SID-01595: infinite loop pattern in Webnotify

Status:	Answered	TWiki version:	5.1.2	Perl version:	5.014002 (linux)
Category:	CategoryEmail	Server OS:	Linux 2.6.42-26-generic (x86_64-linux-gnu-thread-multi)	Last update:	13 years ago

Created a cron job for notifications but am getting the following error

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(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))))))))))))))+ matches null string many times in regex; marked by <-- HERE in m/^\s+\*\s(?^l:(?:Main\.)?)((?^::upper:+:digit:+:upper:+:digit:*))\s+\-\s+((?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))))))))))))))+ <-- HERE )\s*$/ at /var/www/twiki/lib/TWiki/Contrib/MailerContrib/WebNotify.pm line 360 (#1) (W regexp) The pattern you've specified would be an infinite loop if the regular expression engine didn't specifically check for that. The <-- HERE shows in the regular expression about where the problem was discovered. See perlre.

[Thu Nov 29 18:05:01 2012] mailnotify: (?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))))))))))))))+ matches null string many times in regex; marked by <-- HERE in m/^\s+\*\s(?^l:(?:Main\.)?)((?^::upper:+:digit:+:upper:+:digit:*))\s+\-\s+((?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))))))))))))))+ <-- HERE )\s*$/ at /var/www/twiki/lib/TWiki/Contrib/MailerContrib/WebNotify.pm line 360.

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-- LeoList - 2012-11-29

Discussion and Answer

command in cron is

5 * * * * cd /var/www/twiki && perl -I bin tools/mailnotify -q

-- LeoList - 2012-11-29

Not sure, but it might be related to this: I have seen in certain environments (don't know which ones, may be Perl version?) where the configure script adds a strange (?^: ... ) sequence to some variables each time the configure values are saved. Compare twiki/lib/LocalSite.cfg with the default values in twiki/lib/TWiki.spec.

-- PeterThoeny - 2012-11-30

This seems to be Perl 5.14 related. I created TWikibug:Item7067 to track this.

-- PeterThoeny - 2012-11-30

Please apply patch posted at TWikibug:Item7067, run configure, save a change, and let me know if this fixes the issue.

-- PeterThoeny - 2012-11-30

Ok. applied the patch; unfortunately i t made no difference (at least not initially).

Searched a bit more and found that a new installation had a different mailercontrib emailfilter

On the site with the infinite loop it was (?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))))))))))))))))))))

On the new site (fresh install) it was (?^:(?^:(?^:(?^:(?^:(?^:))))))

When I deleted the filter altogether the infinite loop disappeard; now I don't know if this is due to the filter or the patch, but its better. I do howeber get this message

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(?^:(?^:))+ matches null string many times in regex; marked by <-- HERE in
m/^\s+\*\s(?^l:(?:Main\.)?)((?^::upper:+:digit:+:upper:+:digit:*))\s+\-\s+((?^:(?^:))+ <-- HERE )\s*$/ at /var/www/twiki/lib/TWiki/Contrib/MailerContrib/WebNotify.pm line 360 (#1)
(W regexp) The pattern you've specified would be an infinite loop if the
regular expression engine didn't specifically check for that. The <-- HERE
shows in the regular expression about where the problem was discovered.
See perlre.

[Mon Dec 3 12:00:01 2012] mailnotify: (?^:(?^:))+ matches null string many times in regex; marked by <-- HERE in m/^\s+\*\s(?^l:(?:Main\.)?)((?^::upper:+:digit:+:upper:+:digit:*))\s+\-\s+((?^:(?^:))+ <-- HERE )\s*$/ at /var/www/twiki/lib/TWiki/Contrib/MailerContrib/WebNotify.pm line 360.

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BTW, clearing the filer and saving the config makes the filter (?^:(?^:))next time I come in

-- LeoList - 2012-12-03

Do you need more info. I'm still getting this warning, but emails are sent anyway

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(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))+ matches null string many times in regex; marked by <-- HERE in m/^\s+\*\s(?^l:(?:Main\.)?)((?^::upper:+:digit:+:upper:+:digit:*))\s+\-\s+((?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))+ <-- HERE )\s*$/ at /var/www/twiki/lib/TWiki/Contrib/MailerContrib/WebNotify.pm line 360 (#1) (W regexp) The pattern you've specified would be an infinite loop if the regular expression engine didn't specifically check for that. The <-- HERE shows in the regular expression about where the problem was discovered. See perlre.

[Wed Dec 5 09:01:01 2012] mailnotify: (?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))+ matches null string many times in regex; marked by <-- HERE in m/^\s+\*\s(?^l:(?:Main\.)?)((?^::upper:+:digit:+:upper:+:digit:*))\s+\-\s+((?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:(?^:))))))))))+ <-- HERE )\s*$/ at /var/www/twiki/lib/TWiki/Contrib/MailerContrib/WebNotify.pm line 360.

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Thanks

-- LeoList - 2012-12-04

Leo, I re-read the code, and I added manually a (?^:(?^:xxxxx)) to a regex type value in LocalSite.cfg. It all looks kosher, e.g. the extra (?^:(?^:)) gets removed and only xxxxx remains. Can you verify that the patch is applied properly? Specifically code cleanup should be in 3 locations:

• TWiki::Configure::Valuer -- SVN05x01:core/lib/TWiki/Configure/Valuer.pm
  • sub _getValue
• TWiki::Configure::Types::REGEX -- SVN05x01:core/lib/TWiki/Configure/Types/REGEX.pm
  • sub string2value
  • sub equals

Try also to manually cleanup the regexes in LocalSite.cfg.

-- PeterThoeny - 2012-12-05

Have applied the above patches and can confirm that the warnings have disappeared and this now works as expected.

Thanks,

Leo

-- LeoList - 2012-12-06

I am glad it worked out. Marking TWikibug:Item7067 as done.

-- PeterThoeny - 2012-12-06

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