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/syscalls.h>
  14 #include <linux/err.h>
  15 #include <linux/acct.h>
  16 #include <linux/slab.h>
  17 #include <linux/proc_fs.h>
  18 #include <linux/reboot.h>
  19 #include <linux/export.h>
  20
  21 #define BITS_PER_PAGE           (PAGE_SIZE*8)
  22
  23 struct pid_cache {
  24         int nr_ids;
  25         char name[16];
  26         struct kmem_cache *cachep;
  27         struct list_head list;
  28 };
  29
  30 static LIST_HEAD(pid_caches_lh);
  31 static DEFINE_MUTEX(pid_caches_mutex);
  32 static struct kmem_cache *pid_ns_cachep;
  33
  34 /*
  35  * creates the kmem cache to allocate pids from.
  36  * @nr_ids: the number of numerical ids this pid will have to carry
  37  */
  38
  39 static struct kmem_cache *create_pid_cachep(int nr_ids)
  40 {
  41         struct pid_cache *pcache;
  42         struct kmem_cache *cachep;
  43
  44         mutex_lock(&pid_caches_mutex);
  45         list_for_each_entry(pcache, &pid_caches_lh, list)
  46                 if (pcache->nr_ids == nr_ids)
  47                         goto out;
  48
  49         pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
  50         if (pcache == NULL)
  51                 goto err_alloc;
  52
  53         snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
  54         cachep = kmem_cache_create(pcache->name,
  55                         sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
  56                         0, SLAB_HWCACHE_ALIGN, NULL);
  57         if (cachep == NULL)
  58                 goto err_cachep;
  59
  60         pcache->nr_ids = nr_ids;
  61         pcache->cachep = cachep;
  62         list_add(&pcache->list, &pid_caches_lh);
  63 out:
  64         mutex_unlock(&pid_caches_mutex);
  65         return pcache->cachep;
  66
  67 err_cachep:
  68         kfree(pcache);
  69 err_alloc:
  70         mutex_unlock(&pid_caches_mutex);
  71         return NULL;
  72 }
  73
  74 static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)
  75 {
  76         struct pid_namespace *ns;
  77         unsigned int level = parent_pid_ns->level + 1;
  78         int i, err = -ENOMEM;
  79
  80         ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
  81         if (ns == NULL)
  82                 goto out;
  83
  84         ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
  85         if (!ns->pidmap[0].page)
  86                 goto out_free;
  87
  88         ns->pid_cachep = create_pid_cachep(level + 1);
  89         if (ns->pid_cachep == NULL)
  90                 goto out_free_map;
  91
  92         kref_init(&ns->kref);
  93         ns->level = level;
  94         ns->parent = get_pid_ns(parent_pid_ns);
  95
  96         set_bit(0, ns->pidmap[0].page);
  97         atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
  98
  99         for (i = 1; i < PIDMAP_ENTRIES; i++)
 100                 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
 101
 102         err = pid_ns_prepare_proc(ns);
 103         if (err)
 104                 goto out_put_parent_pid_ns;
 105
 106         return ns;
 107
 108 out_put_parent_pid_ns:
 109         put_pid_ns(parent_pid_ns);
 110 out_free_map:
 111         kfree(ns->pidmap[0].page);
 112 out_free:
 113         kmem_cache_free(pid_ns_cachep, ns);
 114 out:
 115         return ERR_PTR(err);
 116 }
 117
 118 static void destroy_pid_namespace(struct pid_namespace *ns)
 119 {
 120         int i;
 121
 122         for (i = 0; i < PIDMAP_ENTRIES; i++)
 123                 kfree(ns->pidmap[i].page);
 124         kmem_cache_free(pid_ns_cachep, ns);
 125 }
 126
 127 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
 128 {
 129         if (!(flags & CLONE_NEWPID))
 130                 return get_pid_ns(old_ns);
 131         if (flags & (CLONE_THREAD|CLONE_PARENT))
 132                 return ERR_PTR(-EINVAL);
 133         return create_pid_namespace(old_ns);
 134 }
 135
 136 static void free_pid_ns(struct kref *kref)
 137 {
 138         struct pid_namespace *ns;
 139
 140         ns = container_of(kref, struct pid_namespace, kref);
 141         destroy_pid_namespace(ns);
 142 }
 143
 144 void put_pid_ns(struct pid_namespace *ns)
 145 {
 146         struct pid_namespace *parent;
 147
 148         while (ns != &init_pid_ns) {
 149                 parent = ns->parent;
 150                 if (!kref_put(&ns->kref, free_pid_ns))
 151                         break;
 152                 ns = parent;
 153         }
 154 }
 155 EXPORT_SYMBOL_GPL(put_pid_ns);
 156
 157 void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 158 {
 159         int nr;
 160         int rc;
 161         struct task_struct *task, *me = current;
 162
 163         /* Ignore SIGCHLD causing any terminated children to autoreap */
 164         spin_lock_irq(&me->sighand->siglock);
 165         me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN;
 166         spin_unlock_irq(&me->sighand->siglock);
 167
 168         /*
 169          * The last thread in the cgroup-init thread group is terminating.
 170          * Find remaining pid_ts in the namespace, signal and wait for them
 171          * to exit.
 172          *
 173          * Note:  This signals each threads in the namespace - even those that
 174          *        belong to the same thread group, To avoid this, we would have
 175          *        to walk the entire tasklist looking a processes in this
 176          *        namespace, but that could be unnecessarily expensive if the
 177          *        pid namespace has just a few processes. Or we need to
 178          *        maintain a tasklist for each pid namespace.
 179          *
 180          */
 181         read_lock(&tasklist_lock);
 182         nr = next_pidmap(pid_ns, 1);
 183         while (nr > 0) {
 184                 rcu_read_lock();
 185
 186                 task = pid_task(find_vpid(nr), PIDTYPE_PID);
 187                 if (task && !__fatal_signal_pending(task))
 188                         send_sig_info(SIGKILL, SEND_SIG_FORCED, task);
 189
 190                 rcu_read_unlock();
 191
 192                 nr = next_pidmap(pid_ns, nr);
 193         }
 194         read_unlock(&tasklist_lock);
 195
 196         /* Firstly reap the EXIT_ZOMBIE children we may have. */
 197         do {
 198                 clear_thread_flag(TIF_SIGPENDING);
 199                 rc = sys_wait4(-1, NULL, __WALL, NULL);
 200         } while (rc != -ECHILD);
 201
 202         /*
 203          * sys_wait4() above can't reap the TASK_DEAD children.
 204          * Make sure they all go away, see __unhash_process().
 205          */
 206         for (;;) {
 207                 bool need_wait = false;
 208
 209                 read_lock(&tasklist_lock);
 210                 if (!list_empty(&current->children)) {
 211                         __set_current_state(TASK_UNINTERRUPTIBLE);
 212                         need_wait = true;
 213                 }
 214                 read_unlock(&tasklist_lock);
 215
 216                 if (!need_wait)
 217                         break;
 218                 schedule();
 219         }
 220
 221         if (pid_ns->reboot)
 222                 current->signal->group_exit_code = pid_ns->reboot;
 223
 224         acct_exit_ns(pid_ns);
 225         return;
 226 }
 227
 228 #ifdef CONFIG_CHECKPOINT_RESTORE
 229 static int pid_ns_ctl_handler(struct ctl_table *table, int write,
 230                 void __user *buffer, size_t *lenp, loff_t *ppos)
 231 {
 232         struct ctl_table tmp = *table;
 233
 234         if (write && !capable(CAP_SYS_ADMIN))
 235                 return -EPERM;
 236
 237         /*
 238          * Writing directly to ns' last_pid field is OK, since this field
 239          * is volatile in a living namespace anyway and a code writing to
 240          * it should synchronize its usage with external means.
 241          */
 242
 243         tmp.data = &current->nsproxy->pid_ns->last_pid;
 244         return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
 245 }
 246
 247 extern int pid_max;
 248 static int zero = 0;
 249 static struct ctl_table pid_ns_ctl_table[] = {
 250         {
 251                 .procname = "ns_last_pid",
 252                 .maxlen = sizeof(int),
 253                 .mode = 0666, /* permissions are checked in the handler */
 254                 .proc_handler = pid_ns_ctl_handler,
 255                 .extra1 = &zero,
 256                 .extra2 = &pid_max,
 257         },
 258         { }
 259 };
 260 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
 261 #endif  /* CONFIG_CHECKPOINT_RESTORE */
 262
 263 int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd)
 264 {
 265         if (pid_ns == &init_pid_ns)
 266                 return 0;
 267
 268         switch (cmd) {
 269         case LINUX_REBOOT_CMD_RESTART2:
 270         case LINUX_REBOOT_CMD_RESTART:
 271                 pid_ns->reboot = SIGHUP;
 272                 break;
 273
 274         case LINUX_REBOOT_CMD_POWER_OFF:
 275         case LINUX_REBOOT_CMD_HALT:
 276                 pid_ns->reboot = SIGINT;
 277                 break;
 278         default:
 279                 return -EINVAL;
 280         }
 281
 282         read_lock(&tasklist_lock);
 283         force_sig(SIGKILL, pid_ns->child_reaper);
 284         read_unlock(&tasklist_lock);
 285
 286         do_exit(0);
 287
 288         /* Not reached */
 289         return 0;
 290 }
 291
 292 static __init int pid_namespaces_init(void)
 293 {
 294         pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
 295
 296 #ifdef CONFIG_CHECKPOINT_RESTORE
 297         register_sysctl_paths(kern_path, pid_ns_ctl_table);
 298 #endif
 299         return 0;
 300 }
 301
 302 __initcall(pid_namespaces_init);