Limit WordPress posts by author.

functions.php

add_filter('pre_get_posts', 'posts_for_current_author');

function posts_for_current_author($query) {

      if(!is_admin()) { return $query; }

    global $pagenow;

    if( 'upload.php' == $pagenow || !$query->is_admin ) {
          if( !current_user_can( 'edit_others_posts' ) ) {
             global $user_ID;
             $query->set('author', $user_ID );
          }
   }
    if( 'edit.php' != $pagenow || !$query->is_admin )
        return $query;

    if( !current_user_can( 'edit_others_posts' ) ) {
        global $user_ID;
        $query->set('author', $user_ID );
    }
    return $query;
}