wp_tempnam gets into loop on ".maintenance" filename

[ridderr]

During update to WP4.2.1 wp_tempnam gets into a loop when filename is ".maintanance".
Error logged is: Allowed memory size of 268435456 bytes exhausted (tried to allocate 65488 bytes) in /home/pi/wordpress/wp-admin/includes/file.php on line 159

I could solve this by adding the following:

        if ( ! $temp_filename ) {
/** begin added code **/
if (dirname ($filename) == "/")
        return dirname ($dir . "x") . $filename;
else
/** end added code **/
                return wp_tempnam( dirname( $filename ), $dir );
        }

[SergeyBiryukov]

Duplicate of #32135.