projects/linux·blob v5.12 · refs

460 lines · 11.2 KiB

1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Pid namespaces
4 *
5 * Authors:
6 * (C) 2007 Pavel Emelyanov <[email protected]>, OpenVZ, SWsoft Inc.
7 * (C) 2007 Sukadev Bhattiprolu <[email protected]>, 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 refcount_set(&ns->ns.count, 1);
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
151void put_pid_ns(struct pid_namespace *ns)
152{
153 struct pid_namespace *parent;
154
155 while (ns != &init_pid_ns) {
156 parent = ns->parent;
157 if (!refcount_dec_and_test(&ns->ns.count))
158 break;
159 destroy_pid_namespace(ns);
160 ns = parent;
161 }
162}
163EXPORT_SYMBOL_GPL(put_pid_ns);
164
165void zap_pid_ns_processes(struct pid_namespace *pid_ns)
166{
167 int nr;
168 int rc;
169 struct task_struct *task, *me = current;
170 int init_pids = thread_group_leader(me) ? 1 : 2;
171 struct pid *pid;
172
173 /* Don't allow any more processes into the pid namespace */
174 disable_pid_allocation(pid_ns);
175
176 /*
177 * Ignore SIGCHLD causing any terminated children to autoreap.
178 * This speeds up the namespace shutdown, plus see the comment
179 * below.
180 */
181 spin_lock_irq(&me->sighand->siglock);
182 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
183 spin_unlock_irq(&me->sighand->siglock);
184
185 /*
186 * The last thread in the cgroup-init thread group is terminating.
187 * Find remaining pid_ts in the namespace, signal and wait for them
188 * to exit.
189 *
190 * Note: This signals each threads in the namespace - even those that
191 * belong to the same thread group, To avoid this, we would have
192 * to walk the entire tasklist looking a processes in this
193 * namespace, but that could be unnecessarily expensive if the
194 * pid namespace has just a few processes. Or we need to
195 * maintain a tasklist for each pid namespace.
196 *
197 */
198 rcu_read_lock();
199 read_lock(&tasklist_lock);
200 nr = 2;
201 idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
202 task = pid_task(pid, PIDTYPE_PID);
203 if (task && !__fatal_signal_pending(task))
204 group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);
205 }
206 read_unlock(&tasklist_lock);
207 rcu_read_unlock();
208
209 /*
210 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
211 * kernel_wait4() will also block until our children traced from the
212 * parent namespace are detached and become EXIT_DEAD.
213 */
214 do {
215 clear_thread_flag(TIF_SIGPENDING);
216 rc = kernel_wait4(-1, NULL, __WALL, NULL);
217 } while (rc != -ECHILD);
218
219 /*
220 * kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE
221 * process whose parents processes are outside of the pid
222 * namespace. Such processes are created with setns()+fork().
223 *
224 * If those EXIT_ZOMBIE processes are not reaped by their
225 * parents before their parents exit, they will be reparented
226 * to pid_ns->child_reaper. Thus pidns->child_reaper needs to
227 * stay valid until they all go away.
228 *
229 * The code relies on the pid_ns->child_reaper ignoring
230 * SIGCHILD to cause those EXIT_ZOMBIE processes to be
231 * autoreaped if reparented.
232 *
233 * Semantically it is also desirable to wait for EXIT_ZOMBIE
234 * processes before allowing the child_reaper to be reaped, as
235 * that gives the invariant that when the init process of a
236 * pid namespace is reaped all of the processes in the pid
237 * namespace are gone.
238 *
239 * Once all of the other tasks are gone from the pid_namespace
240 * free_pid() will awaken this task.
241 */
242 for (;;) {
243 set_current_state(TASK_INTERRUPTIBLE);
244 if (pid_ns->pid_allocated == init_pids)
245 break;
246 schedule();
247 }
248 __set_current_state(TASK_RUNNING);
249
250 if (pid_ns->reboot)
251 current->signal->group_exit_code = pid_ns->reboot;
252
253 acct_exit_ns(pid_ns);
254 return;
255}
256
257#ifdef CONFIG_CHECKPOINT_RESTORE
258static int pid_ns_ctl_handler(struct ctl_table *table, int write,
259 void *buffer, size_t *lenp, loff_t *ppos)
260{
261 struct pid_namespace *pid_ns = task_active_pid_ns(current);
262 struct ctl_table tmp = *table;
263 int ret, next;
264
265 if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns))
266 return -EPERM;
267
268 /*
269 * Writing directly to ns' last_pid field is OK, since this field
270 * is volatile in a living namespace anyway and a code writing to
271 * it should synchronize its usage with external means.
272 */
273
274 next = idr_get_cursor(&pid_ns->idr) - 1;
275
276 tmp.data = &next;
277 ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
278 if (!ret && write)
279 idr_set_cursor(&pid_ns->idr, next + 1);
280
281 return ret;
282}
283
284extern int pid_max;
285static struct ctl_table pid_ns_ctl_table[] = {
286 {
287 .procname = "ns_last_pid",
288 .maxlen = sizeof(int),
289 .mode = 0666, /* permissions are checked in the handler */
290 .proc_handler = pid_ns_ctl_handler,
291 .extra1 = SYSCTL_ZERO,
292 .extra2 = &pid_max,
293 },
294 { }
295};
296static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
297#endif /* CONFIG_CHECKPOINT_RESTORE */
298
299int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
300{
301 if (pid_ns == &init_pid_ns)
302 return 0;
303
304 switch (cmd) {
305 case LINUX_REBOOT_CMD_RESTART2:
306 case LINUX_REBOOT_CMD_RESTART:
307 pid_ns->reboot = SIGHUP;
308 break;
309
310 case LINUX_REBOOT_CMD_POWER_OFF:
311 case LINUX_REBOOT_CMD_HALT:
312 pid_ns->reboot = SIGINT;
313 break;
314 default:
315 return -EINVAL;
316 }
317
318 read_lock(&tasklist_lock);
319 send_sig(SIGKILL, pid_ns->child_reaper, 1);
320 read_unlock(&tasklist_lock);
321
322 do_exit(0);
323
324 /* Not reached */
325 return 0;
326}
327
328static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
329{
330 return container_of(ns, struct pid_namespace, ns);
331}
332
333static struct ns_common *pidns_get(struct task_struct *task)
334{
335 struct pid_namespace *ns;
336
337 rcu_read_lock();
338 ns = task_active_pid_ns(task);
339 if (ns)
340 get_pid_ns(ns);
341 rcu_read_unlock();
342
343 return ns ? &ns->ns : NULL;
344}
345
346static struct ns_common *pidns_for_children_get(struct task_struct *task)
347{
348 struct pid_namespace *ns = NULL;
349
350 task_lock(task);
351 if (task->nsproxy) {
352 ns = task->nsproxy->pid_ns_for_children;
353 get_pid_ns(ns);
354 }
355 task_unlock(task);
356
357 if (ns) {
358 read_lock(&tasklist_lock);
359 if (!ns->child_reaper) {
360 put_pid_ns(ns);
361 ns = NULL;
362 }
363 read_unlock(&tasklist_lock);
364 }
365
366 return ns ? &ns->ns : NULL;
367}
368
369static void pidns_put(struct ns_common *ns)
370{
371 put_pid_ns(to_pid_ns(ns));
372}
373
374static int pidns_install(struct nsset *nsset, struct ns_common *ns)
375{
376 struct nsproxy *nsproxy = nsset->nsproxy;
377 struct pid_namespace *active = task_active_pid_ns(current);
378 struct pid_namespace *ancestor, *new = to_pid_ns(ns);
379
380 if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
381 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
382 return -EPERM;
383
384 /*
385 * Only allow entering the current active pid namespace
386 * or a child of the current active pid namespace.
387 *
388 * This is required for fork to return a usable pid value and
389 * this maintains the property that processes and their
390 * children can not escape their current pid namespace.
391 */
392 if (new->level < active->level)
393 return -EINVAL;
394
395 ancestor = new;
396 while (ancestor->level > active->level)
397 ancestor = ancestor->parent;
398 if (ancestor != active)
399 return -EINVAL;
400
401 put_pid_ns(nsproxy->pid_ns_for_children);
402 nsproxy->pid_ns_for_children = get_pid_ns(new);
403 return 0;
404}
405
406static struct ns_common *pidns_get_parent(struct ns_common *ns)
407{
408 struct pid_namespace *active = task_active_pid_ns(current);
409 struct pid_namespace *pid_ns, *p;
410
411 /* See if the parent is in the current namespace */
412 pid_ns = p = to_pid_ns(ns)->parent;
413 for (;;) {
414 if (!p)
415 return ERR_PTR(-EPERM);
416 if (p == active)
417 break;
418 p = p->parent;
419 }
420
421 return &get_pid_ns(pid_ns)->ns;
422}
423
424static struct user_namespace *pidns_owner(struct ns_common *ns)
425{
426 return to_pid_ns(ns)->user_ns;
427}
428
429const struct proc_ns_operations pidns_operations = {
430 .name = "pid",
431 .type = CLONE_NEWPID,
432 .get = pidns_get,
433 .put = pidns_put,
434 .install = pidns_install,
435 .owner = pidns_owner,
436 .get_parent = pidns_get_parent,
437};
438
439const struct proc_ns_operations pidns_for_children_operations = {
440 .name = "pid_for_children",
441 .real_ns_name = "pid",
442 .type = CLONE_NEWPID,
443 .get = pidns_for_children_get,
444 .put = pidns_put,
445 .install = pidns_install,
446 .owner = pidns_owner,
447 .get_parent = pidns_get_parent,
448};
449
450static __init int pid_namespaces_init(void)
451{
452 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
453
454#ifdef CONFIG_CHECKPOINT_RESTORE
455 register_sysctl_paths(kern_path, pid_ns_ctl_table);
456#endif
457 return 0;
458}
459
460__initcall(pid_namespaces_init);