[wp-trac] [WordPress Trac] #39338: class-wp-hook.php - apply_filters() infinite loop

[WordPress Trac]

#39338: class-wp-hook.php - apply_filters() infinite loop
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 Reporter:  frettled      |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  Future Release
Component:  Plugins       |     Version:  4.7
 Severity:  critical      |  Resolution:
 Keywords:  has-patch     |     Focuses:
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Changes (by frettled):

 * keywords:  needs-patch => has-patch


Comment:

 Replying to [comment:45 dd32]:

 > (edit: Strange observation: This shouldn't be possible to trigger on PHP
 5.2, as `next()` will return `false` on the invalid inputs there, and exit
 the loop)

 No, that's not how next() works in PHP.

 Here's a very simple test for you:

 {{{#!php
 <?php
 $var = NULL;
 $n = 0;
 while ($n < 10 && false !== next($var)) {
     $n++;
     echo $n;
 }
 }}}

 This produces an infinite loop in PHP 5.x and 7.x, only by the kindness of
 the check for $n, your screen's scrollback won't fill infinitely.

 My patch works. If it breaks something that you avoid an infinite loop
 instead of having a log-filling, CPU-gobbling infinite loop, that's
 **perfectly fine**. It's better that the code crashes.

 If Wordpress has some sort of error handler that can be invoked in the
 case that the "impossible" (yet prevalent) NULL condition occurs, invoking
 it at that time seems like a good idea.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/39338#comment:51>
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