CVE request: kernel: taskstats local DoS

[Vasiliy Kulikov <segoon () openwall com>]

"Currently a single process may register exit handlers unlimited times.
It may lead to a bloated listeners chain and very slow process terminations.
E.g. after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of
kernel memory is stolen for the handlers chain and "time id" shows 2-7
seconds instead of normal 0.003.  It makes it possible to exhaust all
kernel memory and to eat much of CPU time by triggerring numerous exits
on a single CPU.

The patch limits the number of times a single process may register
itself on a single CPU to one."

It makes it possible for unprivileged user eat kernel memory and CPU
without triggering OOM killer.

Was introduced in f9fd8914c1acca0d98b69d831b128d5b52f03c51.

http://lists.openwall.net/linux-kernel/2011/06/16/605


Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments