refscale: Use kcalloc() instead of kzalloc()

Use kcalloc() in main_func() to gain built-in overflow protection, making
memory allocation safer when calculating allocation size compared to
explicit multiplication.

Signed-off-by: Qianfeng Rong <rongqianfeng@vivo.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/refscale.c

@@ -1021,7 +1021,7 @@ static int main_func(void *arg)
 	set_user_nice(current, MAX_NICE);
 
 	VERBOSE_SCALEOUT("main_func task started");
-	result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL);
+	result_avg = kcalloc(nruns, sizeof(*result_avg), GFP_KERNEL);
 	buf = kzalloc(800 + 64, GFP_KERNEL);
 	if (!result_avg || !buf) {
 		SCALEOUT_ERRSTRING("out of memory");