s390/zcrypt: additional check to avoid overflow in msg-type 6 requests

Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 23 insertions, 1 deletions

diff --git a/drivers/s390/crypto/zcrypt_msgtype6.c b/drivers/s390/crypto/zcrypt_msgtype6.c
index dc542e0a3055..0bc91e46395a 100644
--- a/drivers/s390/crypto/zcrypt_msgtype6.c
+++ b/drivers/s390/crypto/zcrypt_msgtype6.c
@@ -311,7 +311,7 @@ static int XCRB_msg_to_type6CPRB_msgX(struct zcrypt_device *zdev,
         } __packed * msg = ap_msg->message;
 
         int rcblen = CEIL4(xcRB->request_control_blk_length);
-        int replylen;
+        int replylen, req_sumlen, resp_sumlen;
         char *req_data = ap_msg->message + sizeof(struct type6_hdr) + rcblen;
         char *function_code;
 
@@ -321,12 +321,34 @@ static int XCRB_msg_to_type6CPRB_msgX(struct zcrypt_device *zdev,
                 xcRB->request_data_length;
         if (ap_msg->length > MSGTYPE06_MAX_MSG_SIZE)
                 return -EINVAL;
+
+        /* Overflow check
+           sum must be greater (or equal) than the largest operand */
+        req_sumlen = CEIL4(xcRB->request_control_blk_length) +
+                        xcRB->request_data_length;
+        if ((CEIL4(xcRB->request_control_blk_length) <=
+                                                xcRB->request_data_length) ?
+                (req_sumlen < xcRB->request_data_length) :
+                (req_sumlen < CEIL4(xcRB->request_control_blk_length))) {
+                return -EINVAL;
+        }
+
         replylen = sizeof(struct type86_fmt2_msg) +
                 CEIL4(xcRB->reply_control_blk_length) +
                 xcRB->reply_data_length;
         if (replylen > MSGTYPE06_MAX_MSG_SIZE)
                 return -EINVAL;
 
+        /* Overflow check
+           sum must be greater (or equal) than the largest operand */
+        resp_sumlen = CEIL4(xcRB->reply_control_blk_length) +
+                        xcRB->reply_data_length;
+        if ((CEIL4(xcRB->reply_control_blk_length) <= xcRB->reply_data_length) ?
+                (resp_sumlen < xcRB->reply_data_length) :
+                (resp_sumlen < CEIL4(xcRB->reply_control_blk_length))) {
+                return -EINVAL;
+        }
+
         /* prepare type6 header */
         msg->hdr = static_type6_hdrX;
         memcpy(msg->hdr.agent_id , &(xcRB->agent_ID), sizeof(xcRB->agent_ID));