CVE request: kernel: Multiple DoS issues in epoll

[Nelson Elhage <nelhage () ksplice com>]

Two requests for bugs in epoll:

(1) The epoll subsystem in Linux did not prevent users from creating circular
epoll file structures, potentially leading to a denial of service (kernel
deadlock).

Reference: https://lkml.org/lkml/2011/2/5/220
Upstream commit: http://git.kernel.org/linus/22bacca48a1755f79b7e0f192ddb9fbb7fc6e64e

(2) The epoll subsystem allows users to create large nested epoll structures,
which the kernel will then to walk with preemption disabled, causing a denial of
service via excessive CPU consumption in the kernel.

References:
http://thread.gmane.org/gmane.linux.kernel/1105744
http://thread.gmane.org/gmane.linux.kernel/1105744/focus=1105888

No upstream fix yet for this one.

- Nelson