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
  24struct pid_cache {
  25        int nr_ids;
  26        char name[16];
  27        struct kmem_cache *cachep;
  28        struct list_head list;
  29};
  30
  31static LIST_HEAD(pid_caches_lh);
  32static DEFINE_MUTEX(pid_caches_mutex);
  33static 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
  40static 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);
  64out:
  65        mutex_unlock(&pid_caches_mutex);
  66        return pcache->cachep;
  67
  68err_cachep:
  69        kfree(pcache);
  70err_alloc:
  71        mutex_unlock(&pid_caches_mutex);
  72        return NULL;
  73}
  74
  75static 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
  84static 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
 129out_free_map:
 130        kfree(ns->pidmap[0].page);
 131out_free:
 132        kmem_cache_free(pid_ns_cachep, ns);
 133out:
 134        return ERR_PTR(err);
 135}
 136
 137static 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
 148struct 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
 158static 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
 166void 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}
 177EXPORT_SYMBOL_GPL(put_pid_ns);
 178
 179void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 180{
 181        int nr;
 182        int rc;
 183        struct task_struct *task, *me = current;
 184
 185        /* Don't allow any more processes into the pid namespace */
 186        disable_pid_allocation(pid_ns);
 187
 188        /* Ignore SIGCHLD causing any terminated children to autoreap */
 189        spin_lock_irq(&me->sighand->siglock);
 190        me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
 191        spin_unlock_irq(&me->sighand->siglock);
 192
 193        /*
 194         * The last thread in the cgroup-init thread group is terminating.
 195         * Find remaining pid_ts in the namespace, signal and wait for them
 196         * to exit.
 197         *
 198         * Note:  This signals each threads in the namespace - even those that
 199         *        belong to the same thread group, To avoid this, we would have
 200         *        to walk the entire tasklist looking a processes in this
 201         *        namespace, but that could be unnecessarily expensive if the
 202         *        pid namespace has just a few processes. Or we need to
 203         *        maintain a tasklist for each pid namespace.
 204         *
 205         */
 206        read_lock(&tasklist_lock);
 207        nr = next_pidmap(pid_ns, 1);
 208        while (nr > 0) {
 209                rcu_read_lock();
 210
 211                task = pid_task(find_vpid(nr), PIDTYPE_PID);
 212                if (task && !__fatal_signal_pending(task))
 213                        send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
 214
 215                rcu_read_unlock();
 216
 217                nr = next_pidmap(pid_ns, nr);
 218        }
 219        read_unlock(&tasklist_lock);
 220
 221        /* Firstly reap the EXIT_ZOMBIE children we may have. */
 222        do {
 223                clear_thread_flag(TIF_SIGPENDING);
 224                rc = sys_wait4(-1, NULL, __WALL, NULL);
 225        } while (rc != -ECHILD);
 226
 227        /*
 228         * sys_wait4() above can't reap the TASK_DEAD children.
 229         * Make sure they all go away, see free_pid().
 230         */
 231        for (;;) {
 232                set_current_state(TASK_UNINTERRUPTIBLE);
 233                if (pid_ns->nr_hashed == 1)
 234                        break;
 235                schedule();
 236        }
 237        __set_current_state(TASK_RUNNING);
 238
 239        if (pid_ns->reboot)
 240                current->signal->group_exit_code = pid_ns->reboot;
 241
 242        acct_exit_ns(pid_ns);
 243        return;
 244}
 245
 246#ifdef CONFIG_CHECKPOINT_RESTORE
 247static int pid_ns_ctl_handler(struct ctl_table *table, int write,
 248                void __user *buffer, size_t *lenp, loff_t *ppos)
 249{
 250        struct pid_namespace *pid_ns = task_active_pid_ns(current);
 251        struct ctl_table tmp = *table;
 252
 253        if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN))
 254                return -EPERM;
 255
 256        /*
 257         * Writing directly to ns' last_pid field is OK, since this field
 258         * is volatile in a living namespace anyway and a code writing to
 259         * it should synchronize its usage with external means.
 260         */
 261
 262        tmp.data = &pid_ns->last_pid;
 263        return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
 264}
 265
 266extern int pid_max;
 267static int zero = 0;
 268static struct ctl_table pid_ns_ctl_table[] = {
 269        {
 270                .procname = "ns_last_pid",
 271                .maxlen = sizeof(int),
 272                .mode = 0666, /* permissions are checked in the handler */
 273                .proc_handler = pid_ns_ctl_handler,
 274                .extra1 = &zero,
 275                .extra2 = &pid_max,
 276        },
 277        { }
 278};
 279static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
 280#endif  /* CONFIG_CHECKPOINT_RESTORE */
 281
 282int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
 283{
 284        if (pid_ns == &init_pid_ns)
 285                return 0;
 286
 287        switch (cmd) {
 288        case LINUX_REBOOT_CMD_RESTART2:
 289        case LINUX_REBOOT_CMD_RESTART:
 290                pid_ns->reboot = SIGHUP;
 291                break;
 292
 293        case LINUX_REBOOT_CMD_POWER_OFF:
 294        case LINUX_REBOOT_CMD_HALT:
 295                pid_ns->reboot = SIGINT;
 296                break;
 297        default:
 298                return -EINVAL;
 299        }
 300
 301        read_lock(&tasklist_lock);
 302        force_sig(SIGKILL, pid_ns->child_reaper);
 303        read_unlock(&tasklist_lock);
 304
 305        do_exit(0);
 306
 307        /* Not reached */
 308        return 0;
 309}
 310
 311static void *pidns_get(struct task_struct *task)
 312{
 313        struct pid_namespace *ns;
 314
 315        rcu_read_lock();
 316        ns = get_pid_ns(task_active_pid_ns(task));
 317        rcu_read_unlock();
 318
 319        return ns;
 320}
 321
 322static void pidns_put(void *ns)
 323{
 324        put_pid_ns(ns);
 325}
 326
 327static int pidns_install(struct nsproxy *nsproxy, void *ns)
 328{
 329        struct pid_namespace *active = task_active_pid_ns(current);
 330        struct pid_namespace *ancestor, *new = ns;
 331
 332        if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) ||
 333            !nsown_capable(CAP_SYS_ADMIN))
 334                return -EPERM;
 335
 336        /*
 337         * Only allow entering the current active pid namespace
 338         * or a child of the current active pid namespace.
 339         *
 340         * This is required for fork to return a usable pid value and
 341         * this maintains the property that processes and their
 342         * children can not escape their current pid namespace.
 343         */
 344        if (new->level < active->level)
 345                return -EINVAL;
 346
 347        ancestor = new;
 348        while (ancestor->level > active->level)
 349                ancestor = ancestor->parent;
 350        if (ancestor != active)
 351                return -EINVAL;
 352
 353        put_pid_ns(nsproxy->pid_ns);
 354        nsproxy->pid_ns = get_pid_ns(new);
 355        return 0;
 356}
 357
 358static unsigned int pidns_inum(void *ns)
 359{
 360        struct pid_namespace *pid_ns = ns;
 361        return pid_ns->proc_inum;
 362}
 363
 364const struct proc_ns_operations pidns_operations = {
 365        .name           = "pid",
 366        .type           = CLONE_NEWPID,
 367        .get            = pidns_get,
 368        .put            = pidns_put,
 369        .install        = pidns_install,
 370        .inum           = pidns_inum,
 371};
 372
 373static __init int pid_namespaces_init(void)
 374{
 375        pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
 376
 377#ifdef CONFIG_CHECKPOINT_RESTORE
 378        register_sysctl_paths(kern_path, pid_ns_ctl_table);
 379#endif
 380        return 0;
 381}
 382
 383__initcall(pid_namespaces_init);
 384
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