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Bug #43117 using preg_replace count parameter (in wiki) causes total server meltdown
Submitted: 2007-10-27 18:21 UTC Modified: 2007-11-05 01:00 UTC
From: commentgg at hotmail dot com Assigned:
Status: No Feedback Package: Reproducible crash
PHP Version: 5.2.4 OS: Windows XP SP2
Private report: No CVE-ID: None
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 [2007-10-27 18:21 UTC] commentgg at hotmail dot com
Description:
------------
The wiki in development went from delivering total meltdown on the server to being very stable just by changing the code from:

  $n=0;
  preg_replace(/../,'..',$x,-1,$n);
  if($n) ..

to 

  $new = preg_replace(/../,'..',$x);
  if($new != $x) ..

I.e. do not use the count parameter! 



Reproduce code:
---------------
I can't give you any specifics yet, but I spent 3 days narrowing down and then having the above solve the problem for me. 

Sorry can't help you out better. 


Actual result:
--------------
  
Crashes brought the Apache webserver (not the absolute latest) down on my pre 5.2.4 version. Upgrading to the latest PHP (5.2.4) delivered a better experience as the server managed to recover. 

In both cases no error message was given. It all just ends in the Windows Application Crash - Send Report feedback loop dialog box. Twice. 

Maybe this is a PECL issue, but it is severe enough to warrant attention. 



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 [2007-10-27 19:12 UTC] scottmac@php.net
Thank you for this bug report. To properly diagnose the problem, we
need a short but complete example script to be able to reproduce
this bug ourselves. 

A proper reproducing script starts with <?php and ends with ?>,
is max. 10-20 lines long and does not require any external 
resources such as databases, etc. If the script requires a 
database to demonstrate the issue, please make sure it creates 
all necessary tables, stored procedures etc.

Please avoid embedding huge scripts into the report.
 [2007-11-05 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".
 
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