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
  17 #define BITS_PER_PAGE           (PAGE_SIZE*8)
  18
  19 struct pid_cache {
  20         int nr_ids;
  21         char name[16];
  22         struct kmem_cache *cachep;
  23         struct list_head list;
  24 };
  25
  26 static LIST_HEAD(pid_caches_lh);
  27 static DEFINE_MUTEX(pid_caches_mutex);
  28 static struct kmem_cache *pid_ns_cachep;
  29
  30 /*
  31  * creates the kmem cache to allocate pids from.
  32  * @nr_ids: the number of numerical ids this pid will have to carry
  33  */
  34
  35 static struct kmem_cache *create_pid_cachep(int nr_ids)
  36 {
  37         struct pid_cache *pcache;
  38         struct kmem_cache *cachep;
  39
  40         mutex_lock(&pid_caches_mutex);
  41         list_for_each_entry(pcache, &pid_caches_lh, list)
  42                 if (pcache->nr_ids == nr_ids)
  43                         goto out;
  44
  45         pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
  46         if (pcache == NULL)
  47                 goto err_alloc;
  48
  49         snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
  50         cachep = kmem_cache_create(pcache->name,
  51                         sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
  52                         0, SLAB_HWCACHE_ALIGN, NULL);
  53         if (cachep == NULL)
  54                 goto err_cachep;
  55
  56         pcache->nr_ids = nr_ids;
  57         pcache->cachep = cachep;
  58         list_add(&pcache->list, &pid_caches_lh);
  59 out:
  60         mutex_unlock(&pid_caches_mutex);
  61         return pcache->cachep;
  62
  63 err_cachep:
  64         kfree(pcache);
  65 err_alloc:
  66         mutex_unlock(&pid_caches_mutex);
  67         return NULL;
  68 }
  69
  70 static struct pid_namespace *create_pid_namespace(unsigned int level)
  71 {
  72         struct pid_namespace *ns;
  73         int i;
  74
  75         ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
  76         if (ns == NULL)
  77                 goto out;
  78
  79         ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
  80         if (!ns->pidmap[0].page)
  81                 goto out_free;
  82
  83         ns->pid_cachep = create_pid_cachep(level + 1);
  84         if (ns->pid_cachep == NULL)
  85                 goto out_free_map;
  86
  87         kref_init(&ns->kref);
  88         ns->level = level;
  89
  90         set_bit(0, ns->pidmap[0].page);
  91         atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
  92
  93         for (i = 1; i < PIDMAP_ENTRIES; i++)
  94                 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
  95
  96         return ns;
  97
  98 out_free_map:
  99         kfree(ns->pidmap[0].page);
 100 out_free:
 101         kmem_cache_free(pid_ns_cachep, ns);
 102 out:
 103         return ERR_PTR(-ENOMEM);
 104 }
 105
 106 static void destroy_pid_namespace(struct pid_namespace *ns)
 107 {
 108         int i;
 109
 110         for (i = 0; i < PIDMAP_ENTRIES; i++)
 111                 kfree(ns->pidmap[i].page);
 112         kmem_cache_free(pid_ns_cachep, ns);
 113 }
 114
 115 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
 116 {
 117         struct pid_namespace *new_ns;
 118
 119         BUG_ON(!old_ns);
 120         new_ns = get_pid_ns(old_ns);
 121         if (!(flags & CLONE_NEWPID))
 122                 goto out;
 123
 124         new_ns = ERR_PTR(-EINVAL);
 125         if (flags & CLONE_THREAD)
 126                 goto out_put;
 127
 128         new_ns = create_pid_namespace(old_ns->level + 1);
 129         if (!IS_ERR(new_ns))
 130                 new_ns->parent = get_pid_ns(old_ns);
 131
 132 out_put:
 133         put_pid_ns(old_ns);
 134 out:
 135         return new_ns;
 136 }
 137
 138 void free_pid_ns(struct kref *kref)
 139 {
 140         struct pid_namespace *ns, *parent;
 141
 142         ns = container_of(kref, struct pid_namespace, kref);
 143
 144         parent = ns->parent;
 145         destroy_pid_namespace(ns);
 146
 147         if (parent != NULL)
 148                 put_pid_ns(parent);
 149 }
 150
 151 void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 152 {
 153         int nr;
 154         int rc;
 155         struct task_struct *task;
 156
 157         /*
 158          * The last thread in the cgroup-init thread group is terminating.
 159          * Find remaining pid_ts in the namespace, signal and wait for them
 160          * to exit.
 161          *
 162          * Note:  This signals each threads in the namespace - even those that
 163          *        belong to the same thread group, To avoid this, we would have
 164          *        to walk the entire tasklist looking a processes in this
 165          *        namespace, but that could be unnecessarily expensive if the
 166          *        pid namespace has just a few processes. Or we need to
 167          *        maintain a tasklist for each pid namespace.
 168          *
 169          */
 170         read_lock(&tasklist_lock);
 171         nr = next_pidmap(pid_ns, 1);
 172         while (nr > 0) {
 173                 rcu_read_lock();
 174
 175                 /*
 176                  * Use force_sig() since it clears SIGNAL_UNKILLABLE ensuring
 177                  * any nested-container's init processes don't ignore the
 178                  * signal
 179                  */
 180                 task = pid_task(find_vpid(nr), PIDTYPE_PID);
 181                 if (task)
 182                         force_sig(SIGKILL, task);
 183
 184                 rcu_read_unlock();
 185
 186                 nr = next_pidmap(pid_ns, nr);
 187         }
 188         read_unlock(&tasklist_lock);
 189
 190         do {
 191                 clear_thread_flag(TIF_SIGPENDING);
 192                 rc = sys_wait4(-1, NULL, __WALL, NULL);
 193         } while (rc != -ECHILD);
 194
 195         acct_exit_ns(pid_ns);
 196         return;
 197 }
 198
 199 static __init int pid_namespaces_init(void)
 200 {
 201         pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
 202         return 0;
 203 }
 204
 205 __initcall(pid_namespaces_init);