349021 - Browser hangs when running a specific regular expression

Status: RESOLVED INVALID

(Core :: JavaScript Engine, defect)

Description

[i-senso]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.6) Gecko/20060728 Firefox/1.5.0.6
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.6) Gecko/20060728 Firefox/1.5.0.6

When running a specific regexp against a specific text (see the example I gave), the browser seems to enter an infinite loop.
Notice that the same Regexp against other text, runs as expected.

Please contact me if I can help further.

Reproducible: Always

Steps to Reproduce:
1. Goto http://www.i-senso.com/ff-rx-bug.html;
2. Press GO, to execute the script that uses the regexp;
3. The scripts enters some kind of infinite loop.

Actual Results:  
The script never finishes. The browser locks.

Expected Results:  
The browser should enter some kind of infinite loop.

Run the regexp and stop running.

Comment 1

[Steve England [:stevee]]

Attachment: testcase from reporter's URL

Comment 2

[Steve England [:stevee]]

I see the hang with
Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.8.1b1) Gecko/20060817 BonEcho/2.0b1 ID:2006081703
and
Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.9a1) Gecko/20060816 Minefield/3.0a1
too.

Comment 3

[Brian Crowder]

This is simply a geometrically complex regular expression (worse than O(n^3)).  Using javascript.options.relimit = true in about:config will save you from it (ie., it will throw an exception)