hw/cxl: Ensure there is enough data for the header in cmd_ccls_set_lsa()

The properties of the requested set command cannot be established if
len_in is less than the size of the header.

Reported-by: Esifiel <esifiel@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Message-Id: <20241101133917.27634-10-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/cxl/cxl-mailbox-utils.c

@@ -1503,8 +1503,8 @@ static CXLRetCode cmd_ccls_set_lsa(const struct cxl_cmd *cmd,
     const size_t hdr_len = offsetof(struct set_lsa_pl, data);
 
     *len_out = 0;
-    if (!len_in) {
-        return CXL_MBOX_SUCCESS;
+    if (len_in < hdr_len) {
+        return CXL_MBOX_INVALID_PAYLOAD_LENGTH;
     }
 
     if (set_lsa_payload->offset + len_in > cvc->get_lsa_size(ct3d) + hdr_len) {