How to skip the malformated & invalid utf-8 errors.When csv file uploading in ralis app?

I have handle more-then 5lks data.I have working with CSV & XLSX formats. When i uploading a CSV file i have ('Rails Import CSV Error: invalid byte sequence in UTF-8' and 'Malformed error') and-then i uploading a Xlsx file i have ('Roo spreadsheet uploading OLE2 signature is invalid'). Please someone help me? This my view page code...

<%=form_for[@product],:url{:controller=>"products",:action=>"import_process"} do |f| %>

  <%= f.file_field :file1,:accept=>".csv"%>

   <button type="submit" class="btn btn-info" onclick="return ValidateExtension()" data-qslid="l2"><i class="fa fa-cloud-upload"></i>Upload</button><br/><br/>

    <%end%>