[linux.git] / kernel / ns_cgroup.c

/*
 * 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,
};
Commit	Line	Data
858d72ea SH	1	/*
	2	* ns_cgroup.c - namespace cgroup subsystem
	3	*
	4	* Copyright 2006, 2007 IBM Corp
	5	*/
	6
	7	#include <linux/module.h>
	8	#include <linux/cgroup.h>
	9	#include <linux/fs.h>
	10
	11	struct ns_cgroup {
	12	struct cgroup_subsys_state css;
	13	spinlock_t lock;
	14	};
	15
	16	struct cgroup_subsys ns_subsys;
	17
	18	static inline struct ns_cgroup *cgroup_to_ns(
	19	struct cgroup *cgroup)
	20	{
	21	return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
	22	struct ns_cgroup, css);
	23	}
	24
	25	int ns_cgroup_clone(struct task_struct *task)
	26	{
	27	return cgroup_clone(task, &ns_subsys);
	28	}
	29
	30	/*
	31	* Rules:
	32	* 1. you can only enter a cgroup which is a child of your current
	33	* cgroup
	34	* 2. you can only place another process into a cgroup if
	35	* a. you have CAP_SYS_ADMIN
	36	* b. your cgroup is an ancestor of task's destination cgroup
	37	* (hence either you are in the same cgroup as task, or in an
	38	* ancestor cgroup thereof)
	39	*/
	40	static int ns_can_attach(struct cgroup_subsys *ss,
	41	struct cgroup new_cgroup, struct task_struct task)
	42	{
	43	struct cgroup *orig;
	44
	45	if (current != task) {
	46	if (!capable(CAP_SYS_ADMIN))
	47	return -EPERM;
	48
	49	if (!cgroup_is_descendant(new_cgroup))
	50	return -EPERM;
	51	}
	52
	53	if (atomic_read(&new_cgroup->count) != 0)
	54	return -EPERM;
	55
	56	orig = task_cgroup(task, ns_subsys_id);
	57	if (orig && orig != new_cgroup->parent)
	58	return -EPERM;
	59
	60	return 0;
	61	}
	62
	63	/*
	64	* Rules: you can only create a cgroup if
65	* 1. you are capable(CAP_SYS_ADMIN)
66	* 2. the target cgroup is a descendant of your own cgroup
67	*/
68	static struct cgroup_subsys_state ns_create(struct cgroup_subsys ss,
69	struct cgroup *cgroup)
70	{
71	struct ns_cgroup *ns_cgroup;
72
73	if (!capable(CAP_SYS_ADMIN))
74	return ERR_PTR(-EPERM);
75	if (!cgroup_is_descendant(cgroup))
76	return ERR_PTR(-EPERM);
77
78	ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
79	if (!ns_cgroup)
80	return ERR_PTR(-ENOMEM);
81	spin_lock_init(&ns_cgroup->lock);
82	return &ns_cgroup->css;
83	}
84
85	static void ns_destroy(struct cgroup_subsys *ss,
86	struct cgroup *cgroup)
87	{
88	struct ns_cgroup *ns_cgroup;
89
90	ns_cgroup = cgroup_to_ns(cgroup);
91	kfree(ns_cgroup);
92	}
93
94	struct cgroup_subsys ns_subsys = {
95	.name = "ns",
96	.can_attach = ns_can_attach,
97	.create = ns_create,
98	.destroy = ns_destroy,
99	.subsys_id = ns_subsys_id,
100	};