Frontier Restrict media will restrict users to only access their own media files

Main Features

• Users without the capability edit_others_posts will only have access to their own media files from the media gallery

Frontier Restrict Media on wordpress.org: Download Plugin | Plugin Support

Code is simple, and if you do not want to install the plugin, you can add the below code to your functions.php

//Restrict users who dont have capability edit_others_posts, to only see media they have uploaded themselves
function my_own_restrict_media($query) 
  { 
  //Check if it is an admin query
  if ($query->is_admin && !current_user_can( 'edit_others_posts' ))
    {
    //Check if it is an attachment query
    if ($query->query['post_type'] === 'attachment')
      {
      // Get current user, and author=current user to query
      $current_user = wp_get_current_user();
      $query->set('author', $current_user->ID);
      }
    }
  return $query;
  }
add_filter('pre_get_posts', 'my_own_restrict_media');