diff --git a/drivers/media/dvb-core/dvb_ca_en50221.c b/drivers/media/dvb-core/dvb_ca_en50221.c
index d48b61eb01f4cdc7f11913208a6beef0136a7bff..a3b2754e71247af038bbdd36b7dd585bd4ad10ab 100644
--- a/drivers/media/dvb-core/dvb_ca_en50221.c
+++ b/drivers/media/dvb-core/dvb_ca_en50221.c
@@ -1473,6 +1473,9 @@ static ssize_t dvb_ca_en50221_io_write(struct file *file,
 		return -EFAULT;
 	buf += 2;
 	count -= 2;
+
+	if (slot >= ca->slot_count)
+		return -EINVAL;
 	sl = &ca->slot_info[slot];
 
 	/* check if the slot is actually running */