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
  19 #define BITS_PER_PAGE           (PAGE_SIZE*8)
  20
  21 struct pid_cache {
  22         int nr_ids;
  23         char name[16];
  24         struct kmem_cache *cachep;
  25         struct list_head list;
  26 };
  27
  28 static LIST_HEAD(pid_caches_lh);
  29 static DEFINE_MUTEX(pid_caches_mutex);
  30 static struct kmem_cache *pid_ns_cachep;
  31
  32 /*
  33  * creates the kmem cache to allocate pids from.
  34  * @nr_ids: the number of numerical ids this pid will have to carry
  35  */
  36
  37 static struct kmem_cache *create_pid_cachep(int nr_ids)
  38 {
  39         struct pid_cache *pcache;
  40         struct kmem_cache *cachep;
  41
  42         mutex_lock(&pid_caches_mutex);
  43         list_for_each_entry(pcache, &pid_caches_lh, list)
  44                 if (pcache->nr_ids == nr_ids)
  45                         goto out;
  46
  47         pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
  48         if (pcache == NULL)
  49                 goto err_alloc;
  50
  51         snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
  52         cachep = kmem_cache_create(pcache->name,
  53                         sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
  54                         0, SLAB_HWCACHE_ALIGN, NULL);
  55         if (cachep == NULL)
  56                 goto err_cachep;
  57
  58         pcache->nr_ids = nr_ids;
  59         pcache->cachep = cachep;
  60         list_add(&pcache->list, &pid_caches_lh);
  61 out:
  62         mutex_unlock(&pid_caches_mutex);
  63         return pcache->cachep;
  64
  65 err_cachep:
  66         kfree(pcache);
  67 err_alloc:
  68         mutex_unlock(&pid_caches_mutex);
  69         return NULL;
  70 }
  71
  72 static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)
  73 {
  74         struct pid_namespace *ns;
  75         unsigned int level = parent_pid_ns->level + 1;
  76         int i, err = -ENOMEM;
  77
  78         ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
  79         if (ns == NULL)
  80                 goto out;
  81
  82         ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
  83         if (!ns->pidmap[0].page)
  84                 goto out_free;
  85
  86         ns->pid_cachep = create_pid_cachep(level + 1);
  87         if (ns->pid_cachep == NULL)
  88                 goto out_free_map;
  89
  90         kref_init(&ns->kref);
  91         ns->level = level;
  92         ns->parent = get_pid_ns(parent_pid_ns);
  93
  94         set_bit(0, ns->pidmap[0].page);
  95         atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
  96
  97         for (i = 1; i < PIDMAP_ENTRIES; i++)
  98                 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
  99
 100         err = pid_ns_prepare_proc(ns);
 101         if (err)
 102                 goto out_put_parent_pid_ns;
 103
 104         return ns;
 105
 106 out_put_parent_pid_ns:
 107         put_pid_ns(parent_pid_ns);
 108 out_free_map:
 109         kfree(ns->pidmap[0].page);
 110 out_free:
 111         kmem_cache_free(pid_ns_cachep, ns);
 112 out:
 113         return ERR_PTR(err);
 114 }
 115
 116 static void destroy_pid_namespace(struct pid_namespace *ns)
 117 {
 118         int i;
 119
 120         for (i = 0; i < PIDMAP_ENTRIES; i++)
 121                 kfree(ns->pidmap[i].page);
 122         kmem_cache_free(pid_ns_cachep, ns);
 123 }
 124
 125 struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
 126 {
 127         if (!(flags & CLONE_NEWPID))
 128                 return get_pid_ns(old_ns);
 129         if (flags & (CLONE_THREAD|CLONE_PARENT))
 130                 return ERR_PTR(-EINVAL);
 131         return create_pid_namespace(old_ns);
 132 }
 133
 134 void free_pid_ns(struct kref *kref)
 135 {
 136         struct pid_namespace *ns, *parent;
 137
 138         ns = container_of(kref, struct pid_namespace, kref);
 139
 140         parent = ns->parent;
 141         destroy_pid_namespace(ns);
 142
 143         if (parent != NULL)
 144                 put_pid_ns(parent);
 145 }
 146
 147 void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 148 {
 149         int nr;
 150         int rc;
 151         struct task_struct *task;
 152
 153         /*
 154          * The last thread in the cgroup-init thread group is terminating.
 155          * Find remaining pid_ts in the namespace, signal and wait for them
 156          * to exit.
 157          *
 158          * Note:  This signals each threads in the namespace - even those that
 159          *        belong to the same thread group, To avoid this, we would have
 160          *        to walk the entire tasklist looking a processes in this
 161          *        namespace, but that could be unnecessarily expensive if the
 162          *        pid namespace has just a few processes. Or we need to
 163          *        maintain a tasklist for each pid namespace.
 164          *
 165          */
 166         read_lock(&tasklist_lock);
 167         nr = next_pidmap(pid_ns, 1);
 168         while (nr > 0) {
 169                 rcu_read_lock();
 170
 171                 /*
 172                  * Any nested-container's init processes won't ignore the
 173                  * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser().
 174                  */
 175                 task = pid_task(find_vpid(nr), PIDTYPE_PID);
 176                 if (task)
 177                         send_sig_info(SIGKILL, SEND_SIG_NOINFO, task);
 178
 179                 rcu_read_unlock();
 180
 181                 nr = next_pidmap(pid_ns, nr);
 182         }
 183         read_unlock(&tasklist_lock);
 184
 185         do {
 186                 clear_thread_flag(TIF_SIGPENDING);
 187                 rc = sys_wait4(-1, NULL, __WALL, NULL);
 188         } while (rc != -ECHILD);
 189
 190         acct_exit_ns(pid_ns);
 191         return;
 192 }
 193
 194 static int pid_ns_ctl_handler(struct ctl_table *table, int write,
 195                 void __user *buffer, size_t *lenp, loff_t *ppos)
 196 {
 197         struct ctl_table tmp = *table;
 198
 199         if (write && !capable(CAP_SYS_ADMIN))
 200                 return -EPERM;
 201
 202         /*
 203          * Writing directly to ns' last_pid field is OK, since this field
 204          * is volatile in a living namespace anyway and a code writing to
 205          * it should synchronize its usage with external means.
 206          */
 207
 208         tmp.data = &current->nsproxy->pid_ns->last_pid;
 209         return proc_dointvec(&tmp, write, buffer, lenp, ppos);
 210 }
 211
 212 static struct ctl_table pid_ns_ctl_table[] = {
 213         {
 214                 .procname = "ns_last_pid",
 215                 .maxlen = sizeof(int),
 216                 .mode = 0666, /* permissions are checked in the handler */
 217                 .proc_handler = pid_ns_ctl_handler,
 218         },
 219         { }
 220 };
 221
 222 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } };
 223
 224 static __init int pid_namespaces_init(void)
 225 {
 226         pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
 227         register_sysctl_paths(kern_path, pid_ns_ctl_table);
 228         return 0;
 229 }
 230
 231 __initcall(pid_namespaces_init);