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_ns.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->rwsem);
  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                rcu_read_lock();
  93                ipc_lock_object(perm);
  94                free(ns, perm);
  95                total++;
  96        }
  97        up_write(&ids->rwsem);
  98}
  99
 100static void free_ipc_ns(struct ipc_namespace *ns)
 101{
 102        /*
 103         * Unregistering the hotplug notifier at the beginning guarantees
 104         * that the ipc namespace won't be freed while we are inside the
 105         * callback routine. Since the blocking_notifier_chain_XXX routines
 106         * hold a rw lock on the notifier list, unregister_ipcns_notifier()
 107         * won't take the rw lock before blocking_notifier_call_chain() has
 108         * released the rd lock.
 109         */
 110        unregister_ipcns_notifier(ns);
 111        sem_exit_ns(ns);
 112        msg_exit_ns(ns);
 113        shm_exit_ns(ns);
 114        atomic_dec(&nr_ipc_ns);
 115
 116        /*
 117         * Do the ipcns removal notification after decrementing nr_ipc_ns in
 118         * order to have a correct value when recomputing msgmni.
 119         */
 120        ipcns_notify(IPCNS_REMOVED);
 121        put_user_ns(ns->user_ns);
 122        proc_free_inum(ns->proc_inum);
 123        kfree(ns);
 124}
 125
 126/*
 127 * put_ipc_ns - drop a reference to an ipc namespace.
 128 * @ns: the namespace to put
 129 *
 130 * If this is the last task in the namespace exiting, and
 131 * it is dropping the refcount to 0, then it can race with
 132 * a task in another ipc namespace but in a mounts namespace
 133 * which has this ipcns's mqueuefs mounted, doing some action
 134 * with one of the mqueuefs files.  That can raise the refcount.
 135 * So dropping the refcount, and raising the refcount when
 136 * accessing it through the VFS, are protected with mq_lock.
 137 *
 138 * (Clearly, a task raising the refcount on its own ipc_ns
 139 * needn't take mq_lock since it can't race with the last task
 140 * in the ipcns exiting).
 141 */
 142void put_ipc_ns(struct ipc_namespace *ns)
 143{
 144        if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 145                mq_clear_sbinfo(ns);
 146                spin_unlock(&mq_lock);
 147                mq_put_mnt(ns);
 148                free_ipc_ns(ns);
 149        }
 150}
 151
 152static void *ipcns_get(struct task_struct *task)
 153{
 154        struct ipc_namespace *ns = NULL;
 155        struct nsproxy *nsproxy;
 156
 157        rcu_read_lock();
 158        nsproxy = task_nsproxy(task);
 159        if (nsproxy)
 160                ns = get_ipc_ns(nsproxy->ipc_ns);
 161        rcu_read_unlock();
 162
 163        return ns;
 164}
 165
 166static void ipcns_put(void *ns)
 167{
 168        return put_ipc_ns(ns);
 169}
 170
 171static int ipcns_install(struct nsproxy *nsproxy, void *new)
 172{
 173        struct ipc_namespace *ns = new;
 174        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 175            !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 176                return -EPERM;
 177
 178        /* Ditch state from the old ipc namespace */
 179        exit_sem(current);
 180        put_ipc_ns(nsproxy->ipc_ns);
 181        nsproxy->ipc_ns = get_ipc_ns(ns);
 182        return 0;
 183}
 184
 185static unsigned int ipcns_inum(void *vp)
 186{
 187        struct ipc_namespace *ns = vp;
 188
 189        return ns->proc_inum;
 190}
 191
 192const struct proc_ns_operations ipcns_operations = {
 193        .name           = "ipc",
 194        .type           = CLONE_NEWIPC,
 195        .get            = ipcns_get,
 196        .put            = ipcns_put,
 197        .install        = ipcns_install,
 198        .inum           = ipcns_inum,
 199};
 200
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