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Bug #34232 Crash (double free or corruption) using DOM functions
Submitted: 2005-08-24 10:55 UTC Modified: 2005-09-10 17:39 UTC
From: anders at kaseorg dot com Assigned: rrichards (profile)
Status: Not a bug Package: DOM XML related
PHP Version: 5CVS-2005-08-30 OS: *
Private report: No CVE-ID: None
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 [2005-08-24 10:55 UTC] anders at kaseorg dot com 
Description:
------------
Running PHP (5.0.4-10.3 on Fedora Core 4) on this code crashes with a "double free" error after producing correct output. If you comment the last appendChild line, it segfaults instead.

Reproduce code:
---------------
<?php
$imp = new DOMImplementation();
$doc = $imp->createDocument(
  'http://www.w3.org/1999/xhtml',
  'html',
  $imp->createDocumentType('html',
    '-//W3C//DTD XHTML 1.0 Strict//EN',
    'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd')
);
$html = $doc->documentElement;
$head = $html->appendChild($doc->createElement('head'));
$meta = $head->appendChild($doc->createElement('meta'));
$meta->setAttribute('http-equiv', 'Content-Type');
$meta->setAttribute('content', 'application/xhtml+xml; charset=utf-8');
$head->appendChild($doc->createElement('title'));
echo $doc->saveXML();
?>


Expected result:
----------------
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title></title></head></html>


Actual result:
--------------
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title></title></head></html>
*** glibc detected *** php: double free or corruption (!prev): 0x0985dcf0 ***
======= Backtrace: =========
/lib/libc.so.6[0x984124]
/lib/libc.so.6(__libc_free+0x77)[0x98465f]
/usr/lib/libxml2.so.2(xmlFreeNode+0x1ce)[0x7535b66]
php[0x80728be]
php[0x80733cb]
php[0x807339f]
php(php_libxml_node_free_resource+0x3f)[0x8073423]
php(php_libxml_node_decrement_resource+0x41)[0x807349b]
/usr/lib/php/modules/dom.so(dom_objects_free_storage+0x54)[0xc14576]
php(zend_objects_store_del_ref+0x72)[0x8187e48]
php(_zval_ptr_dtor+0x36)[0x8168e3c]
php[0x8179ffc]
php(zend_hash_graceful_reverse_destroy+0x18)[0x817a116]
php(shutdown_executor+0x7c)[0x8169a60]
php(zend_deactivate+0x93)[0x81740de]
php(php_request_shutdown+0x180)[0x813e197]
php(main+0x174)[0x81a7895]
/lib/libc.so.6(__libc_start_main+0xdf)[0x935d5f]
php[0x80727b1]

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 [2005-08-24 15:42 UTC] rrichards@php.net 
Not yet sure if this will require changes to DOM and SimpleXML or libxml2 specific bug. Assigning to self for now.

Current work around: Don't add meta element as its going to be destroyed and a new one added anyways when serializing.
 [2005-09-10 17:39 UTC] rrichards@php.net 
Sorry, but your problem does not imply a bug in PHP itself.  For a
list of more appropriate places to ask for help using PHP, please
visit http://www.php.net/support.php as this bug system is not the
appropriate forum for asking support questions.  Due to the volume
of reports we can not explain in detail here why your report is not
a bug.  The support channels will be able to provide an explanation
for you.

Thank you for your interest in PHP.

was fixed in libxml release 2.6.21.
 
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