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 :
27 : static DEFINE_MUTEX(pid_caches_mutex);
28 : static struct kmem_cache *pid_ns_cachep;
29 : /* Write once array, filled from the beginning. */
30 : static 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 :
37 0 : static struct kmem_cache *create_pid_cachep(unsigned int level)
38 : {
39 : /* Level 0 is init_pid_ns.pid_cachep */
40 0 : 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 0 : kc = READ_ONCE(*pkc);
46 0 : if (kc)
47 : return kc;
48 :
49 0 : snprintf(name, sizeof(name), "pid_%u", level + 1);
50 0 : len = sizeof(struct pid) + level * sizeof(struct upid);
51 0 : mutex_lock(&pid_caches_mutex);
52 : /* Name collision forces to do allocation under mutex. */
53 0 : if (!*pkc)
54 0 : *pkc = kmem_cache_create(name, len, 0,
55 : SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT, 0);
56 0 : mutex_unlock(&pid_caches_mutex);
57 : /* current can fail, but someone else can succeed. */
58 0 : return READ_ONCE(*pkc);
59 : }
60 :
61 : static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
62 : {
63 0 : return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
64 : }
65 :
66 : static void dec_pid_namespaces(struct ucounts *ucounts)
67 : {
68 0 : dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
69 : }
70 :
71 0 : static 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 0 : unsigned int level = parent_pid_ns->level + 1;
76 : struct ucounts *ucounts;
77 : int err;
78 :
79 0 : err = -EINVAL;
80 0 : if (!in_userns(parent_pid_ns->user_ns, user_ns))
81 : goto out;
82 :
83 0 : err = -ENOSPC;
84 0 : if (level > MAX_PID_NS_LEVEL)
85 : goto out;
86 0 : ucounts = inc_pid_namespaces(user_ns);
87 0 : if (!ucounts)
88 : goto out;
89 :
90 0 : err = -ENOMEM;
91 0 : ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
92 0 : if (ns == NULL)
93 : goto out_dec;
94 :
95 0 : idr_init(&ns->idr);
96 :
97 0 : ns->pid_cachep = create_pid_cachep(level);
98 0 : if (ns->pid_cachep == NULL)
99 : goto out_free_idr;
100 :
101 0 : err = ns_alloc_inum(&ns->ns);
102 0 : if (err)
103 : goto out_free_idr;
104 0 : ns->ns.ops = &pidns_operations;
105 :
106 0 : refcount_set(&ns->ns.count, 1);
107 0 : ns->level = level;
108 0 : ns->parent = get_pid_ns(parent_pid_ns);
109 0 : ns->user_ns = get_user_ns(user_ns);
110 0 : ns->ucounts = ucounts;
111 0 : ns->pid_allocated = PIDNS_ADDING;
112 :
113 0 : return ns;
114 :
115 : out_free_idr:
116 0 : idr_destroy(&ns->idr);
117 0 : kmem_cache_free(pid_ns_cachep, ns);
118 : out_dec:
119 : dec_pid_namespaces(ucounts);
120 : out:
121 0 : return ERR_PTR(err);
122 : }
123 :
124 0 : static void delayed_free_pidns(struct rcu_head *p)
125 : {
126 0 : struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
127 :
128 0 : dec_pid_namespaces(ns->ucounts);
129 0 : put_user_ns(ns->user_ns);
130 :
131 0 : kmem_cache_free(pid_ns_cachep, ns);
132 0 : }
133 :
134 0 : static void destroy_pid_namespace(struct pid_namespace *ns)
135 : {
136 0 : ns_free_inum(&ns->ns);
137 :
138 0 : idr_destroy(&ns->idr);
139 0 : call_rcu(&ns->rcu, delayed_free_pidns);
140 0 : }
141 :
142 0 : struct pid_namespace *copy_pid_ns(unsigned long flags,
143 : struct user_namespace *user_ns, struct pid_namespace *old_ns)
144 : {
145 0 : if (!(flags & CLONE_NEWPID))
146 : return get_pid_ns(old_ns);
147 0 : if (task_active_pid_ns(current) != old_ns)
148 : return ERR_PTR(-EINVAL);
149 0 : return create_pid_namespace(user_ns, old_ns);
150 : }
151 :
152 93 : void put_pid_ns(struct pid_namespace *ns)
153 : {
154 : struct pid_namespace *parent;
155 :
156 186 : while (ns != &init_pid_ns) {
157 0 : parent = ns->parent;
158 0 : if (!refcount_dec_and_test(&ns->ns.count))
159 : break;
160 0 : destroy_pid_namespace(ns);
161 0 : ns = parent;
162 : }
163 93 : }
164 : EXPORT_SYMBOL_GPL(put_pid_ns);
165 :
166 0 : void zap_pid_ns_processes(struct pid_namespace *pid_ns)
167 : {
168 : int nr;
169 : int rc;
170 0 : struct task_struct *task, *me = current;
171 0 : 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 0 : 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 0 : spin_lock_irq(&me->sighand->siglock);
183 0 : me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
184 0 : 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 0 : read_lock(&tasklist_lock);
201 0 : nr = 2;
202 0 : idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
203 0 : task = pid_task(pid, PIDTYPE_PID);
204 0 : if (task && !__fatal_signal_pending(task))
205 0 : group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);
206 : }
207 0 : 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 0 : clear_thread_flag(TIF_SIGPENDING);
217 0 : rc = kernel_wait4(-1, NULL, __WALL, NULL);
218 0 : } 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 0 : set_current_state(TASK_INTERRUPTIBLE);
245 0 : if (pid_ns->pid_allocated == init_pids)
246 : break;
247 0 : schedule();
248 : }
249 0 : __set_current_state(TASK_RUNNING);
250 :
251 0 : if (pid_ns->reboot)
252 0 : current->signal->group_exit_code = pid_ns->reboot;
253 :
254 : acct_exit_ns(pid_ns);
255 0 : return;
256 : }
257 :
258 : #ifdef CONFIG_CHECKPOINT_RESTORE
259 : static 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 :
285 : extern int pid_max;
286 : static 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 : };
297 : static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
298 : #endif /* CONFIG_CHECKPOINT_RESTORE */
299 :
300 0 : int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
301 : {
302 0 : if (pid_ns == &init_pid_ns)
303 : return 0;
304 :
305 0 : switch (cmd) {
306 : case LINUX_REBOOT_CMD_RESTART2:
307 : case LINUX_REBOOT_CMD_RESTART:
308 0 : pid_ns->reboot = SIGHUP;
309 0 : break;
310 :
311 : case LINUX_REBOOT_CMD_POWER_OFF:
312 : case LINUX_REBOOT_CMD_HALT:
313 0 : pid_ns->reboot = SIGINT;
314 0 : break;
315 : default:
316 : return -EINVAL;
317 : }
318 :
319 0 : read_lock(&tasklist_lock);
320 0 : send_sig(SIGKILL, pid_ns->child_reaper, 1);
321 0 : read_unlock(&tasklist_lock);
322 :
323 0 : do_exit(0);
324 :
325 : /* Not reached */
326 : return 0;
327 : }
328 :
329 : static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
330 : {
331 0 : return container_of(ns, struct pid_namespace, ns);
332 : }
333 :
334 0 : static struct ns_common *pidns_get(struct task_struct *task)
335 : {
336 : struct pid_namespace *ns;
337 :
338 : rcu_read_lock();
339 0 : ns = task_active_pid_ns(task);
340 0 : if (ns)
341 : get_pid_ns(ns);
342 : rcu_read_unlock();
343 :
344 0 : return ns ? &ns->ns : NULL;
345 : }
346 :
347 0 : static struct ns_common *pidns_for_children_get(struct task_struct *task)
348 : {
349 0 : struct pid_namespace *ns = NULL;
350 :
351 0 : task_lock(task);
352 0 : if (task->nsproxy) {
353 0 : ns = task->nsproxy->pid_ns_for_children;
354 : get_pid_ns(ns);
355 : }
356 0 : task_unlock(task);
357 :
358 0 : if (ns) {
359 0 : read_lock(&tasklist_lock);
360 0 : if (!ns->child_reaper) {
361 0 : put_pid_ns(ns);
362 0 : ns = NULL;
363 : }
364 0 : read_unlock(&tasklist_lock);
365 : }
366 :
367 0 : return ns ? &ns->ns : NULL;
368 : }
369 :
370 0 : static void pidns_put(struct ns_common *ns)
371 : {
372 0 : put_pid_ns(to_pid_ns(ns));
373 0 : }
374 :
375 0 : static int pidns_install(struct nsset *nsset, struct ns_common *ns)
376 : {
377 0 : struct nsproxy *nsproxy = nsset->nsproxy;
378 0 : struct pid_namespace *active = task_active_pid_ns(current);
379 0 : struct pid_namespace *ancestor, *new = to_pid_ns(ns);
380 :
381 0 : if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
382 0 : !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 0 : if (new->level < active->level)
394 : return -EINVAL;
395 :
396 : ancestor = new;
397 0 : while (ancestor->level > active->level)
398 0 : ancestor = ancestor->parent;
399 0 : if (ancestor != active)
400 : return -EINVAL;
401 :
402 0 : put_pid_ns(nsproxy->pid_ns_for_children);
403 0 : nsproxy->pid_ns_for_children = get_pid_ns(new);
404 0 : return 0;
405 : }
406 :
407 0 : static struct ns_common *pidns_get_parent(struct ns_common *ns)
408 : {
409 0 : 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 0 : pid_ns = p = to_pid_ns(ns)->parent;
414 : for (;;) {
415 0 : if (!p)
416 : return ERR_PTR(-EPERM);
417 0 : if (p == active)
418 : break;
419 0 : p = p->parent;
420 : }
421 :
422 0 : return &get_pid_ns(pid_ns)->ns;
423 : }
424 :
425 0 : static struct user_namespace *pidns_owner(struct ns_common *ns)
426 : {
427 0 : return to_pid_ns(ns)->user_ns;
428 : }
429 :
430 : const 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 :
440 : const 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 :
451 1 : static __init int pid_namespaces_init(void)
452 : {
453 1 : 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 1 : return 0;
459 : }
460 :
461 : __initcall(pid_namespaces_init);
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