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 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
 127 out_free_map:
 128         kfree(ns->pidmap[0].page);
 129 out_free:
 130         kmem_cache_free(pid_ns_cachep, ns);
 131 out:
 132         return ERR_PTR(err);
 133 }
 134
 135 static 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
 141 static 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
 152 struct 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
 162 static 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
 170 void 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 }
 181 EXPORT_SYMBOL_GPL(put_pid_ns);
 182
 183 void 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
 252 static 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
 271 extern int pid_max;
 272 static int zero = 0;
 273 static 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 };
 284 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
 285 #endif  /* CONFIG_CHECKPOINT_RESTORE */
 286
 287 int 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
 316 static 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
 329 static void pidns_put(void *ns)
 330 {
 331         put_pid_ns(ns);
 332 }
 333
 334 static 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
 365 static unsigned int pidns_inum(void *ns)
 366 {
 367         struct pid_namespace *pid_ns = ns;
 368         return pid_ns->proc_inum;
 369 }
 370
 371 const 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
 380 static __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);