 Jan 2023 16:23:41 +0000
From:   Pietro Borrello <borrello@...g.uniroma1.it>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jkl820.git@...il.com>,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        Pietro Borrello <borrello@...g.uniroma1.it>
Subject: [PATCH] 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.

Fixes: 60d53e2c3b75 ("tracing/probe: Split trace_event related data from trace_probe")
Signed-off-by: Pietro Borrello <borrello@...g.uniroma1.it>
---
 kernel/trace/trace_probe.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 23acfd1c3812..f6b565dced56 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -307,7 +307,7 @@ 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)

---
base-commit: 2241ab53cbb5cdb08a6b2d4688feb13971058f65
change-id: 20230128-list-entry-null-check-37778efda18c

Best regards,
-- 
Pietro Borrello <borrello@...g.uniroma1.it>