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 task_struct *tsk,
  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(task_cred_xxx(tsk, user)->user_ns);
  50
  51         return ns;
  52 }
  53
  54 struct ipc_namespace *copy_ipcs(unsigned long flags,
  55                                 struct task_struct *tsk)
  56 {
  57         struct ipc_namespace *ns = tsk->nsproxy->ipc_ns;
  58
  59         if (!(flags & CLONE_NEWIPC))
  60                 return get_ipc_ns(ns);
  61         return create_ipc_ns(tsk, ns);
  62 }
  63
  64 /*
  65  * free_ipcs - free all ipcs of one type
  66  * @ns:   the namespace to remove the ipcs from
  67  * @ids:  the table of ipcs to free
  68  * @free: the function called to free each individual ipc
  69  *
  70  * Called for each kind of ipc when an ipc_namespace exits.
  71  */
  72 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  73                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  74 {
  75         struct kern_ipc_perm *perm;
  76         int next_id;
  77         int total, in_use;
  78
  79         down_write(&ids->rw_mutex);
  80
  81         in_use = ids->in_use;
  82
  83         for (total = 0, next_id = 0; total < in_use; next_id++) {
  84                 perm = idr_find(&ids->ipcs_idr, next_id);
  85                 if (perm == NULL)
  86                         continue;
  87                 ipc_lock_by_ptr(perm);
  88                 free(ns, perm);
  89                 total++;
  90         }
  91         up_write(&ids->rw_mutex);
  92 }
  93
  94 static void free_ipc_ns(struct ipc_namespace *ns)
  95 {
  96         /*
  97          * Unregistering the hotplug notifier at the beginning guarantees
  98          * that the ipc namespace won't be freed while we are inside the
  99          * callback routine. Since the blocking_notifier_chain_XXX routines
 100          * hold a rw lock on the notifier list, unregister_ipcns_notifier()
 101          * won't take the rw lock before blocking_notifier_call_chain() has
 102          * released the rd lock.
 103          */
 104         unregister_ipcns_notifier(ns);
 105         sem_exit_ns(ns);
 106         msg_exit_ns(ns);
 107         shm_exit_ns(ns);
 108         atomic_dec(&nr_ipc_ns);
 109
 110         /*
 111          * Do the ipcns removal notification after decrementing nr_ipc_ns in
 112          * order to have a correct value when recomputing msgmni.
 113          */
 114         ipcns_notify(IPCNS_REMOVED);
 115         put_user_ns(ns->user_ns);
 116         kfree(ns);
 117 }
 118
 119 /*
 120  * put_ipc_ns - drop a reference to an ipc namespace.
 121  * @ns: the namespace to put
 122  *
 123  * If this is the last task in the namespace exiting, and
 124  * it is dropping the refcount to 0, then it can race with
 125  * a task in another ipc namespace but in a mounts namespace
 126  * which has this ipcns's mqueuefs mounted, doing some action
 127  * with one of the mqueuefs files.  That can raise the refcount.
 128  * So dropping the refcount, and raising the refcount when
 129  * accessing it through the VFS, are protected with mq_lock.
 130  *
 131  * (Clearly, a task raising the refcount on its own ipc_ns
 132  * needn't take mq_lock since it can't race with the last task
 133  * in the ipcns exiting).
 134  */
 135 void put_ipc_ns(struct ipc_namespace *ns)
 136 {
 137         if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 138                 mq_clear_sbinfo(ns);
 139                 spin_unlock(&mq_lock);
 140                 mq_put_mnt(ns);
 141                 free_ipc_ns(ns);
 142         }
 143 }
 144
 145 static void *ipcns_get(struct task_struct *task)
 146 {
 147         struct ipc_namespace *ns = NULL;
 148         struct nsproxy *nsproxy;
 149
 150         rcu_read_lock();
 151         nsproxy = task_nsproxy(task);
 152         if (nsproxy)
 153                 ns = get_ipc_ns(nsproxy->ipc_ns);
 154         rcu_read_unlock();
 155
 156         return ns;
 157 }
 158
 159 static void ipcns_put(void *ns)
 160 {
 161         return put_ipc_ns(ns);
 162 }
 163
 164 static int ipcns_install(struct nsproxy *nsproxy, void *ns)
 165 {
 166         /* Ditch state from the old ipc namespace */
 167         exit_sem(current);
 168         put_ipc_ns(nsproxy->ipc_ns);
 169         nsproxy->ipc_ns = get_ipc_ns(ns);
 170         return 0;
 171 }
 172
 173 const struct proc_ns_operations ipcns_operations = {
 174         .name           = "ipc",
 175         .type           = CLONE_NEWIPC,
 176         .get            = ipcns_get,
 177         .put            = ipcns_put,
 178         .install        = ipcns_install,
 179 };