linux/ipc/namespace.c
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   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
  19static 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        err = proc_alloc_inum(&ns->proc_inum);
  30        if (err) {
  31                kfree(ns);
  32                return ERR_PTR(err);
  33        }
  34
  35        atomic_set(&ns->count, 1);
  36        err = mq_init_ns(ns);
  37        if (err) {
  38                proc_free_inum(ns->proc_inum);
  39                kfree(ns);
  40                return ERR_PTR(err);
  41        }
  42        atomic_inc(&nr_ipc_ns);
  43
  44        sem_init_ns(ns);
  45        msg_init_ns(ns);
  46        shm_init_ns(ns);
  47
  48        /*
  49         * msgmni has already been computed for the new ipc ns.
  50         * Thus, do the ipcns creation notification before registering that
  51         * new ipcns in the chain.
  52         */
  53        ipcns_notify(IPCNS_CREATED);
  54        register_ipcns_notifier(ns);
  55
  56        ns->user_ns = get_user_ns(user_ns);
  57
  58        return ns;
  59}
  60
  61struct ipc_namespace *copy_ipcs(unsigned long flags,
  62        struct user_namespace *user_ns, struct ipc_namespace *ns)
  63{
  64        if (!(flags & CLONE_NEWIPC))
  65                return get_ipc_ns(ns);
  66        return create_ipc_ns(user_ns, ns);
  67}
  68
  69/*
  70 * free_ipcs - free all ipcs of one type
  71 * @ns:   the namespace to remove the ipcs from
  72 * @ids:  the table of ipcs to free
  73 * @free: the function called to free each individual ipc
  74 *
  75 * Called for each kind of ipc when an ipc_namespace exits.
  76 */
  77void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  78               void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  79{
  80        struct kern_ipc_perm *perm;
  81        int next_id;
  82        int total, in_use;
  83
  84        down_write(&ids->rw_mutex);
  85
  86        in_use = ids->in_use;
  87
  88        for (total = 0, next_id = 0; total < in_use; next_id++) {
  89                perm = idr_find(&ids->ipcs_idr, next_id);
  90                if (perm == NULL)
  91                        continue;
  92                ipc_lock_by_ptr(perm);
  93                free(ns, perm);
  94                total++;
  95        }
  96        up_write(&ids->rw_mutex);
  97}
  98
  99static void free_ipc_ns(struct ipc_namespace *ns)
 100{
 101        /*
 102         * Unregistering the hotplug notifier at the beginning guarantees
 103         * that the ipc namespace won't be freed while we are inside the
 104         * callback routine. Since the blocking_notifier_chain_XXX routines
 105         * hold a rw lock on the notifier list, unregister_ipcns_notifier()
 106         * won't take the rw lock before blocking_notifier_call_chain() has
 107         * released the rd lock.
 108         */
 109        unregister_ipcns_notifier(ns);
 110        sem_exit_ns(ns);
 111        msg_exit_ns(ns);
 112        shm_exit_ns(ns);
 113        atomic_dec(&nr_ipc_ns);
 114
 115        /*
 116         * Do the ipcns removal notification after decrementing nr_ipc_ns in
 117         * order to have a correct value when recomputing msgmni.
 118         */
 119        ipcns_notify(IPCNS_REMOVED);
 120        put_user_ns(ns->user_ns);
 121        proc_free_inum(ns->proc_inum);
 122        kfree(ns);
 123}
 124
 125/*
 126 * put_ipc_ns - drop a reference to an ipc namespace.
 127 * @ns: the namespace to put
 128 *
 129 * If this is the last task in the namespace exiting, and
 130 * it is dropping the refcount to 0, then it can race with
 131 * a task in another ipc namespace but in a mounts namespace
 132 * which has this ipcns's mqueuefs mounted, doing some action
 133 * with one of the mqueuefs files.  That can raise the refcount.
 134 * So dropping the refcount, and raising the refcount when
 135 * accessing it through the VFS, are protected with mq_lock.
 136 *
 137 * (Clearly, a task raising the refcount on its own ipc_ns
 138 * needn't take mq_lock since it can't race with the last task
 139 * in the ipcns exiting).
 140 */
 141void put_ipc_ns(struct ipc_namespace *ns)
 142{
 143        if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 144                mq_clear_sbinfo(ns);
 145                spin_unlock(&mq_lock);
 146                mq_put_mnt(ns);
 147                free_ipc_ns(ns);
 148        }
 149}
 150
 151static void *ipcns_get(struct task_struct *task)
 152{
 153        struct ipc_namespace *ns = NULL;
 154        struct nsproxy *nsproxy;
 155
 156        rcu_read_lock();
 157        nsproxy = task_nsproxy(task);
 158        if (nsproxy)
 159                ns = get_ipc_ns(nsproxy->ipc_ns);
 160        rcu_read_unlock();
 161
 162        return ns;
 163}
 164
 165static void ipcns_put(void *ns)
 166{
 167        return put_ipc_ns(ns);
 168}
 169
 170static int ipcns_install(struct nsproxy *nsproxy, void *new)
 171{
 172        struct ipc_namespace *ns = new;
 173        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 174            !nsown_capable(CAP_SYS_ADMIN))
 175                return -EPERM;
 176
 177        /* Ditch state from the old ipc namespace */
 178        exit_sem(current);
 179        put_ipc_ns(nsproxy->ipc_ns);
 180        nsproxy->ipc_ns = get_ipc_ns(ns);
 181        return 0;
 182}
 183
 184static unsigned int ipcns_inum(void *vp)
 185{
 186        struct ipc_namespace *ns = vp;
 187
 188        return ns->proc_inum;
 189}
 190
 191const struct proc_ns_operations ipcns_operations = {
 192        .name           = "ipc",
 193        .type           = CLONE_NEWIPC,
 194        .get            = ipcns_get,
 195        .put            = ipcns_put,
 196        .install        = ipcns_install,
 197        .inum           = ipcns_inum,
 198};
 199
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