I'm running Ubuntu 8.04.4 LTS and Piwik 1.4 and the problem persists, even after the fixes given in this thread. (ie. installing the latest php packages, malloc_check etc).
Database Connector is PDO_MYSQL (with MYSQLI I get Apache Segfaults for every request), PHP is loaded is a module. I don't use Zend Cache but php5_xcache.
The problem seems to have somewhat shifted. With 1.3 I would get messages like this
ALERT - canary mismatch on efree() - heap overflow detected (attacker '220.127.116.11', file '/var/www/www_v2/app/webroot/piwik/piwik.php')
With 1.4 these messages have dissappeared but after about 24h of continuous operation I start getting efree messages on all sorts of random files from my website
ALERT - canary mismatch on efree() - heap overflow detected (attacker '18.104.22.168', file '/var/www/www_v2/app/views/layouts/fullscreen_v2.ctp', line 41)
This is a file from CakePHP, the site has been running this system for over a year now and never did it have any problems in it. After about 20 lines like these, apache stalls. It is still running but only returns empty replies. After restarting Apache, the site is fully operational again.
I'm positive that this has something to do with Piwik, because when I disable it, all of this doesn't happen.
So guys, please admit ... who broke it
I'm just kidding, this seems to have something to do with a heap/memory corruption but this is really outside of my knowledge of PHP
All the best and thanks for this awesome software!