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tracing: Fix race where eprobes can be called before the event

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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/
Link: https://lore.kernel.org/all/20221117214249.2addbe10@gandalf.local.home/

Cc: stable@vger.kernel.org
Fixes: 7491e2c442 ("tracing: Add a probe that attaches to trace events")
Reported-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Steven Rostedt (Google) 2022-11-17 21:42:49 -05:00 committed by Masami Hiramatsu (Google)
parent 40adaf51cb
commit d5f30a7da8
1 changed files with 3 additions and 0 deletions
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3
kernel/trace/trace_eprobe.c
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@ -564,6 +564,9 @@ 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);
}