PHP Segmentation fault during preg_replace

Question

I'm using Magento and got PHP Segmentation fault during rollback database from admin. I make and investigation and see that the reason is such line:

preg_replace("/'(\\'|\\\\{2}|[^'])*'/", '', $sql);

$sql string is big enough, I'm attaching it.

https://drive.google.com/file/d/0B9UbKYbywcABOTRSVG5KRl9La0k/edit?usp=sharing

You may use such script to reproduce the problem:

<?php
    $test = file_get_contents('test.txt');
    $sql = preg_replace("/'(\\'|\\\\{2}|[^'])*'/", '', $test);

May be somebody knows about this problem and can help me to solve it?

P.S. Class that directly causes the problem is abstract class Zend_Db_Statement 204:208

This is not my code. This is code from Magento, it uses it to rollback own backups (SQL). It goes throw statements one by one and execute it using Zend Framework. On my server (and some others) rollback does not work, so I tried to localize the problem. After investigation I understood that problem is in preg_replace. — freento
– freento, Commented Dec 23, 2013 at 20:58

bahoo · Accepted Answer · 2014-02-13 04:22:49Z

5

I've been struggling with this myself, and stumbled upon this thread which recommends changing a php.ini value:

http://zend-framework-community.634137.n4.nabble.com/Fixing-Zend-Db-Statement-stripQuoted-seg-faults-on-large-SQL-strings-in-ZF-1-x-td4648143.html

[PCRE]
pcre.recursion_limit = 1000

Works like a charm for me. Hope this helps!

Edit: also available in convenient .htaccess format:

php_value pcre.recursion_limit 1000

answered Feb 13, 2014 at 4:22

bahoo

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STW Over a year ago

+1 - I encountered this issue when a module's upgrade script ran a large preg_replace() call; lowering the recursion limit cleared up the segfault and let the module upgrade successfully

Lajos Veres · Accepted Answer · 2013-12-23 20:58:40Z

0

Base on this article: http://man.he.net/man3/pcrestack

You can try to modify the regexp to use less stack.

I would try something similar for example:

preg_replace("/'([^']+|\\'|\\\\{2})*'/", '', $sql);

Or here: https://bugs.php.net/bug.php?id=61579

They mention these two alternatives also:

"/'(\\\\'|\\\\{2}|[^']+)*'/"

"/'[^'\\\\]*(?:\\\\.[^'\\\\]*)*'/"

answered Dec 23, 2013 at 20:58

Lajos Veres

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1 Comment

STW Over a year ago

The OP's question relates to a piece of core (do not ever, ever, ever touch) Magento code; altering the RegEx might work but should be the extreme last-resort.

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