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