projects/linux·blob v3.9 · refs

384 lines · 8.9 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/err.h>
16#include <linux/acct.h>
17#include <linux/slab.h>
18#include <linux/proc_fs.h>
19#include <linux/reboot.h>
20#include <linux/export.h>
21
22#define BITS_PER_PAGE (PAGE_SIZE*8)
23
24struct pid_cache {
25 int nr_ids;
26 char name[16];
27 struct kmem_cache *cachep;
28 struct list_head list;
29};
30
31static LIST_HEAD(pid_caches_lh);
32static DEFINE_MUTEX(pid_caches_mutex);
33static struct kmem_cache *pid_ns_cachep;
34
35/*
36 * creates the kmem cache to allocate pids from.
37 * @nr_ids: the number of numerical ids this pid will have to carry
38 */
39
40static struct kmem_cache *create_pid_cachep(int nr_ids)
41{
42 struct pid_cache *pcache;
43 struct kmem_cache *cachep;
44
45 mutex_lock(&pid_caches_mutex);
46 list_for_each_entry(pcache, &pid_caches_lh, list)
47 if (pcache->nr_ids == nr_ids)
48 goto out;
49
50 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
51 if (pcache == NULL)
52 goto err_alloc;
53
54 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
55 cachep = kmem_cache_create(pcache->name,
56 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
57 0, SLAB_HWCACHE_ALIGN, NULL);
58 if (cachep == NULL)
59 goto err_cachep;
60
61 pcache->nr_ids = nr_ids;
62 pcache->cachep = cachep;
63 list_add(&pcache->list, &pid_caches_lh);
64out:
65 mutex_unlock(&pid_caches_mutex);
66 return pcache->cachep;
67
68err_cachep:
69 kfree(pcache);
70err_alloc:
71 mutex_unlock(&pid_caches_mutex);
72 return NULL;
73}
74
75static void proc_cleanup_work(struct work_struct *work)
76{
77 struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
78 pid_ns_release_proc(ns);
79}
80
81/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
82#define MAX_PID_NS_LEVEL 32
83
84static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
85 struct pid_namespace *parent_pid_ns)
86{
87 struct pid_namespace *ns;
88 unsigned int level = parent_pid_ns->level + 1;
89 int i;
90 int err;
91
92 if (level > MAX_PID_NS_LEVEL) {
93 err = -EINVAL;
94 goto out;
95 }
96
97 err = -ENOMEM;
98 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
99 if (ns == NULL)
100 goto out;
101
102 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
103 if (!ns->pidmap[0].page)
104 goto out_free;
105
106 ns->pid_cachep = create_pid_cachep(level + 1);
107 if (ns->pid_cachep == NULL)
108 goto out_free_map;
109
110 err = proc_alloc_inum(&ns->proc_inum);
111 if (err)
112 goto out_free_map;
113
114 kref_init(&ns->kref);
115 ns->level = level;
116 ns->parent = get_pid_ns(parent_pid_ns);
117 ns->user_ns = get_user_ns(user_ns);
118 ns->nr_hashed = PIDNS_HASH_ADDING;
119 INIT_WORK(&ns->proc_work, proc_cleanup_work);
120
121 set_bit(0, ns->pidmap[0].page);
122 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
123
124 for (i = 1; i < PIDMAP_ENTRIES; i++)
125 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
126
127 return ns;
128
129out_free_map:
130 kfree(ns->pidmap[0].page);
131out_free:
132 kmem_cache_free(pid_ns_cachep, ns);
133out:
134 return ERR_PTR(err);
135}
136
137static void destroy_pid_namespace(struct pid_namespace *ns)
138{
139 int i;
140
141 proc_free_inum(ns->proc_inum);
142 for (i = 0; i < PIDMAP_ENTRIES; i++)
143 kfree(ns->pidmap[i].page);
144 put_user_ns(ns->user_ns);
145 kmem_cache_free(pid_ns_cachep, ns);
146}
147
148struct pid_namespace *copy_pid_ns(unsigned long flags,
149 struct user_namespace *user_ns, struct pid_namespace *old_ns)
150{
151 if (!(flags & CLONE_NEWPID))
152 return get_pid_ns(old_ns);
153 if (task_active_pid_ns(current) != old_ns)
154 return ERR_PTR(-EINVAL);
155 return create_pid_namespace(user_ns, old_ns);
156}
157
158static void free_pid_ns(struct kref *kref)
159{
160 struct pid_namespace *ns;
161
162 ns = container_of(kref, struct pid_namespace, kref);
163 destroy_pid_namespace(ns);
164}
165
166void put_pid_ns(struct pid_namespace *ns)
167{
168 struct pid_namespace *parent;
169
170 while (ns != &init_pid_ns) {
171 parent = ns->parent;
172 if (!kref_put(&ns->kref, free_pid_ns))
173 break;
174 ns = parent;
175 }
176}
177EXPORT_SYMBOL_GPL(put_pid_ns);
178
179void zap_pid_ns_processes(struct pid_namespace *pid_ns)
180{
181 int nr;
182 int rc;
183 struct task_struct *task, *me = current;
184 int init_pids = thread_group_leader(me) ? 1 : 2;
185
186 /* Don't allow any more processes into the pid namespace */
187 disable_pid_allocation(pid_ns);
188
189 /* Ignore SIGCHLD causing any terminated children to autoreap */
190 spin_lock_irq(&me->sighand->siglock);
191 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
192 spin_unlock_irq(&me->sighand->siglock);
193
194 /*
195 * The last thread in the cgroup-init thread group is terminating.
196 * Find remaining pid_ts in the namespace, signal and wait for them
197 * to exit.
198 *
199 * Note: This signals each threads in the namespace - even those that
200 * belong to the same thread group, To avoid this, we would have
201 * to walk the entire tasklist looking a processes in this
202 * namespace, but that could be unnecessarily expensive if the
203 * pid namespace has just a few processes. Or we need to
204 * maintain a tasklist for each pid namespace.
205 *
206 */
207 read_lock(&tasklist_lock);
208 nr = next_pidmap(pid_ns, 1);
209 while (nr > 0) {
210 rcu_read_lock();
211
212 task = pid_task(find_vpid(nr), PIDTYPE_PID);
213 if (task && !__fatal_signal_pending(task))
214 send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
215
216 rcu_read_unlock();
217
218 nr = next_pidmap(pid_ns, nr);
219 }
220 read_unlock(&tasklist_lock);
221
222 /* Firstly reap the EXIT_ZOMBIE children we may have. */
223 do {
224 clear_thread_flag(TIF_SIGPENDING);
225 rc = sys_wait4(-1, NULL, __WALL, NULL);
226 } while (rc != -ECHILD);
227
228 /*
229 * sys_wait4() above can't reap the TASK_DEAD children.
230 * Make sure they all go away, see free_pid().
231 */
232 for (;;) {
233 set_current_state(TASK_UNINTERRUPTIBLE);
234 if (pid_ns->nr_hashed == init_pids)
235 break;
236 schedule();
237 }
238 __set_current_state(TASK_RUNNING);
239
240 if (pid_ns->reboot)
241 current->signal->group_exit_code = pid_ns->reboot;
242
243 acct_exit_ns(pid_ns);
244 return;
245}
246
247#ifdef CONFIG_CHECKPOINT_RESTORE
248static int pid_ns_ctl_handler(struct ctl_table *table, int write,
249 void __user *buffer, size_t *lenp, loff_t *ppos)
250{
251 struct pid_namespace *pid_ns = task_active_pid_ns(current);
252 struct ctl_table tmp = *table;
253
254 if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
255 return -EPERM;
256
257 /*
258 * Writing directly to ns' last_pid field is OK, since this field
259 * is volatile in a living namespace anyway and a code writing to
260 * it should synchronize its usage with external means.
261 */
262
263 tmp.data = &pid_ns->last_pid;
264 return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
265}
266
267extern int pid_max;
268static int zero = 0;
269static struct ctl_table pid_ns_ctl_table[] = {
270 {
271 .procname = "ns_last_pid",
272 .maxlen = sizeof(int),
273 .mode = 0666, /* permissions are checked in the handler */
274 .proc_handler = pid_ns_ctl_handler,
275 .extra1 = &zero,
276 .extra2 = &pid_max,
277 },
278 { }
279};
280static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
281#endif /* CONFIG_CHECKPOINT_RESTORE */
282
283int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
284{
285 if (pid_ns == &init_pid_ns)
286 return 0;
287
288 switch (cmd) {
289 case LINUX_REBOOT_CMD_RESTART2:
290 case LINUX_REBOOT_CMD_RESTART:
291 pid_ns->reboot = SIGHUP;
292 break;
293
294 case LINUX_REBOOT_CMD_POWER_OFF:
295 case LINUX_REBOOT_CMD_HALT:
296 pid_ns->reboot = SIGINT;
297 break;
298 default:
299 return -EINVAL;
300 }
301
302 read_lock(&tasklist_lock);
303 force_sig(SIGKILL, pid_ns->child_reaper);
304 read_unlock(&tasklist_lock);
305
306 do_exit(0);
307
308 /* Not reached */
309 return 0;
310}
311
312static void *pidns_get(struct task_struct *task)
313{
314 struct pid_namespace *ns;
315
316 rcu_read_lock();
317 ns = get_pid_ns(task_active_pid_ns(task));
318 rcu_read_unlock();
319
320 return ns;
321}
322
323static void pidns_put(void *ns)
324{
325 put_pid_ns(ns);
326}
327
328static int pidns_install(struct nsproxy *nsproxy, void *ns)
329{
330 struct pid_namespace *active = task_active_pid_ns(current);
331 struct pid_namespace *ancestor, *new = ns;
332
333 if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
334 !nsown_capable(CAP_SYS_ADMIN))
335 return -EPERM;
336
337 /*
338 * Only allow entering the current active pid namespace
339 * or a child of the current active pid namespace.
340 *
341 * This is required for fork to return a usable pid value and
342 * this maintains the property that processes and their
343 * children can not escape their current pid namespace.
344 */
345 if (new->level < active->level)
346 return -EINVAL;
347
348 ancestor = new;
349 while (ancestor->level > active->level)
350 ancestor = ancestor->parent;
351 if (ancestor != active)
352 return -EINVAL;
353
354 put_pid_ns(nsproxy->pid_ns);
355 nsproxy->pid_ns = get_pid_ns(new);
356 return 0;
357}
358
359static unsigned int pidns_inum(void *ns)
360{
361 struct pid_namespace *pid_ns = ns;
362 return pid_ns->proc_inum;
363}
364
365const struct proc_ns_operations pidns_operations = {
366 .name = "pid",
367 .type = CLONE_NEWPID,
368 .get = pidns_get,
369 .put = pidns_put,
370 .install = pidns_install,
371 .inum = pidns_inum,
372};
373
374static __init int pid_namespaces_init(void)
375{
376 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
377
378#ifdef CONFIG_CHECKPOINT_RESTORE
379 register_sysctl_paths(kern_path, pid_ns_ctl_table);
380#endif
381 return 0;
382}
383
384__initcall(pid_namespaces_init);