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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/syscalls.h>
14#include <linux/err.h>
15#include <linux/acct.h>
16#include <linux/slab.h>
17#include <linux/proc_fs.h>
18
19#define BITS_PER_PAGE (PAGE_SIZE*8)
20
21struct pid_cache {
22 int nr_ids;
23 char name[16];
24 struct kmem_cache *cachep;
25 struct list_head list;
26};
27
28static LIST_HEAD(pid_caches_lh);
29static DEFINE_MUTEX(pid_caches_mutex);
30static struct kmem_cache *pid_ns_cachep;
31
32/*
33 * creates the kmem cache to allocate pids from.
34 * @nr_ids: the number of numerical ids this pid will have to carry
35 */
36
37static struct kmem_cache *create_pid_cachep(int nr_ids)
38{
39 struct pid_cache *pcache;
40 struct kmem_cache *cachep;
41
42 mutex_lock(&pid_caches_mutex);
43 list_for_each_entry(pcache, &pid_caches_lh, list)
44 if (pcache->nr_ids == nr_ids)
45 goto out;
46
47 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
48 if (pcache == NULL)
49 goto err_alloc;
50
51 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
52 cachep = kmem_cache_create(pcache->name,
53 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
54 0, SLAB_HWCACHE_ALIGN, NULL);
55 if (cachep == NULL)
56 goto err_cachep;
57
58 pcache->nr_ids = nr_ids;
59 pcache->cachep = cachep;
60 list_add(&pcache->list, &pid_caches_lh);
61out:
62 mutex_unlock(&pid_caches_mutex);
63 return pcache->cachep;
64
65err_cachep:
66 kfree(pcache);
67err_alloc:
68 mutex_unlock(&pid_caches_mutex);
69 return NULL;
70}
71
72static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)
73{
74 struct pid_namespace *ns;
75 unsigned int level = parent_pid_ns->level + 1;
76 int i, err = -ENOMEM;
77
78 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
79 if (ns == NULL)
80 goto out;
81
82 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
83 if (!ns->pidmap[0].page)
84 goto out_free;
85
86 ns->pid_cachep = create_pid_cachep(level + 1);
87 if (ns->pid_cachep == NULL)
88 goto out_free_map;
89
90 kref_init(&ns->kref);
91 ns->level = level;
92 ns->parent = get_pid_ns(parent_pid_ns);
93
94 set_bit(0, ns->pidmap[0].page);
95 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
96
97 for (i = 1; i < PIDMAP_ENTRIES; i++)
98 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
99
100 err = pid_ns_prepare_proc(ns);
101 if (err)
102 goto out_put_parent_pid_ns;
103
104 return ns;
105
106out_put_parent_pid_ns:
107 put_pid_ns(parent_pid_ns);
108out_free_map:
109 kfree(ns->pidmap[0].page);
110out_free:
111 kmem_cache_free(pid_ns_cachep, ns);
112out:
113 return ERR_PTR(err);
114}
115
116static void destroy_pid_namespace(struct pid_namespace *ns)
117{
118 int i;
119
120 for (i = 0; i < PIDMAP_ENTRIES; i++)
121 kfree(ns->pidmap[i].page);
122 kmem_cache_free(pid_ns_cachep, ns);
123}
124
125struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
126{
127 if (!(flags & CLONE_NEWPID))
128 return get_pid_ns(old_ns);
129 if (flags & (CLONE_THREAD|CLONE_PARENT))
130 return ERR_PTR(-EINVAL);
131 return create_pid_namespace(old_ns);
132}
133
134void free_pid_ns(struct kref *kref)
135{
136 struct pid_namespace *ns, *parent;
137
138 ns = container_of(kref, struct pid_namespace, kref);
139
140 parent = ns->parent;
141 destroy_pid_namespace(ns);
142
143 if (parent != NULL)
144 put_pid_ns(parent);
145}
146
147void zap_pid_ns_processes(struct pid_namespace *pid_ns)
148{
149 int nr;
150 int rc;
151 struct task_struct *task;
152
153 /*
154 * The last thread in the cgroup-init thread group is terminating.
155 * Find remaining pid_ts in the namespace, signal and wait for them
156 * to exit.
157 *
158 * Note: This signals each threads in the namespace - even those that
159 * belong to the same thread group, To avoid this, we would have
160 * to walk the entire tasklist looking a processes in this
161 * namespace, but that could be unnecessarily expensive if the
162 * pid namespace has just a few processes. Or we need to
163 * maintain a tasklist for each pid namespace.
164 *
165 */
166 read_lock(&tasklist_lock);
167 nr = next_pidmap(pid_ns, 1);
168 while (nr > 0) {
169 rcu_read_lock();
170
171 /*
172 * Any nested-container's init processes won't ignore the
173 * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser().
174 */
175 task = pid_task(find_vpid(nr), PIDTYPE_PID);
176 if (task)
177 send_sig_info(SIGKILL, SEND_SIG_NOINFO, task);
178
179 rcu_read_unlock();
180
181 nr = next_pidmap(pid_ns, nr);
182 }
183 read_unlock(&tasklist_lock);
184
185 do {
186 clear_thread_flag(TIF_SIGPENDING);
187 rc = sys_wait4(-1, NULL, __WALL, NULL);
188 } while (rc != -ECHILD);
189
190 acct_exit_ns(pid_ns);
191 return;
192}
193
194static __init int pid_namespaces_init(void)
195{
196 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
197 return 0;
198}
199
200__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
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, SLAB_HWCACHE_ALIGN, 0);
55 mutex_unlock(&pid_caches_mutex);
56 /* current can fail, but someone else can succeed. */
57 return READ_ONCE(*pkc);
58}
59
60static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
61{
62 return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
63}
64
65static void dec_pid_namespaces(struct ucounts *ucounts)
66{
67 dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
68}
69
70static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
71 struct pid_namespace *parent_pid_ns)
72{
73 struct pid_namespace *ns;
74 unsigned int level = parent_pid_ns->level + 1;
75 struct ucounts *ucounts;
76 int err;
77
78 err = -EINVAL;
79 if (!in_userns(parent_pid_ns->user_ns, user_ns))
80 goto out;
81
82 err = -ENOSPC;
83 if (level > MAX_PID_NS_LEVEL)
84 goto out;
85 ucounts = inc_pid_namespaces(user_ns);
86 if (!ucounts)
87 goto out;
88
89 err = -ENOMEM;
90 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
91 if (ns == NULL)
92 goto out_dec;
93
94 idr_init(&ns->idr);
95
96 ns->pid_cachep = create_pid_cachep(level);
97 if (ns->pid_cachep == NULL)
98 goto out_free_idr;
99
100 err = ns_alloc_inum(&ns->ns);
101 if (err)
102 goto out_free_idr;
103 ns->ns.ops = &pidns_operations;
104
105 kref_init(&ns->kref);
106 ns->level = level;
107 ns->parent = get_pid_ns(parent_pid_ns);
108 ns->user_ns = get_user_ns(user_ns);
109 ns->ucounts = ucounts;
110 ns->pid_allocated = PIDNS_ADDING;
111
112 return ns;
113
114out_free_idr:
115 idr_destroy(&ns->idr);
116 kmem_cache_free(pid_ns_cachep, ns);
117out_dec:
118 dec_pid_namespaces(ucounts);
119out:
120 return ERR_PTR(err);
121}
122
123static void delayed_free_pidns(struct rcu_head *p)
124{
125 struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
126
127 dec_pid_namespaces(ns->ucounts);
128 put_user_ns(ns->user_ns);
129
130 kmem_cache_free(pid_ns_cachep, ns);
131}
132
133static void destroy_pid_namespace(struct pid_namespace *ns)
134{
135 ns_free_inum(&ns->ns);
136
137 idr_destroy(&ns->idr);
138 call_rcu(&ns->rcu, delayed_free_pidns);
139}
140
141struct pid_namespace *copy_pid_ns(unsigned long flags,
142 struct user_namespace *user_ns, struct pid_namespace *old_ns)
143{
144 if (!(flags & CLONE_NEWPID))
145 return get_pid_ns(old_ns);
146 if (task_active_pid_ns(current) != old_ns)
147 return ERR_PTR(-EINVAL);
148 return create_pid_namespace(user_ns, old_ns);
149}
150
151static void free_pid_ns(struct kref *kref)
152{
153 struct pid_namespace *ns;
154
155 ns = container_of(kref, struct pid_namespace, kref);
156 destroy_pid_namespace(ns);
157}
158
159void put_pid_ns(struct pid_namespace *ns)
160{
161 struct pid_namespace *parent;
162
163 while (ns != &init_pid_ns) {
164 parent = ns->parent;
165 if (!kref_put(&ns->kref, free_pid_ns))
166 break;
167 ns = parent;
168 }
169}
170EXPORT_SYMBOL_GPL(put_pid_ns);
171
172void zap_pid_ns_processes(struct pid_namespace *pid_ns)
173{
174 int nr;
175 int rc;
176 struct task_struct *task, *me = current;
177 int init_pids = thread_group_leader(me) ? 1 : 2;
178 struct pid *pid;
179
180 /* Don't allow any more processes into the pid namespace */
181 disable_pid_allocation(pid_ns);
182
183 /*
184 * Ignore SIGCHLD causing any terminated children to autoreap.
185 * This speeds up the namespace shutdown, plus see the comment
186 * below.
187 */
188 spin_lock_irq(&me->sighand->siglock);
189 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
190 spin_unlock_irq(&me->sighand->siglock);
191
192 /*
193 * The last thread in the cgroup-init thread group is terminating.
194 * Find remaining pid_ts in the namespace, signal and wait for them
195 * to exit.
196 *
197 * Note: This signals each threads in the namespace - even those that
198 * belong to the same thread group, To avoid this, we would have
199 * to walk the entire tasklist looking a processes in this
200 * namespace, but that could be unnecessarily expensive if the
201 * pid namespace has just a few processes. Or we need to
202 * maintain a tasklist for each pid namespace.
203 *
204 */
205 rcu_read_lock();
206 read_lock(&tasklist_lock);
207 nr = 2;
208 idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
209 task = pid_task(pid, PIDTYPE_PID);
210 if (task && !__fatal_signal_pending(task))
211 group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);
212 }
213 read_unlock(&tasklist_lock);
214 rcu_read_unlock();
215
216 /*
217 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
218 * kernel_wait4() will also block until our children traced from the
219 * parent namespace are detached and become EXIT_DEAD.
220 */
221 do {
222 clear_thread_flag(TIF_SIGPENDING);
223 rc = kernel_wait4(-1, NULL, __WALL, NULL);
224 } while (rc != -ECHILD);
225
226 /*
227 * kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE
228 * process whose parents processes are outside of the pid
229 * namespace. Such processes are created with setns()+fork().
230 *
231 * If those EXIT_ZOMBIE processes are not reaped by their
232 * parents before their parents exit, they will be reparented
233 * to pid_ns->child_reaper. Thus pidns->child_reaper needs to
234 * stay valid until they all go away.
235 *
236 * The code relies on the the pid_ns->child_reaper ignoring
237 * SIGCHILD to cause those EXIT_ZOMBIE processes to be
238 * autoreaped if reparented.
239 *
240 * Semantically it is also desirable to wait for EXIT_ZOMBIE
241 * processes before allowing the child_reaper to be reaped, as
242 * that gives the invariant that when the init process of a
243 * pid namespace is reaped all of the processes in the pid
244 * namespace are gone.
245 *
246 * Once all of the other tasks are gone from the pid_namespace
247 * free_pid() will awaken this task.
248 */
249 for (;;) {
250 set_current_state(TASK_INTERRUPTIBLE);
251 if (pid_ns->pid_allocated == init_pids)
252 break;
253 schedule();
254 }
255 __set_current_state(TASK_RUNNING);
256
257 if (pid_ns->reboot)
258 current->signal->group_exit_code = pid_ns->reboot;
259
260 acct_exit_ns(pid_ns);
261 return;
262}
263
264#ifdef CONFIG_CHECKPOINT_RESTORE
265static int pid_ns_ctl_handler(struct ctl_table *table, int write,
266 void *buffer, size_t *lenp, loff_t *ppos)
267{
268 struct pid_namespace *pid_ns = task_active_pid_ns(current);
269 struct ctl_table tmp = *table;
270 int ret, next;
271
272 if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
273 return -EPERM;
274
275 /*
276 * Writing directly to ns' last_pid field is OK, since this field
277 * is volatile in a living namespace anyway and a code writing to
278 * it should synchronize its usage with external means.
279 */
280
281 next = idr_get_cursor(&pid_ns->idr) - 1;
282
283 tmp.data = &next;
284 ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
285 if (!ret && write)
286 idr_set_cursor(&pid_ns->idr, next + 1);
287
288 return ret;
289}
290
291extern int pid_max;
292static struct ctl_table pid_ns_ctl_table[] = {
293 {
294 .procname = "ns_last_pid",
295 .maxlen = sizeof(int),
296 .mode = 0666, /* permissions are checked in the handler */
297 .proc_handler = pid_ns_ctl_handler,
298 .extra1 = SYSCTL_ZERO,
299 .extra2 = &pid_max,
300 },
301 { }
302};
303static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
304#endif /* CONFIG_CHECKPOINT_RESTORE */
305
306int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
307{
308 if (pid_ns == &init_pid_ns)
309 return 0;
310
311 switch (cmd) {
312 case LINUX_REBOOT_CMD_RESTART2:
313 case LINUX_REBOOT_CMD_RESTART:
314 pid_ns->reboot = SIGHUP;
315 break;
316
317 case LINUX_REBOOT_CMD_POWER_OFF:
318 case LINUX_REBOOT_CMD_HALT:
319 pid_ns->reboot = SIGINT;
320 break;
321 default:
322 return -EINVAL;
323 }
324
325 read_lock(&tasklist_lock);
326 send_sig(SIGKILL, pid_ns->child_reaper, 1);
327 read_unlock(&tasklist_lock);
328
329 do_exit(0);
330
331 /* Not reached */
332 return 0;
333}
334
335static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
336{
337 return container_of(ns, struct pid_namespace, ns);
338}
339
340static struct ns_common *pidns_get(struct task_struct *task)
341{
342 struct pid_namespace *ns;
343
344 rcu_read_lock();
345 ns = task_active_pid_ns(task);
346 if (ns)
347 get_pid_ns(ns);
348 rcu_read_unlock();
349
350 return ns ? &ns->ns : NULL;
351}
352
353static struct ns_common *pidns_for_children_get(struct task_struct *task)
354{
355 struct pid_namespace *ns = NULL;
356
357 task_lock(task);
358 if (task->nsproxy) {
359 ns = task->nsproxy->pid_ns_for_children;
360 get_pid_ns(ns);
361 }
362 task_unlock(task);
363
364 if (ns) {
365 read_lock(&tasklist_lock);
366 if (!ns->child_reaper) {
367 put_pid_ns(ns);
368 ns = NULL;
369 }
370 read_unlock(&tasklist_lock);
371 }
372
373 return ns ? &ns->ns : NULL;
374}
375
376static void pidns_put(struct ns_common *ns)
377{
378 put_pid_ns(to_pid_ns(ns));
379}
380
381static int pidns_install(struct nsset *nsset, struct ns_common *ns)
382{
383 struct nsproxy *nsproxy = nsset->nsproxy;
384 struct pid_namespace *active = task_active_pid_ns(current);
385 struct pid_namespace *ancestor, *new = to_pid_ns(ns);
386
387 if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
388 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
389 return -EPERM;
390
391 /*
392 * Only allow entering the current active pid namespace
393 * or a child of the current active pid namespace.
394 *
395 * This is required for fork to return a usable pid value and
396 * this maintains the property that processes and their
397 * children can not escape their current pid namespace.
398 */
399 if (new->level < active->level)
400 return -EINVAL;
401
402 ancestor = new;
403 while (ancestor->level > active->level)
404 ancestor = ancestor->parent;
405 if (ancestor != active)
406 return -EINVAL;
407
408 put_pid_ns(nsproxy->pid_ns_for_children);
409 nsproxy->pid_ns_for_children = get_pid_ns(new);
410 return 0;
411}
412
413static struct ns_common *pidns_get_parent(struct ns_common *ns)
414{
415 struct pid_namespace *active = task_active_pid_ns(current);
416 struct pid_namespace *pid_ns, *p;
417
418 /* See if the parent is in the current namespace */
419 pid_ns = p = to_pid_ns(ns)->parent;
420 for (;;) {
421 if (!p)
422 return ERR_PTR(-EPERM);
423 if (p == active)
424 break;
425 p = p->parent;
426 }
427
428 return &get_pid_ns(pid_ns)->ns;
429}
430
431static struct user_namespace *pidns_owner(struct ns_common *ns)
432{
433 return to_pid_ns(ns)->user_ns;
434}
435
436const struct proc_ns_operations pidns_operations = {
437 .name = "pid",
438 .type = CLONE_NEWPID,
439 .get = pidns_get,
440 .put = pidns_put,
441 .install = pidns_install,
442 .owner = pidns_owner,
443 .get_parent = pidns_get_parent,
444};
445
446const struct proc_ns_operations pidns_for_children_operations = {
447 .name = "pid_for_children",
448 .real_ns_name = "pid",
449 .type = CLONE_NEWPID,
450 .get = pidns_for_children_get,
451 .put = pidns_put,
452 .install = pidns_install,
453 .owner = pidns_owner,
454 .get_parent = pidns_get_parent,
455};
456
457static __init int pid_namespaces_init(void)
458{
459 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
460
461#ifdef CONFIG_CHECKPOINT_RESTORE
462 register_sysctl_paths(kern_path, pid_ns_ctl_table);
463#endif
464 return 0;
465}
466
467__initcall(pid_namespaces_init);