2 Commits

Author	SHA1	Message	Date
Aleksa Sarai	ce52399520	cgroup: pids: fix invalid get/put usage ... Fix incorrect usage of css_get and css_put to put a different css in pids_{cancel_,}attach() than the one grabbed in pids_can_attach(). This could lead to quite serious memory leakage (and unsafe operations on the putted css). tj: minor comment update Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Tejun Heo <tj@kernel.org>	2015-08-25 14:19:25 -04:00
Aleksa Sarai	49b786ea14	cgroup: implement the PIDs subsystem ... Adds a new single-purpose PIDs subsystem to limit the number of tasks that can be forked inside a cgroup. Essentially this is an implementation of RLIMIT_NPROC that applies to a cgroup rather than a process tree. However, it should be noted that organisational operations (adding and removing tasks from a PIDs hierarchy) will *not* be prevented. Rather, the number of tasks in the hierarchy cannot exceed the limit through forking. This is due to the fact that, in the unified hierarchy, attach cannot fail (and it is not possible for a task to overcome its PIDs cgroup policy limit by attaching to a child cgroup -- even if migrating mid-fork it must be able to fork in the parent first). PIDs are fundamentally a global resource, and it is possible to reach PID exhaustion inside a cgroup without hitting any reasonable kmemcg policy. Once you've hit PID exhaustion, you're only in a marginally better state than OOM. This subsystem allows PID exhaustion inside a cgroup to be prevented. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> Signed-off-by: Tejun Heo <tj@kernel.org>	2015-07-14 17:29:23 -04:00