projects/linux·blob v3.5 · refs

289 lines · 6.6 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/syscalls.h>
14#include <linux/err.h>
15#include <linux/acct.h>
16#include <linux/slab.h>
17#include <linux/proc_fs.h>
18#include <linux/reboot.h>
19
20#define BITS_PER_PAGE (PAGE_SIZE*8)
21
22struct pid_cache {
23 int nr_ids;
24 char name[16];
25 struct kmem_cache *cachep;
26 struct list_head list;
27};
28
29static LIST_HEAD(pid_caches_lh);
30static DEFINE_MUTEX(pid_caches_mutex);
31static 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
38static struct kmem_cache *create_pid_cachep(int nr_ids)
39{
40 struct pid_cache *pcache;
41 struct kmem_cache *cachep;
42
43 mutex_lock(&pid_caches_mutex);
44 list_for_each_entry(pcache, &pid_caches_lh, list)
45 if (pcache->nr_ids == nr_ids)
46 goto out;
47
48 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
49 if (pcache == NULL)
50 goto err_alloc;
51
52 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
53 cachep = kmem_cache_create(pcache->name,
54 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
55 0, SLAB_HWCACHE_ALIGN, NULL);
56 if (cachep == NULL)
57 goto err_cachep;
58
59 pcache->nr_ids = nr_ids;
60 pcache->cachep = cachep;
61 list_add(&pcache->list, &pid_caches_lh);
62out:
63 mutex_unlock(&pid_caches_mutex);
64 return pcache->cachep;
65
66err_cachep:
67 kfree(pcache);
68err_alloc:
69 mutex_unlock(&pid_caches_mutex);
70 return NULL;
71}
72
73static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)
74{
75 struct pid_namespace *ns;
76 unsigned int level = parent_pid_ns->level + 1;
77 int i, err = -ENOMEM;
78
79 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
80 if (ns == NULL)
81 goto out;
82
83 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
84 if (!ns->pidmap[0].page)
85 goto out_free;
86
87 ns->pid_cachep = create_pid_cachep(level + 1);
88 if (ns->pid_cachep == NULL)
89 goto out_free_map;
90
91 kref_init(&ns->kref);
92 ns->level = level;
93 ns->parent = get_pid_ns(parent_pid_ns);
94
95 set_bit(0, ns->pidmap[0].page);
96 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
97
98 for (i = 1; i < PIDMAP_ENTRIES; i++)
99 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
100
101 err = pid_ns_prepare_proc(ns);
102 if (err)
103 goto out_put_parent_pid_ns;
104
105 return ns;
106
107out_put_parent_pid_ns:
108 put_pid_ns(parent_pid_ns);
109out_free_map:
110 kfree(ns->pidmap[0].page);
111out_free:
112 kmem_cache_free(pid_ns_cachep, ns);
113out:
114 return ERR_PTR(err);
115}
116
117static void destroy_pid_namespace(struct pid_namespace *ns)
118{
119 int i;
120
121 for (i = 0; i < PIDMAP_ENTRIES; i++)
122 kfree(ns->pidmap[i].page);
123 kmem_cache_free(pid_ns_cachep, ns);
124}
125
126struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
127{
128 if (!(flags & CLONE_NEWPID))
129 return get_pid_ns(old_ns);
130 if (flags & (CLONE_THREAD|CLONE_PARENT))
131 return ERR_PTR(-EINVAL);
132 return create_pid_namespace(old_ns);
133}
134
135void free_pid_ns(struct kref *kref)
136{
137 struct pid_namespace *ns, *parent;
138
139 ns = container_of(kref, struct pid_namespace, kref);
140
141 parent = ns->parent;
142 destroy_pid_namespace(ns);
143
144 if (parent != NULL)
145 put_pid_ns(parent);
146}
147
148void zap_pid_ns_processes(struct pid_namespace *pid_ns)
149{
150 int nr;
151 int rc;
152 struct task_struct *task, *me = current;
153
154 /* Ignore SIGCHLD causing any terminated children to autoreap */
155 spin_lock_irq(&me->sighand->siglock);
156 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
157 spin_unlock_irq(&me->sighand->siglock);
158
159 /*
160 * The last thread in the cgroup-init thread group is terminating.
161 * Find remaining pid_ts in the namespace, signal and wait for them
162 * to exit.
163 *
164 * Note: This signals each threads in the namespace - even those that
165 * belong to the same thread group, To avoid this, we would have
166 * to walk the entire tasklist looking a processes in this
167 * namespace, but that could be unnecessarily expensive if the
168 * pid namespace has just a few processes. Or we need to
169 * maintain a tasklist for each pid namespace.
170 *
171 */
172 read_lock(&tasklist_lock);
173 nr = next_pidmap(pid_ns, 1);
174 while (nr > 0) {
175 rcu_read_lock();
176
177 task = pid_task(find_vpid(nr), PIDTYPE_PID);
178 if (task && !__fatal_signal_pending(task))
179 send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
180
181 rcu_read_unlock();
182
183 nr = next_pidmap(pid_ns, nr);
184 }
185 read_unlock(&tasklist_lock);
186
187 /* Firstly reap the EXIT_ZOMBIE children we may have. */
188 do {
189 clear_thread_flag(TIF_SIGPENDING);
190 rc = sys_wait4(-1, NULL, __WALL, NULL);
191 } while (rc != -ECHILD);
192
193 /*
194 * sys_wait4() above can't reap the TASK_DEAD children.
195 * Make sure they all go away, see __unhash_process().
196 */
197 for (;;) {
198 bool need_wait = false;
199
200 read_lock(&tasklist_lock);
201 if (!list_empty(&current->children)) {
202 __set_current_state(TASK_UNINTERRUPTIBLE);
203 need_wait = true;
204 }
205 read_unlock(&tasklist_lock);
206
207 if (!need_wait)
208 break;
209 schedule();
210 }
211
212 if (pid_ns->reboot)
213 current->signal->group_exit_code = pid_ns->reboot;
214
215 acct_exit_ns(pid_ns);
216 return;
217}
218
219#ifdef CONFIG_CHECKPOINT_RESTORE
220static int pid_ns_ctl_handler(struct ctl_table *table, int write,
221 void __user *buffer, size_t *lenp, loff_t *ppos)
222{
223 struct ctl_table tmp = *table;
224
225 if (write && !capable(CAP_SYS_ADMIN))
226 return -EPERM;
227
228 /*
229 * Writing directly to ns' last_pid field is OK, since this field
230 * is volatile in a living namespace anyway and a code writing to
231 * it should synchronize its usage with external means.
232 */
233
234 tmp.data = &current->nsproxy->pid_ns->last_pid;
235 return proc_dointvec(&tmp, write, buffer, lenp, ppos);
236}
237
238static struct ctl_table pid_ns_ctl_table[] = {
239 {
240 .procname = "ns_last_pid",
241 .maxlen = sizeof(int),
242 .mode = 0666, /* permissions are checked in the handler */
243 .proc_handler = pid_ns_ctl_handler,
244 },
245 { }
246};
247static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
248#endif /* CONFIG_CHECKPOINT_RESTORE */
249
250int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
251{
252 if (pid_ns == &init_pid_ns)
253 return 0;
254
255 switch (cmd) {
256 case LINUX_REBOOT_CMD_RESTART2:
257 case LINUX_REBOOT_CMD_RESTART:
258 pid_ns->reboot = SIGHUP;
259 break;
260
261 case LINUX_REBOOT_CMD_POWER_OFF:
262 case LINUX_REBOOT_CMD_HALT:
263 pid_ns->reboot = SIGINT;
264 break;
265 default:
266 return -EINVAL;
267 }
268
269 read_lock(&tasklist_lock);
270 force_sig(SIGKILL, pid_ns->child_reaper);
271 read_unlock(&tasklist_lock);
272
273 do_exit(0);
274
275 /* Not reached */
276 return 0;
277}
278
279static __init int pid_namespaces_init(void)
280{
281 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
282
283#ifdef CONFIG_CHECKPOINT_RESTORE
284 register_sysctl_paths(kern_path, pid_ns_ctl_table);
285#endif
286 return 0;
287}
288
289__initcall(pid_namespaces_init);