I ran across a bizarre problem today. I was editing a page. After clicking the button to publish, I got a blank screen. I looked in the Apache error log and found this error.

ALERT - linked list corrupt on efree() - heap corruption detected (attacker '<my ip address>', file '/path/to/index.php')

A Google search indicates that this is some kind of issue with APC that causes a seg fault, and the Suhosin patch in PHP catches it as a possible attack. Clearing the cache did not solve the problem, but restarting Apache did fix the problem (which released and recreated the cache).

I thought I would document this problem so that if someone else searches for it, they will find some information. Hopefully, this is a rare problem. I have not seen it, before. APC tells me that there is a newer version, but it is not available in the Debian stable release, yet.