From: Steven Rostedt (Google) <rostedt@goodmis.org>

commit 94eedf3dded5fb472ce97bfaf3ac1c6c29c35d26 upstream.

The flag that tells the event to call its triggers after reading the event
is set for eprobes after the eprobe is enabled. This leads to a race where
the eprobe may be triggered at the beginning of the event where the record
information is NULL. The eprobe then dereferences the NULL record causing
a NULL kernel pointer bug.

Test for a NULL record to keep this from happening.

Link: https://lore.kernel.org/linux-trace-kernel/20221116192552.1066630-1-rafaelmendsr@gmail.com/ (local)
Link: https://lore.kernel.org/linux-trace-kernel/20221117214249.2addbe10@gandalf.local.home (local)

Cc: Linux Trace Kernel <redacted>
Cc: Tzvetomir Stoyanov <redacted>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reported-by: Rafael Mendonca <redacted>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 kernel/trace/trace_eprobe.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c

@@ -560,6 +560,9 @@ static void eprobe_trigger_func(struct e
 {
 	struct eprobe_data *edata = data->private_data;
 
+	if (unlikely(!rec))
+		return;
+
 	__eprobe_trace_func(edata, rec);
 }