projects/linux·blob v4.15 · refs

487 lines · 11.6 KiB

1/*
2 * Pid namespaces
3 *
4 * Authors:
5 * (C) 2007 Pavel Emelyanov <[email protected]>, OpenVZ, SWsoft Inc.
6 * (C) 2007 Sukadev Bhattiprolu <[email protected]>, 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/user_namespace.h>
14#include <linux/syscalls.h>
15#include <linux/cred.h>
16#include <linux/err.h>
17#include <linux/acct.h>
18#include <linux/slab.h>
19#include <linux/proc_ns.h>
20#include <linux/reboot.h>
21#include <linux/export.h>
22#include <linux/sched/task.h>
23#include <linux/sched/signal.h>
24#include <linux/idr.h>
25
26struct pid_cache {
27 int nr_ids;
28 char name[16];
29 struct kmem_cache *cachep;
30 struct list_head list;
31};
32
33static LIST_HEAD(pid_caches_lh);
34static DEFINE_MUTEX(pid_caches_mutex);
35static struct kmem_cache *pid_ns_cachep;
36
37/*
38 * creates the kmem cache to allocate pids from.
39 * @nr_ids: the number of numerical ids this pid will have to carry
40 */
41
42static struct kmem_cache *create_pid_cachep(int nr_ids)
43{
44 struct pid_cache *pcache;
45 struct kmem_cache *cachep;
46
47 mutex_lock(&pid_caches_mutex);
48 list_for_each_entry(pcache, &pid_caches_lh, list)
49 if (pcache->nr_ids == nr_ids)
50 goto out;
51
52 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
53 if (pcache == NULL)
54 goto err_alloc;
55
56 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
57 cachep = kmem_cache_create(pcache->name,
58 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
59 0, SLAB_HWCACHE_ALIGN, NULL);
60 if (cachep == NULL)
61 goto err_cachep;
62
63 pcache->nr_ids = nr_ids;
64 pcache->cachep = cachep;
65 list_add(&pcache->list, &pid_caches_lh);
66out:
67 mutex_unlock(&pid_caches_mutex);
68 return pcache->cachep;
69
70err_cachep:
71 kfree(pcache);
72err_alloc:
73 mutex_unlock(&pid_caches_mutex);
74 return NULL;
75}
76
77static void proc_cleanup_work(struct work_struct *work)
78{
79 struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
80 pid_ns_release_proc(ns);
81}
82
83/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
84#define MAX_PID_NS_LEVEL 32
85
86static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
87{
88 return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
89}
90
91static void dec_pid_namespaces(struct ucounts *ucounts)
92{
93 dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
94}
95
96static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
97 struct pid_namespace *parent_pid_ns)
98{
99 struct pid_namespace *ns;
100 unsigned int level = parent_pid_ns->level + 1;
101 struct ucounts *ucounts;
102 int err;
103
104 err = -EINVAL;
105 if (!in_userns(parent_pid_ns->user_ns, user_ns))
106 goto out;
107
108 err = -ENOSPC;
109 if (level > MAX_PID_NS_LEVEL)
110 goto out;
111 ucounts = inc_pid_namespaces(user_ns);
112 if (!ucounts)
113 goto out;
114
115 err = -ENOMEM;
116 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
117 if (ns == NULL)
118 goto out_dec;
119
120 idr_init(&ns->idr);
121
122 ns->pid_cachep = create_pid_cachep(level + 1);
123 if (ns->pid_cachep == NULL)
124 goto out_free_idr;
125
126 err = ns_alloc_inum(&ns->ns);
127 if (err)
128 goto out_free_idr;
129 ns->ns.ops = &pidns_operations;
130
131 kref_init(&ns->kref);
132 ns->level = level;
133 ns->parent = get_pid_ns(parent_pid_ns);
134 ns->user_ns = get_user_ns(user_ns);
135 ns->ucounts = ucounts;
136 ns->pid_allocated = PIDNS_ADDING;
137 INIT_WORK(&ns->proc_work, proc_cleanup_work);
138
139 return ns;
140
141out_free_idr:
142 idr_destroy(&ns->idr);
143 kmem_cache_free(pid_ns_cachep, ns);
144out_dec:
145 dec_pid_namespaces(ucounts);
146out:
147 return ERR_PTR(err);
148}
149
150static void delayed_free_pidns(struct rcu_head *p)
151{
152 struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
153
154 dec_pid_namespaces(ns->ucounts);
155 put_user_ns(ns->user_ns);
156
157 kmem_cache_free(pid_ns_cachep, ns);
158}
159
160static void destroy_pid_namespace(struct pid_namespace *ns)
161{
162 ns_free_inum(&ns->ns);
163
164 idr_destroy(&ns->idr);
165 call_rcu(&ns->rcu, delayed_free_pidns);
166}
167
168struct pid_namespace *copy_pid_ns(unsigned long flags,
169 struct user_namespace *user_ns, struct pid_namespace *old_ns)
170{
171 if (!(flags & CLONE_NEWPID))
172 return get_pid_ns(old_ns);
173 if (task_active_pid_ns(current) != old_ns)
174 return ERR_PTR(-EINVAL);
175 return create_pid_namespace(user_ns, old_ns);
176}
177
178static void free_pid_ns(struct kref *kref)
179{
180 struct pid_namespace *ns;
181
182 ns = container_of(kref, struct pid_namespace, kref);
183 destroy_pid_namespace(ns);
184}
185
186void put_pid_ns(struct pid_namespace *ns)
187{
188 struct pid_namespace *parent;
189
190 while (ns != &init_pid_ns) {
191 parent = ns->parent;
192 if (!kref_put(&ns->kref, free_pid_ns))
193 break;
194 ns = parent;
195 }
196}
197EXPORT_SYMBOL_GPL(put_pid_ns);
198
199void zap_pid_ns_processes(struct pid_namespace *pid_ns)
200{
201 int nr;
202 int rc;
203 struct task_struct *task, *me = current;
204 int init_pids = thread_group_leader(me) ? 1 : 2;
205 struct pid *pid;
206
207 /* Don't allow any more processes into the pid namespace */
208 disable_pid_allocation(pid_ns);
209
210 /*
211 * Ignore SIGCHLD causing any terminated children to autoreap.
212 * This speeds up the namespace shutdown, plus see the comment
213 * below.
214 */
215 spin_lock_irq(&me->sighand->siglock);
216 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
217 spin_unlock_irq(&me->sighand->siglock);
218
219 /*
220 * The last thread in the cgroup-init thread group is terminating.
221 * Find remaining pid_ts in the namespace, signal and wait for them
222 * to exit.
223 *
224 * Note: This signals each threads in the namespace - even those that
225 * belong to the same thread group, To avoid this, we would have
226 * to walk the entire tasklist looking a processes in this
227 * namespace, but that could be unnecessarily expensive if the
228 * pid namespace has just a few processes. Or we need to
229 * maintain a tasklist for each pid namespace.
230 *
231 */
232 rcu_read_lock();
233 read_lock(&tasklist_lock);
234 nr = 2;
235 idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
236 task = pid_task(pid, PIDTYPE_PID);
237 if (task && !__fatal_signal_pending(task))
238 send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
239 }
240 read_unlock(&tasklist_lock);
241 rcu_read_unlock();
242
243 /*
244 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
245 * sys_wait4() will also block until our children traced from the
246 * parent namespace are detached and become EXIT_DEAD.
247 */
248 do {
249 clear_thread_flag(TIF_SIGPENDING);
250 rc = sys_wait4(-1, NULL, __WALL, NULL);
251 } while (rc != -ECHILD);
252
253 /*
254 * sys_wait4() above can't reap the EXIT_DEAD children but we do not
255 * really care, we could reparent them to the global init. We could
256 * exit and reap ->child_reaper even if it is not the last thread in
257 * this pid_ns, free_pid(pid_allocated == 0) calls proc_cleanup_work(),
258 * pid_ns can not go away until proc_kill_sb() drops the reference.
259 *
260 * But this ns can also have other tasks injected by setns()+fork().
261 * Again, ignoring the user visible semantics we do not really need
262 * to wait until they are all reaped, but they can be reparented to
263 * us and thus we need to ensure that pid->child_reaper stays valid
264 * until they all go away. See free_pid()->wake_up_process().
265 *
266 * We rely on ignored SIGCHLD, an injected zombie must be autoreaped
267 * if reparented.
268 */
269 for (;;) {
270 set_current_state(TASK_INTERRUPTIBLE);
271 if (pid_ns->pid_allocated == init_pids)
272 break;
273 schedule();
274 }
275 __set_current_state(TASK_RUNNING);
276
277 if (pid_ns->reboot)
278 current->signal->group_exit_code = pid_ns->reboot;
279
280 acct_exit_ns(pid_ns);
281 return;
282}
283
284#ifdef CONFIG_CHECKPOINT_RESTORE
285static int pid_ns_ctl_handler(struct ctl_table *table, int write,
286 void __user *buffer, size_t *lenp, loff_t *ppos)
287{
288 struct pid_namespace *pid_ns = task_active_pid_ns(current);
289 struct ctl_table tmp = *table;
290 int ret, next;
291
292 if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
293 return -EPERM;
294
295 /*
296 * Writing directly to ns' last_pid field is OK, since this field
297 * is volatile in a living namespace anyway and a code writing to
298 * it should synchronize its usage with external means.
299 */
300
301 next = idr_get_cursor(&pid_ns->idr) - 1;
302
303 tmp.data = &next;
304 ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
305 if (!ret && write)
306 idr_set_cursor(&pid_ns->idr, next + 1);
307
308 return ret;
309}
310
311extern int pid_max;
312static int zero = 0;
313static struct ctl_table pid_ns_ctl_table[] = {
314 {
315 .procname = "ns_last_pid",
316 .maxlen = sizeof(int),
317 .mode = 0666, /* permissions are checked in the handler */
318 .proc_handler = pid_ns_ctl_handler,
319 .extra1 = &zero,
320 .extra2 = &pid_max,
321 },
322 { }
323};
324static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
325#endif /* CONFIG_CHECKPOINT_RESTORE */
326
327int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
328{
329 if (pid_ns == &init_pid_ns)
330 return 0;
331
332 switch (cmd) {
333 case LINUX_REBOOT_CMD_RESTART2:
334 case LINUX_REBOOT_CMD_RESTART:
335 pid_ns->reboot = SIGHUP;
336 break;
337
338 case LINUX_REBOOT_CMD_POWER_OFF:
339 case LINUX_REBOOT_CMD_HALT:
340 pid_ns->reboot = SIGINT;
341 break;
342 default:
343 return -EINVAL;
344 }
345
346 read_lock(&tasklist_lock);
347 force_sig(SIGKILL, pid_ns->child_reaper);
348 read_unlock(&tasklist_lock);
349
350 do_exit(0);
351
352 /* Not reached */
353 return 0;
354}
355
356static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
357{
358 return container_of(ns, struct pid_namespace, ns);
359}
360
361static struct ns_common *pidns_get(struct task_struct *task)
362{
363 struct pid_namespace *ns;
364
365 rcu_read_lock();
366 ns = task_active_pid_ns(task);
367 if (ns)
368 get_pid_ns(ns);
369 rcu_read_unlock();
370
371 return ns ? &ns->ns : NULL;
372}
373
374static struct ns_common *pidns_for_children_get(struct task_struct *task)
375{
376 struct pid_namespace *ns = NULL;
377
378 task_lock(task);
379 if (task->nsproxy) {
380 ns = task->nsproxy->pid_ns_for_children;
381 get_pid_ns(ns);
382 }
383 task_unlock(task);
384
385 if (ns) {
386 read_lock(&tasklist_lock);
387 if (!ns->child_reaper) {
388 put_pid_ns(ns);
389 ns = NULL;
390 }
391 read_unlock(&tasklist_lock);
392 }
393
394 return ns ? &ns->ns : NULL;
395}
396
397static void pidns_put(struct ns_common *ns)
398{
399 put_pid_ns(to_pid_ns(ns));
400}
401
402static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
403{
404 struct pid_namespace *active = task_active_pid_ns(current);
405 struct pid_namespace *ancestor, *new = to_pid_ns(ns);
406
407 if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
408 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
409 return -EPERM;
410
411 /*
412 * Only allow entering the current active pid namespace
413 * or a child of the current active pid namespace.
414 *
415 * This is required for fork to return a usable pid value and
416 * this maintains the property that processes and their
417 * children can not escape their current pid namespace.
418 */
419 if (new->level < active->level)
420 return -EINVAL;
421
422 ancestor = new;
423 while (ancestor->level > active->level)
424 ancestor = ancestor->parent;
425 if (ancestor != active)
426 return -EINVAL;
427
428 put_pid_ns(nsproxy->pid_ns_for_children);
429 nsproxy->pid_ns_for_children = get_pid_ns(new);
430 return 0;
431}
432
433static struct ns_common *pidns_get_parent(struct ns_common *ns)
434{
435 struct pid_namespace *active = task_active_pid_ns(current);
436 struct pid_namespace *pid_ns, *p;
437
438 /* See if the parent is in the current namespace */
439 pid_ns = p = to_pid_ns(ns)->parent;
440 for (;;) {
441 if (!p)
442 return ERR_PTR(-EPERM);
443 if (p == active)
444 break;
445 p = p->parent;
446 }
447
448 return &get_pid_ns(pid_ns)->ns;
449}
450
451static struct user_namespace *pidns_owner(struct ns_common *ns)
452{
453 return to_pid_ns(ns)->user_ns;
454}
455
456const struct proc_ns_operations pidns_operations = {
457 .name = "pid",
458 .type = CLONE_NEWPID,
459 .get = pidns_get,
460 .put = pidns_put,
461 .install = pidns_install,
462 .owner = pidns_owner,
463 .get_parent = pidns_get_parent,
464};
465
466const struct proc_ns_operations pidns_for_children_operations = {
467 .name = "pid_for_children",
468 .real_ns_name = "pid",
469 .type = CLONE_NEWPID,
470 .get = pidns_for_children_get,
471 .put = pidns_put,
472 .install = pidns_install,
473 .owner = pidns_owner,
474 .get_parent = pidns_get_parent,
475};
476
477static __init int pid_namespaces_init(void)
478{
479 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
480
481#ifdef CONFIG_CHECKPOINT_RESTORE
482 register_sysctl_paths(kern_path, pid_ns_ctl_table);
483#endif
484 return 0;
485}
486
487__initcall(pid_namespaces_init);