After upgrading to Nginx 1.4.7 and PHP 5.4.28 (or 5.5.12), you may start seeing errors like the following:
2014/05/03 13:27:41 [crit] 4202#0: *1 connect() to unix:/var/run/php5-fpm.sock failed (13: Permission denied) while connecting to upstream, client: xx.xxx.xx.xx, server: localhost, request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "xx.xx.xx.xx"
The fix is to edit /etc/php5/fpm/pool.d/www.conf and set the listen.mode to 666 (be sure to uncomment the line as well):
listen.mode = 0666
Ramblings on startups, NYC, advertising and hacking (mostly Python) 
Thanks. None of the other solutions I found online fixed this problem.
Thanx, it works.
Thanks this also fixed my problem. The other solutions like setting listen to 127.0.0.1:9000 also worked but that isn’t a real solution to the problem. Your solution is the real solution!
Thanks again.
Kind regards,
Sander
Thank you for this solution.
Check which user runs nginx. As of Ubuntu 12.04 nginx runs by nginx user which is not a member of www-data group.
sudo usermod -a -G www-data nginx
and restarting nginx and php5-fpm daemons solves the problem.