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