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/cred.h>
 16#include <linux/err.h>
 17#include <linux/acct.h>
 18#include <linux/slab.h>
 19#include <linux/proc_ns.h>
 20#include <linux/reboot.h>
 21#include <linux/export.h>
 22#include <linux/sched/task.h>
 23#include <linux/sched/signal.h>
 24#include <linux/idr.h>
 25
 
 
 
 
 
 
 
 
 26static DEFINE_MUTEX(pid_caches_mutex);
 27static struct kmem_cache *pid_ns_cachep;
 28/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
 29#define MAX_PID_NS_LEVEL 32
 30/* Write once array, filled from the beginning. */
 31static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL];
 32
 33/*
 34 * creates the kmem cache to allocate pids from.
 35 * @level: pid namespace level
 36 */
 37
 38static struct kmem_cache *create_pid_cachep(unsigned int level)
 39{
 40	/* Level 0 is init_pid_ns.pid_cachep */
 41	struct kmem_cache **pkc = &pid_cache[level - 1];
 42	struct kmem_cache *kc;
 43	char name[4 + 10 + 1];
 44	unsigned int len;
 45
 46	kc = READ_ONCE(*pkc);
 47	if (kc)
 48		return kc;
 49
 50	snprintf(name, sizeof(name), "pid_%u", level + 1);
 51	len = sizeof(struct pid) + level * sizeof(struct upid);
 52	mutex_lock(&pid_caches_mutex);
 53	/* Name collision forces to do allocation under mutex. */
 54	if (!*pkc)
 55		*pkc = kmem_cache_create(name, len, 0, SLAB_HWCACHE_ALIGN, 0);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 56	mutex_unlock(&pid_caches_mutex);
 57	/* current can fail, but someone else can succeed. */
 58	return READ_ONCE(*pkc);
 
 
 
 
 
 59}
 60
 61static void proc_cleanup_work(struct work_struct *work)
 62{
 63	struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
 64	pid_ns_release_proc(ns);
 65}
 66
 67static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
 68{
 69	return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
 70}
 71
 72static void dec_pid_namespaces(struct ucounts *ucounts)
 73{
 74	dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
 75}
 76
 77static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
 78	struct pid_namespace *parent_pid_ns)
 79{
 80	struct pid_namespace *ns;
 81	unsigned int level = parent_pid_ns->level + 1;
 82	struct ucounts *ucounts;
 83	int err;
 84
 85	err = -EINVAL;
 86	if (!in_userns(parent_pid_ns->user_ns, user_ns))
 87		goto out;
 88
 89	err = -ENOSPC;
 90	if (level > MAX_PID_NS_LEVEL)
 91		goto out;
 92	ucounts = inc_pid_namespaces(user_ns);
 93	if (!ucounts)
 94		goto out;
 
 95
 96	err = -ENOMEM;
 97	ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
 98	if (ns == NULL)
 99		goto out_dec;
100
101	idr_init(&ns->idr);
 
 
102
103	ns->pid_cachep = create_pid_cachep(level);
104	if (ns->pid_cachep == NULL)
105		goto out_free_idr;
106
107	err = ns_alloc_inum(&ns->ns);
108	if (err)
109		goto out_free_idr;
110	ns->ns.ops = &pidns_operations;
111
112	kref_init(&ns->kref);
113	ns->level = level;
114	ns->parent = get_pid_ns(parent_pid_ns);
115	ns->user_ns = get_user_ns(user_ns);
116	ns->ucounts = ucounts;
117	ns->pid_allocated = PIDNS_ADDING;
118	INIT_WORK(&ns->proc_work, proc_cleanup_work);
119
 
 
 
 
 
 
120	return ns;
121
122out_free_idr:
123	idr_destroy(&ns->idr);
 
124	kmem_cache_free(pid_ns_cachep, ns);
125out_dec:
126	dec_pid_namespaces(ucounts);
127out:
128	return ERR_PTR(err);
129}
130
131static void delayed_free_pidns(struct rcu_head *p)
132{
133	struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
134
135	dec_pid_namespaces(ns->ucounts);
136	put_user_ns(ns->user_ns);
137
138	kmem_cache_free(pid_ns_cachep, ns);
139}
140
141static void destroy_pid_namespace(struct pid_namespace *ns)
142{
143	ns_free_inum(&ns->ns);
144
145	idr_destroy(&ns->idr);
 
 
 
146	call_rcu(&ns->rcu, delayed_free_pidns);
147}
148
149struct pid_namespace *copy_pid_ns(unsigned long flags,
150	struct user_namespace *user_ns, struct pid_namespace *old_ns)
151{
152	if (!(flags & CLONE_NEWPID))
153		return get_pid_ns(old_ns);
154	if (task_active_pid_ns(current) != old_ns)
155		return ERR_PTR(-EINVAL);
156	return create_pid_namespace(user_ns, old_ns);
157}
158
159static void free_pid_ns(struct kref *kref)
160{
161	struct pid_namespace *ns;
162
163	ns = container_of(kref, struct pid_namespace, kref);
164	destroy_pid_namespace(ns);
165}
166
167void put_pid_ns(struct pid_namespace *ns)
168{
169	struct pid_namespace *parent;
170
171	while (ns != &init_pid_ns) {
172		parent = ns->parent;
173		if (!kref_put(&ns->kref, free_pid_ns))
174			break;
175		ns = parent;
176	}
177}
178EXPORT_SYMBOL_GPL(put_pid_ns);
179
180void zap_pid_ns_processes(struct pid_namespace *pid_ns)
181{
182	int nr;
183	int rc;
184	struct task_struct *task, *me = current;
185	int init_pids = thread_group_leader(me) ? 1 : 2;
186	struct pid *pid;
187
188	/* Don't allow any more processes into the pid namespace */
189	disable_pid_allocation(pid_ns);
190
191	/*
192	 * Ignore SIGCHLD causing any terminated children to autoreap.
193	 * This speeds up the namespace shutdown, plus see the comment
194	 * below.
195	 */
196	spin_lock_irq(&me->sighand->siglock);
197	me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
198	spin_unlock_irq(&me->sighand->siglock);
199
200	/*
201	 * The last thread in the cgroup-init thread group is terminating.
202	 * Find remaining pid_ts in the namespace, signal and wait for them
203	 * to exit.
204	 *
205	 * Note:  This signals each threads in the namespace - even those that
206	 * 	  belong to the same thread group, To avoid this, we would have
207	 * 	  to walk the entire tasklist looking a processes in this
208	 * 	  namespace, but that could be unnecessarily expensive if the
209	 * 	  pid namespace has just a few processes. Or we need to
210	 * 	  maintain a tasklist for each pid namespace.
211	 *
212	 */
213	rcu_read_lock();
214	read_lock(&tasklist_lock);
215	nr = 2;
216	idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
217		task = pid_task(pid, PIDTYPE_PID);
 
 
218		if (task && !__fatal_signal_pending(task))
219			send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
 
 
 
 
220	}
221	read_unlock(&tasklist_lock);
222	rcu_read_unlock();
223
224	/*
225	 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
226	 * kernel_wait4() will also block until our children traced from the
227	 * parent namespace are detached and become EXIT_DEAD.
228	 */
229	do {
230		clear_thread_flag(TIF_SIGPENDING);
231		rc = kernel_wait4(-1, NULL, __WALL, NULL);
232	} while (rc != -ECHILD);
233
234	/*
235	 * kernel_wait4() above can't reap the EXIT_DEAD children but we do not
236	 * really care, we could reparent them to the global init. We could
237	 * exit and reap ->child_reaper even if it is not the last thread in
238	 * this pid_ns, free_pid(pid_allocated == 0) calls proc_cleanup_work(),
239	 * pid_ns can not go away until proc_kill_sb() drops the reference.
240	 *
241	 * But this ns can also have other tasks injected by setns()+fork().
242	 * Again, ignoring the user visible semantics we do not really need
243	 * to wait until they are all reaped, but they can be reparented to
244	 * us and thus we need to ensure that pid->child_reaper stays valid
245	 * until they all go away. See free_pid()->wake_up_process().
246	 *
247	 * We rely on ignored SIGCHLD, an injected zombie must be autoreaped
248	 * if reparented.
249	 */
250	for (;;) {
251		set_current_state(TASK_INTERRUPTIBLE);
252		if (pid_ns->pid_allocated == init_pids)
253			break;
254		schedule();
255	}
256	__set_current_state(TASK_RUNNING);
257
258	if (pid_ns->reboot)
259		current->signal->group_exit_code = pid_ns->reboot;
260
261	acct_exit_ns(pid_ns);
262	return;
263}
264
265#ifdef CONFIG_CHECKPOINT_RESTORE
266static int pid_ns_ctl_handler(struct ctl_table *table, int write,
267		void __user *buffer, size_t *lenp, loff_t *ppos)
268{
269	struct pid_namespace *pid_ns = task_active_pid_ns(current);
270	struct ctl_table tmp = *table;
271	int ret, next;
272
273	if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
274		return -EPERM;
275
276	/*
277	 * Writing directly to ns' last_pid field is OK, since this field
278	 * is volatile in a living namespace anyway and a code writing to
279	 * it should synchronize its usage with external means.
280	 */
281
282	next = idr_get_cursor(&pid_ns->idr) - 1;
283
284	tmp.data = &next;
285	ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
286	if (!ret && write)
287		idr_set_cursor(&pid_ns->idr, next + 1);
288
289	return ret;
290}
291
292extern int pid_max;
293static int zero = 0;
294static struct ctl_table pid_ns_ctl_table[] = {
295	{
296		.procname = "ns_last_pid",
297		.maxlen = sizeof(int),
298		.mode = 0666, /* permissions are checked in the handler */
299		.proc_handler = pid_ns_ctl_handler,
300		.extra1 = &zero,
301		.extra2 = &pid_max,
302	},
303	{ }
304};
305static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
306#endif	/* CONFIG_CHECKPOINT_RESTORE */
307
308int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
309{
310	if (pid_ns == &init_pid_ns)
311		return 0;
312
313	switch (cmd) {
314	case LINUX_REBOOT_CMD_RESTART2:
315	case LINUX_REBOOT_CMD_RESTART:
316		pid_ns->reboot = SIGHUP;
317		break;
318
319	case LINUX_REBOOT_CMD_POWER_OFF:
320	case LINUX_REBOOT_CMD_HALT:
321		pid_ns->reboot = SIGINT;
322		break;
323	default:
324		return -EINVAL;
325	}
326
327	read_lock(&tasklist_lock);
328	force_sig(SIGKILL, pid_ns->child_reaper);
329	read_unlock(&tasklist_lock);
330
331	do_exit(0);
332
333	/* Not reached */
334	return 0;
335}
336
337static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
338{
339	return container_of(ns, struct pid_namespace, ns);
340}
341
342static struct ns_common *pidns_get(struct task_struct *task)
343{
344	struct pid_namespace *ns;
345
346	rcu_read_lock();
347	ns = task_active_pid_ns(task);
348	if (ns)
349		get_pid_ns(ns);
350	rcu_read_unlock();
351
352	return ns ? &ns->ns : NULL;
353}
354
355static struct ns_common *pidns_for_children_get(struct task_struct *task)
356{
357	struct pid_namespace *ns = NULL;
358
359	task_lock(task);
360	if (task->nsproxy) {
361		ns = task->nsproxy->pid_ns_for_children;
362		get_pid_ns(ns);
363	}
364	task_unlock(task);
365
366	if (ns) {
367		read_lock(&tasklist_lock);
368		if (!ns->child_reaper) {
369			put_pid_ns(ns);
370			ns = NULL;
371		}
372		read_unlock(&tasklist_lock);
373	}
374
375	return ns ? &ns->ns : NULL;
376}
377
378static void pidns_put(struct ns_common *ns)
379{
380	put_pid_ns(to_pid_ns(ns));
381}
382
383static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
384{
385	struct pid_namespace *active = task_active_pid_ns(current);
386	struct pid_namespace *ancestor, *new = to_pid_ns(ns);
387
388	if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
389	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
390		return -EPERM;
391
392	/*
393	 * Only allow entering the current active pid namespace
394	 * or a child of the current active pid namespace.
395	 *
396	 * This is required for fork to return a usable pid value and
397	 * this maintains the property that processes and their
398	 * children can not escape their current pid namespace.
399	 */
400	if (new->level < active->level)
401		return -EINVAL;
402
403	ancestor = new;
404	while (ancestor->level > active->level)
405		ancestor = ancestor->parent;
406	if (ancestor != active)
407		return -EINVAL;
408
409	put_pid_ns(nsproxy->pid_ns_for_children);
410	nsproxy->pid_ns_for_children = get_pid_ns(new);
411	return 0;
412}
413
414static struct ns_common *pidns_get_parent(struct ns_common *ns)
415{
416	struct pid_namespace *active = task_active_pid_ns(current);
417	struct pid_namespace *pid_ns, *p;
418
419	/* See if the parent is in the current namespace */
420	pid_ns = p = to_pid_ns(ns)->parent;
421	for (;;) {
422		if (!p)
423			return ERR_PTR(-EPERM);
424		if (p == active)
425			break;
426		p = p->parent;
427	}
428
429	return &get_pid_ns(pid_ns)->ns;
430}
431
432static struct user_namespace *pidns_owner(struct ns_common *ns)
433{
434	return to_pid_ns(ns)->user_ns;
 
435}
436
437const struct proc_ns_operations pidns_operations = {
438	.name		= "pid",
439	.type		= CLONE_NEWPID,
440	.get		= pidns_get,
441	.put		= pidns_put,
442	.install	= pidns_install,
443	.owner		= pidns_owner,
444	.get_parent	= pidns_get_parent,
445};
446
447const struct proc_ns_operations pidns_for_children_operations = {
448	.name		= "pid_for_children",
449	.real_ns_name	= "pid",
450	.type		= CLONE_NEWPID,
451	.get		= pidns_for_children_get,
452	.put		= pidns_put,
453	.install	= pidns_install,
454	.owner		= pidns_owner,
455	.get_parent	= pidns_get_parent,
456};
457
458static __init int pid_namespaces_init(void)
459{
460	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
461
462#ifdef CONFIG_CHECKPOINT_RESTORE
463	register_sysctl_paths(kern_path, pid_ns_ctl_table);
464#endif
465	return 0;
466}
467
468__initcall(pid_namespaces_init);

  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
 22struct pid_cache {
 23	int nr_ids;
 24	char name[16];
 25	struct kmem_cache *cachep;
 26	struct list_head list;
 27};
 28
 29static LIST_HEAD(pid_caches_lh);
 30static DEFINE_MUTEX(pid_caches_mutex);
 31static 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
 38static 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);
 62out:
 63	mutex_unlock(&pid_caches_mutex);
 64	return pcache->cachep;
 65
 66err_cachep:
 67	kfree(pcache);
 68err_alloc:
 69	mutex_unlock(&pid_caches_mutex);
 70	return NULL;
 71}
 72
 73static 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
 82static 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 = proc_alloc_inum(&ns->proc_inum);
109	if (err)
110		goto out_free_map;
 
111
112	kref_init(&ns->kref);
113	ns->level = level;
114	ns->parent = get_pid_ns(parent_pid_ns);
115	ns->user_ns = get_user_ns(user_ns);
116	ns->nr_hashed = PIDNS_HASH_ADDING;
 
117	INIT_WORK(&ns->proc_work, proc_cleanup_work);
118
119	set_bit(0, ns->pidmap[0].page);
120	atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
121
122	for (i = 1; i < PIDMAP_ENTRIES; i++)
123		atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
124
125	return ns;
126
127out_free_map:
128	kfree(ns->pidmap[0].page);
129out_free:
130	kmem_cache_free(pid_ns_cachep, ns);
 
 
131out:
132	return ERR_PTR(err);
133}
134
135static void delayed_free_pidns(struct rcu_head *p)
136{
137	kmem_cache_free(pid_ns_cachep,
138			container_of(p, struct pid_namespace, rcu));
 
 
 
 
139}
140
141static void destroy_pid_namespace(struct pid_namespace *ns)
142{
143	int i;
144
145	proc_free_inum(ns->proc_inum);
146	for (i = 0; i < PIDMAP_ENTRIES; i++)
147		kfree(ns->pidmap[i].page);
148	put_user_ns(ns->user_ns);
149	call_rcu(&ns->rcu, delayed_free_pidns);
150}
151
152struct pid_namespace *copy_pid_ns(unsigned long flags,
153	struct user_namespace *user_ns, struct pid_namespace *old_ns)
154{
155	if (!(flags & CLONE_NEWPID))
156		return get_pid_ns(old_ns);
157	if (task_active_pid_ns(current) != old_ns)
158		return ERR_PTR(-EINVAL);
159	return create_pid_namespace(user_ns, old_ns);
160}
161
162static void free_pid_ns(struct kref *kref)
163{
164	struct pid_namespace *ns;
165
166	ns = container_of(kref, struct pid_namespace, kref);
167	destroy_pid_namespace(ns);
168}
169
170void put_pid_ns(struct pid_namespace *ns)
171{
172	struct pid_namespace *parent;
173
174	while (ns != &init_pid_ns) {
175		parent = ns->parent;
176		if (!kref_put(&ns->kref, free_pid_ns))
177			break;
178		ns = parent;
179	}
180}
181EXPORT_SYMBOL_GPL(put_pid_ns);
182
183void zap_pid_ns_processes(struct pid_namespace *pid_ns)
184{
185	int nr;
186	int rc;
187	struct task_struct *task, *me = current;
188	int init_pids = thread_group_leader(me) ? 1 : 2;
 
189
190	/* Don't allow any more processes into the pid namespace */
191	disable_pid_allocation(pid_ns);
192
193	/* Ignore SIGCHLD causing any terminated children to autoreap */
 
 
 
 
194	spin_lock_irq(&me->sighand->siglock);
195	me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
196	spin_unlock_irq(&me->sighand->siglock);
197
198	/*
199	 * The last thread in the cgroup-init thread group is terminating.
200	 * Find remaining pid_ts in the namespace, signal and wait for them
201	 * to exit.
202	 *
203	 * Note:  This signals each threads in the namespace - even those that
204	 * 	  belong to the same thread group, To avoid this, we would have
205	 * 	  to walk the entire tasklist looking a processes in this
206	 * 	  namespace, but that could be unnecessarily expensive if the
207	 * 	  pid namespace has just a few processes. Or we need to
208	 * 	  maintain a tasklist for each pid namespace.
209	 *
210	 */
 
211	read_lock(&tasklist_lock);
212	nr = next_pidmap(pid_ns, 1);
213	while (nr > 0) {
214		rcu_read_lock();
215
216		task = pid_task(find_vpid(nr), PIDTYPE_PID);
217		if (task && !__fatal_signal_pending(task))
218			send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
219
220		rcu_read_unlock();
221
222		nr = next_pidmap(pid_ns, nr);
223	}
224	read_unlock(&tasklist_lock);
 
225
226	/* Firstly reap the EXIT_ZOMBIE children we may have. */
 
 
 
 
227	do {
228		clear_thread_flag(TIF_SIGPENDING);
229		rc = sys_wait4(-1, NULL, __WALL, NULL);
230	} while (rc != -ECHILD);
231
232	/*
233	 * sys_wait4() above can't reap the TASK_DEAD children.
234	 * Make sure they all go away, see free_pid().
 
 
 
 
 
 
 
 
 
 
 
 
235	 */
236	for (;;) {
237		set_current_state(TASK_UNINTERRUPTIBLE);
238		if (pid_ns->nr_hashed == init_pids)
239			break;
240		schedule();
241	}
242	__set_current_state(TASK_RUNNING);
243
244	if (pid_ns->reboot)
245		current->signal->group_exit_code = pid_ns->reboot;
246
247	acct_exit_ns(pid_ns);
248	return;
249}
250
251#ifdef CONFIG_CHECKPOINT_RESTORE
252static int pid_ns_ctl_handler(struct ctl_table *table, int write,
253		void __user *buffer, size_t *lenp, loff_t *ppos)
254{
255	struct pid_namespace *pid_ns = task_active_pid_ns(current);
256	struct ctl_table tmp = *table;
 
257
258	if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
259		return -EPERM;
260
261	/*
262	 * Writing directly to ns' last_pid field is OK, since this field
263	 * is volatile in a living namespace anyway and a code writing to
264	 * it should synchronize its usage with external means.
265	 */
266
267	tmp.data = &pid_ns->last_pid;
268	return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
 
 
 
 
 
 
269}
270
271extern int pid_max;
272static int zero = 0;
273static struct ctl_table pid_ns_ctl_table[] = {
274	{
275		.procname = "ns_last_pid",
276		.maxlen = sizeof(int),
277		.mode = 0666, /* permissions are checked in the handler */
278		.proc_handler = pid_ns_ctl_handler,
279		.extra1 = &zero,
280		.extra2 = &pid_max,
281	},
282	{ }
283};
284static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
285#endif	/* CONFIG_CHECKPOINT_RESTORE */
286
287int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
288{
289	if (pid_ns == &init_pid_ns)
290		return 0;
291
292	switch (cmd) {
293	case LINUX_REBOOT_CMD_RESTART2:
294	case LINUX_REBOOT_CMD_RESTART:
295		pid_ns->reboot = SIGHUP;
296		break;
297
298	case LINUX_REBOOT_CMD_POWER_OFF:
299	case LINUX_REBOOT_CMD_HALT:
300		pid_ns->reboot = SIGINT;
301		break;
302	default:
303		return -EINVAL;
304	}
305
306	read_lock(&tasklist_lock);
307	force_sig(SIGKILL, pid_ns->child_reaper);
308	read_unlock(&tasklist_lock);
309
310	do_exit(0);
311
312	/* Not reached */
313	return 0;
314}
315
316static void *pidns_get(struct task_struct *task)
 
 
 
 
 
317{
318	struct pid_namespace *ns;
319
320	rcu_read_lock();
321	ns = task_active_pid_ns(task);
322	if (ns)
323		get_pid_ns(ns);
324	rcu_read_unlock();
325
326	return ns;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
327}
328
329static void pidns_put(void *ns)
330{
331	put_pid_ns(ns);
332}
333
334static int pidns_install(struct nsproxy *nsproxy, void *ns)
335{
336	struct pid_namespace *active = task_active_pid_ns(current);
337	struct pid_namespace *ancestor, *new = ns;
338
339	if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
340	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
341		return -EPERM;
342
343	/*
344	 * Only allow entering the current active pid namespace
345	 * or a child of the current active pid namespace.
346	 *
347	 * This is required for fork to return a usable pid value and
348	 * this maintains the property that processes and their
349	 * children can not escape their current pid namespace.
350	 */
351	if (new->level < active->level)
352		return -EINVAL;
353
354	ancestor = new;
355	while (ancestor->level > active->level)
356		ancestor = ancestor->parent;
357	if (ancestor != active)
358		return -EINVAL;
359
360	put_pid_ns(nsproxy->pid_ns_for_children);
361	nsproxy->pid_ns_for_children = get_pid_ns(new);
362	return 0;
363}
364
365static unsigned int pidns_inum(void *ns)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
366{
367	struct pid_namespace *pid_ns = ns;
368	return pid_ns->proc_inum;
369}
370
371const 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	.inum		= pidns_inum,
 
 
 
 
 
 
 
 
 
 
 
 
378};
379
380static __init int pid_namespaces_init(void)
381{
382	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
383
384#ifdef CONFIG_CHECKPOINT_RESTORE
385	register_sysctl_paths(kern_path, pid_ns_ctl_table);
386#endif
387	return 0;
388}
389
390__initcall(pid_namespaces_init);