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.
git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e
openwall.com/lists/oss-security/2011/03/02/1
openwall.com/lists/oss-security/2011/03/02/2
www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.38
bugzilla.redhat.com/show_bug.cgi?id=681575
lkml.org/lkml/2011/2/5/220