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 = ns_alloc_inum(&ns->ns);
  30        if (err) {
  31                kfree(ns);
  32                return ERR_PTR(err);
  33        }
  34        ns->ns.ops = &ipcns_operations;
  35
  36        atomic_set(&ns->count, 1);
  37        err = mq_init_ns(ns);
  38        if (err) {
  39                ns_free_inum(&ns->ns);
  40                kfree(ns);
  41                return ERR_PTR(err);
  42        }
  43        atomic_inc(&nr_ipc_ns);
  44
  45        sem_init_ns(ns);
  46        msg_init_ns(ns);
  47        shm_init_ns(ns);
  48
  49        ns->user_ns = get_user_ns(user_ns);
  50
  51        return ns;
  52}
  53
  54struct 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 */
  70void 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->rwsem);
  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                rcu_read_lock();
  86                ipc_lock_object(perm);
  87                free(ns, perm);
  88                total++;
  89        }
  90        up_write(&ids->rwsem);
  91}
  92
  93static void free_ipc_ns(struct ipc_namespace *ns)
  94{
  95        sem_exit_ns(ns);
  96        msg_exit_ns(ns);
  97        shm_exit_ns(ns);
  98        atomic_dec(&nr_ipc_ns);
  99
 100        put_user_ns(ns->user_ns);
 101        ns_free_inum(&ns->ns);
 102        kfree(ns);
 103}
 104
 105/*
 106 * put_ipc_ns - drop a reference to an ipc namespace.
 107 * @ns: the namespace to put
 108 *
 109 * If this is the last task in the namespace exiting, and
 110 * it is dropping the refcount to 0, then it can race with
 111 * a task in another ipc namespace but in a mounts namespace
 112 * which has this ipcns's mqueuefs mounted, doing some action
 113 * with one of the mqueuefs files.  That can raise the refcount.
 114 * So dropping the refcount, and raising the refcount when
 115 * accessing it through the VFS, are protected with mq_lock.
 116 *
 117 * (Clearly, a task raising the refcount on its own ipc_ns
 118 * needn't take mq_lock since it can't race with the last task
 119 * in the ipcns exiting).
 120 */
 121void put_ipc_ns(struct ipc_namespace *ns)
 122{
 123        if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 124                mq_clear_sbinfo(ns);
 125                spin_unlock(&mq_lock);
 126                mq_put_mnt(ns);
 127                free_ipc_ns(ns);
 128        }
 129}
 130
 131static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 132{
 133        return container_of(ns, struct ipc_namespace, ns);
 134}
 135
 136static struct ns_common *ipcns_get(struct task_struct *task)
 137{
 138        struct ipc_namespace *ns = NULL;
 139        struct nsproxy *nsproxy;
 140
 141        task_lock(task);
 142        nsproxy = task->nsproxy;
 143        if (nsproxy)
 144                ns = get_ipc_ns(nsproxy->ipc_ns);
 145        task_unlock(task);
 146
 147        return ns ? &ns->ns : NULL;
 148}
 149
 150static void ipcns_put(struct ns_common *ns)
 151{
 152        return put_ipc_ns(to_ipc_ns(ns));
 153}
 154
 155static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
 156{
 157        struct ipc_namespace *ns = to_ipc_ns(new);
 158        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 159            !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 160                return -EPERM;
 161
 162        /* Ditch state from the old ipc namespace */
 163        exit_sem(current);
 164        put_ipc_ns(nsproxy->ipc_ns);
 165        nsproxy->ipc_ns = get_ipc_ns(ns);
 166        return 0;
 167}
 168
 169const struct proc_ns_operations ipcns_operations = {
 170        .name           = "ipc",
 171        .type           = CLONE_NEWIPC,
 172        .get            = ipcns_get,
 173        .put            = ipcns_put,
 174        .install        = ipcns_install,
 175};
 176
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