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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Pid namespaces
4 *
5 * Authors:
6 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
7 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
8 * Many thanks to Oleg Nesterov for comments and help
9 *
10 */
11
12#include <linux/pid.h>
13#include <linux/pid_namespace.h>
14#include <linux/user_namespace.h>
15#include <linux/syscalls.h>
16#include <linux/cred.h>
17#include <linux/err.h>
18#include <linux/acct.h>
19#include <linux/slab.h>
20#include <linux/proc_ns.h>
21#include <linux/reboot.h>
22#include <linux/export.h>
23#include <linux/sched/task.h>
24#include <linux/sched/signal.h>
25#include <linux/idr.h>
26
27static DEFINE_MUTEX(pid_caches_mutex);
28static struct kmem_cache *pid_ns_cachep;
29/* Write once array, filled from the beginning. */
30static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL];
31
32/*
33 * creates the kmem cache to allocate pids from.
34 * @level: pid namespace level
35 */
36
37static struct kmem_cache *create_pid_cachep(unsigned int level)
38{
39 /* Level 0 is init_pid_ns.pid_cachep */
40 struct kmem_cache **pkc = &pid_cache[level - 1];
41 struct kmem_cache *kc;
42 char name[4 + 10 + 1];
43 unsigned int len;
44
45 kc = READ_ONCE(*pkc);
46 if (kc)
47 return kc;
48
49 snprintf(name, sizeof(name), "pid_%u", level + 1);
50 len = sizeof(struct pid) + level * sizeof(struct upid);
51 mutex_lock(&pid_caches_mutex);
52 /* Name collision forces to do allocation under mutex. */
53 if (!*pkc)
54 *pkc = kmem_cache_create(name, len, 0,
55 SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT, NULL);
56 mutex_unlock(&pid_caches_mutex);
57 /* current can fail, but someone else can succeed. */
58 return READ_ONCE(*pkc);
59}
60
61static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
62{
63 return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
64}
65
66static void dec_pid_namespaces(struct ucounts *ucounts)
67{
68 dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
69}
70
71static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
72 struct pid_namespace *parent_pid_ns)
73{
74 struct pid_namespace *ns;
75 unsigned int level = parent_pid_ns->level + 1;
76 struct ucounts *ucounts;
77 int err;
78
79 err = -EINVAL;
80 if (!in_userns(parent_pid_ns->user_ns, user_ns))
81 goto out;
82
83 err = -ENOSPC;
84 if (level > MAX_PID_NS_LEVEL)
85 goto out;
86 ucounts = inc_pid_namespaces(user_ns);
87 if (!ucounts)
88 goto out;
89
90 err = -ENOMEM;
91 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
92 if (ns == NULL)
93 goto out_dec;
94
95 idr_init(&ns->idr);
96
97 ns->pid_cachep = create_pid_cachep(level);
98 if (ns->pid_cachep == NULL)
99 goto out_free_idr;
100
101 err = ns_alloc_inum(&ns->ns);
102 if (err)
103 goto out_free_idr;
104 ns->ns.ops = &pidns_operations;
105
106 refcount_set(&ns->ns.count, 1);
107 ns->level = level;
108 ns->parent = get_pid_ns(parent_pid_ns);
109 ns->user_ns = get_user_ns(user_ns);
110 ns->ucounts = ucounts;
111 ns->pid_allocated = PIDNS_ADDING;
112
113 return ns;
114
115out_free_idr:
116 idr_destroy(&ns->idr);
117 kmem_cache_free(pid_ns_cachep, ns);
118out_dec:
119 dec_pid_namespaces(ucounts);
120out:
121 return ERR_PTR(err);
122}
123
124static void delayed_free_pidns(struct rcu_head *p)
125{
126 struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
127
128 dec_pid_namespaces(ns->ucounts);
129 put_user_ns(ns->user_ns);
130
131 kmem_cache_free(pid_ns_cachep, ns);
132}
133
134static void destroy_pid_namespace(struct pid_namespace *ns)
135{
136 ns_free_inum(&ns->ns);
137
138 idr_destroy(&ns->idr);
139 call_rcu(&ns->rcu, delayed_free_pidns);
140}
141
142struct pid_namespace *copy_pid_ns(unsigned long flags,
143 struct user_namespace *user_ns, struct pid_namespace *old_ns)
144{
145 if (!(flags & CLONE_NEWPID))
146 return get_pid_ns(old_ns);
147 if (task_active_pid_ns(current) != old_ns)
148 return ERR_PTR(-EINVAL);
149 return create_pid_namespace(user_ns, old_ns);
150}
151
152void put_pid_ns(struct pid_namespace *ns)
153{
154 struct pid_namespace *parent;
155
156 while (ns != &init_pid_ns) {
157 parent = ns->parent;
158 if (!refcount_dec_and_test(&ns->ns.count))
159 break;
160 destroy_pid_namespace(ns);
161 ns = parent;
162 }
163}
164EXPORT_SYMBOL_GPL(put_pid_ns);
165
166void zap_pid_ns_processes(struct pid_namespace *pid_ns)
167{
168 int nr;
169 int rc;
170 struct task_struct *task, *me = current;
171 int init_pids = thread_group_leader(me) ? 1 : 2;
172 struct pid *pid;
173
174 /* Don't allow any more processes into the pid namespace */
175 disable_pid_allocation(pid_ns);
176
177 /*
178 * Ignore SIGCHLD causing any terminated children to autoreap.
179 * This speeds up the namespace shutdown, plus see the comment
180 * below.
181 */
182 spin_lock_irq(&me->sighand->siglock);
183 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
184 spin_unlock_irq(&me->sighand->siglock);
185
186 /*
187 * The last thread in the cgroup-init thread group is terminating.
188 * Find remaining pid_ts in the namespace, signal and wait for them
189 * to exit.
190 *
191 * Note: This signals each threads in the namespace - even those that
192 * belong to the same thread group, To avoid this, we would have
193 * to walk the entire tasklist looking a processes in this
194 * namespace, but that could be unnecessarily expensive if the
195 * pid namespace has just a few processes. Or we need to
196 * maintain a tasklist for each pid namespace.
197 *
198 */
199 rcu_read_lock();
200 read_lock(&tasklist_lock);
201 nr = 2;
202 idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
203 task = pid_task(pid, PIDTYPE_PID);
204 if (task && !__fatal_signal_pending(task))
205 group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);
206 }
207 read_unlock(&tasklist_lock);
208 rcu_read_unlock();
209
210 /*
211 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
212 * kernel_wait4() will also block until our children traced from the
213 * parent namespace are detached and become EXIT_DEAD.
214 */
215 do {
216 clear_thread_flag(TIF_SIGPENDING);
217 rc = kernel_wait4(-1, NULL, __WALL, NULL);
218 } while (rc != -ECHILD);
219
220 /*
221 * kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE
222 * process whose parents processes are outside of the pid
223 * namespace. Such processes are created with setns()+fork().
224 *
225 * If those EXIT_ZOMBIE processes are not reaped by their
226 * parents before their parents exit, they will be reparented
227 * to pid_ns->child_reaper. Thus pidns->child_reaper needs to
228 * stay valid until they all go away.
229 *
230 * The code relies on the pid_ns->child_reaper ignoring
231 * SIGCHILD to cause those EXIT_ZOMBIE processes to be
232 * autoreaped if reparented.
233 *
234 * Semantically it is also desirable to wait for EXIT_ZOMBIE
235 * processes before allowing the child_reaper to be reaped, as
236 * that gives the invariant that when the init process of a
237 * pid namespace is reaped all of the processes in the pid
238 * namespace are gone.
239 *
240 * Once all of the other tasks are gone from the pid_namespace
241 * free_pid() will awaken this task.
242 */
243 for (;;) {
244 set_current_state(TASK_INTERRUPTIBLE);
245 if (pid_ns->pid_allocated == init_pids)
246 break;
247 schedule();
248 }
249 __set_current_state(TASK_RUNNING);
250
251 if (pid_ns->reboot)
252 current->signal->group_exit_code = pid_ns->reboot;
253
254 acct_exit_ns(pid_ns);
255 return;
256}
257
258#ifdef CONFIG_CHECKPOINT_RESTORE
259static int pid_ns_ctl_handler(struct ctl_table *table, int write,
260 void *buffer, size_t *lenp, loff_t *ppos)
261{
262 struct pid_namespace *pid_ns = task_active_pid_ns(current);
263 struct ctl_table tmp = *table;
264 int ret, next;
265
266 if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
267 return -EPERM;
268
269 /*
270 * Writing directly to ns' last_pid field is OK, since this field
271 * is volatile in a living namespace anyway and a code writing to
272 * it should synchronize its usage with external means.
273 */
274
275 next = idr_get_cursor(&pid_ns->idr) - 1;
276
277 tmp.data = &next;
278 ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
279 if (!ret && write)
280 idr_set_cursor(&pid_ns->idr, next + 1);
281
282 return ret;
283}
284
285extern int pid_max;
286static struct ctl_table pid_ns_ctl_table[] = {
287 {
288 .procname = "ns_last_pid",
289 .maxlen = sizeof(int),
290 .mode = 0666, /* permissions are checked in the handler */
291 .proc_handler = pid_ns_ctl_handler,
292 .extra1 = SYSCTL_ZERO,
293 .extra2 = &pid_max,
294 },
295 { }
296};
297static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
298#endif /* CONFIG_CHECKPOINT_RESTORE */
299
300int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
301{
302 if (pid_ns == &init_pid_ns)
303 return 0;
304
305 switch (cmd) {
306 case LINUX_REBOOT_CMD_RESTART2:
307 case LINUX_REBOOT_CMD_RESTART:
308 pid_ns->reboot = SIGHUP;
309 break;
310
311 case LINUX_REBOOT_CMD_POWER_OFF:
312 case LINUX_REBOOT_CMD_HALT:
313 pid_ns->reboot = SIGINT;
314 break;
315 default:
316 return -EINVAL;
317 }
318
319 read_lock(&tasklist_lock);
320 send_sig(SIGKILL, pid_ns->child_reaper, 1);
321 read_unlock(&tasklist_lock);
322
323 do_exit(0);
324
325 /* Not reached */
326 return 0;
327}
328
329static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
330{
331 return container_of(ns, struct pid_namespace, ns);
332}
333
334static struct ns_common *pidns_get(struct task_struct *task)
335{
336 struct pid_namespace *ns;
337
338 rcu_read_lock();
339 ns = task_active_pid_ns(task);
340 if (ns)
341 get_pid_ns(ns);
342 rcu_read_unlock();
343
344 return ns ? &ns->ns : NULL;
345}
346
347static struct ns_common *pidns_for_children_get(struct task_struct *task)
348{
349 struct pid_namespace *ns = NULL;
350
351 task_lock(task);
352 if (task->nsproxy) {
353 ns = task->nsproxy->pid_ns_for_children;
354 get_pid_ns(ns);
355 }
356 task_unlock(task);
357
358 if (ns) {
359 read_lock(&tasklist_lock);
360 if (!ns->child_reaper) {
361 put_pid_ns(ns);
362 ns = NULL;
363 }
364 read_unlock(&tasklist_lock);
365 }
366
367 return ns ? &ns->ns : NULL;
368}
369
370static void pidns_put(struct ns_common *ns)
371{
372 put_pid_ns(to_pid_ns(ns));
373}
374
375static int pidns_install(struct nsset *nsset, struct ns_common *ns)
376{
377 struct nsproxy *nsproxy = nsset->nsproxy;
378 struct pid_namespace *active = task_active_pid_ns(current);
379 struct pid_namespace *ancestor, *new = to_pid_ns(ns);
380
381 if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
382 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
383 return -EPERM;
384
385 /*
386 * Only allow entering the current active pid namespace
387 * or a child of the current active pid namespace.
388 *
389 * This is required for fork to return a usable pid value and
390 * this maintains the property that processes and their
391 * children can not escape their current pid namespace.
392 */
393 if (new->level < active->level)
394 return -EINVAL;
395
396 ancestor = new;
397 while (ancestor->level > active->level)
398 ancestor = ancestor->parent;
399 if (ancestor != active)
400 return -EINVAL;
401
402 put_pid_ns(nsproxy->pid_ns_for_children);
403 nsproxy->pid_ns_for_children = get_pid_ns(new);
404 return 0;
405}
406
407static struct ns_common *pidns_get_parent(struct ns_common *ns)
408{
409 struct pid_namespace *active = task_active_pid_ns(current);
410 struct pid_namespace *pid_ns, *p;
411
412 /* See if the parent is in the current namespace */
413 pid_ns = p = to_pid_ns(ns)->parent;
414 for (;;) {
415 if (!p)
416 return ERR_PTR(-EPERM);
417 if (p == active)
418 break;
419 p = p->parent;
420 }
421
422 return &get_pid_ns(pid_ns)->ns;
423}
424
425static struct user_namespace *pidns_owner(struct ns_common *ns)
426{
427 return to_pid_ns(ns)->user_ns;
428}
429
430const struct proc_ns_operations pidns_operations = {
431 .name = "pid",
432 .type = CLONE_NEWPID,
433 .get = pidns_get,
434 .put = pidns_put,
435 .install = pidns_install,
436 .owner = pidns_owner,
437 .get_parent = pidns_get_parent,
438};
439
440const struct proc_ns_operations pidns_for_children_operations = {
441 .name = "pid_for_children",
442 .real_ns_name = "pid",
443 .type = CLONE_NEWPID,
444 .get = pidns_for_children_get,
445 .put = pidns_put,
446 .install = pidns_install,
447 .owner = pidns_owner,
448 .get_parent = pidns_get_parent,
449};
450
451static __init int pid_namespaces_init(void)
452{
453 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC | SLAB_ACCOUNT);
454
455#ifdef CONFIG_CHECKPOINT_RESTORE
456 register_sysctl_paths(kern_path, pid_ns_ctl_table);
457#endif
458 return 0;
459}
460
461__initcall(pid_namespaces_init);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Pid namespaces
4 *
5 * Authors:
6 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
7 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
8 * Many thanks to Oleg Nesterov for comments and help
9 *
10 */
11
12#include <linux/pid.h>
13#include <linux/pid_namespace.h>
14#include <linux/user_namespace.h>
15#include <linux/syscalls.h>
16#include <linux/cred.h>
17#include <linux/err.h>
18#include <linux/acct.h>
19#include <linux/slab.h>
20#include <linux/proc_ns.h>
21#include <linux/reboot.h>
22#include <linux/export.h>
23#include <linux/sched/task.h>
24#include <linux/sched/signal.h>
25#include <linux/idr.h>
26#include <uapi/linux/wait.h>
27#include "pid_sysctl.h"
28
29static DEFINE_MUTEX(pid_caches_mutex);
30static struct kmem_cache *pid_ns_cachep;
31/* Write once array, filled from the beginning. */
32static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL];
33
34/*
35 * creates the kmem cache to allocate pids from.
36 * @level: pid namespace level
37 */
38
39static struct kmem_cache *create_pid_cachep(unsigned int level)
40{
41 /* Level 0 is init_pid_ns.pid_cachep */
42 struct kmem_cache **pkc = &pid_cache[level - 1];
43 struct kmem_cache *kc;
44 char name[4 + 10 + 1];
45 unsigned int len;
46
47 kc = READ_ONCE(*pkc);
48 if (kc)
49 return kc;
50
51 snprintf(name, sizeof(name), "pid_%u", level + 1);
52 len = struct_size_t(struct pid, numbers, level + 1);
53 mutex_lock(&pid_caches_mutex);
54 /* Name collision forces to do allocation under mutex. */
55 if (!*pkc)
56 *pkc = kmem_cache_create(name, len, 0,
57 SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT, NULL);
58 mutex_unlock(&pid_caches_mutex);
59 /* current can fail, but someone else can succeed. */
60 return READ_ONCE(*pkc);
61}
62
63static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
64{
65 return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
66}
67
68static void dec_pid_namespaces(struct ucounts *ucounts)
69{
70 dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
71}
72
73static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
74 struct pid_namespace *parent_pid_ns)
75{
76 struct pid_namespace *ns;
77 unsigned int level = parent_pid_ns->level + 1;
78 struct ucounts *ucounts;
79 int err;
80
81 err = -EINVAL;
82 if (!in_userns(parent_pid_ns->user_ns, user_ns))
83 goto out;
84
85 err = -ENOSPC;
86 if (level > MAX_PID_NS_LEVEL)
87 goto out;
88 ucounts = inc_pid_namespaces(user_ns);
89 if (!ucounts)
90 goto out;
91
92 err = -ENOMEM;
93 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
94 if (ns == NULL)
95 goto out_dec;
96
97 idr_init(&ns->idr);
98
99 ns->pid_cachep = create_pid_cachep(level);
100 if (ns->pid_cachep == NULL)
101 goto out_free_idr;
102
103 err = ns_alloc_inum(&ns->ns);
104 if (err)
105 goto out_free_idr;
106 ns->ns.ops = &pidns_operations;
107
108 refcount_set(&ns->ns.count, 1);
109 ns->level = level;
110 ns->parent = get_pid_ns(parent_pid_ns);
111 ns->user_ns = get_user_ns(user_ns);
112 ns->ucounts = ucounts;
113 ns->pid_allocated = PIDNS_ADDING;
114#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
115 ns->memfd_noexec_scope = pidns_memfd_noexec_scope(parent_pid_ns);
116#endif
117 return ns;
118
119out_free_idr:
120 idr_destroy(&ns->idr);
121 kmem_cache_free(pid_ns_cachep, ns);
122out_dec:
123 dec_pid_namespaces(ucounts);
124out:
125 return ERR_PTR(err);
126}
127
128static void delayed_free_pidns(struct rcu_head *p)
129{
130 struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
131
132 dec_pid_namespaces(ns->ucounts);
133 put_user_ns(ns->user_ns);
134
135 kmem_cache_free(pid_ns_cachep, ns);
136}
137
138static void destroy_pid_namespace(struct pid_namespace *ns)
139{
140 ns_free_inum(&ns->ns);
141
142 idr_destroy(&ns->idr);
143 call_rcu(&ns->rcu, delayed_free_pidns);
144}
145
146struct pid_namespace *copy_pid_ns(unsigned long flags,
147 struct user_namespace *user_ns, struct pid_namespace *old_ns)
148{
149 if (!(flags & CLONE_NEWPID))
150 return get_pid_ns(old_ns);
151 if (task_active_pid_ns(current) != old_ns)
152 return ERR_PTR(-EINVAL);
153 return create_pid_namespace(user_ns, old_ns);
154}
155
156void put_pid_ns(struct pid_namespace *ns)
157{
158 struct pid_namespace *parent;
159
160 while (ns != &init_pid_ns) {
161 parent = ns->parent;
162 if (!refcount_dec_and_test(&ns->ns.count))
163 break;
164 destroy_pid_namespace(ns);
165 ns = parent;
166 }
167}
168EXPORT_SYMBOL_GPL(put_pid_ns);
169
170void zap_pid_ns_processes(struct pid_namespace *pid_ns)
171{
172 int nr;
173 int rc;
174 struct task_struct *task, *me = current;
175 int init_pids = thread_group_leader(me) ? 1 : 2;
176 struct pid *pid;
177
178 /* Don't allow any more processes into the pid namespace */
179 disable_pid_allocation(pid_ns);
180
181 /*
182 * Ignore SIGCHLD causing any terminated children to autoreap.
183 * This speeds up the namespace shutdown, plus see the comment
184 * below.
185 */
186 spin_lock_irq(&me->sighand->siglock);
187 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
188 spin_unlock_irq(&me->sighand->siglock);
189
190 /*
191 * The last thread in the cgroup-init thread group is terminating.
192 * Find remaining pid_ts in the namespace, signal and wait for them
193 * to exit.
194 *
195 * Note: This signals each threads in the namespace - even those that
196 * belong to the same thread group, To avoid this, we would have
197 * to walk the entire tasklist looking a processes in this
198 * namespace, but that could be unnecessarily expensive if the
199 * pid namespace has just a few processes. Or we need to
200 * maintain a tasklist for each pid namespace.
201 *
202 */
203 rcu_read_lock();
204 read_lock(&tasklist_lock);
205 nr = 2;
206 idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
207 task = pid_task(pid, PIDTYPE_PID);
208 if (task && !__fatal_signal_pending(task))
209 group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);
210 }
211 read_unlock(&tasklist_lock);
212 rcu_read_unlock();
213
214 /*
215 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
216 * kernel_wait4() will also block until our children traced from the
217 * parent namespace are detached and become EXIT_DEAD.
218 */
219 do {
220 clear_thread_flag(TIF_SIGPENDING);
221 rc = kernel_wait4(-1, NULL, __WALL, NULL);
222 } while (rc != -ECHILD);
223
224 /*
225 * kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE
226 * process whose parents processes are outside of the pid
227 * namespace. Such processes are created with setns()+fork().
228 *
229 * If those EXIT_ZOMBIE processes are not reaped by their
230 * parents before their parents exit, they will be reparented
231 * to pid_ns->child_reaper. Thus pidns->child_reaper needs to
232 * stay valid until they all go away.
233 *
234 * The code relies on the pid_ns->child_reaper ignoring
235 * SIGCHILD to cause those EXIT_ZOMBIE processes to be
236 * autoreaped if reparented.
237 *
238 * Semantically it is also desirable to wait for EXIT_ZOMBIE
239 * processes before allowing the child_reaper to be reaped, as
240 * that gives the invariant that when the init process of a
241 * pid namespace is reaped all of the processes in the pid
242 * namespace are gone.
243 *
244 * Once all of the other tasks are gone from the pid_namespace
245 * free_pid() will awaken this task.
246 */
247 for (;;) {
248 set_current_state(TASK_INTERRUPTIBLE);
249 if (pid_ns->pid_allocated == init_pids)
250 break;
251 /*
252 * Release tasks_rcu_exit_srcu to avoid following deadlock:
253 *
254 * 1) TASK A unshare(CLONE_NEWPID)
255 * 2) TASK A fork() twice -> TASK B (child reaper for new ns)
256 * and TASK C
257 * 3) TASK B exits, kills TASK C, waits for TASK A to reap it
258 * 4) TASK A calls synchronize_rcu_tasks()
259 * -> synchronize_srcu(tasks_rcu_exit_srcu)
260 * 5) *DEADLOCK*
261 *
262 * It is considered safe to release tasks_rcu_exit_srcu here
263 * because we assume the current task can not be concurrently
264 * reaped at this point.
265 */
266 exit_tasks_rcu_stop();
267 schedule();
268 exit_tasks_rcu_start();
269 }
270 __set_current_state(TASK_RUNNING);
271
272 if (pid_ns->reboot)
273 current->signal->group_exit_code = pid_ns->reboot;
274
275 acct_exit_ns(pid_ns);
276 return;
277}
278
279#ifdef CONFIG_CHECKPOINT_RESTORE
280static int pid_ns_ctl_handler(struct ctl_table *table, int write,
281 void *buffer, size_t *lenp, loff_t *ppos)
282{
283 struct pid_namespace *pid_ns = task_active_pid_ns(current);
284 struct ctl_table tmp = *table;
285 int ret, next;
286
287 if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
288 return -EPERM;
289
290 next = idr_get_cursor(&pid_ns->idr) - 1;
291
292 tmp.data = &next;
293 ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
294 if (!ret && write)
295 idr_set_cursor(&pid_ns->idr, next + 1);
296
297 return ret;
298}
299
300extern int pid_max;
301static struct ctl_table pid_ns_ctl_table[] = {
302 {
303 .procname = "ns_last_pid",
304 .maxlen = sizeof(int),
305 .mode = 0666, /* permissions are checked in the handler */
306 .proc_handler = pid_ns_ctl_handler,
307 .extra1 = SYSCTL_ZERO,
308 .extra2 = &pid_max,
309 },
310 { }
311};
312#endif /* CONFIG_CHECKPOINT_RESTORE */
313
314int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
315{
316 if (pid_ns == &init_pid_ns)
317 return 0;
318
319 switch (cmd) {
320 case LINUX_REBOOT_CMD_RESTART2:
321 case LINUX_REBOOT_CMD_RESTART:
322 pid_ns->reboot = SIGHUP;
323 break;
324
325 case LINUX_REBOOT_CMD_POWER_OFF:
326 case LINUX_REBOOT_CMD_HALT:
327 pid_ns->reboot = SIGINT;
328 break;
329 default:
330 return -EINVAL;
331 }
332
333 read_lock(&tasklist_lock);
334 send_sig(SIGKILL, pid_ns->child_reaper, 1);
335 read_unlock(&tasklist_lock);
336
337 do_exit(0);
338
339 /* Not reached */
340 return 0;
341}
342
343static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
344{
345 return container_of(ns, struct pid_namespace, ns);
346}
347
348static struct ns_common *pidns_get(struct task_struct *task)
349{
350 struct pid_namespace *ns;
351
352 rcu_read_lock();
353 ns = task_active_pid_ns(task);
354 if (ns)
355 get_pid_ns(ns);
356 rcu_read_unlock();
357
358 return ns ? &ns->ns : NULL;
359}
360
361static struct ns_common *pidns_for_children_get(struct task_struct *task)
362{
363 struct pid_namespace *ns = NULL;
364
365 task_lock(task);
366 if (task->nsproxy) {
367 ns = task->nsproxy->pid_ns_for_children;
368 get_pid_ns(ns);
369 }
370 task_unlock(task);
371
372 if (ns) {
373 read_lock(&tasklist_lock);
374 if (!ns->child_reaper) {
375 put_pid_ns(ns);
376 ns = NULL;
377 }
378 read_unlock(&tasklist_lock);
379 }
380
381 return ns ? &ns->ns : NULL;
382}
383
384static void pidns_put(struct ns_common *ns)
385{
386 put_pid_ns(to_pid_ns(ns));
387}
388
389static int pidns_install(struct nsset *nsset, struct ns_common *ns)
390{
391 struct nsproxy *nsproxy = nsset->nsproxy;
392 struct pid_namespace *active = task_active_pid_ns(current);
393 struct pid_namespace *ancestor, *new = to_pid_ns(ns);
394
395 if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
396 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
397 return -EPERM;
398
399 /*
400 * Only allow entering the current active pid namespace
401 * or a child of the current active pid namespace.
402 *
403 * This is required for fork to return a usable pid value and
404 * this maintains the property that processes and their
405 * children can not escape their current pid namespace.
406 */
407 if (new->level < active->level)
408 return -EINVAL;
409
410 ancestor = new;
411 while (ancestor->level > active->level)
412 ancestor = ancestor->parent;
413 if (ancestor != active)
414 return -EINVAL;
415
416 put_pid_ns(nsproxy->pid_ns_for_children);
417 nsproxy->pid_ns_for_children = get_pid_ns(new);
418 return 0;
419}
420
421static struct ns_common *pidns_get_parent(struct ns_common *ns)
422{
423 struct pid_namespace *active = task_active_pid_ns(current);
424 struct pid_namespace *pid_ns, *p;
425
426 /* See if the parent is in the current namespace */
427 pid_ns = p = to_pid_ns(ns)->parent;
428 for (;;) {
429 if (!p)
430 return ERR_PTR(-EPERM);
431 if (p == active)
432 break;
433 p = p->parent;
434 }
435
436 return &get_pid_ns(pid_ns)->ns;
437}
438
439static struct user_namespace *pidns_owner(struct ns_common *ns)
440{
441 return to_pid_ns(ns)->user_ns;
442}
443
444const struct proc_ns_operations pidns_operations = {
445 .name = "pid",
446 .type = CLONE_NEWPID,
447 .get = pidns_get,
448 .put = pidns_put,
449 .install = pidns_install,
450 .owner = pidns_owner,
451 .get_parent = pidns_get_parent,
452};
453
454const struct proc_ns_operations pidns_for_children_operations = {
455 .name = "pid_for_children",
456 .real_ns_name = "pid",
457 .type = CLONE_NEWPID,
458 .get = pidns_for_children_get,
459 .put = pidns_put,
460 .install = pidns_install,
461 .owner = pidns_owner,
462 .get_parent = pidns_get_parent,
463};
464
465static __init int pid_namespaces_init(void)
466{
467 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC | SLAB_ACCOUNT);
468
469#ifdef CONFIG_CHECKPOINT_RESTORE
470 register_sysctl_init("kernel", pid_ns_ctl_table);
471#endif
472
473 register_pid_ns_sysctl_table_vm();
474 return 0;
475}
476
477__initcall(pid_namespaces_init);