ipc/namespace.c

   1 /*
   2  * linux/ipc/namespace.c
   3  * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
   4  */
   5
   6 #include <linux/ipc.h>
   7 #include <linux/msg.h>
   8 #include <linux/ipc_namespace.h>
   9 #include <linux/rcupdate.h>
  10 #include <linux/nsproxy.h>
  11 #include <linux/slab.h>
  12 #include <linux/fs.h>
  13 #include <linux/mount.h>
  14 #include <linux/user_namespace.h>
  15 #include <linux/proc_fs.h>
  16
  17 #include "util.h"
  18
  19 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
  20                                            struct ipc_namespace *old_ns)
  21 {
  22         struct ipc_namespace *ns;
  23         int err;
  24
  25         ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
  26         if (ns == NULL)
  27                 return ERR_PTR(-ENOMEM);
  28
  29         atomic_set(&ns->count, 1);
  30         err = mq_init_ns(ns);
  31         if (err) {
  32                 kfree(ns);
  33                 return ERR_PTR(err);
  34         }
  35         atomic_inc(&nr_ipc_ns);
  36
  37         sem_init_ns(ns);
  38         msg_init_ns(ns);
  39         shm_init_ns(ns);
  40
  41         /*
  42          * msgmni has already been computed for the new ipc ns.
  43          * Thus, do the ipcns creation notification before registering that
  44          * new ipcns in the chain.
  45          */
  46         ipcns_notify(IPCNS_CREATED);
  47         register_ipcns_notifier(ns);
  48
  49         ns->user_ns = get_user_ns(user_ns);
  50
  51         return ns;
  52 }
  53
  54 struct ipc_namespace *copy_ipcs(unsigned long flags,
  55         struct user_namespace *user_ns, struct ipc_namespace *ns)
  56 {
  57         if (!(flags & CLONE_NEWIPC))
  58                 return get_ipc_ns(ns);
  59         return create_ipc_ns(user_ns, ns);
  60 }
  61
  62 /*
  63  * free_ipcs - free all ipcs of one type
  64  * @ns:   the namespace to remove the ipcs from
  65  * @ids:  the table of ipcs to free
  66  * @free: the function called to free each individual ipc
  67  *
  68  * Called for each kind of ipc when an ipc_namespace exits.
  69  */
  70 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  71                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  72 {
  73         struct kern_ipc_perm *perm;
  74         int next_id;
  75         int total, in_use;
  76
  77         down_write(&ids->rw_mutex);
  78
  79         in_use = ids->in_use;
  80
  81         for (total = 0, next_id = 0; total < in_use; next_id++) {
  82                 perm = idr_find(&ids->ipcs_idr, next_id);
  83                 if (perm == NULL)
  84                         continue;
  85                 ipc_lock_by_ptr(perm);
  86                 free(ns, perm);
  87                 total++;
  88         }
  89         up_write(&ids->rw_mutex);
  90 }
  91
  92 static void free_ipc_ns(struct ipc_namespace *ns)
  93 {
  94         /*
  95          * Unregistering the hotplug notifier at the beginning guarantees
  96          * that the ipc namespace won't be freed while we are inside the
  97          * callback routine. Since the blocking_notifier_chain_XXX routines
  98          * hold a rw lock on the notifier list, unregister_ipcns_notifier()
  99          * won't take the rw lock before blocking_notifier_call_chain() has
 100          * released the rd lock.
 101          */
 102         unregister_ipcns_notifier(ns);
 103         sem_exit_ns(ns);
 104         msg_exit_ns(ns);
 105         shm_exit_ns(ns);
 106         atomic_dec(&nr_ipc_ns);
 107
 108         /*
 109          * Do the ipcns removal notification after decrementing nr_ipc_ns in
 110          * order to have a correct value when recomputing msgmni.
 111          */
 112         ipcns_notify(IPCNS_REMOVED);
 113         put_user_ns(ns->user_ns);
 114         kfree(ns);
 115 }
 116
 117 /*
 118  * put_ipc_ns - drop a reference to an ipc namespace.
 119  * @ns: the namespace to put
 120  *
 121  * If this is the last task in the namespace exiting, and
 122  * it is dropping the refcount to 0, then it can race with
 123  * a task in another ipc namespace but in a mounts namespace
 124  * which has this ipcns's mqueuefs mounted, doing some action
 125  * with one of the mqueuefs files.  That can raise the refcount.
 126  * So dropping the refcount, and raising the refcount when
 127  * accessing it through the VFS, are protected with mq_lock.
 128  *
 129  * (Clearly, a task raising the refcount on its own ipc_ns
 130  * needn't take mq_lock since it can't race with the last task
 131  * in the ipcns exiting).
 132  */
 133 void put_ipc_ns(struct ipc_namespace *ns)
 134 {
 135         if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 136                 mq_clear_sbinfo(ns);
 137                 spin_unlock(&mq_lock);
 138                 mq_put_mnt(ns);
 139                 free_ipc_ns(ns);
 140         }
 141 }
 142
 143 static void *ipcns_get(struct task_struct *task)
 144 {
 145         struct ipc_namespace *ns = NULL;
 146         struct nsproxy *nsproxy;
 147
 148         rcu_read_lock();
 149         nsproxy = task_nsproxy(task);
 150         if (nsproxy)
 151                 ns = get_ipc_ns(nsproxy->ipc_ns);
 152         rcu_read_unlock();
 153
 154         return ns;
 155 }
 156
 157 static void ipcns_put(void *ns)
 158 {
 159         return put_ipc_ns(ns);
 160 }
 161
 162 static int ipcns_install(struct nsproxy *nsproxy, void *new)
 163 {
 164         struct ipc_namespace *ns = new;
 165         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 166                 return -EPERM;
 167
 168         /* Ditch state from the old ipc namespace */
 169         exit_sem(current);
 170         put_ipc_ns(nsproxy->ipc_ns);
 171         nsproxy->ipc_ns = get_ipc_ns(ns);
 172         return 0;
 173 }
 174
 175 const struct proc_ns_operations ipcns_operations = {
 176         .name           = "ipc",
 177         .type           = CLONE_NEWIPC,
 178         .get            = ipcns_get,
 179         .put            = ipcns_put,
 180         .install        = ipcns_install,
 181 };