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 
   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);
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FreeBSD/Linux Kernel Cross Reference sys/kernel/pid_namespace.c

FreeBSD/Linux Kernel Cross Reference
sys/kernel/pid_namespace.c
