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Bug #48907 Apache restarts due to a regular expression
Submitted: 2009-07-13 19:35 UTC Modified: 2009-07-16 19:19 UTC
From: sworddragon2 at aol dot com Assigned:
Status: Not a bug Package: PCRE related
PHP Version: 5.3.0 OS: Windows XP Professional SP3
Private report: No CVE-ID: None
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 [2009-07-13 19:35 UTC] sworddragon2 at aol dot com 
Description:
------------
I found a regular expression with which i can restart the apache service with the notification: [notice] Parent: child process exited with status 3221225477 -- Restarting. I'm using Apache 2.2.11.

Reproduce code:
---------------
<?php
preg_replace('#a((?:.|\n)*?)a#','a$1a','a11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111a');
?>

Expected result:
----------------
I expected that preg_replace() repaces the string.

Actual result:
--------------
Apache restarts with the above message an Firefox 3.5 tells me that the connection to the server was recessed.

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 [2009-07-15 12:08 UTC] jani@php.net 
Exactly what PHP version are you using? This works fine on both 5.2.10 and 5.3.0 for me..
 [2009-07-16 00:56 UTC] sworddragon2 at aol dot com 
I'm using PHP 5.3.0 x86 VC6 Thread Safe. I have installed PHP 5.2.10 and can reproduce it too. After this i have installed PHP 5.3.0 again without any extensions and have used a standard php.ini and httpd.conf (just the entry from the PHP installer is written).

I have cleared the error.log from Apache and after executing the reproduce code the log says:

[Thu Jul 16 02:40:03 2009] [notice] Parent: child process exited with status 3221225477 -- Restarting.
httpd.exe: Could not reliably determine the server's fully qualified domain name, using 192.168.1.2 for ServerName
[Thu Jul 16 02:40:03 2009] [notice] Apache/2.2.11 (Win32) PHP/5.3.0 configured -- resuming normal operations
[Thu Jul 16 02:40:03 2009] [notice] Server built: Dec 10 2008 00:10:06
[Thu Jul 16 02:40:03 2009] [notice] Parent: Created child process 3196
httpd.exe: Could not reliably determine the server's fully qualified domain name, using 192.168.1.2 for ServerName
httpd.exe: Could not reliably determine the server's fully qualified domain name, using 192.168.1.2 for ServerName
[Thu Jul 16 02:40:03 2009] [notice] Child 3196: Child process is running
[Thu Jul 16 02:40:03 2009] [notice] Child 3196: Acquired the start mutex.
[Thu Jul 16 02:40:03 2009] [notice] Child 3196: Starting 64 worker threads.
[Thu Jul 16 02:40:03 2009] [notice] Child 3196: Starting thread to listen on port 80.


But i figured out another thing. If I'm changing the pattern from '#a((?:.|\n)*?)a#' to '#a((?:\n|.)*?)a#' all works fine. Oddly seems that Avira AntiVir Personal with the definition file from the last days and today says after saving the reproduce code that the file is a heuristic found HEUR/HTML.Malware.
 [2009-07-16 13:34 UTC] jani@php.net 
Check for these in your php.ini:

[Pcre]
;PCRE library backtracking limit.
; http://php.net/pcre.backtrack-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).
; http://php.net/pcre.recursion-limit
;pcre.recursion_limit=100000
 [2009-07-16 18:52 UTC] sworddragon2 at aol dot com 
In the PCRE block of my php.ini stands the same:

[Pcre]
;PCRE library backtracking limit.
; http://php.net/pcre.backtrack-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).
; http://php.net/pcre.recursion-limit
;pcre.recursion_limit=100000
 [2009-07-16 19:19 UTC] pajoye@php.net 
There was already many bug reports about this issue, that's not something we can change from php. See #47689.
 
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