diff --git a/drivers/s390/crypto/zcrypt_msgtype6.c b/drivers/s390/crypto/zcrypt_msgtype6.c
index e79e68b4dd41..3df1d676de5d 100644
--- a/drivers/s390/crypto/zcrypt_msgtype6.c
+++ b/drivers/s390/crypto/zcrypt_msgtype6.c
@@ -398,6 +398,10 @@ static int xcrb_msg_to_type6cprb_msgx(bool userspace, struct ap_message *ap_msg,
 			     xcrb->request_control_blk_addr,
 			     xcrb->request_control_blk_length))
 		return -EFAULT;
+	/* pad tail with 0 up to req_cblen */
+	if (xcrb->request_control_blk_length < req_cblen)
+		memset(msg->userdata + xcrb->request_control_blk_length,
+		       0, req_cblen - xcrb->request_control_blk_length);
 	/* copy subfunction code into AP msg type 6 function code field */
 	if (msg->cprbx.cprb_len > req_cblen - sizeof(msg->hdr.function_code))
 		return -EINVAL;
@@ -542,6 +546,10 @@ static int xcrb_msg_to_type6_ep11cprb_msgx(bool userspace, struct ap_message *ap
 	if (z_copy_from_user(userspace, msg->userdata,
 			     (char __force __user *)xcrb->req, xcrb->req_len))
 		return -EFAULT;
+	/* pad tail with 0 up to req_len */
+	if (xcrb->req_len < req_len)
+		memset(msg->userdata + xcrb->req_len, 0,
+		       req_len - xcrb->req_len);
 
 	pld = msg->userdata + sizeof(struct ep11_cprb);
 	pld_len = msg->cprbx.payload_len;