How to restrict wordpress search to pages and disable products listing search?

There are better ways, but one easy way to achieve this if you wanted to customise the search results is to edit the search.php template and make the WP_Query a custom one:

<?php
$args = array(
    's' => get_search_query(),
    'post_type' => array('page'),
);

$search_query = new WP_Query($args);

if ( have_posts() ) :

    while ( $search_query->have_posts() ) : $search_query->the_post();
        // do stuff here
    endwhile;

    wp_reset_query();

endif;
?>