Published: 04 April 2011
fs/eventpoll.c in the Linux kernel before 2.6.38 places epoll file descriptors within other epoll data structures without properly checking for (1) closed loops or (2) deep chains, which allows local users to cause a denial of service (deadlock or stack memory consumption) via a crafted application that makes epoll_create and epoll_ctl system calls.
From the Ubuntu security team
Nelson Elhage discovered that the epoll subsystem did not correctly handle certain structures. A local attacker could create malicious requests that would hang the system, leading to a denial of service.