/* * ns_cgroup.c - namespace cgroup subsystem * * Copyright 2006, 2007 IBM Corp */ #include <linux/module.h>#include <linux/cgroup.h>#include <linux/fs.h>#include <linux/proc_fs.h>#include <linux/slab.h>#include <linux/nsproxy.h> struct ns_cgroup {	struct cgroup_subsys_state css;}; 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, struct pid *pid){	char name[PROC_NUMBUF]; 	snprintf(name, PROC_NUMBUF, "%d", pid_vnr(pid));	return cgroup_clone(task, &ns_subsys, name);} /* * Rules: *   1. you can only enter a cgroup which is a descendant 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, bool threadgroup){	if (current != task) {		if (!capable(CAP_SYS_ADMIN))			return -EPERM; 		if (!cgroup_is_descendant(new_cgroup, current))			return -EPERM;	} 	if (!cgroup_is_descendant(new_cgroup, task))		return -EPERM; 	if (threadgroup) {		struct task_struct *c;		rcu_read_lock();		list_for_each_entry_rcu(c, &task->thread_group, thread_group) {			if (!cgroup_is_descendant(new_cgroup, c)) {				rcu_read_unlock();				return -EPERM;			}		}		rcu_read_unlock();	} 	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, current))		return ERR_PTR(-EPERM);	if (test_bit(CGRP_CLONE_CHILDREN, &cgroup->flags)) {		printk("ns_cgroup can't be created with parent "		       "'clone_children' set.\n");		return ERR_PTR(-EINVAL);	} 	printk_once("ns_cgroup deprecated: consider using the "		    "'clone_children' flag without the ns_cgroup.\n"); 	ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);	if (!ns_cgroup)		return ERR_PTR(-ENOMEM);	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,};