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
  16 #define BITS_PER_PAGE           (PAGE_SIZE*8)
  17
  18 struct pid_cache {
  19         int nr_ids;
  20         char name[16];
  21         struct kmem_cache *cachep;
  22         struct list_head list;
  23 };
  24
  25 static LIST_HEAD(pid_caches_lh);
  26 static DEFINE_MUTEX(pid_caches_mutex);
  27 static struct kmem_cache *pid_ns_cachep;
  28
  29 /*
  30  * creates the kmem cache to allocate pids from.
  31  * @nr_ids: the number of numerical ids this pid will have to carry
  32  */
  33
  34 static struct kmem_cache *create_pid_cachep(int nr_ids)
  35 {
  36         struct pid_cache *pcache;
  37         struct kmem_cache *cachep;
  38
  39         mutex_lock(&pid_caches_mutex);
  40         list_for_each_entry(pcache, &pid_caches_lh, list)
  41                 if (pcache->nr_ids == nr_ids)
  42                         goto out;
  43
  44         pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
  45         if (pcache == NULL)
  46                 goto err_alloc;
  47
  48         snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
  49         cachep = kmem_cache_create(pcache->name,
  50                         sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
  51                         0, SLAB_HWCACHE_ALIGN, NULL);
  52         if (cachep == NULL)
  53                 goto err_cachep;
  54
  55         pcache->nr_ids = nr_ids;
  56         pcache->cachep = cachep;
  57         list_add(&pcache->list, &pid_caches_lh);
  58 out:
  59         mutex_unlock(&pid_caches_mutex);
  60         return pcache->cachep;
  61
  62 err_cachep:
  63         kfree(pcache);
  64 err_alloc:
  65         mutex_unlock(&pid_caches_mutex);
  66         return NULL;
  67 }
  68
  69 static struct pid_namespace *create_pid_namespace(unsigned int level)
  70 {
  71         struct pid_namespace *ns;
  72         int i;
  73
  74         ns = kmem_cache_alloc(pid_ns_cachep, GFP_KERNEL);
  75         if (ns == NULL)
  76                 goto out;
  77
  78         ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
  79         if (!ns->pidmap[0].page)
  80                 goto out_free;
  81
  82         ns->pid_cachep = create_pid_cachep(level + 1);
  83         if (ns->pid_cachep == NULL)
  84                 goto out_free_map;
  85
  86         kref_init(&ns->kref);
  87         ns->last_pid = 0;
  88         ns->child_reaper = NULL;
  89         ns->level = level;
  90
  91         set_bit(0, ns->pidmap[0].page);
  92         atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
  93
  94         for (i = 1; i < PIDMAP_ENTRIES; i++) {
  95                 ns->pidmap[i].page = NULL;
  96                 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
  97         }
  98
  99         return ns;
 100
 101 out_free_map:
 102         kfree(ns->pidmap[0].page);
 103 out_free:
 104         kmem_cache_free(pid_ns_cachep, ns);
 105 out:
 106         return ERR_PTR(-ENOMEM);
 107 }
 108
 109 static void destroy_pid_namespace(struct pid_namespace *ns)
 110 {
 111         int i;
 112
 113         for (i = 0; i < PIDMAP_ENTRIES; i++)
 114                 kfree(ns->pidmap[i].page);
 115         kmem_cache_free(pid_ns_cachep, ns);
 116 }
 117
 118 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
 119 {
 120         struct pid_namespace *new_ns;
 121
 122         BUG_ON(!old_ns);
 123         new_ns = get_pid_ns(old_ns);
 124         if (!(flags & CLONE_NEWPID))
 125                 goto out;
 126
 127         new_ns = ERR_PTR(-EINVAL);
 128         if (flags & CLONE_THREAD)
 129                 goto out_put;
 130
 131         new_ns = create_pid_namespace(old_ns->level + 1);
 132         if (!IS_ERR(new_ns))
 133                 new_ns->parent = get_pid_ns(old_ns);
 134
 135 out_put:
 136         put_pid_ns(old_ns);
 137 out:
 138         return new_ns;
 139 }
 140
 141 void free_pid_ns(struct kref *kref)
 142 {
 143         struct pid_namespace *ns, *parent;
 144
 145         ns = container_of(kref, struct pid_namespace, kref);
 146
 147         parent = ns->parent;
 148         destroy_pid_namespace(ns);
 149
 150         if (parent != NULL)
 151                 put_pid_ns(parent);
 152 }
 153
 154 void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 155 {
 156         int nr;
 157         int rc;
 158
 159         /*
 160          * The last thread in the cgroup-init thread group is terminating.
 161          * Find remaining pid_ts in the namespace, signal and wait for them
 162          * to exit.
 163          *
 164          * Note:  This signals each threads in the namespace - even those that
 165          *        belong to the same thread group, To avoid this, we would have
 166          *        to walk the entire tasklist looking a processes in this
 167          *        namespace, but that could be unnecessarily expensive if the
 168          *        pid namespace has just a few processes. Or we need to
 169          *        maintain a tasklist for each pid namespace.
 170          *
 171          */
 172         read_lock(&tasklist_lock);
 173         nr = next_pidmap(pid_ns, 1);
 174         while (nr > 0) {
 175                 kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
 176                 nr = next_pidmap(pid_ns, nr);
 177         }
 178         read_unlock(&tasklist_lock);
 179
 180         do {
 181                 clear_thread_flag(TIF_SIGPENDING);
 182                 rc = sys_wait4(-1, NULL, __WALL, NULL);
 183         } while (rc != -ECHILD);
 184
 185
 186         /* Child reaper for the pid namespace is going away */
 187         pid_ns->child_reaper = NULL;
 188         return;
 189 }
 190
 191 static __init int pid_namespaces_init(void)
 192 {
 193         pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
 194         return 0;
 195 }
 196
 197 __initcall(pid_namespaces_init);