/* * ns_cgroup.c - namespace cgroup subsystem * * Copyright 2006, 2007 IBM Corp */ #include <linux/module.h> #include <linux/cgroup.h> #include <linux/fs.h> struct ns_cgroup { struct cgroup_subsys_state css; spinlock_t lock; }; struct cgroup_subsys ns_subsys; static inline struct ns_cgroup *cgroup_to_ns( struct cgroup *cgroup) { return container_of(cgroup_subsys_state(cgroup, ns_subsys_id), struct ns_cgroup, css); } int ns_cgroup_clone(struct task_struct *task) { return cgroup_clone(task, &ns_subsys); } /* * Rules: * 1. you can only enter a cgroup which is a child of your current * cgroup * 2. you can only place another process into a cgroup if * a. you have CAP_SYS_ADMIN * b. your cgroup is an ancestor of task's destination cgroup * (hence either you are in the same cgroup as task, or in an * ancestor cgroup thereof) */ static int ns_can_attach(struct cgroup_subsys *ss, struct cgroup *new_cgroup, struct task_struct *task) { struct cgroup *orig; if (current != task) { if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (!cgroup_is_descendant(new_cgroup)) return -EPERM; } if (atomic_read(&new_cgroup->count) != 0) return -EPERM; orig = task_cgroup(task, ns_subsys_id); if (orig && orig != new_cgroup->parent) return -EPERM; return 0; } /* * Rules: you can only create a cgroup if * 1. you are capable(CAP_SYS_ADMIN) * 2. the target cgroup is a descendant of your own cgroup */ static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss, struct cgroup *cgroup) { struct ns_cgroup *ns_cgroup; if (!capable(CAP_SYS_ADMIN)) return ERR_PTR(-EPERM); if (!cgroup_is_descendant(cgroup)) return ERR_PTR(-EPERM); ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL); if (!ns_cgroup) return ERR_PTR(-ENOMEM); spin_lock_init(&ns_cgroup->lock); return &ns_cgroup->css; } static void ns_destroy(struct cgroup_subsys *ss, struct cgroup *cgroup) { struct ns_cgroup *ns_cgroup; ns_cgroup = cgroup_to_ns(cgroup); kfree(ns_cgroup); } struct cgroup_subsys ns_subsys = { .name = "ns", .can_attach = ns_can_attach, .create = ns_create, .destroy = ns_destroy, .subsys_id = ns_subsys_id, };