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

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-rafaelme... Link: https://lore.kernel.org/linux-trace-kernel/20221117214249.2addbe10@gandalf.l...

Cc: Linux Trace Kernel linux-trace-kernel@vger.kernel.org Cc: Tzvetomir Stoyanov tz.stoyanov@gmail.com 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 rafaelmendsr@gmail.com Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org --- kernel/trace/trace_eprobe.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c index 5dd0617e5df6..9cda9a38422c 100644 --- a/kernel/trace/trace_eprobe.c +++ b/kernel/trace/trace_eprobe.c @@ -563,6 +563,9 @@ static void eprobe_trigger_func(struct event_trigger_data *data, { struct eprobe_data *edata = data->private_data;

+ if (unlikely(!rec)) + return; + __eprobe_trace_func(edata, rec); }