Description

The following code:

<?php
$doc = new DOMDocument();
$doc->load('xinclude-fail-original.xml');
$xi = $doc->createElementNS('http://www.w3.org/2001/XInclude', 'xi:include');
$xi->setAttribute('href', $_SERVER['DOCUMENT_ROOT'] . '/xinclude-included.xml');

$fallback = $doc->createElementNS('http://www.w3.org/2001/XInclude', 'xi:fallback');
$xi->appendChild($fallback);

$xpath = new DOMXPath($doc);
$toReplace = $xpath->query('//child')->item(0);
$toReplace->parentNode->replaceChild($xi, $toReplace);

$doc->xinclude();
echo "No crash!";

With the following 2 XML files:

xinclude-fail-original.xml

<?xml version="1.0"?>
<root>
<child/>
</root>

xinclude-included.xml

<replaced>
  <somechild></somechild>
</replaced>

Resulted in this output:
Crash of the php-fpm child process, about 50% of the time. In the logs i could see 3 different errors depending on how i alter the XML files. The most common is:

• corrupted size vs. prev_size in fastbins

I also encountered:

• malloc_consolidate(): invalid chunk size
• free(): double free detected in tcache 2

Followed by:

• [28-Jun-2024 12:06:20] WARNING: [pool www] child 1088 exited on signal 6 (SIGABRT) after 475.706249 seconds from start
• [28-Jun-2024 12:06:20] NOTICE: [pool www] child 1100 started

But I expected this output instead:

No crash!

I was able to isolate this issue on PHP 8.2 in Docker Desktop on Apple Silicon (base image php:8.2-fpm). However we encountered the same error on different servers running our XML-based CMS on PHP 7.4. We switched from SLES (SUSE Support # 00520126: PHP-FPM process crash after SLES 15 SP4 upgrade) to CentOS thinking it was a distribution bug but could not fix it. PHP 7.4 in Docker (Desktop, Mac, WSL2 or SLES) however didn't seem to be affected by the issue.

PHP Version

PHP 8.2.20

Operating System

Docker image php:8.2-fpm