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_ns.h>
  16
  17 #include "util.h"
  18
  19 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
  20 {
  21         return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
  22 }
  23
  24 static void dec_ipc_namespaces(struct ucounts *ucounts)
  25 {
  26         dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
  27 }
  28
  29 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
  30                                            struct ipc_namespace *old_ns)
  31 {
  32         struct ipc_namespace *ns;
  33         struct ucounts *ucounts;
  34         int err;
  35
  36         err = -ENOSPC;
  37         ucounts = inc_ipc_namespaces(user_ns);
  38         if (!ucounts)
  39                 goto fail;
  40
  41         err = -ENOMEM;
  42         ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
  43         if (ns == NULL)
  44                 goto fail_dec;
  45
  46         err = ns_alloc_inum(&ns->ns);
  47         if (err)
  48                 goto fail_free;
  49         ns->ns.ops = &ipcns_operations;
  50
  51         atomic_set(&ns->count, 1);
  52         ns->user_ns = get_user_ns(user_ns);
  53         ns->ucounts = ucounts;
  54
  55         err = mq_init_ns(ns);
  56         if (err)
  57                 goto fail_put;
  58
  59         sem_init_ns(ns);
  60         msg_init_ns(ns);
  61         shm_init_ns(ns);
  62
  63         return ns;
  64
  65 fail_put:
  66         put_user_ns(ns->user_ns);
  67         ns_free_inum(&ns->ns);
  68 fail_free:
  69         kfree(ns);
  70 fail_dec:
  71         dec_ipc_namespaces(ucounts);
  72 fail:
  73         return ERR_PTR(err);
  74 }
  75
  76 struct ipc_namespace *copy_ipcs(unsigned long flags,
  77         struct user_namespace *user_ns, struct ipc_namespace *ns)
  78 {
  79         if (!(flags & CLONE_NEWIPC))
  80                 return get_ipc_ns(ns);
  81         return create_ipc_ns(user_ns, ns);
  82 }
  83
  84 /*
  85  * free_ipcs - free all ipcs of one type
  86  * @ns:   the namespace to remove the ipcs from
  87  * @ids:  the table of ipcs to free
  88  * @free: the function called to free each individual ipc
  89  *
  90  * Called for each kind of ipc when an ipc_namespace exits.
  91  */
  92 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  93                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  94 {
  95         struct kern_ipc_perm *perm;
  96         int next_id;
  97         int total, in_use;
  98
  99         down_write(&ids->rwsem);
 100
 101         in_use = ids->in_use;
 102
 103         for (total = 0, next_id = 0; total < in_use; next_id++) {
 104                 perm = idr_find(&ids->ipcs_idr, next_id);
 105                 if (perm == NULL)
 106                         continue;
 107                 rcu_read_lock();
 108                 ipc_lock_object(perm);
 109                 free(ns, perm);
 110                 total++;
 111         }
 112         up_write(&ids->rwsem);
 113 }
 114
 115 static void free_ipc_ns(struct ipc_namespace *ns)
 116 {
 117         sem_exit_ns(ns);
 118         msg_exit_ns(ns);
 119         shm_exit_ns(ns);
 120
 121         dec_ipc_namespaces(ns->ucounts);
 122         put_user_ns(ns->user_ns);
 123         ns_free_inum(&ns->ns);
 124         kfree(ns);
 125 }
 126
 127 /*
 128  * put_ipc_ns - drop a reference to an ipc namespace.
 129  * @ns: the namespace to put
 130  *
 131  * If this is the last task in the namespace exiting, and
 132  * it is dropping the refcount to 0, then it can race with
 133  * a task in another ipc namespace but in a mounts namespace
 134  * which has this ipcns's mqueuefs mounted, doing some action
 135  * with one of the mqueuefs files.  That can raise the refcount.
 136  * So dropping the refcount, and raising the refcount when
 137  * accessing it through the VFS, are protected with mq_lock.
 138  *
 139  * (Clearly, a task raising the refcount on its own ipc_ns
 140  * needn't take mq_lock since it can't race with the last task
 141  * in the ipcns exiting).
 142  */
 143 void put_ipc_ns(struct ipc_namespace *ns)
 144 {
 145         if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 146                 mq_clear_sbinfo(ns);
 147                 spin_unlock(&mq_lock);
 148                 mq_put_mnt(ns);
 149                 free_ipc_ns(ns);
 150         }
 151 }
 152
 153 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 154 {
 155         return container_of(ns, struct ipc_namespace, ns);
 156 }
 157
 158 static struct ns_common *ipcns_get(struct task_struct *task)
 159 {
 160         struct ipc_namespace *ns = NULL;
 161         struct nsproxy *nsproxy;
 162
 163         task_lock(task);
 164         nsproxy = task->nsproxy;
 165         if (nsproxy)
 166                 ns = get_ipc_ns(nsproxy->ipc_ns);
 167         task_unlock(task);
 168
 169         return ns ? &ns->ns : NULL;
 170 }
 171
 172 static void ipcns_put(struct ns_common *ns)
 173 {
 174         return put_ipc_ns(to_ipc_ns(ns));
 175 }
 176
 177 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
 178 {
 179         struct ipc_namespace *ns = to_ipc_ns(new);
 180         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 181             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 182                 return -EPERM;
 183
 184         /* Ditch state from the old ipc namespace */
 185         exit_sem(current);
 186         put_ipc_ns(nsproxy->ipc_ns);
 187         nsproxy->ipc_ns = get_ipc_ns(ns);
 188         return 0;
 189 }
 190
 191 static struct user_namespace *ipcns_owner(struct ns_common *ns)
 192 {
 193         return to_ipc_ns(ns)->user_ns;
 194 }
 195
 196 const struct proc_ns_operations ipcns_operations = {
 197         .name           = "ipc",
 198         .type           = CLONE_NEWIPC,
 199         .get            = ipcns_get,
 200         .put            = ipcns_put,
 201         .install        = ipcns_install,
 202         .owner          = ipcns_owner,
 203 };