function cc_mime_types($mimes) {
  $mimes['svg'] = 'image/svg+xml';
  return $mimes;
}
add_filter('upload_mimes', 'cc_mime_types');

function ignore_upload_ext($checked, $file, $filename, $mimes){

//we only need to worry if WP failed the first pass
if(!$checked['type']){
//rebuild the type info
$wp_filetype = wp_check_filetype( $filename, $mimes );
$ext = $wp_filetype['ext'];
$type = $wp_filetype['type'];
$proper_filename = $filename;

//preserve failure for non-svg images
if($type && 0 === strpos($type, 'image/') && $ext !== 'svg'){
$ext = $type = false;
}

//everything else gets an OK, so e.g. we've disabled the error-prone finfo-related checks WP just went through. whether or not the upload will be allowed depends on the upload_mimes, etc.

$checked = compact('ext','type','proper_filename');
}

return $checked;
}
add_filter('wp_check_filetype_and_ext', 'ignore_upload_ext', 10, 4);