VMCI: integer overflow in vmci_datagram_dispatch()

This is untrusted user data from vmci_host_do_send_datagram() so the
VMCI_DG_SIZE() macro can have an integer overflow.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/vmw_vmci/vmci_datagram.c

@@ -328,7 +328,8 @@ int vmci_datagram_dispatch(u32 context_id,
 
 	BUILD_BUG_ON(sizeof(struct vmci_datagram) != 24);
 
-	if (VMCI_DG_SIZE(dg) > VMCI_MAX_DG_SIZE) {
+	if (dg->payload_size > VMCI_MAX_DG_SIZE ||
+	    VMCI_DG_SIZE(dg) > VMCI_MAX_DG_SIZE) {
 		pr_devel("Payload (size=%llu bytes) too big to send\n",
 			 (unsigned long long)dg->payload_size);
 		return VMCI_ERROR_INVALID_ARGS;