release/src-rt-6.x.4708/linux/linux-2.6.36/kernel/nsproxy.c

   1 /*
   2  *  Copyright (C) 2006 IBM Corporation
   3  *
   4  *  Author: Serge Hallyn <serue@us.ibm.com>
   5  *
   6  *  This program is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU General Public License as
   8  *  published by the Free Software Foundation, version 2 of the
   9  *  License.
  10  *
  11  *  Jun 2006 - namespaces support
  12  *             OpenVZ, SWsoft Inc.
  13  *             Pavel Emelianov <xemul@openvz.org>
  14  */
  15
  16 #include <linux/slab.h>
  17 #include <linux/module.h>
  18 #include <linux/nsproxy.h>
  19 #include <linux/init_task.h>
  20 #include <linux/mnt_namespace.h>
  21 #include <linux/utsname.h>
  22 #include <linux/pid_namespace.h>
  23 #include <net/net_namespace.h>
  24 #include <linux/ipc_namespace.h>
  25
  26 static struct kmem_cache *nsproxy_cachep;
  27
  28 struct nsproxy init_nsproxy = {
  29         .count  = ATOMIC_INIT(1),
  30         .uts_ns = &init_uts_ns,
  31 #if defined(CONFIG_POSIX_MQUEUE) || defined(CONFIG_SYSVIPC)
  32         .ipc_ns = &init_ipc_ns,
  33 #endif
  34         .mnt_ns = NULL,
  35         .pid_ns = &init_pid_ns,
  36 #ifdef CONFIG_NET
  37         .net_ns = &init_net,
  38 #endif
  39 };
  40
  41 static inline struct nsproxy *create_nsproxy(void)
  42 {
  43         struct nsproxy *nsproxy;
  44
  45         nsproxy = kmem_cache_alloc(nsproxy_cachep, GFP_KERNEL);
  46         if (nsproxy)
  47                 atomic_set(&nsproxy->count, 1);
  48         return nsproxy;
  49 }
  50
  51 /*
  52  * Create new nsproxy and all of its the associated namespaces.
  53  * Return the newly created nsproxy.  Do not attach this to the task,
  54  * leave it to the caller to do proper locking and attach it to task.
  55  */
  56 static struct nsproxy *create_new_namespaces(unsigned long flags,
  57                         struct task_struct *tsk, struct fs_struct *new_fs)
  58 {
  59         struct nsproxy *new_nsp;
  60         int err;
  61
  62         new_nsp = create_nsproxy();
  63         if (!new_nsp)
  64                 return ERR_PTR(-ENOMEM);
  65
  66         new_nsp->mnt_ns = copy_mnt_ns(flags, tsk->nsproxy->mnt_ns, new_fs);
  67         if (IS_ERR(new_nsp->mnt_ns)) {
  68                 err = PTR_ERR(new_nsp->mnt_ns);
  69                 goto out_ns;
  70         }
  71
  72         new_nsp->uts_ns = copy_utsname(flags, tsk->nsproxy->uts_ns);
  73         if (IS_ERR(new_nsp->uts_ns)) {
  74                 err = PTR_ERR(new_nsp->uts_ns);
  75                 goto out_uts;
  76         }
  77
  78         new_nsp->ipc_ns = copy_ipcs(flags, tsk->nsproxy->ipc_ns);
  79         if (IS_ERR(new_nsp->ipc_ns)) {
  80                 err = PTR_ERR(new_nsp->ipc_ns);
  81                 goto out_ipc;
  82         }
  83
  84         new_nsp->pid_ns = copy_pid_ns(flags, task_active_pid_ns(tsk));
  85         if (IS_ERR(new_nsp->pid_ns)) {
  86                 err = PTR_ERR(new_nsp->pid_ns);
  87                 goto out_pid;
  88         }
  89
  90         new_nsp->net_ns = copy_net_ns(flags, tsk->nsproxy->net_ns);
  91         if (IS_ERR(new_nsp->net_ns)) {
  92                 err = PTR_ERR(new_nsp->net_ns);
  93                 goto out_net;
  94         }
  95
  96         return new_nsp;
  97
  98 out_net:
  99         if (new_nsp->pid_ns)
 100                 put_pid_ns(new_nsp->pid_ns);
 101 out_pid:
 102         if (new_nsp->ipc_ns)
 103                 put_ipc_ns(new_nsp->ipc_ns);
 104 out_ipc:
 105         if (new_nsp->uts_ns)
 106                 put_uts_ns(new_nsp->uts_ns);
 107 out_uts:
 108         if (new_nsp->mnt_ns)
 109                 put_mnt_ns(new_nsp->mnt_ns);
 110 out_ns:
 111         kmem_cache_free(nsproxy_cachep, new_nsp);
 112         return ERR_PTR(err);
 113 }
 114
 115 /*
 116  * called from clone.  This now handles copy for nsproxy and all
 117  * namespaces therein.
 118  */
 119 int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 120 {
 121         struct nsproxy *old_ns = tsk->nsproxy;
 122         struct nsproxy *new_ns;
 123         int err = 0;
 124
 125         if (!old_ns)
 126                 return 0;
 127
 128         get_nsproxy(old_ns);
 129
 130         if (!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
 131                                 CLONE_NEWPID | CLONE_NEWNET)))
 132                 return 0;
 133
 134         if (!capable(CAP_SYS_ADMIN)) {
 135                 err = -EPERM;
 136                 goto out;
 137         }
 138
 139         /*
 140          * CLONE_NEWIPC must detach from the undolist: after switching
 141          * to a new ipc namespace, the semaphore arrays from the old
 142          * namespace are unreachable.  In clone parlance, CLONE_SYSVSEM
 143          * means share undolist with parent, so we must forbid using
 144          * it along with CLONE_NEWIPC.
 145          */
 146         if ((flags & CLONE_NEWIPC) && (flags & CLONE_SYSVSEM)) {
 147                 err = -EINVAL;
 148                 goto out;
 149         }
 150
 151         new_ns = create_new_namespaces(flags, tsk, tsk->fs);
 152         if (IS_ERR(new_ns)) {
 153                 err = PTR_ERR(new_ns);
 154                 goto out;
 155         }
 156
 157         tsk->nsproxy = new_ns;
 158
 159 out:
 160         put_nsproxy(old_ns);
 161         return err;
 162 }
 163
 164 void free_nsproxy(struct nsproxy *ns)
 165 {
 166         if (ns->mnt_ns)
 167                 put_mnt_ns(ns->mnt_ns);
 168         if (ns->uts_ns)
 169                 put_uts_ns(ns->uts_ns);
 170         if (ns->ipc_ns)
 171                 put_ipc_ns(ns->ipc_ns);
 172         if (ns->pid_ns)
 173                 put_pid_ns(ns->pid_ns);
 174         put_net(ns->net_ns);
 175         kmem_cache_free(nsproxy_cachep, ns);
 176 }
 177
 178 /*
 179  * Called from unshare. Unshare all the namespaces part of nsproxy.
 180  * On success, returns the new nsproxy.
 181  */
 182 int unshare_nsproxy_namespaces(unsigned long unshare_flags,
 183                 struct nsproxy **new_nsp, struct fs_struct *new_fs)
 184 {
 185         int err = 0;
 186
 187         if (!(unshare_flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC |
 188                                CLONE_NEWNET)))
 189                 return 0;
 190
 191         if (!capable(CAP_SYS_ADMIN))
 192                 return -EPERM;
 193
 194         *new_nsp = create_new_namespaces(unshare_flags, current,
 195                                 new_fs ? new_fs : current->fs);
 196         if (IS_ERR(*new_nsp)) {
 197                 err = PTR_ERR(*new_nsp);
 198                 goto out;
 199         }
 200
 201         err = ns_cgroup_clone(current, task_pid(current));
 202         if (err)
 203                 put_nsproxy(*new_nsp);
 204
 205 out:
 206         return err;
 207 }
 208
 209 void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
 210 {
 211         struct nsproxy *ns;
 212
 213         might_sleep();
 214
 215         ns = p->nsproxy;
 216
 217         rcu_assign_pointer(p->nsproxy, new);
 218
 219         if (ns && atomic_dec_and_test(&ns->count)) {
 220                 /*
 221                  * wait for others to get what they want from this nsproxy.
 222                  *
 223                  * cannot release this nsproxy via the call_rcu() since
 224                  * put_mnt_ns() will want to sleep
 225                  */
 226                 synchronize_rcu();
 227                 free_nsproxy(ns);
 228         }
 229 }
 230
 231 void exit_task_namespaces(struct task_struct *p)
 232 {
 233         switch_task_namespaces(p, NULL);
 234 }
 235
 236 static int __init nsproxy_cache_init(void)
 237 {
 238         nsproxy_cachep = KMEM_CACHE(nsproxy, SLAB_PANIC);
 239         return 0;
 240 }
 241
 242 module_init(nsproxy_cache_init);