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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_fs.h> |
19 | #include <linux/reboot.h> |
20 | #include <linux/export.h> |
21 | |
22 | #define BITS_PER_PAGE (PAGE_SIZE*8) |
23 | |
24 | struct pid_cache { |
25 | int nr_ids; |
26 | char name[16]; |
27 | struct kmem_cache *cachep; |
28 | struct list_head list; |
29 | }; |
30 | |
31 | static LIST_HEAD(pid_caches_lh); |
32 | static DEFINE_MUTEX(pid_caches_mutex); |
33 | static 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 | |
40 | static 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); |
64 | out: |
65 | mutex_unlock(&pid_caches_mutex); |
66 | return pcache->cachep; |
67 | |
68 | err_cachep: |
69 | kfree(pcache); |
70 | err_alloc: |
71 | mutex_unlock(&pid_caches_mutex); |
72 | return NULL; |
73 | } |
74 | |
75 | static 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 | |
84 | static 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 | |
129 | out_free_map: |
130 | kfree(ns->pidmap[0].page); |
131 | out_free: |
132 | kmem_cache_free(pid_ns_cachep, ns); |
133 | out: |
134 | return ERR_PTR(err); |
135 | } |
136 | |
137 | static 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 | |
148 | struct 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 | |
158 | static 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 | |
166 | void 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 | } |
177 | EXPORT_SYMBOL_GPL(put_pid_ns); |
178 | |
179 | void 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 |
248 | static 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 | |
267 | extern int pid_max; |
268 | static int zero = 0; |
269 | static 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 | }; |
280 | static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; |
281 | #endif /* CONFIG_CHECKPOINT_RESTORE */ |
282 | |
283 | int 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 | |
312 | static 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 | |
323 | static void pidns_put(void *ns) |
324 | { |
325 | put_pid_ns(ns); |
326 | } |
327 | |
328 | static 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 | |
359 | static unsigned int pidns_inum(void *ns) |
360 | { |
361 | struct pid_namespace *pid_ns = ns; |
362 | return pid_ns->proc_inum; |
363 | } |
364 | |
365 | const 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 | |
374 | static __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); |
385 |
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