Line data Source code
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/user_namespace.h>
14 : #include <linux/syscalls.h>
15 : #include <linux/err.h>
16 : #include <linux/acct.h>
17 : #include <linux/slab.h>
18 : #include <linux/proc_ns.h>
19 : #include <linux/reboot.h>
20 : #include <linux/export.h>
21 :
22 : struct pid_cache {
23 : int nr_ids;
24 : char name[16];
25 : struct kmem_cache *cachep;
26 : struct list_head list;
27 : };
28 :
29 : static LIST_HEAD(pid_caches_lh);
30 : static DEFINE_MUTEX(pid_caches_mutex);
31 : static struct kmem_cache *pid_ns_cachep;
32 :
33 : /*
34 : * creates the kmem cache to allocate pids from.
35 : * @nr_ids: the number of numerical ids this pid will have to carry
36 : */
37 :
38 0 : static struct kmem_cache *create_pid_cachep(int nr_ids)
39 : {
40 : struct pid_cache *pcache;
41 : struct kmem_cache *cachep;
42 :
43 0 : mutex_lock(&pid_caches_mutex);
44 0 : list_for_each_entry(pcache, &pid_caches_lh, list)
45 0 : if (pcache->nr_ids == nr_ids)
46 : goto out;
47 :
48 : pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
49 0 : if (pcache == NULL)
50 : goto err_alloc;
51 :
52 0 : snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
53 0 : cachep = kmem_cache_create(pcache->name,
54 0 : sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
55 : 0, SLAB_HWCACHE_ALIGN, NULL);
56 0 : if (cachep == NULL)
57 : goto err_cachep;
58 :
59 0 : pcache->nr_ids = nr_ids;
60 0 : pcache->cachep = cachep;
61 0 : list_add(&pcache->list, &pid_caches_lh);
62 : out:
63 0 : mutex_unlock(&pid_caches_mutex);
64 0 : return pcache->cachep;
65 :
66 : err_cachep:
67 0 : kfree(pcache);
68 : err_alloc:
69 0 : mutex_unlock(&pid_caches_mutex);
70 0 : return NULL;
71 : }
72 :
73 0 : static void proc_cleanup_work(struct work_struct *work)
74 : {
75 0 : struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
76 0 : pid_ns_release_proc(ns);
77 0 : }
78 :
79 : /* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
80 : #define MAX_PID_NS_LEVEL 32
81 :
82 0 : static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
83 : struct pid_namespace *parent_pid_ns)
84 : {
85 : struct pid_namespace *ns;
86 0 : unsigned int level = parent_pid_ns->level + 1;
87 : int i;
88 : int err;
89 :
90 0 : if (level > MAX_PID_NS_LEVEL) {
91 : err = -EINVAL;
92 : goto out;
93 : }
94 :
95 : err = -ENOMEM;
96 0 : ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
97 0 : if (ns == NULL)
98 : goto out;
99 :
100 0 : ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
101 0 : if (!ns->pidmap[0].page)
102 : goto out_free;
103 :
104 0 : ns->pid_cachep = create_pid_cachep(level + 1);
105 0 : if (ns->pid_cachep == NULL)
106 : goto out_free_map;
107 :
108 : err = ns_alloc_inum(&ns->ns);
109 0 : if (err)
110 : goto out_free_map;
111 0 : ns->ns.ops = &pidns_operations;
112 :
113 : kref_init(&ns->kref);
114 0 : ns->level = level;
115 0 : ns->parent = get_pid_ns(parent_pid_ns);
116 0 : ns->user_ns = get_user_ns(user_ns);
117 0 : ns->nr_hashed = PIDNS_HASH_ADDING;
118 0 : INIT_WORK(&ns->proc_work, proc_cleanup_work);
119 :
120 0 : set_bit(0, ns->pidmap[0].page);
121 0 : atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
122 :
123 : for (i = 1; i < PIDMAP_ENTRIES; i++)
124 : atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
125 :
126 : return ns;
127 :
128 : out_free_map:
129 0 : kfree(ns->pidmap[0].page);
130 : out_free:
131 0 : kmem_cache_free(pid_ns_cachep, ns);
132 : out:
133 : return ERR_PTR(err);
134 : }
135 :
136 0 : static void delayed_free_pidns(struct rcu_head *p)
137 : {
138 0 : kmem_cache_free(pid_ns_cachep,
139 0 : container_of(p, struct pid_namespace, rcu));
140 0 : }
141 :
142 0 : static void destroy_pid_namespace(struct pid_namespace *ns)
143 : {
144 : int i;
145 :
146 0 : ns_free_inum(&ns->ns);
147 0 : for (i = 0; i < PIDMAP_ENTRIES; i++)
148 0 : kfree(ns->pidmap[i].page);
149 : put_user_ns(ns->user_ns);
150 0 : call_rcu(&ns->rcu, delayed_free_pidns);
151 0 : }
152 :
153 1 : struct pid_namespace *copy_pid_ns(unsigned long flags,
154 : struct user_namespace *user_ns, struct pid_namespace *old_ns)
155 : {
156 1 : if (!(flags & CLONE_NEWPID))
157 1 : return get_pid_ns(old_ns);
158 0 : if (task_active_pid_ns(current) != old_ns)
159 : return ERR_PTR(-EINVAL);
160 0 : return create_pid_namespace(user_ns, old_ns);
161 : }
162 :
163 0 : static void free_pid_ns(struct kref *kref)
164 : {
165 : struct pid_namespace *ns;
166 :
167 : ns = container_of(kref, struct pid_namespace, kref);
168 0 : destroy_pid_namespace(ns);
169 0 : }
170 :
171 2908 : void put_pid_ns(struct pid_namespace *ns)
172 : {
173 : struct pid_namespace *parent;
174 :
175 5816 : while (ns != &init_pid_ns) {
176 0 : parent = ns->parent;
177 0 : if (!kref_put(&ns->kref, free_pid_ns))
178 : break;
179 : ns = parent;
180 : }
181 2908 : }
182 : EXPORT_SYMBOL_GPL(put_pid_ns);
183 :
184 0 : void zap_pid_ns_processes(struct pid_namespace *pid_ns)
185 : {
186 : int nr;
187 : int rc;
188 0 : struct task_struct *task, *me = current;
189 0 : int init_pids = thread_group_leader(me) ? 1 : 2;
190 :
191 : /* Don't allow any more processes into the pid namespace */
192 0 : disable_pid_allocation(pid_ns);
193 :
194 : /*
195 : * Ignore SIGCHLD causing any terminated children to autoreap.
196 : * This speeds up the namespace shutdown, plus see the comment
197 : * below.
198 : */
199 : spin_lock_irq(&me->sighand->siglock);
200 0 : me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
201 : spin_unlock_irq(&me->sighand->siglock);
202 :
203 : /*
204 : * The last thread in the cgroup-init thread group is terminating.
205 : * Find remaining pid_ts in the namespace, signal and wait for them
206 : * to exit.
207 : *
208 : * Note: This signals each threads in the namespace - even those that
209 : * belong to the same thread group, To avoid this, we would have
210 : * to walk the entire tasklist looking a processes in this
211 : * namespace, but that could be unnecessarily expensive if the
212 : * pid namespace has just a few processes. Or we need to
213 : * maintain a tasklist for each pid namespace.
214 : *
215 : */
216 0 : read_lock(&tasklist_lock);
217 0 : nr = next_pidmap(pid_ns, 1);
218 0 : while (nr > 0) {
219 : rcu_read_lock();
220 :
221 0 : task = pid_task(find_vpid(nr), PIDTYPE_PID);
222 0 : if (task && !__fatal_signal_pending(task))
223 0 : send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
224 :
225 : rcu_read_unlock();
226 :
227 0 : nr = next_pidmap(pid_ns, nr);
228 : }
229 0 : read_unlock(&tasklist_lock);
230 :
231 : /*
232 : * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
233 : * sys_wait4() will also block until our children traced from the
234 : * parent namespace are detached and become EXIT_DEAD.
235 : */
236 : do {
237 : clear_thread_flag(TIF_SIGPENDING);
238 0 : rc = sys_wait4(-1, NULL, __WALL, NULL);
239 0 : } while (rc != -ECHILD);
240 :
241 : /*
242 : * sys_wait4() above can't reap the EXIT_DEAD children but we do not
243 : * really care, we could reparent them to the global init. We could
244 : * exit and reap ->child_reaper even if it is not the last thread in
245 : * this pid_ns, free_pid(nr_hashed == 0) calls proc_cleanup_work(),
246 : * pid_ns can not go away until proc_kill_sb() drops the reference.
247 : *
248 : * But this ns can also have other tasks injected by setns()+fork().
249 : * Again, ignoring the user visible semantics we do not really need
250 : * to wait until they are all reaped, but they can be reparented to
251 : * us and thus we need to ensure that pid->child_reaper stays valid
252 : * until they all go away. See free_pid()->wake_up_process().
253 : *
254 : * We rely on ignored SIGCHLD, an injected zombie must be autoreaped
255 : * if reparented.
256 : */
257 : for (;;) {
258 0 : set_current_state(TASK_UNINTERRUPTIBLE);
259 0 : if (pid_ns->nr_hashed == init_pids)
260 : break;
261 0 : schedule();
262 0 : }
263 0 : __set_current_state(TASK_RUNNING);
264 :
265 0 : if (pid_ns->reboot)
266 0 : current->signal->group_exit_code = pid_ns->reboot;
267 :
268 0 : acct_exit_ns(pid_ns);
269 0 : return;
270 : }
271 :
272 : #ifdef CONFIG_CHECKPOINT_RESTORE
273 : static int pid_ns_ctl_handler(struct ctl_table *table, int write,
274 : void __user *buffer, size_t *lenp, loff_t *ppos)
275 : {
276 : struct pid_namespace *pid_ns = task_active_pid_ns(current);
277 : struct ctl_table tmp = *table;
278 :
279 : if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
280 : return -EPERM;
281 :
282 : /*
283 : * Writing directly to ns' last_pid field is OK, since this field
284 : * is volatile in a living namespace anyway and a code writing to
285 : * it should synchronize its usage with external means.
286 : */
287 :
288 : tmp.data = &pid_ns->last_pid;
289 : return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
290 : }
291 :
292 : extern int pid_max;
293 : static int zero = 0;
294 : static struct ctl_table pid_ns_ctl_table[] = {
295 : {
296 : .procname = "ns_last_pid",
297 : .maxlen = sizeof(int),
298 : .mode = 0666, /* permissions are checked in the handler */
299 : .proc_handler = pid_ns_ctl_handler,
300 : .extra1 = &zero,
301 : .extra2 = &pid_max,
302 : },
303 : { }
304 : };
305 : static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
306 : #endif /* CONFIG_CHECKPOINT_RESTORE */
307 :
308 1 : int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
309 : {
310 1 : if (pid_ns == &init_pid_ns)
311 : return 0;
312 :
313 0 : switch (cmd) {
314 : case LINUX_REBOOT_CMD_RESTART2:
315 : case LINUX_REBOOT_CMD_RESTART:
316 0 : pid_ns->reboot = SIGHUP;
317 0 : break;
318 :
319 : case LINUX_REBOOT_CMD_POWER_OFF:
320 : case LINUX_REBOOT_CMD_HALT:
321 0 : pid_ns->reboot = SIGINT;
322 0 : break;
323 : default:
324 : return -EINVAL;
325 : }
326 :
327 0 : read_lock(&tasklist_lock);
328 0 : force_sig(SIGKILL, pid_ns->child_reaper);
329 0 : read_unlock(&tasklist_lock);
330 :
331 0 : do_exit(0);
332 :
333 : /* Not reached */
334 : return 0;
335 : }
336 :
337 : static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
338 : {
339 : return container_of(ns, struct pid_namespace, ns);
340 : }
341 :
342 0 : static struct ns_common *pidns_get(struct task_struct *task)
343 : {
344 : struct pid_namespace *ns;
345 :
346 : rcu_read_lock();
347 0 : ns = task_active_pid_ns(task);
348 0 : if (ns)
349 : get_pid_ns(ns);
350 : rcu_read_unlock();
351 :
352 0 : return ns ? &ns->ns : NULL;
353 : }
354 :
355 0 : static void pidns_put(struct ns_common *ns)
356 : {
357 0 : put_pid_ns(to_pid_ns(ns));
358 0 : }
359 :
360 0 : static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
361 : {
362 0 : struct pid_namespace *active = task_active_pid_ns(current);
363 0 : struct pid_namespace *ancestor, *new = to_pid_ns(ns);
364 :
365 0 : if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
366 0 : !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
367 : return -EPERM;
368 :
369 : /*
370 : * Only allow entering the current active pid namespace
371 : * or a child of the current active pid namespace.
372 : *
373 : * This is required for fork to return a usable pid value and
374 : * this maintains the property that processes and their
375 : * children can not escape their current pid namespace.
376 : */
377 0 : if (new->level < active->level)
378 : return -EINVAL;
379 :
380 : ancestor = new;
381 0 : while (ancestor->level > active->level)
382 0 : ancestor = ancestor->parent;
383 0 : if (ancestor != active)
384 : return -EINVAL;
385 :
386 0 : put_pid_ns(nsproxy->pid_ns_for_children);
387 0 : nsproxy->pid_ns_for_children = get_pid_ns(new);
388 0 : return 0;
389 : }
390 :
391 : const struct proc_ns_operations pidns_operations = {
392 : .name = "pid",
393 : .type = CLONE_NEWPID,
394 : .get = pidns_get,
395 : .put = pidns_put,
396 : .install = pidns_install,
397 : };
398 :
399 1 : static __init int pid_namespaces_init(void)
400 : {
401 1 : pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
402 :
403 : #ifdef CONFIG_CHECKPOINT_RESTORE
404 : register_sysctl_paths(kern_path, pid_ns_ctl_table);
405 : #endif
406 1 : return 0;
407 : }
408 :
409 : __initcall(pid_namespaces_init);
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