rcu-tasks: Fix show_rcu_tasks_trace_gp_kthread buffer overflow

commit cc5645fddb0ce28492b15520306d092730dffa48 upstream.

There is a possibility of buffer overflow in
show_rcu_tasks_trace_gp_kthread() if counters, passed
to sprintf() are huge. Counter numbers, needed for this
are unrealistically high, but buffer overflow is still
possible.

Use snprintf() with buffer size instead of sprintf().

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: edf3775f0ad6 ("rcu-tasks: Add count for idle tasks on offline CPUs")
Signed-off-by: Nikita Kiryushin <kiryushin@ancud.ru>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Vamsi Krishna Brahmajosyula <vamsi-krishna.brahmajosyula@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 105fdc2bb004cfc65872d3ca5c6e86dd5b8bb94e..bede3a4f108e328267a759a8e535b6f8ea6dbfdd 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1240,7 +1240,7 @@ static void show_rcu_tasks_trace_gp_kthread(void)
 {
        char buf[64];
 
-       sprintf(buf, "N%d h:%lu/%lu/%lu", atomic_read(&trc_n_readers_need_end),
+       snprintf(buf, sizeof(buf), "N%d h:%lu/%lu/%lu", atomic_read(&trc_n_readers_need_end),
                data_race(n_heavy_reader_ofl_updates),
                data_race(n_heavy_reader_updates),
                data_race(n_heavy_reader_attempts));