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Linux/kernel/pid_namespace.c

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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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