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_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
 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
 247 static 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
 266 extern int pid_max;
 267 static int zero = 0;
 268 static 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 };
 279 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
 280 #endif  /* CONFIG_CHECKPOINT_RESTORE */
 281
 282 int 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
 311 static 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
 322 static void pidns_put(void *ns)
 323 {
 324         put_pid_ns(ns);
 325 }
 326
 327 static 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
 358 static unsigned int pidns_inum(void *ns)
 359 {
 360         struct pid_namespace *pid_ns = ns;
 361         return pid_ns->proc_inum;
 362 }
 363
 364 const 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
 373 static __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);