Root/kernel/pid_namespace.c

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
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 void proc_cleanup_work(struct work_struct *work)
74{
75    struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work);
76    pid_ns_release_proc(ns);
77}
78
79/* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */
80#define MAX_PID_NS_LEVEL 32
81
82static 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    unsigned int level = parent_pid_ns->level + 1;
87    int i;
88    int err;
89
90    if (level > MAX_PID_NS_LEVEL) {
91        err = -EINVAL;
92        goto out;
93    }
94
95    err = -ENOMEM;
96    ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
97    if (ns == NULL)
98        goto out;
99
100    ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
101    if (!ns->pidmap[0].page)
102        goto out_free;
103
104    ns->pid_cachep = create_pid_cachep(level + 1);
105    if (ns->pid_cachep == NULL)
106        goto out_free_map;
107
108    err = proc_alloc_inum(&ns->proc_inum);
109    if (err)
110        goto out_free_map;
111
112    kref_init(&ns->kref);
113    ns->level = level;
114    ns->parent = get_pid_ns(parent_pid_ns);
115    ns->user_ns = get_user_ns(user_ns);
116    ns->nr_hashed = PIDNS_HASH_ADDING;
117    INIT_WORK(&ns->proc_work, proc_cleanup_work);
118
119    set_bit(0, ns->pidmap[0].page);
120    atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
121
122    for (i = 1; i < PIDMAP_ENTRIES; i++)
123        atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
124
125    return ns;
126
127out_free_map:
128    kfree(ns->pidmap[0].page);
129out_free:
130    kmem_cache_free(pid_ns_cachep, ns);
131out:
132    return ERR_PTR(err);
133}
134
135static void delayed_free_pidns(struct rcu_head *p)
136{
137    kmem_cache_free(pid_ns_cachep,
138            container_of(p, struct pid_namespace, rcu));
139}
140
141static void destroy_pid_namespace(struct pid_namespace *ns)
142{
143    int i;
144
145    proc_free_inum(ns->proc_inum);
146    for (i = 0; i < PIDMAP_ENTRIES; i++)
147        kfree(ns->pidmap[i].page);
148    put_user_ns(ns->user_ns);
149    call_rcu(&ns->rcu, delayed_free_pidns);
150}
151
152struct pid_namespace *copy_pid_ns(unsigned long flags,
153    struct user_namespace *user_ns, struct pid_namespace *old_ns)
154{
155    if (!(flags & CLONE_NEWPID))
156        return get_pid_ns(old_ns);
157    if (task_active_pid_ns(current) != old_ns)
158        return ERR_PTR(-EINVAL);
159    return create_pid_namespace(user_ns, old_ns);
160}
161
162static void free_pid_ns(struct kref *kref)
163{
164    struct pid_namespace *ns;
165
166    ns = container_of(kref, struct pid_namespace, kref);
167    destroy_pid_namespace(ns);
168}
169
170void put_pid_ns(struct pid_namespace *ns)
171{
172    struct pid_namespace *parent;
173
174    while (ns != &init_pid_ns) {
175        parent = ns->parent;
176        if (!kref_put(&ns->kref, free_pid_ns))
177            break;
178        ns = parent;
179    }
180}
181EXPORT_SYMBOL_GPL(put_pid_ns);
182
183void zap_pid_ns_processes(struct pid_namespace *pid_ns)
184{
185    int nr;
186    int rc;
187    struct task_struct *task, *me = current;
188    int init_pids = thread_group_leader(me) ? 1 : 2;
189
190    /* Don't allow any more processes into the pid namespace */
191    disable_pid_allocation(pid_ns);
192
193    /* Ignore SIGCHLD causing any terminated children to autoreap */
194    spin_lock_irq(&me->sighand->siglock);
195    me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
196    spin_unlock_irq(&me->sighand->siglock);
197
198    /*
199     * The last thread in the cgroup-init thread group is terminating.
200     * Find remaining pid_ts in the namespace, signal and wait for them
201     * to exit.
202     *
203     * Note: This signals each threads in the namespace - even those that
204     * belong to the same thread group, To avoid this, we would have
205     * to walk the entire tasklist looking a processes in this
206     * namespace, but that could be unnecessarily expensive if the
207     * pid namespace has just a few processes. Or we need to
208     * maintain a tasklist for each pid namespace.
209     *
210     */
211    read_lock(&tasklist_lock);
212    nr = next_pidmap(pid_ns, 1);
213    while (nr > 0) {
214        rcu_read_lock();
215
216        task = pid_task(find_vpid(nr), PIDTYPE_PID);
217        if (task && !__fatal_signal_pending(task))
218            send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
219
220        rcu_read_unlock();
221
222        nr = next_pidmap(pid_ns, nr);
223    }
224    read_unlock(&tasklist_lock);
225
226    /* Firstly reap the EXIT_ZOMBIE children we may have. */
227    do {
228        clear_thread_flag(TIF_SIGPENDING);
229        rc = sys_wait4(-1, NULL, __WALL, NULL);
230    } while (rc != -ECHILD);
231
232    /*
233     * sys_wait4() above can't reap the TASK_DEAD children.
234     * Make sure they all go away, see free_pid().
235     */
236    for (;;) {
237        set_current_state(TASK_UNINTERRUPTIBLE);
238        if (pid_ns->nr_hashed == init_pids)
239            break;
240        schedule();
241    }
242    __set_current_state(TASK_RUNNING);
243
244    if (pid_ns->reboot)
245        current->signal->group_exit_code = pid_ns->reboot;
246
247    acct_exit_ns(pid_ns);
248    return;
249}
250
251#ifdef CONFIG_CHECKPOINT_RESTORE
252static int pid_ns_ctl_handler(struct ctl_table *table, int write,
253        void __user *buffer, size_t *lenp, loff_t *ppos)
254{
255    struct pid_namespace *pid_ns = task_active_pid_ns(current);
256    struct ctl_table tmp = *table;
257
258    if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
259        return -EPERM;
260
261    /*
262     * Writing directly to ns' last_pid field is OK, since this field
263     * is volatile in a living namespace anyway and a code writing to
264     * it should synchronize its usage with external means.
265     */
266
267    tmp.data = &pid_ns->last_pid;
268    return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
269}
270
271extern int pid_max;
272static int zero = 0;
273static struct ctl_table pid_ns_ctl_table[] = {
274    {
275        .procname = "ns_last_pid",
276        .maxlen = sizeof(int),
277        .mode = 0666, /* permissions are checked in the handler */
278        .proc_handler = pid_ns_ctl_handler,
279        .extra1 = &zero,
280        .extra2 = &pid_max,
281    },
282    { }
283};
284static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
285#endif /* CONFIG_CHECKPOINT_RESTORE */
286
287int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
288{
289    if (pid_ns == &init_pid_ns)
290        return 0;
291
292    switch (cmd) {
293    case LINUX_REBOOT_CMD_RESTART2:
294    case LINUX_REBOOT_CMD_RESTART:
295        pid_ns->reboot = SIGHUP;
296        break;
297
298    case LINUX_REBOOT_CMD_POWER_OFF:
299    case LINUX_REBOOT_CMD_HALT:
300        pid_ns->reboot = SIGINT;
301        break;
302    default:
303        return -EINVAL;
304    }
305
306    read_lock(&tasklist_lock);
307    force_sig(SIGKILL, pid_ns->child_reaper);
308    read_unlock(&tasklist_lock);
309
310    do_exit(0);
311
312    /* Not reached */
313    return 0;
314}
315
316static void *pidns_get(struct task_struct *task)
317{
318    struct pid_namespace *ns;
319
320    rcu_read_lock();
321    ns = task_active_pid_ns(task);
322    if (ns)
323        get_pid_ns(ns);
324    rcu_read_unlock();
325
326    return ns;
327}
328
329static void pidns_put(void *ns)
330{
331    put_pid_ns(ns);
332}
333
334static int pidns_install(struct nsproxy *nsproxy, void *ns)
335{
336    struct pid_namespace *active = task_active_pid_ns(current);
337    struct pid_namespace *ancestor, *new = ns;
338
339    if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
340        !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
341        return -EPERM;
342
343    /*
344     * Only allow entering the current active pid namespace
345     * or a child of the current active pid namespace.
346     *
347     * This is required for fork to return a usable pid value and
348     * this maintains the property that processes and their
349     * children can not escape their current pid namespace.
350     */
351    if (new->level < active->level)
352        return -EINVAL;
353
354    ancestor = new;
355    while (ancestor->level > active->level)
356        ancestor = ancestor->parent;
357    if (ancestor != active)
358        return -EINVAL;
359
360    put_pid_ns(nsproxy->pid_ns_for_children);
361    nsproxy->pid_ns_for_children = get_pid_ns(new);
362    return 0;
363}
364
365static unsigned int pidns_inum(void *ns)
366{
367    struct pid_namespace *pid_ns = ns;
368    return pid_ns->proc_inum;
369}
370
371const struct proc_ns_operations pidns_operations = {
372    .name = "pid",
373    .type = CLONE_NEWPID,
374    .get = pidns_get,
375    .put = pidns_put,
376    .install = pidns_install,
377    .inum = pidns_inum,
378};
379
380static __init int pid_namespaces_init(void)
381{
382    pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
383
384#ifdef CONFIG_CHECKPOINT_RESTORE
385    register_sysctl_paths(kern_path, pid_ns_ctl_table);
386#endif
387    return 0;
388}
389
390__initcall(pid_namespaces_init);
391

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