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Crash on using unitialized vals and __get/__set

Bug #43201 Crash on using unitialized vals and __get/__set
Submitted: 2007-11-05 18:15 UTC Modified: 2007-11-09 09:28 UTC
From: stas at zend dot com Assigned: dmitry (profile)
Status: Closed Package: Scripting Engine problem
PHP Version: 5.2CVS-2007-11-05 (CVS) OS: *
Private report: No CVE-ID: None

 [2007-11-05 18:15 UTC] stas at zend dot com

Description:
------------
Code modifying the result of __get (erroneously) and using undefined variables crashes, apparently because of unitialized_zval being freed. 

Reproduce code:
---------------
<?php
class Foo {
	function __get($k) {
		return null;
	}
	function __set($k, $v) {
		$this->$k = $v;
	}
}

$c = new Foo();

$c->arr[0]["k"] = 1;
$c->arr[0]["k2"] = $ref;
for($cnt=0;$cnt<6;$cnt++) {
	$ref = chop($undef);	
	$c->arr[$cnt]["k2"] = $ref;
}
?>

Expected result:
----------------
No crash :)

Actual result:
--------------
On windows - crash
On Unix debug - 
php5/Zend/zend_hash.c(517) : ht=0xa533520 is being destroyed

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 [2007-11-05 18:20 UTC] stas@php.net

Shorter version:

<?php
class Foo {
	function __get($k) {
		return null;
	}
}

$c = new Foo();

$c->arr[0]["k"] = 1;
$c->arr[0]["k2"] = $undef;
for($cnt=0;$cnt<6;++$cnt) {
	$c->arr[$cnt]["k2"] = chop($undef);
}
?>

 [2007-11-09 09:28 UTC] dmitry@php.net

This bug has been fixed in CVS.

Snapshots of the sources are packaged every three hours; this change
will be in the next snapshot. You can grab the snapshot at
http://snaps.php.net/.
 
Thank you for the report, and for helping us make PHP better.