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Bug #49697 preg_replace crashes my system.
Submitted: 2009-09-28 05:26 UTC Modified: 2010-06-22 00:26 UTC
From: donquixote dot phplist at googlemail dot com Assigned:
Status: Not a bug Package: PCRE related
PHP Version: 5.2.11 OS: Windows XP
Private report: No CVE-ID: None
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From: donquixote dot phplist at googlemail dot com
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 [2009-09-28 05:26 UTC] donquixote dot phplist at googlemail dot com 
Description:
------------
I found a regex / text combination that causes my apache to crash / restart with preg_replace. The example is a reduced version of Drupal's CSS compression regex.

The regex is not overly complex, and the text is not overly long.

Reproducing this depends on system configuration: On my webspace it does not crash.
But, on my localhost it always crashes with this regex / text combination. Removing a few letters in the text (no matter which) makes the bug not happen.

More info in the linked file.

So:
It seems that preg_replace is not the most robust piece of code. No matter what you feed it, it should never ever crash!

And, btw:
I was going to report this as a comment on http://bugs.php.net/bug.php?id=46551, but the comment form results in an error page.
("Authentication failed: Incorrect username 
Warning: Cannot modify header information - headers already sent by (output started at /home/Web/sites/php-bugs-web/include/auth.inc:30) in /home/Web/sites/php-bugs-web/bug.php on line 232")

Reproduce code:
---------------
standalone script at
http://drupal.org/files/issues/test.php__1.txt

posted here
http://drupal.org/node/444228#comment-2089300

Expected result:
----------------
preg_replace should do its job (compressing the CSS).
Or show a meaningful error message, if there is a valid reason why this is not possible.

Actual result:
--------------
Apache crash / restart, with no useful error message in error.log, except the usual restart messages.

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 [2009-09-28 06:57 UTC] jani@php.net 
From php.ini-dist:

[Pcre]
;PCRE library backtracking limit.
;pcre.backtrack_limit=100000

;PCRE library recursion limit. 
;Please note that if you set this value to a high number you may consume all 
;the available process stack and eventually crash PHP (due to reaching the 
;stack size limit imposed by the Operating System).
;pcre.recursion_limit=100000

So you should tune these to be such that it won't crash anymore.
 [2009-10-06 01:00 UTC] php-bugs at lists dot php dot net 
No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".
 [2010-04-25 20:53 UTC] felipe@php.net 
Not a PHP bug.
 [2010-06-22 00:26 UTC] felipe@php.net
-Status: No Feedback +Status: Bogus
 [2010-06-22 00:26 UTC] felipe@php.net 
.
 
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