Bug: Treeview plugin can cause apache to hang

If a twiki user creates a loop of topic parents, the display of tree view outline mode causes apache to hang due to out of memory error.

Reported error in apache log:
[Tue Mar 29 07:17:11 2005] view: Deep recursion on subroutine "TWiki::Plugins::TreePlugin::ImgNodeFormatter::isNodeLast" at ../lib/TWiki/Plugins/TreePlugin/ImgNodeFormatter.pm line 247., referer: http://twiki.corp.purisma.com/do/search/Howto/?search=CategoryDevEnv&web=Howto&scope=all

Test case

Create three topics:

• CategoryOne has topic parent of CategoryTwo
• CategoryTwo has topic parent of CategoryThree
• CategoryThree has topic parent of CategoryOne

Now the tree view of this is not possible: it is an infinite loop.

The code in Cairo release of TreePlugin does not detect this case and does an infinite recursion. Using apache+speedycgi, twiki hangs with cpu at 100% until apache is killed.

The specific treeview we used was this: %TREEVIEW{topic="CategoryTwo" stoplevel="3" formatting="imageoutline:thread"}%

NOTE: once this kind of rendering problem is introduced, twiki 'search' is not usable since it also seems to trigger the bug.

Environment

-- StanleyKnutson - 30 Mar 2005

Impact and Available Solutions

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