Line data Source code
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 "pid_sysctl.h"
27 :
28 : static DEFINE_MUTEX(pid_caches_mutex);
29 : static struct kmem_cache *pid_ns_cachep;
30 : /* Write once array, filled from the beginning. */
31 : static 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 :
38 0 : static struct kmem_cache *create_pid_cachep(unsigned int level)
39 : {
40 : /* Level 0 is init_pid_ns.pid_cachep */
41 0 : 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 0 : kc = READ_ONCE(*pkc);
47 0 : if (kc)
48 : return kc;
49 :
50 0 : snprintf(name, sizeof(name), "pid_%u", level + 1);
51 0 : len = struct_size_t(struct pid, numbers, level + 1);
52 0 : mutex_lock(&pid_caches_mutex);
53 : /* Name collision forces to do allocation under mutex. */
54 0 : if (!*pkc)
55 0 : *pkc = kmem_cache_create(name, len, 0,
56 : SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT, NULL);
57 0 : mutex_unlock(&pid_caches_mutex);
58 : /* current can fail, but someone else can succeed. */
59 0 : return READ_ONCE(*pkc);
60 : }
61 :
62 : static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
63 : {
64 0 : return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
65 : }
66 :
67 : static void dec_pid_namespaces(struct ucounts *ucounts)
68 : {
69 0 : dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
70 : }
71 :
72 0 : static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
73 : struct pid_namespace *parent_pid_ns)
74 : {
75 : struct pid_namespace *ns;
76 0 : unsigned int level = parent_pid_ns->level + 1;
77 : struct ucounts *ucounts;
78 : int err;
79 :
80 0 : err = -EINVAL;
81 0 : if (!in_userns(parent_pid_ns->user_ns, user_ns))
82 : goto out;
83 :
84 0 : err = -ENOSPC;
85 0 : if (level > MAX_PID_NS_LEVEL)
86 : goto out;
87 0 : ucounts = inc_pid_namespaces(user_ns);
88 0 : if (!ucounts)
89 : goto out;
90 :
91 0 : err = -ENOMEM;
92 0 : ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
93 0 : if (ns == NULL)
94 : goto out_dec;
95 :
96 0 : idr_init(&ns->idr);
97 :
98 0 : ns->pid_cachep = create_pid_cachep(level);
99 0 : if (ns->pid_cachep == NULL)
100 : goto out_free_idr;
101 :
102 0 : err = ns_alloc_inum(&ns->ns);
103 0 : if (err)
104 : goto out_free_idr;
105 0 : ns->ns.ops = &pidns_operations;
106 :
107 0 : refcount_set(&ns->ns.count, 1);
108 0 : ns->level = level;
109 0 : ns->parent = get_pid_ns(parent_pid_ns);
110 0 : ns->user_ns = get_user_ns(user_ns);
111 0 : ns->ucounts = ucounts;
112 0 : ns->pid_allocated = PIDNS_ADDING;
113 :
114 : initialize_memfd_noexec_scope(ns);
115 :
116 0 : return ns;
117 :
118 : out_free_idr:
119 0 : idr_destroy(&ns->idr);
120 0 : kmem_cache_free(pid_ns_cachep, ns);
121 : out_dec:
122 : dec_pid_namespaces(ucounts);
123 : out:
124 0 : return ERR_PTR(err);
125 : }
126 :
127 0 : static void delayed_free_pidns(struct rcu_head *p)
128 : {
129 0 : struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
130 :
131 0 : dec_pid_namespaces(ns->ucounts);
132 0 : put_user_ns(ns->user_ns);
133 :
134 0 : kmem_cache_free(pid_ns_cachep, ns);
135 0 : }
136 :
137 0 : static void destroy_pid_namespace(struct pid_namespace *ns)
138 : {
139 0 : ns_free_inum(&ns->ns);
140 :
141 0 : idr_destroy(&ns->idr);
142 0 : call_rcu(&ns->rcu, delayed_free_pidns);
143 0 : }
144 :
145 0 : struct pid_namespace *copy_pid_ns(unsigned long flags,
146 : struct user_namespace *user_ns, struct pid_namespace *old_ns)
147 : {
148 0 : if (!(flags & CLONE_NEWPID))
149 : return get_pid_ns(old_ns);
150 0 : if (task_active_pid_ns(current) != old_ns)
151 : return ERR_PTR(-EINVAL);
152 0 : return create_pid_namespace(user_ns, old_ns);
153 : }
154 :
155 160 : void put_pid_ns(struct pid_namespace *ns)
156 : {
157 : struct pid_namespace *parent;
158 :
159 320 : while (ns != &init_pid_ns) {
160 0 : parent = ns->parent;
161 0 : if (!refcount_dec_and_test(&ns->ns.count))
162 : break;
163 0 : destroy_pid_namespace(ns);
164 0 : ns = parent;
165 : }
166 160 : }
167 : EXPORT_SYMBOL_GPL(put_pid_ns);
168 :
169 0 : void zap_pid_ns_processes(struct pid_namespace *pid_ns)
170 : {
171 : int nr;
172 : int rc;
173 0 : struct task_struct *task, *me = current;
174 0 : int init_pids = thread_group_leader(me) ? 1 : 2;
175 : struct pid *pid;
176 :
177 : /* Don't allow any more processes into the pid namespace */
178 0 : disable_pid_allocation(pid_ns);
179 :
180 : /*
181 : * Ignore SIGCHLD causing any terminated children to autoreap.
182 : * This speeds up the namespace shutdown, plus see the comment
183 : * below.
184 : */
185 0 : spin_lock_irq(&me->sighand->siglock);
186 0 : me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
187 0 : spin_unlock_irq(&me->sighand->siglock);
188 :
189 : /*
190 : * The last thread in the cgroup-init thread group is terminating.
191 : * Find remaining pid_ts in the namespace, signal and wait for them
192 : * to exit.
193 : *
194 : * Note: This signals each threads in the namespace - even those that
195 : * belong to the same thread group, To avoid this, we would have
196 : * to walk the entire tasklist looking a processes in this
197 : * namespace, but that could be unnecessarily expensive if the
198 : * pid namespace has just a few processes. Or we need to
199 : * maintain a tasklist for each pid namespace.
200 : *
201 : */
202 : rcu_read_lock();
203 0 : read_lock(&tasklist_lock);
204 0 : nr = 2;
205 0 : idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
206 0 : task = pid_task(pid, PIDTYPE_PID);
207 0 : if (task && !__fatal_signal_pending(task))
208 0 : group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);
209 : }
210 0 : read_unlock(&tasklist_lock);
211 : rcu_read_unlock();
212 :
213 : /*
214 : * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
215 : * kernel_wait4() will also block until our children traced from the
216 : * parent namespace are detached and become EXIT_DEAD.
217 : */
218 : do {
219 0 : clear_thread_flag(TIF_SIGPENDING);
220 0 : rc = kernel_wait4(-1, NULL, __WALL, NULL);
221 0 : } while (rc != -ECHILD);
222 :
223 : /*
224 : * kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE
225 : * process whose parents processes are outside of the pid
226 : * namespace. Such processes are created with setns()+fork().
227 : *
228 : * If those EXIT_ZOMBIE processes are not reaped by their
229 : * parents before their parents exit, they will be reparented
230 : * to pid_ns->child_reaper. Thus pidns->child_reaper needs to
231 : * stay valid until they all go away.
232 : *
233 : * The code relies on the pid_ns->child_reaper ignoring
234 : * SIGCHILD to cause those EXIT_ZOMBIE processes to be
235 : * autoreaped if reparented.
236 : *
237 : * Semantically it is also desirable to wait for EXIT_ZOMBIE
238 : * processes before allowing the child_reaper to be reaped, as
239 : * that gives the invariant that when the init process of a
240 : * pid namespace is reaped all of the processes in the pid
241 : * namespace are gone.
242 : *
243 : * Once all of the other tasks are gone from the pid_namespace
244 : * free_pid() will awaken this task.
245 : */
246 : for (;;) {
247 0 : set_current_state(TASK_INTERRUPTIBLE);
248 0 : if (pid_ns->pid_allocated == init_pids)
249 : break;
250 : /*
251 : * Release tasks_rcu_exit_srcu to avoid following deadlock:
252 : *
253 : * 1) TASK A unshare(CLONE_NEWPID)
254 : * 2) TASK A fork() twice -> TASK B (child reaper for new ns)
255 : * and TASK C
256 : * 3) TASK B exits, kills TASK C, waits for TASK A to reap it
257 : * 4) TASK A calls synchronize_rcu_tasks()
258 : * -> synchronize_srcu(tasks_rcu_exit_srcu)
259 : * 5) *DEADLOCK*
260 : *
261 : * It is considered safe to release tasks_rcu_exit_srcu here
262 : * because we assume the current task can not be concurrently
263 : * reaped at this point.
264 : */
265 : exit_tasks_rcu_stop();
266 0 : schedule();
267 : exit_tasks_rcu_start();
268 : }
269 0 : __set_current_state(TASK_RUNNING);
270 :
271 0 : if (pid_ns->reboot)
272 0 : current->signal->group_exit_code = pid_ns->reboot;
273 :
274 : acct_exit_ns(pid_ns);
275 0 : return;
276 : }
277 :
278 : #ifdef CONFIG_CHECKPOINT_RESTORE
279 : static int pid_ns_ctl_handler(struct ctl_table *table, int write,
280 : void *buffer, size_t *lenp, loff_t *ppos)
281 : {
282 : struct pid_namespace *pid_ns = task_active_pid_ns(current);
283 : struct ctl_table tmp = *table;
284 : int ret, next;
285 :
286 : if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
287 : return -EPERM;
288 :
289 : /*
290 : * Writing directly to ns' last_pid field is OK, since this field
291 : * is volatile in a living namespace anyway and a code writing to
292 : * it should synchronize its usage with external means.
293 : */
294 :
295 : next = idr_get_cursor(&pid_ns->idr) - 1;
296 :
297 : tmp.data = &next;
298 : ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
299 : if (!ret && write)
300 : idr_set_cursor(&pid_ns->idr, next + 1);
301 :
302 : return ret;
303 : }
304 :
305 : extern int pid_max;
306 : static struct ctl_table pid_ns_ctl_table[] = {
307 : {
308 : .procname = "ns_last_pid",
309 : .maxlen = sizeof(int),
310 : .mode = 0666, /* permissions are checked in the handler */
311 : .proc_handler = pid_ns_ctl_handler,
312 : .extra1 = SYSCTL_ZERO,
313 : .extra2 = &pid_max,
314 : },
315 : { }
316 : };
317 : #endif /* CONFIG_CHECKPOINT_RESTORE */
318 :
319 0 : int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
320 : {
321 0 : if (pid_ns == &init_pid_ns)
322 : return 0;
323 :
324 0 : switch (cmd) {
325 : case LINUX_REBOOT_CMD_RESTART2:
326 : case LINUX_REBOOT_CMD_RESTART:
327 0 : pid_ns->reboot = SIGHUP;
328 0 : break;
329 :
330 : case LINUX_REBOOT_CMD_POWER_OFF:
331 : case LINUX_REBOOT_CMD_HALT:
332 0 : pid_ns->reboot = SIGINT;
333 0 : break;
334 : default:
335 : return -EINVAL;
336 : }
337 :
338 0 : read_lock(&tasklist_lock);
339 0 : send_sig(SIGKILL, pid_ns->child_reaper, 1);
340 0 : read_unlock(&tasklist_lock);
341 :
342 0 : do_exit(0);
343 :
344 : /* Not reached */
345 : return 0;
346 : }
347 :
348 : static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
349 : {
350 0 : return container_of(ns, struct pid_namespace, ns);
351 : }
352 :
353 0 : static struct ns_common *pidns_get(struct task_struct *task)
354 : {
355 : struct pid_namespace *ns;
356 :
357 : rcu_read_lock();
358 0 : ns = task_active_pid_ns(task);
359 0 : if (ns)
360 : get_pid_ns(ns);
361 : rcu_read_unlock();
362 :
363 0 : return ns ? &ns->ns : NULL;
364 : }
365 :
366 0 : static struct ns_common *pidns_for_children_get(struct task_struct *task)
367 : {
368 0 : struct pid_namespace *ns = NULL;
369 :
370 0 : task_lock(task);
371 0 : if (task->nsproxy) {
372 0 : ns = task->nsproxy->pid_ns_for_children;
373 : get_pid_ns(ns);
374 : }
375 0 : task_unlock(task);
376 :
377 0 : if (ns) {
378 0 : read_lock(&tasklist_lock);
379 0 : if (!ns->child_reaper) {
380 0 : put_pid_ns(ns);
381 0 : ns = NULL;
382 : }
383 0 : read_unlock(&tasklist_lock);
384 : }
385 :
386 0 : return ns ? &ns->ns : NULL;
387 : }
388 :
389 0 : static void pidns_put(struct ns_common *ns)
390 : {
391 0 : put_pid_ns(to_pid_ns(ns));
392 0 : }
393 :
394 0 : static int pidns_install(struct nsset *nsset, struct ns_common *ns)
395 : {
396 0 : struct nsproxy *nsproxy = nsset->nsproxy;
397 0 : struct pid_namespace *active = task_active_pid_ns(current);
398 0 : struct pid_namespace *ancestor, *new = to_pid_ns(ns);
399 :
400 0 : if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
401 0 : !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
402 : return -EPERM;
403 :
404 : /*
405 : * Only allow entering the current active pid namespace
406 : * or a child of the current active pid namespace.
407 : *
408 : * This is required for fork to return a usable pid value and
409 : * this maintains the property that processes and their
410 : * children can not escape their current pid namespace.
411 : */
412 0 : if (new->level < active->level)
413 : return -EINVAL;
414 :
415 : ancestor = new;
416 0 : while (ancestor->level > active->level)
417 0 : ancestor = ancestor->parent;
418 0 : if (ancestor != active)
419 : return -EINVAL;
420 :
421 0 : put_pid_ns(nsproxy->pid_ns_for_children);
422 0 : nsproxy->pid_ns_for_children = get_pid_ns(new);
423 0 : return 0;
424 : }
425 :
426 0 : static struct ns_common *pidns_get_parent(struct ns_common *ns)
427 : {
428 0 : struct pid_namespace *active = task_active_pid_ns(current);
429 : struct pid_namespace *pid_ns, *p;
430 :
431 : /* See if the parent is in the current namespace */
432 0 : pid_ns = p = to_pid_ns(ns)->parent;
433 : for (;;) {
434 0 : if (!p)
435 : return ERR_PTR(-EPERM);
436 0 : if (p == active)
437 : break;
438 0 : p = p->parent;
439 : }
440 :
441 0 : return &get_pid_ns(pid_ns)->ns;
442 : }
443 :
444 0 : static struct user_namespace *pidns_owner(struct ns_common *ns)
445 : {
446 0 : return to_pid_ns(ns)->user_ns;
447 : }
448 :
449 : const struct proc_ns_operations pidns_operations = {
450 : .name = "pid",
451 : .type = CLONE_NEWPID,
452 : .get = pidns_get,
453 : .put = pidns_put,
454 : .install = pidns_install,
455 : .owner = pidns_owner,
456 : .get_parent = pidns_get_parent,
457 : };
458 :
459 : const struct proc_ns_operations pidns_for_children_operations = {
460 : .name = "pid_for_children",
461 : .real_ns_name = "pid",
462 : .type = CLONE_NEWPID,
463 : .get = pidns_for_children_get,
464 : .put = pidns_put,
465 : .install = pidns_install,
466 : .owner = pidns_owner,
467 : .get_parent = pidns_get_parent,
468 : };
469 :
470 1 : static __init int pid_namespaces_init(void)
471 : {
472 1 : pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC | SLAB_ACCOUNT);
473 :
474 : #ifdef CONFIG_CHECKPOINT_RESTORE
475 : register_sysctl_init("kernel", pid_ns_ctl_table);
476 : #endif
477 :
478 : register_pid_ns_sysctl_table_vm();
479 1 : return 0;
480 : }
481 :
482 : __initcall(pid_namespaces_init);
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