linux/ipc/namespace.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * linux/ipc/namespace.c
   4 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
   5 */
   6
   7#include <linux/ipc.h>
   8#include <linux/msg.h>
   9#include <linux/ipc_namespace.h>
  10#include <linux/rcupdate.h>
  11#include <linux/nsproxy.h>
  12#include <linux/slab.h>
  13#include <linux/cred.h>
  14#include <linux/fs.h>
  15#include <linux/mount.h>
  16#include <linux/user_namespace.h>
  17#include <linux/proc_ns.h>
  18#include <linux/sched/task.h>
  19
  20#include "util.h"
  21
  22static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
  23{
  24        return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
  25}
  26
  27static void dec_ipc_namespaces(struct ucounts *ucounts)
  28{
  29        dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
  30}
  31
  32static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
  33                                           struct ipc_namespace *old_ns)
  34{
  35        struct ipc_namespace *ns;
  36        struct ucounts *ucounts;
  37        int err;
  38
  39        err = -ENOSPC;
  40        ucounts = inc_ipc_namespaces(user_ns);
  41        if (!ucounts)
  42                goto fail;
  43
  44        err = -ENOMEM;
  45        ns = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL_ACCOUNT);
  46        if (ns == NULL)
  47                goto fail_dec;
  48
  49        err = ns_alloc_inum(&ns->ns);
  50        if (err)
  51                goto fail_free;
  52        ns->ns.ops = &ipcns_operations;
  53
  54        refcount_set(&ns->ns.count, 1);
  55        ns->user_ns = get_user_ns(user_ns);
  56        ns->ucounts = ucounts;
  57
  58        err = mq_init_ns(ns);
  59        if (err)
  60                goto fail_put;
  61
  62        err = -ENOMEM;
  63        if (!setup_mq_sysctls(ns))
  64                goto fail_put;
  65
  66        if (!setup_ipc_sysctls(ns))
  67                goto fail_mq;
  68
  69        sem_init_ns(ns);
  70        msg_init_ns(ns);
  71        shm_init_ns(ns);
  72
  73        return ns;
  74
  75fail_mq:
  76        retire_mq_sysctls(ns);
  77
  78fail_put:
  79        put_user_ns(ns->user_ns);
  80        ns_free_inum(&ns->ns);
  81fail_free:
  82        kfree(ns);
  83fail_dec:
  84        dec_ipc_namespaces(ucounts);
  85fail:
  86        return ERR_PTR(err);
  87}
  88
  89struct ipc_namespace *copy_ipcs(unsigned long flags,
  90        struct user_namespace *user_ns, struct ipc_namespace *ns)
  91{
  92        if (!(flags & CLONE_NEWIPC))
  93                return get_ipc_ns(ns);
  94        return create_ipc_ns(user_ns, ns);
  95}
  96
  97/*
  98 * free_ipcs - free all ipcs of one type
  99 * @ns:   the namespace to remove the ipcs from
 100 * @ids:  the table of ipcs to free
 101 * @free: the function called to free each individual ipc
 102 *
 103 * Called for each kind of ipc when an ipc_namespace exits.
 104 */
 105void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
 106               void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
 107{
 108        struct kern_ipc_perm *perm;
 109        int next_id;
 110        int total, in_use;
 111
 112        down_write(&ids->rwsem);
 113
 114        in_use = ids->in_use;
 115
 116        for (total = 0, next_id = 0; total < in_use; next_id++) {
 117                perm = idr_find(&ids->ipcs_idr, next_id);
 118                if (perm == NULL)
 119                        continue;
 120                rcu_read_lock();
 121                ipc_lock_object(perm);
 122                free(ns, perm);
 123                total++;
 124        }
 125        up_write(&ids->rwsem);
 126}
 127
 128static void free_ipc_ns(struct ipc_namespace *ns)
 129{
 130        /* mq_put_mnt() waits for a grace period as kern_unmount()
 131         * uses synchronize_rcu().
 132         */
 133        mq_put_mnt(ns);
 134        sem_exit_ns(ns);
 135        msg_exit_ns(ns);
 136        shm_exit_ns(ns);
 137
 138        retire_mq_sysctls(ns);
 139        retire_ipc_sysctls(ns);
 140
 141        dec_ipc_namespaces(ns->ucounts);
 142        put_user_ns(ns->user_ns);
 143        ns_free_inum(&ns->ns);
 144        kfree(ns);
 145}
 146
 147static LLIST_HEAD(free_ipc_list);
 148static void free_ipc(struct work_struct *unused)
 149{
 150        struct llist_node *node = llist_del_all(&free_ipc_list);
 151        struct ipc_namespace *n, *t;
 152
 153        llist_for_each_entry_safe(n, t, node, mnt_llist)
 154                free_ipc_ns(n);
 155}
 156
 157/*
 158 * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
 159 */
 160static DECLARE_WORK(free_ipc_work, free_ipc);
 161
 162/*
 163 * put_ipc_ns - drop a reference to an ipc namespace.
 164 * @ns: the namespace to put
 165 *
 166 * If this is the last task in the namespace exiting, and
 167 * it is dropping the refcount to 0, then it can race with
 168 * a task in another ipc namespace but in a mounts namespace
 169 * which has this ipcns's mqueuefs mounted, doing some action
 170 * with one of the mqueuefs files.  That can raise the refcount.
 171 * So dropping the refcount, and raising the refcount when
 172 * accessing it through the VFS, are protected with mq_lock.
 173 *
 174 * (Clearly, a task raising the refcount on its own ipc_ns
 175 * needn't take mq_lock since it can't race with the last task
 176 * in the ipcns exiting).
 177 */
 178void put_ipc_ns(struct ipc_namespace *ns)
 179{
 180        if (refcount_dec_and_lock(&ns->ns.count, &mq_lock)) {
 181                mq_clear_sbinfo(ns);
 182                spin_unlock(&mq_lock);
 183
 184                if (llist_add(&ns->mnt_llist, &free_ipc_list))
 185                        schedule_work(&free_ipc_work);
 186        }
 187}
 188
 189static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 190{
 191        return container_of(ns, struct ipc_namespace, ns);
 192}
 193
 194static struct ns_common *ipcns_get(struct task_struct *task)
 195{
 196        struct ipc_namespace *ns = NULL;
 197        struct nsproxy *nsproxy;
 198
 199        task_lock(task);
 200        nsproxy = task->nsproxy;
 201        if (nsproxy)
 202                ns = get_ipc_ns(nsproxy->ipc_ns);
 203        task_unlock(task);
 204
 205        return ns ? &ns->ns : NULL;
 206}
 207
 208static void ipcns_put(struct ns_common *ns)
 209{
 210        return put_ipc_ns(to_ipc_ns(ns));
 211}
 212
 213static int ipcns_install(struct nsset *nsset, struct ns_common *new)
 214{
 215        struct nsproxy *nsproxy = nsset->nsproxy;
 216        struct ipc_namespace *ns = to_ipc_ns(new);
 217        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 218            !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
 219                return -EPERM;
 220
 221        put_ipc_ns(nsproxy->ipc_ns);
 222        nsproxy->ipc_ns = get_ipc_ns(ns);
 223        return 0;
 224}
 225
 226static struct user_namespace *ipcns_owner(struct ns_common *ns)
 227{
 228        return to_ipc_ns(ns)->user_ns;
 229}
 230
 231const struct proc_ns_operations ipcns_operations = {
 232        .name           = "ipc",
 233        .type           = CLONE_NEWIPC,
 234        .get            = ipcns_get,
 235        .put            = ipcns_put,
 236        .install        = ipcns_install,
 237        .owner          = ipcns_owner,
 238};
 239