[linux-2.6-block.git] / kernel / pid_namespace.c

/*
 * Pid namespaces
 *
 * Authors:
 *    (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
 *    (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
 *     Many thanks to Oleg Nesterov for comments and help
 *
 */

#include <linux/pid.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <linux/syscalls.h>
#include <linux/err.h>
#include <linux/acct.h>
#include <linux/slab.h>
#include <linux/proc_ns.h>
#include <linux/reboot.h>
#include <linux/export.h>

struct pid_cache {
	int nr_ids;
	char name[16];
	struct kmem_cache *cachep;
	struct list_head list;
};

static LIST_HEAD(pid_caches_lh);
static DEFINE_MUTEX(pid_caches_mutex);
static struct kmem_cache *pid_ns_cachep;

/*
 * creates the kmem cache to allocate pids from.
 * @nr_ids: the number of numerical ids this pid will have to carry
 */

static struct kmem_cache *create_pid_cachep(int nr_ids)
{
	struct pid_cache *pcache;
	struct kmem_cache *cachep;

	mutex_lock(&pid_caches_mutex);
	list_for_each_entry(pcache, &pid_caches_lh, list)
		if (pcache->nr_ids == nr_ids)
			goto out;

	pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
	if (pcache == NULL)
		goto err_alloc;

	snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
	cachep = kmem_cache_create(pcache->name,
			sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
			0, SLAB_HWCACHE_ALIGN, NULL);
	if (cachep == NULL)
		goto err_cachep;

	pcache->nr_ids = nr_ids;
	pcache->cachep = cachep;
	list_add(&pcache->list, &pid_caches_lh);
out:
	mutex_unlock(&pid_caches_mutex);
	return pcache->cachep;

err_cachep:
	kfree(pcache);
err_alloc:
	mutex_unlock(&pid_caches_mutex);
	return NULL;
}

static void proc_cleanup_work(struct work_struct *work)
{
	struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
	pid_ns_release_proc(ns);
}

/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
#define MAX_PID_NS_LEVEL 32

static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
	struct pid_namespace *parent_pid_ns)
{
	struct pid_namespace *ns;
	unsigned int level = parent_pid_ns->level + 1;
	int i;
	int err;

	if (level > MAX_PID_NS_LEVEL) {
		err = -EINVAL;
		goto out;
	}

	err = -ENOMEM;
	ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
	if (ns == NULL)
		goto out;

	ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
	if (!ns->pidmap[0].page)
		goto out_free;

	ns->pid_cachep = create_pid_cachep(level + 1);
	if (ns->pid_cachep == NULL)
		goto out_free_map;

	err = ns_alloc_inum(&ns->ns);
	if (err)
		goto out_free_map;
	ns->ns.ops = &pidns_operations;

	kref_init(&ns->kref);
	ns->level = level;
	ns->parent = get_pid_ns(parent_pid_ns);
	ns->user_ns = get_user_ns(user_ns);
	ns->nr_hashed = PIDNS_HASH_ADDING;
	INIT_WORK(&ns->proc_work, proc_cleanup_work);

	set_bit(0, ns->pidmap[0].page);
	atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);

	for (i = 1; i < PIDMAP_ENTRIES; i++)
		atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);

	return ns;

out_free_map:
	kfree(ns->pidmap[0].page);
out_free:
	kmem_cache_free(pid_ns_cachep, ns);
out:
	return ERR_PTR(err);
}

static void delayed_free_pidns(struct rcu_head *p)
{
	kmem_cache_free(pid_ns_cachep,
			container_of(p, struct pid_namespace, rcu));
}

static void destroy_pid_namespace(struct pid_namespace *ns)
{
	int i;

	ns_free_inum(&ns->ns);
	for (i = 0; i < PIDMAP_ENTRIES; i++)
		kfree(ns->pidmap[i].page);
	put_user_ns(ns->user_ns);
	call_rcu(&ns->rcu, delayed_free_pidns);
}

struct pid_namespace *copy_pid_ns(unsigned long flags,
	struct user_namespace *user_ns, struct pid_namespace *old_ns)
{
	if (!(flags & CLONE_NEWPID))
		return get_pid_ns(old_ns);
	if (task_active_pid_ns(current) != old_ns)
		return ERR_PTR(-EINVAL);
	return create_pid_namespace(user_ns, old_ns);
}

static void free_pid_ns(struct kref *kref)
{
	struct pid_namespace *ns;

	ns = container_of(kref, struct pid_namespace, kref);
	destroy_pid_namespace(ns);
}

void put_pid_ns(struct pid_namespace *ns)
{
	struct pid_namespace *parent;

	while (ns != &init_pid_ns) {
		parent = ns->parent;
		if (!kref_put(&ns->kref, free_pid_ns))
			break;
		ns = parent;
	}
}
EXPORT_SYMBOL_GPL(put_pid_ns);

void zap_pid_ns_processes(struct pid_namespace *pid_ns)
{
	int nr;
	int rc;
	struct task_struct *task, *me = current;
	int init_pids = thread_group_leader(me) ? 1 : 2;

	/* Don't allow any more processes into the pid namespace */
	disable_pid_allocation(pid_ns);

	/* Ignore SIGCHLD causing any terminated children to autoreap */
	spin_lock_irq(&me->sighand->siglock);
	me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
	spin_unlock_irq(&me->sighand->siglock);

	/*
	 * The last thread in the cgroup-init thread group is terminating.
	 * Find remaining pid_ts in the namespace, signal and wait for them
	 * to exit.
	 *
	 * Note:  This signals each threads in the namespace - even those that
	 * 	  belong to the same thread group, To avoid this, we would have
	 * 	  to walk the entire tasklist looking a processes in this
	 * 	  namespace, but that could be unnecessarily expensive if the
	 * 	  pid namespace has just a few processes. Or we need to
	 * 	  maintain a tasklist for each pid namespace.
	 *
	 */
	read_lock(&tasklist_lock);
	nr = next_pidmap(pid_ns, 1);
	while (nr > 0) {
		rcu_read_lock();

		task = pid_task(find_vpid(nr), PIDTYPE_PID);
		if (task && !__fatal_signal_pending(task))
			send_sig_info(SIGKILL, SEND_SIG_FORCED, task);

		rcu_read_unlock();

		nr = next_pidmap(pid_ns, nr);
	}
	read_unlock(&tasklist_lock);

	/* Firstly reap the EXIT_ZOMBIE children we may have. */
	do {
		clear_thread_flag(TIF_SIGPENDING);
		rc = sys_wait4(-1, NULL, __WALL, NULL);
	} while (rc != -ECHILD);

	/*
	 * sys_wait4() above can't reap the TASK_DEAD children.
	 * Make sure they all go away, see free_pid().
	 */
	for (;;) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		if (pid_ns->nr_hashed == init_pids)
			break;
		schedule();
	}
	__set_current_state(TASK_RUNNING);

	if (pid_ns->reboot)
		current->signal->group_exit_code = pid_ns->reboot;

	acct_exit_ns(pid_ns);
	return;
}

#ifdef CONFIG_CHECKPOINT_RESTORE
static int pid_ns_ctl_handler(struct ctl_table *table, int write,
		void __user *buffer, size_t *lenp, loff_t *ppos)
{
	struct pid_namespace *pid_ns = task_active_pid_ns(current);
	struct ctl_table tmp = *table;

	if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
		return -EPERM;

	/*
	 * Writing directly to ns' last_pid field is OK, since this field
	 * is volatile in a living namespace anyway and a code writing to
	 * it should synchronize its usage with external means.
	 */

	tmp.data = &pid_ns->last_pid;
	return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
}

extern int pid_max;
static int zero = 0;
static struct ctl_table pid_ns_ctl_table[] = {
	{
		.procname = "ns_last_pid",
		.maxlen = sizeof(int),
		.mode = 0666, /* permissions are checked in the handler */
		.proc_handler = pid_ns_ctl_handler,
		.extra1 = &zero,
		.extra2 = &pid_max,
	},
	{ }
};
static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
#endif	/* CONFIG_CHECKPOINT_RESTORE */

int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
{
	if (pid_ns == &init_pid_ns)
		return 0;

	switch (cmd) {
	case LINUX_REBOOT_CMD_RESTART2:
	case LINUX_REBOOT_CMD_RESTART:
		pid_ns->reboot = SIGHUP;
		break;

	case LINUX_REBOOT_CMD_POWER_OFF:
	case LINUX_REBOOT_CMD_HALT:
		pid_ns->reboot = SIGINT;
		break;
	default:
		return -EINVAL;
	}

	read_lock(&tasklist_lock);
	force_sig(SIGKILL, pid_ns->child_reaper);
	read_unlock(&tasklist_lock);

	do_exit(0);

	/* Not reached */
	return 0;
}

static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
{
	return container_of(ns, struct pid_namespace, ns);
}

static struct ns_common *pidns_get(struct task_struct *task)
{
	struct pid_namespace *ns;

	rcu_read_lock();
	ns = task_active_pid_ns(task);
	if (ns)
		get_pid_ns(ns);
	rcu_read_unlock();

	return ns ? &ns->ns : NULL;
}

static void pidns_put(struct ns_common *ns)
{
	put_pid_ns(to_pid_ns(ns));
}

static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
{
	struct pid_namespace *active = task_active_pid_ns(current);
	struct pid_namespace *ancestor, *new = to_pid_ns(ns);

	if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
		return -EPERM;

	/*
	 * Only allow entering the current active pid namespace
	 * or a child of the current active pid namespace.
	 *
	 * This is required for fork to return a usable pid value and
	 * this maintains the property that processes and their
	 * children can not escape their current pid namespace.
	 */
	if (new->level < active->level)
		return -EINVAL;

	ancestor = new;
	while (ancestor->level > active->level)
		ancestor = ancestor->parent;
	if (ancestor != active)
		return -EINVAL;

	put_pid_ns(nsproxy->pid_ns_for_children);
	nsproxy->pid_ns_for_children = get_pid_ns(new);
	return 0;
}

const struct proc_ns_operations pidns_operations = {
	.name		= "pid",
	.type		= CLONE_NEWPID,
	.get		= pidns_get,
	.put		= pidns_put,
	.install	= pidns_install,
};

static __init int pid_namespaces_init(void)
{
	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);

#ifdef CONFIG_CHECKPOINT_RESTORE
	register_sysctl_paths(kern_path, pid_ns_ctl_table);
#endif
	return 0;
}

__initcall(pid_namespaces_init);
Commit	Line	Data
	1	/*
	2	* Pid namespaces
	3	*
	4	* Authors:
	5	* (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
	6	* (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
	7	* Many thanks to Oleg Nesterov for comments and help
	8	*
	9	*/
	10
	11	#include <linux/pid.h>
	12	#include <linux/pid_namespace.h>
	13	#include <linux/user_namespace.h>
	14	#include <linux/syscalls.h>
	15	#include <linux/err.h>
	16	#include <linux/acct.h>
	17	#include <linux/slab.h>
	18	#include <linux/proc_ns.h>
	19	#include <linux/reboot.h>
	20	#include <linux/export.h>
	21
	22	struct pid_cache {
	23	int nr_ids;
	24	char name[16];
	25	struct kmem_cache *cachep;
	26	struct list_head list;
	27	};
	28
	29	static LIST_HEAD(pid_caches_lh);
	30	static DEFINE_MUTEX(pid_caches_mutex);
	31	static struct kmem_cache *pid_ns_cachep;
	32
	33	/*
	34	* creates the kmem cache to allocate pids from.
	35	* @nr_ids: the number of numerical ids this pid will have to carry
	36	*/
	37
	38	static struct kmem_cache *create_pid_cachep(int nr_ids)
	39	{
	40	struct pid_cache *pcache;
	41	struct kmem_cache *cachep;
	42
	43	mutex_lock(&pid_caches_mutex);
	44	list_for_each_entry(pcache, &pid_caches_lh, list)
	45	if (pcache->nr_ids == nr_ids)
	46	goto out;
	47
	48	pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
	49	if (pcache == NULL)
	50	goto err_alloc;
	51
	52	snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
	53	cachep = kmem_cache_create(pcache->name,
	54	sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
	55	0, SLAB_HWCACHE_ALIGN, NULL);
	56	if (cachep == NULL)
	57	goto err_cachep;
	58
	59	pcache->nr_ids = nr_ids;
	60	pcache->cachep = cachep;
	61	list_add(&pcache->list, &pid_caches_lh);
	62	out:
	63	mutex_unlock(&pid_caches_mutex);
	64	return pcache->cachep;
	65
	66	err_cachep:
	67	kfree(pcache);
	68	err_alloc:
	69	mutex_unlock(&pid_caches_mutex);
	70	return NULL;
	71	}
	72
	73	static void proc_cleanup_work(struct work_struct *work)
	74	{
	75	struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
	76	pid_ns_release_proc(ns);
	77	}
	78
	79	/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
	80	#define MAX_PID_NS_LEVEL 32
	81
	82	static struct pid_namespace create_pid_namespace(struct user_namespace user_ns,
	83	struct pid_namespace *parent_pid_ns)
	84	{
	85	struct pid_namespace *ns;
	86	unsigned int level = parent_pid_ns->level + 1;
	87	int i;
	88	int err;
	89
	90	if (level > MAX_PID_NS_LEVEL) {
	91	err = -EINVAL;
	92	goto out;
	93	}
	94
	95	err = -ENOMEM;
	96	ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
	97	if (ns == NULL)
	98	goto out;
	99
	100	ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
	101	if (!ns->pidmap[0].page)
	102	goto out_free;
	103
	104	ns->pid_cachep = create_pid_cachep(level + 1);
	105	if (ns->pid_cachep == NULL)
	106	goto out_free_map;
	107
	108	err = ns_alloc_inum(&ns->ns);
	109	if (err)
	110	goto out_free_map;
	111	ns->ns.ops = &pidns_operations;
	112
	113	kref_init(&ns->kref);
	114	ns->level = level;
	115	ns->parent = get_pid_ns(parent_pid_ns);
	116	ns->user_ns = get_user_ns(user_ns);
	117	ns->nr_hashed = PIDNS_HASH_ADDING;
	118	INIT_WORK(&ns->proc_work, proc_cleanup_work);
	119
	120	set_bit(0, ns->pidmap[0].page);
	121	atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
	122
	123	for (i = 1; i < PIDMAP_ENTRIES; i++)
	124	atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
	125
	126	return ns;
	127
	128	out_free_map:
	129	kfree(ns->pidmap[0].page);
	130	out_free:
	131	kmem_cache_free(pid_ns_cachep, ns);
	132	out:
	133	return ERR_PTR(err);
	134	}
	135
	136	static void delayed_free_pidns(struct rcu_head *p)
	137	{
	138	kmem_cache_free(pid_ns_cachep,
	139	container_of(p, struct pid_namespace, rcu));
	140	}
	141
	142	static void destroy_pid_namespace(struct pid_namespace *ns)
	143	{
	144	int i;
	145
	146	ns_free_inum(&ns->ns);
	147	for (i = 0; i < PIDMAP_ENTRIES; i++)
	148	kfree(ns->pidmap[i].page);
	149	put_user_ns(ns->user_ns);
	150	call_rcu(&ns->rcu, delayed_free_pidns);
	151	}
	152
	153	struct pid_namespace *copy_pid_ns(unsigned long flags,
	154	struct user_namespace user_ns, struct pid_namespace old_ns)
	155	{
	156	if (!(flags & CLONE_NEWPID))
	157	return get_pid_ns(old_ns);
	158	if (task_active_pid_ns(current) != old_ns)
	159	return ERR_PTR(-EINVAL);
	160	return create_pid_namespace(user_ns, old_ns);
	161	}
	162
	163	static void free_pid_ns(struct kref *kref)
	164	{
	165	struct pid_namespace *ns;
	166
	167	ns = container_of(kref, struct pid_namespace, kref);
	168	destroy_pid_namespace(ns);
	169	}
	170
	171	void put_pid_ns(struct pid_namespace *ns)
	172	{
	173	struct pid_namespace *parent;
	174
	175	while (ns != &init_pid_ns) {
	176	parent = ns->parent;
	177	if (!kref_put(&ns->kref, free_pid_ns))
	178	break;
	179	ns = parent;
	180	}
	181	}
	182	EXPORT_SYMBOL_GPL(put_pid_ns);
	183
	184	void zap_pid_ns_processes(struct pid_namespace *pid_ns)
	185	{
	186	int nr;
	187	int rc;
	188	struct task_struct task, me = current;
	189	int init_pids = thread_group_leader(me) ? 1 : 2;
	190
	191	/* Don't allow any more processes into the pid namespace */
	192	disable_pid_allocation(pid_ns);
	193
	194	/* Ignore SIGCHLD causing any terminated children to autoreap */
	195	spin_lock_irq(&me->sighand->siglock);
	196	me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
	197	spin_unlock_irq(&me->sighand->siglock);
	198
	199	/*
	200	* The last thread in the cgroup-init thread group is terminating.
	201	* Find remaining pid_ts in the namespace, signal and wait for them
	202	* to exit.
	203	*
	204	* Note: This signals each threads in the namespace - even those that
	205	* belong to the same thread group, To avoid this, we would have
	206	* to walk the entire tasklist looking a processes in this
	207	* namespace, but that could be unnecessarily expensive if the
	208	* pid namespace has just a few processes. Or we need to
	209	* maintain a tasklist for each pid namespace.
	210	*
	211	*/
	212	read_lock(&tasklist_lock);
	213	nr = next_pidmap(pid_ns, 1);
	214	while (nr > 0) {
	215	rcu_read_lock();
	216
	217	task = pid_task(find_vpid(nr), PIDTYPE_PID);
	218	if (task && !__fatal_signal_pending(task))
	219	send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
	220
	221	rcu_read_unlock();
	222
	223	nr = next_pidmap(pid_ns, nr);
	224	}
	225	read_unlock(&tasklist_lock);
	226
	227	/* Firstly reap the EXIT_ZOMBIE children we may have. */
	228	do {
	229	clear_thread_flag(TIF_SIGPENDING);
	230	rc = sys_wait4(-1, NULL, __WALL, NULL);
	231	} while (rc != -ECHILD);
	232
	233	/*
	234	* sys_wait4() above can't reap the TASK_DEAD children.
	235	* Make sure they all go away, see free_pid().
	236	*/
	237	for (;;) {
	238	set_current_state(TASK_UNINTERRUPTIBLE);
	239	if (pid_ns->nr_hashed == init_pids)
	240	break;
	241	schedule();
	242	}
	243	__set_current_state(TASK_RUNNING);
	244
	245	if (pid_ns->reboot)
	246	current->signal->group_exit_code = pid_ns->reboot;
	247
	248	acct_exit_ns(pid_ns);
	249	return;
	250	}
	251
	252	#ifdef CONFIG_CHECKPOINT_RESTORE
	253	static int pid_ns_ctl_handler(struct ctl_table *table, int write,
	254	void __user buffer, size_t lenp, loff_t *ppos)
	255	{
	256	struct pid_namespace *pid_ns = task_active_pid_ns(current);
	257	struct ctl_table tmp = *table;
	258
	259	if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
	260	return -EPERM;
	261
	262	/*
	263	* Writing directly to ns' last_pid field is OK, since this field
	264	* is volatile in a living namespace anyway and a code writing to
	265	* it should synchronize its usage with external means.
	266	*/
	267
	268	tmp.data = &pid_ns->last_pid;
	269	return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
	270	}
	271
	272	extern int pid_max;
	273	static int zero = 0;
	274	static struct ctl_table pid_ns_ctl_table[] = {
	275	{
	276	.procname = "ns_last_pid",
	277	.maxlen = sizeof(int),
	278	.mode = 0666, /* permissions are checked in the handler */
	279	.proc_handler = pid_ns_ctl_handler,
	280	.extra1 = &zero,
	281	.extra2 = &pid_max,
	282	},
	283	{ }
	284	};
	285	static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
	286	#endif /* CONFIG_CHECKPOINT_RESTORE */
	287
	288	int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
	289	{
	290	if (pid_ns == &init_pid_ns)
	291	return 0;
	292
	293	switch (cmd) {
	294	case LINUX_REBOOT_CMD_RESTART2:
	295	case LINUX_REBOOT_CMD_RESTART:
	296	pid_ns->reboot = SIGHUP;
	297	break;
	298
	299	case LINUX_REBOOT_CMD_POWER_OFF:
	300	case LINUX_REBOOT_CMD_HALT:
	301	pid_ns->reboot = SIGINT;
	302	break;
	303	default:
	304	return -EINVAL;
	305	}
	306
	307	read_lock(&tasklist_lock);
	308	force_sig(SIGKILL, pid_ns->child_reaper);
	309	read_unlock(&tasklist_lock);
	310
	311	do_exit(0);
	312
	313	/* Not reached */
	314	return 0;
	315	}
	316
	317	static inline struct pid_namespace to_pid_ns(struct ns_common ns)
	318	{
	319	return container_of(ns, struct pid_namespace, ns);
	320	}
	321
	322	static struct ns_common pidns_get(struct task_struct task)
	323	{
	324	struct pid_namespace *ns;
	325
	326	rcu_read_lock();
	327	ns = task_active_pid_ns(task);
	328	if (ns)
	329	get_pid_ns(ns);
	330	rcu_read_unlock();
	331
	332	return ns ? &ns->ns : NULL;
	333	}
	334
	335	static void pidns_put(struct ns_common *ns)
	336	{
	337	put_pid_ns(to_pid_ns(ns));
	338	}
	339
	340	static int pidns_install(struct nsproxy nsproxy, struct ns_common ns)
	341	{
	342	struct pid_namespace *active = task_active_pid_ns(current);
	343	struct pid_namespace ancestor, new = to_pid_ns(ns);
	344
	345	if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) \|\|
	346	!ns_capable(current_user_ns(), CAP_SYS_ADMIN))
	347	return -EPERM;
	348
	349	/*
	350	* Only allow entering the current active pid namespace
	351	* or a child of the current active pid namespace.
	352	*
	353	* This is required for fork to return a usable pid value and
	354	* this maintains the property that processes and their
	355	* children can not escape their current pid namespace.
	356	*/
	357	if (new->level < active->level)
	358	return -EINVAL;
	359
	360	ancestor = new;
	361	while (ancestor->level > active->level)
	362	ancestor = ancestor->parent;
	363	if (ancestor != active)
	364	return -EINVAL;
	365
	366	put_pid_ns(nsproxy->pid_ns_for_children);
	367	nsproxy->pid_ns_for_children = get_pid_ns(new);
	368	return 0;
	369	}
	370
	371	const struct proc_ns_operations pidns_operations = {
	372	.name = "pid",
	373	.type = CLONE_NEWPID,
	374	.get = pidns_get,
	375	.put = pidns_put,
	376	.install = pidns_install,
	377	};
	378
	379	static __init int pid_namespaces_init(void)
	380	{
	381	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
	382
	383	#ifdef CONFIG_CHECKPOINT_RESTORE
	384	register_sysctl_paths(kern_path, pid_ns_ctl_table);
	385	#endif
	386	return 0;
	387	}
	388
	389	__initcall(pid_namespaces_init);