Loading...
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);
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 = 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
128out_free_map:
129 kfree(ns->pidmap[0].page);
130out_free:
131 kmem_cache_free(pid_ns_cachep, ns);
132out:
133 return ERR_PTR(err);
134}
135
136static 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
142static 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
153struct 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
163static 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
171void 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}
182EXPORT_SYMBOL_GPL(put_pid_ns);
183
184void 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 /*
195 * Ignore SIGCHLD causing any terminated children to autoreap.
196 * This speeds up the namespace shutdown, plus see the comment
197 * below.
198 */
199 spin_lock_irq(&me->sighand->siglock);
200 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
201 spin_unlock_irq(&me->sighand->siglock);
202
203 /*
204 * The last thread in the cgroup-init thread group is terminating.
205 * Find remaining pid_ts in the namespace, signal and wait for them
206 * to exit.
207 *
208 * Note: This signals each threads in the namespace - even those that
209 * belong to the same thread group, To avoid this, we would have
210 * to walk the entire tasklist looking a processes in this
211 * namespace, but that could be unnecessarily expensive if the
212 * pid namespace has just a few processes. Or we need to
213 * maintain a tasklist for each pid namespace.
214 *
215 */
216 read_lock(&tasklist_lock);
217 nr = next_pidmap(pid_ns, 1);
218 while (nr > 0) {
219 rcu_read_lock();
220
221 task = pid_task(find_vpid(nr), PIDTYPE_PID);
222 if (task && !__fatal_signal_pending(task))
223 send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
224
225 rcu_read_unlock();
226
227 nr = next_pidmap(pid_ns, nr);
228 }
229 read_unlock(&tasklist_lock);
230
231 /*
232 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
233 * sys_wait4() will also block until our children traced from the
234 * parent namespace are detached and become EXIT_DEAD.
235 */
236 do {
237 clear_thread_flag(TIF_SIGPENDING);
238 rc = sys_wait4(-1, NULL, __WALL, NULL);
239 } while (rc != -ECHILD);
240
241 /*
242 * sys_wait4() above can't reap the EXIT_DEAD children but we do not
243 * really care, we could reparent them to the global init. We could
244 * exit and reap ->child_reaper even if it is not the last thread in
245 * this pid_ns, free_pid(nr_hashed == 0) calls proc_cleanup_work(),
246 * pid_ns can not go away until proc_kill_sb() drops the reference.
247 *
248 * But this ns can also have other tasks injected by setns()+fork().
249 * Again, ignoring the user visible semantics we do not really need
250 * to wait until they are all reaped, but they can be reparented to
251 * us and thus we need to ensure that pid->child_reaper stays valid
252 * until they all go away. See free_pid()->wake_up_process().
253 *
254 * We rely on ignored SIGCHLD, an injected zombie must be autoreaped
255 * if reparented.
256 */
257 for (;;) {
258 set_current_state(TASK_UNINTERRUPTIBLE);
259 if (pid_ns->nr_hashed == init_pids)
260 break;
261 schedule();
262 }
263 __set_current_state(TASK_RUNNING);
264
265 if (pid_ns->reboot)
266 current->signal->group_exit_code = pid_ns->reboot;
267
268 acct_exit_ns(pid_ns);
269 return;
270}
271
272#ifdef CONFIG_CHECKPOINT_RESTORE
273static int pid_ns_ctl_handler(struct ctl_table *table, int write,
274 void __user *buffer, size_t *lenp, loff_t *ppos)
275{
276 struct pid_namespace *pid_ns = task_active_pid_ns(current);
277 struct ctl_table tmp = *table;
278
279 if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
280 return -EPERM;
281
282 /*
283 * Writing directly to ns' last_pid field is OK, since this field
284 * is volatile in a living namespace anyway and a code writing to
285 * it should synchronize its usage with external means.
286 */
287
288 tmp.data = &pid_ns->last_pid;
289 return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
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 void pidns_put(struct ns_common *ns)
356{
357 put_pid_ns(to_pid_ns(ns));
358}
359
360static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
361{
362 struct pid_namespace *active = task_active_pid_ns(current);
363 struct pid_namespace *ancestor, *new = to_pid_ns(ns);
364
365 if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
366 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
367 return -EPERM;
368
369 /*
370 * Only allow entering the current active pid namespace
371 * or a child of the current active pid namespace.
372 *
373 * This is required for fork to return a usable pid value and
374 * this maintains the property that processes and their
375 * children can not escape their current pid namespace.
376 */
377 if (new->level < active->level)
378 return -EINVAL;
379
380 ancestor = new;
381 while (ancestor->level > active->level)
382 ancestor = ancestor->parent;
383 if (ancestor != active)
384 return -EINVAL;
385
386 put_pid_ns(nsproxy->pid_ns_for_children);
387 nsproxy->pid_ns_for_children = get_pid_ns(new);
388 return 0;
389}
390
391const struct proc_ns_operations pidns_operations = {
392 .name = "pid",
393 .type = CLONE_NEWPID,
394 .get = pidns_get,
395 .put = pidns_put,
396 .install = pidns_install,
397};
398
399static __init int pid_namespaces_init(void)
400{
401 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
402
403#ifdef CONFIG_CHECKPOINT_RESTORE
404 register_sysctl_paths(kern_path, pid_ns_ctl_table);
405#endif
406 return 0;
407}
408
409__initcall(pid_namespaces_init);