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
  22 struct pid_cache {
  23         int nr_ids;
  24         char name[16];
  25         struct kmem_cache *cachep;
  26         struct list_head list;
  27 };
  28
  29 static LIST_HEAD(pid_caches_lh);
  30 static DEFINE_MUTEX(pid_caches_mutex);
  31 static 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
  38 static 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);
  62 out:
  63         mutex_unlock(&pid_caches_mutex);
  64         return pcache->cachep;
  65
  66 err_cachep:
  67         kfree(pcache);
  68 err_alloc:
  69         mutex_unlock(&pid_caches_mutex);
  70         return NULL;
  71 }
  72
  73 static 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
  82 static struct ucounts *inc_pid_namespaces(struct user_namespace *ns)
  83 {
  84         return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES);
  85 }
  86
  87 static void dec_pid_namespaces(struct ucounts *ucounts)
  88 {
  89         dec_ucount(ucounts, UCOUNT_PID_NAMESPACES);
  90 }
  91
  92 static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns,
  93         struct pid_namespace *parent_pid_ns)
  94 {
  95         struct pid_namespace *ns;
  96         unsigned int level = parent_pid_ns->level + 1;
  97         struct ucounts *ucounts;
  98         int i;
  99         int err;
 100
 101         err = -ENOSPC;
 102         if (level > MAX_PID_NS_LEVEL)
 103                 goto out;
 104         ucounts = inc_pid_namespaces(user_ns);
 105         if (!ucounts)
 106                 goto out;
 107
 108         err = -ENOMEM;
 109         ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
 110         if (ns == NULL)
 111                 goto out_dec;
 112
 113         ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
 114         if (!ns->pidmap[0].page)
 115                 goto out_free;
 116
 117         ns->pid_cachep = create_pid_cachep(level + 1);
 118         if (ns->pid_cachep == NULL)
 119                 goto out_free_map;
 120
 121         err = ns_alloc_inum(&ns->ns);
 122         if (err)
 123                 goto out_free_map;
 124         ns->ns.ops = &pidns_operations;
 125
 126         kref_init(&ns->kref);
 127         ns->level = level;
 128         ns->parent = get_pid_ns(parent_pid_ns);
 129         ns->user_ns = get_user_ns(user_ns);
 130         ns->ucounts = ucounts;
 131         ns->nr_hashed = PIDNS_HASH_ADDING;
 132         INIT_WORK(&ns->proc_work, proc_cleanup_work);
 133
 134         set_bit(0, ns->pidmap[0].page);
 135         atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
 136
 137         for (i = 1; i < PIDMAP_ENTRIES; i++)
 138                 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
 139
 140         return ns;
 141
 142 out_free_map:
 143         kfree(ns->pidmap[0].page);
 144 out_free:
 145         kmem_cache_free(pid_ns_cachep, ns);
 146 out_dec:
 147         dec_pid_namespaces(ucounts);
 148 out:
 149         return ERR_PTR(err);
 150 }
 151
 152 static void delayed_free_pidns(struct rcu_head *p)
 153 {
 154         kmem_cache_free(pid_ns_cachep,
 155                         container_of(p, struct pid_namespace, rcu));
 156 }
 157
 158 static void destroy_pid_namespace(struct pid_namespace *ns)
 159 {
 160         int i;
 161
 162         ns_free_inum(&ns->ns);
 163         for (i = 0; i < PIDMAP_ENTRIES; i++)
 164                 kfree(ns->pidmap[i].page);
 165         dec_pid_namespaces(ns->ucounts);
 166         put_user_ns(ns->user_ns);
 167         call_rcu(&ns->rcu, delayed_free_pidns);
 168 }
 169
 170 struct pid_namespace *copy_pid_ns(unsigned long flags,
 171         struct user_namespace *user_ns, struct pid_namespace *old_ns)
 172 {
 173         if (!(flags & CLONE_NEWPID))
 174                 return get_pid_ns(old_ns);
 175         if (task_active_pid_ns(current) != old_ns)
 176                 return ERR_PTR(-EINVAL);
 177         return create_pid_namespace(user_ns, old_ns);
 178 }
 179
 180 static void free_pid_ns(struct kref *kref)
 181 {
 182         struct pid_namespace *ns;
 183
 184         ns = container_of(kref, struct pid_namespace, kref);
 185         destroy_pid_namespace(ns);
 186 }
 187
 188 void put_pid_ns(struct pid_namespace *ns)
 189 {
 190         struct pid_namespace *parent;
 191
 192         while (ns != &init_pid_ns) {
 193                 parent = ns->parent;
 194                 if (!kref_put(&ns->kref, free_pid_ns))
 195                         break;
 196                 ns = parent;
 197         }
 198 }
 199 EXPORT_SYMBOL_GPL(put_pid_ns);
 200
 201 void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 202 {
 203         int nr;
 204         int rc;
 205         struct task_struct *task, *me = current;
 206         int init_pids = thread_group_leader(me) ? 1 : 2;
 207
 208         /* Don't allow any more processes into the pid namespace */
 209         disable_pid_allocation(pid_ns);
 210
 211         /*
 212          * Ignore SIGCHLD causing any terminated children to autoreap.
 213          * This speeds up the namespace shutdown, plus see the comment
 214          * below.
 215          */
 216         spin_lock_irq(&me->sighand->siglock);
 217         me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
 218         spin_unlock_irq(&me->sighand->siglock);
 219
 220         /*
 221          * The last thread in the cgroup-init thread group is terminating.
 222          * Find remaining pid_ts in the namespace, signal and wait for them
 223          * to exit.
 224          *
 225          * Note:  This signals each threads in the namespace - even those that
 226          *        belong to the same thread group, To avoid this, we would have
 227          *        to walk the entire tasklist looking a processes in this
 228          *        namespace, but that could be unnecessarily expensive if the
 229          *        pid namespace has just a few processes. Or we need to
 230          *        maintain a tasklist for each pid namespace.
 231          *
 232          */
 233         read_lock(&tasklist_lock);
 234         nr = next_pidmap(pid_ns, 1);
 235         while (nr > 0) {
 236                 rcu_read_lock();
 237
 238                 task = pid_task(find_vpid(nr), PIDTYPE_PID);
 239                 if (task && !__fatal_signal_pending(task))
 240                         send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
 241
 242                 rcu_read_unlock();
 243
 244                 nr = next_pidmap(pid_ns, nr);
 245         }
 246         read_unlock(&tasklist_lock);
 247
 248         /*
 249          * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
 250          * sys_wait4() will also block until our children traced from the
 251          * parent namespace are detached and become EXIT_DEAD.
 252          */
 253         do {
 254                 clear_thread_flag(TIF_SIGPENDING);
 255                 rc = sys_wait4(-1, NULL, __WALL, NULL);
 256         } while (rc != -ECHILD);
 257
 258         /*
 259          * sys_wait4() above can't reap the EXIT_DEAD children but we do not
 260          * really care, we could reparent them to the global init. We could
 261          * exit and reap ->child_reaper even if it is not the last thread in
 262          * this pid_ns, free_pid(nr_hashed == 0) calls proc_cleanup_work(),
 263          * pid_ns can not go away until proc_kill_sb() drops the reference.
 264          *
 265          * But this ns can also have other tasks injected by setns()+fork().
 266          * Again, ignoring the user visible semantics we do not really need
 267          * to wait until they are all reaped, but they can be reparented to
 268          * us and thus we need to ensure that pid->child_reaper stays valid
 269          * until they all go away. See free_pid()->wake_up_process().
 270          *
 271          * We rely on ignored SIGCHLD, an injected zombie must be autoreaped
 272          * if reparented.
 273          */
 274         for (;;) {
 275                 set_current_state(TASK_UNINTERRUPTIBLE);
 276                 if (pid_ns->nr_hashed == init_pids)
 277                         break;
 278                 schedule();
 279         }
 280         __set_current_state(TASK_RUNNING);
 281
 282         if (pid_ns->reboot)
 283                 current->signal->group_exit_code = pid_ns->reboot;
 284
 285         acct_exit_ns(pid_ns);
 286         return;
 287 }
 288
 289 #ifdef CONFIG_CHECKPOINT_RESTORE
 290 static int pid_ns_ctl_handler(struct ctl_table *table, int write,
 291                 void __user *buffer, size_t *lenp, loff_t *ppos)
 292 {
 293         struct pid_namespace *pid_ns = task_active_pid_ns(current);
 294         struct ctl_table tmp = *table;
 295
 296         if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
 297                 return -EPERM;
 298
 299         /*
 300          * Writing directly to ns' last_pid field is OK, since this field
 301          * is volatile in a living namespace anyway and a code writing to
 302          * it should synchronize its usage with external means.
 303          */
 304
 305         tmp.data = &pid_ns->last_pid;
 306         return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
 307 }
 308
 309 extern int pid_max;
 310 static int zero = 0;
 311 static struct ctl_table pid_ns_ctl_table[] = {
 312         {
 313                 .procname = "ns_last_pid",
 314                 .maxlen = sizeof(int),
 315                 .mode = 0666, /* permissions are checked in the handler */
 316                 .proc_handler = pid_ns_ctl_handler,
 317                 .extra1 = &zero,
 318                 .extra2 = &pid_max,
 319         },
 320         { }
 321 };
 322 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
 323 #endif  /* CONFIG_CHECKPOINT_RESTORE */
 324
 325 int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
 326 {
 327         if (pid_ns == &init_pid_ns)
 328                 return 0;
 329
 330         switch (cmd) {
 331         case LINUX_REBOOT_CMD_RESTART2:
 332         case LINUX_REBOOT_CMD_RESTART:
 333                 pid_ns->reboot = SIGHUP;
 334                 break;
 335
 336         case LINUX_REBOOT_CMD_POWER_OFF:
 337         case LINUX_REBOOT_CMD_HALT:
 338                 pid_ns->reboot = SIGINT;
 339                 break;
 340         default:
 341                 return -EINVAL;
 342         }
 343
 344         read_lock(&tasklist_lock);
 345         force_sig(SIGKILL, pid_ns->child_reaper);
 346         read_unlock(&tasklist_lock);
 347
 348         do_exit(0);
 349
 350         /* Not reached */
 351         return 0;
 352 }
 353
 354 static inline struct pid_namespace *to_pid_ns(struct ns_common *ns)
 355 {
 356         return container_of(ns, struct pid_namespace, ns);
 357 }
 358
 359 static struct ns_common *pidns_get(struct task_struct *task)
 360 {
 361         struct pid_namespace *ns;
 362
 363         rcu_read_lock();
 364         ns = task_active_pid_ns(task);
 365         if (ns)
 366                 get_pid_ns(ns);
 367         rcu_read_unlock();
 368
 369         return ns ? &ns->ns : NULL;
 370 }
 371
 372 static void pidns_put(struct ns_common *ns)
 373 {
 374         put_pid_ns(to_pid_ns(ns));
 375 }
 376
 377 static int pidns_install(struct nsproxy *nsproxy, struct ns_common *ns)
 378 {
 379         struct pid_namespace *active = task_active_pid_ns(current);
 380         struct pid_namespace *ancestor, *new = to_pid_ns(ns);
 381
 382         if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
 383             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 384                 return -EPERM;
 385
 386         /*
 387          * Only allow entering the current active pid namespace
 388          * or a child of the current active pid namespace.
 389          *
 390          * This is required for fork to return a usable pid value and
 391          * this maintains the property that processes and their
 392          * children can not escape their current pid namespace.
 393          */
 394         if (new->level < active->level)
 395                 return -EINVAL;
 396
 397         ancestor = new;
 398         while (ancestor->level > active->level)
 399                 ancestor = ancestor->parent;
 400         if (ancestor != active)
 401                 return -EINVAL;
 402
 403         put_pid_ns(nsproxy->pid_ns_for_children);
 404         nsproxy->pid_ns_for_children = get_pid_ns(new);
 405         return 0;
 406 }
 407
 408 static struct ns_common *pidns_get_parent(struct ns_common *ns)
 409 {
 410         struct pid_namespace *active = task_active_pid_ns(current);
 411         struct pid_namespace *pid_ns, *p;
 412
 413         /* See if the parent is in the current namespace */
 414         pid_ns = p = to_pid_ns(ns)->parent;
 415         for (;;) {
 416                 if (!p)
 417                         return ERR_PTR(-EPERM);
 418                 if (p == active)
 419                         break;
 420                 p = p->parent;
 421         }
 422
 423         return &get_pid_ns(pid_ns)->ns;
 424 }
 425
 426 static struct user_namespace *pidns_owner(struct ns_common *ns)
 427 {
 428         return to_pid_ns(ns)->user_ns;
 429 }
 430
 431 const struct proc_ns_operations pidns_operations = {
 432         .name           = "pid",
 433         .type           = CLONE_NEWPID,
 434         .get            = pidns_get,
 435         .put            = pidns_put,
 436         .install        = pidns_install,
 437         .owner          = pidns_owner,
 438         .get_parent     = pidns_get_parent,
 439 };
 440
 441 static __init int pid_namespaces_init(void)
 442 {
 443         pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
 444
 445 #ifdef CONFIG_CHECKPOINT_RESTORE
 446         register_sysctl_paths(kern_path, pid_ns_ctl_table);
 447 #endif
 448         return 0;
 449 }
 450
 451 __initcall(pid_namespaces_init);