[#MDL-11237] preg_xxxx() critical bug under PHP 5.2.4, tests required...

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Key:	MDL-11237
Type:	Bug
Status:	Resolved
Resolution:	Fixed
Priority:	Critical
Assignee:	Martin Dougiamas
Reporter:	Eloy Lafuente (stronk7)
Votes:	1
Watchers:	2

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Moodle

preg_xxxx() critical bug under PHP 5.2.4, tests required...

Created: 13/Sep/07 07:46 AM Updated: 29/Sep/07 03:08 AM

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Component/s:

Unknown

Affects Version/s:

1.7.3, 1.8.3, 1.9

Fix Version/s:

1.7.3, 1.8.3, 1.9

File Attachments:

preg_match_all_test.php (0.6 kB)

Environment:

PHP 5.2.4

Issue Links:

Duplicate

This issue is duplicated by:

~~MDL-11502~~ HTML files will not display if >100KB and filteruploadedfiles setting is set to "HTML files only" or "All files"

Participants:	Eloy Lafuente (stronk7), Martin Dougiamas, Penny Leach and Petr Skoda
Security Level:	None
Resolved date:	25/Sep/07
Affected Branches:	MOODLE_17_STABLE, MOODLE_18_STABLE, MOODLE_19_STABLE
Fixed Branches:	MOODLE_17_STABLE, MOODLE_18_STABLE, MOODLE_19_STABLE

Description

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I was trying to detect why one MSSQL server was causing a lot of problems with simple SQLs when I've discovered that the root of the problem was that one preg_match_all() function wasn't performing its job under BIG texts.

I've attached one script (preg_match_all_test.php) that reproduce the problem in my system. Curiously, the limit seems to be 99998 chars. By adding one more char (99999) the function doesn't work properly.

It's a major problem because it can break tons of things (the mssql_n driver, backup & restore relinking, filters...) potentially anything trying to grep over more than 99998 chars.

Please, can you execute the script and add your results here? TIA!

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Eloy Lafuente (stronk7) added a comment - 13/Sep/07 07:51 AM

Some results:

PHP: 5.2.4
OS: Darwin mbp 8.10.1 Darwin Kernel Version 8.10.1: Wed May 23 16:33:00 PDT 2007; root:xnu-792.22.5~1/RELEASE_I386 i386
ERROR, preg_match_all() has NOT been able to capture one text of 99999 bytes.

PHP: 5.1.6
OS: Darwin mbp 8.10.1 Darwin Kernel Version 8.10.1: Wed May 23 16:33:00 PDT 2007; root:xnu-792.22.5~1/RELEASE_I386 i386
OK, preg_match_all() has been able to capture one text of 99999 bytes.

PHP: 4.3.10
OS: Darwin mbp 8.10.1 Darwin Kernel Version 8.10.1: Wed May 23 16:33:00 PDT 2007; root:xnu-792.22.5~1/RELEASE_I386 i386
OK, preg_match_all() has been able to capture one text of 99999 bytes.

[ Permalink | « Hide ]

Penny Leach added a comment - 13/Sep/07 08:01 AM

PHP: 5.2.0-8+etch7

OS: Linux build 2.6.18-4-vserver-686 #1 SMP Thu May 10 01:37:59 UTC 2007 i686

ERROR, preg_match_all() has NOT been able to capture one text of 99999 bytes

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Eloy Lafuente (stronk7) added a comment - 13/Sep/07 08:41 AM

Bah!

It seems that, since 5.2.0 it's necessary to adjust the "pcre.backtrack_limit' setting to allow more chars to be returned (in ungreedy matches). So, something like:

ini_set('pcre.backtrack_limit', 20971520); /// 20 MB

will allow up to 20MB of text to be matched.

So, I' would vote to add it to all branches ASAP, or the problem will be breaking a lot of things.

Bah!

Thanks to Penny and Matt!

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Eloy Lafuente (stronk7) added a comment - 13/Sep/07 08:47 AM

To have everything inter-linked, this is the bug i submitted to PHP:

http://bugs.php.net/bug.php?id=42649

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Martin Dougiamas added a comment - 13/Sep/07 02:43 PM

I've added this to HEAD for a bit of testing before backporting to other branches.

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Petr Skoda added a comment - 25/Sep/07 12:28 AM

PHP: 5.2.4
OS: Linux nahore 2.6.22.5-23-default #1 SMP 2007/09/18 05:23:45 UTC i686
ERROR, preg_match_all() has NOT been able to capture one text of 99999 bytes.

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