[PATCH 32/48] rcu-tasks: Fix show_rcu_tasks_trace_gp_kthread buffer overflow

[Uladzislau Rezki (Sony)]

From: Nikita Kiryushin <kiryushin@xxxxxxxx>

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@xxxxxxxx>
Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
---
 kernel/rcu/tasks.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index d5319bbe8c98..08a92bffeb84 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -1997,7 +1997,7 @@ 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),
-- 
2.39.2