rcu-tasks: Fix show_rcu_tasks_trace_gp_kthread buffer overflow

[ Upstream commit cc5645fddb0ce28492b15520306d092730dffa48 ]

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>

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 732ad5b39946a519bb0ba7a0de35537d4d19f38b..3f64268fe9ead8334e66c2937d062839f5a4c671 100644 (file)
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1941,7 +1941,7 @@ void show_rcu_tasks_trace_gp_kthread(void)
 {
        char buf[64];
 
-       sprintf(buf, "N%lu h:%lu/%lu/%lu",
+       snprintf(buf, sizeof(buf), "N%lu h:%lu/%lu/%lu",
                data_race(n_trc_holdouts),
                data_race(n_heavy_reader_ofl_updates),
                data_race(n_heavy_reader_updates),