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/cred.h>
  13 #include <linux/fs.h>
  14 #include <linux/mount.h>
  15 #include <linux/user_namespace.h>
  16 #include <linux/proc_ns.h>
  17
  18 #include "util.h"
  19
  20 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
  21 {
  22         return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
  23 }
  24
  25 static void dec_ipc_namespaces(struct ucounts *ucounts)
  26 {
  27         dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
  28 }
  29
  30 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
  31                                            struct ipc_namespace *old_ns)
  32 {
  33         struct ipc_namespace *ns;
  34         struct ucounts *ucounts;
  35         int err;
  36
  37         err = -ENOSPC;
  38         ucounts = inc_ipc_namespaces(user_ns);
  39         if (!ucounts)
  40                 goto fail;
  41
  42         err = -ENOMEM;
  43         ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
  44         if (ns == NULL)
  45                 goto fail_dec;
  46
  47         err = ns_alloc_inum(&ns->ns);
  48         if (err)
  49                 goto fail_free;
  50         ns->ns.ops = &ipcns_operations;
  51
  52         atomic_set(&ns->count, 1);
  53         ns->user_ns = get_user_ns(user_ns);
  54         ns->ucounts = ucounts;
  55
  56         err = mq_init_ns(ns);
  57         if (err)
  58                 goto fail_put;
  59
  60         sem_init_ns(ns);
  61         msg_init_ns(ns);
  62         shm_init_ns(ns);
  63
  64         return ns;
  65
  66 fail_put:
  67         put_user_ns(ns->user_ns);
  68         ns_free_inum(&ns->ns);
  69 fail_free:
  70         kfree(ns);
  71 fail_dec:
  72         dec_ipc_namespaces(ucounts);
  73 fail:
  74         return ERR_PTR(err);
  75 }
  76
  77 struct ipc_namespace *copy_ipcs(unsigned long flags,
  78         struct user_namespace *user_ns, struct ipc_namespace *ns)
  79 {
  80         if (!(flags & CLONE_NEWIPC))
  81                 return get_ipc_ns(ns);
  82         return create_ipc_ns(user_ns, ns);
  83 }
  84
  85 /*
  86  * free_ipcs - free all ipcs of one type
  87  * @ns:   the namespace to remove the ipcs from
  88  * @ids:  the table of ipcs to free
  89  * @free: the function called to free each individual ipc
  90  *
  91  * Called for each kind of ipc when an ipc_namespace exits.
  92  */
  93 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  94                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  95 {
  96         struct kern_ipc_perm *perm;
  97         int next_id;
  98         int total, in_use;
  99
 100         down_write(&ids->rwsem);
 101
 102         in_use = ids->in_use;
 103
 104         for (total = 0, next_id = 0; total < in_use; next_id++) {
 105                 perm = idr_find(&ids->ipcs_idr, next_id);
 106                 if (perm == NULL)
 107                         continue;
 108                 rcu_read_lock();
 109                 ipc_lock_object(perm);
 110                 free(ns, perm);
 111                 total++;
 112         }
 113         up_write(&ids->rwsem);
 114 }
 115
 116 static void free_ipc_ns(struct ipc_namespace *ns)
 117 {
 118         sem_exit_ns(ns);
 119         msg_exit_ns(ns);
 120         shm_exit_ns(ns);
 121
 122         dec_ipc_namespaces(ns->ucounts);
 123         put_user_ns(ns->user_ns);
 124         ns_free_inum(&ns->ns);
 125         kfree(ns);
 126 }
 127
 128 /*
 129  * put_ipc_ns - drop a reference to an ipc namespace.
 130  * @ns: the namespace to put
 131  *
 132  * If this is the last task in the namespace exiting, and
 133  * it is dropping the refcount to 0, then it can race with
 134  * a task in another ipc namespace but in a mounts namespace
 135  * which has this ipcns's mqueuefs mounted, doing some action
 136  * with one of the mqueuefs files.  That can raise the refcount.
 137  * So dropping the refcount, and raising the refcount when
 138  * accessing it through the VFS, are protected with mq_lock.
 139  *
 140  * (Clearly, a task raising the refcount on its own ipc_ns
 141  * needn't take mq_lock since it can't race with the last task
 142  * in the ipcns exiting).
 143  */
 144 void put_ipc_ns(struct ipc_namespace *ns)
 145 {
 146         if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 147                 mq_clear_sbinfo(ns);
 148                 spin_unlock(&mq_lock);
 149                 mq_put_mnt(ns);
 150                 free_ipc_ns(ns);
 151         }
 152 }
 153
 154 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 155 {
 156         return container_of(ns, struct ipc_namespace, ns);
 157 }
 158
 159 static struct ns_common *ipcns_get(struct task_struct *task)
 160 {
 161         struct ipc_namespace *ns = NULL;
 162         struct nsproxy *nsproxy;
 163
 164         task_lock(task);
 165         nsproxy = task->nsproxy;
 166         if (nsproxy)
 167                 ns = get_ipc_ns(nsproxy->ipc_ns);
 168         task_unlock(task);
 169
 170         return ns ? &ns->ns : NULL;
 171 }
 172
 173 static void ipcns_put(struct ns_common *ns)
 174 {
 175         return put_ipc_ns(to_ipc_ns(ns));
 176 }
 177
 178 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
 179 {
 180         struct ipc_namespace *ns = to_ipc_ns(new);
 181         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 182             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 183                 return -EPERM;
 184
 185         /* Ditch state from the old ipc namespace */
 186         exit_sem(current);
 187         put_ipc_ns(nsproxy->ipc_ns);
 188         nsproxy->ipc_ns = get_ipc_ns(ns);
 189         return 0;
 190 }
 191
 192 static struct user_namespace *ipcns_owner(struct ns_common *ns)
 193 {
 194         return to_ipc_ns(ns)->user_ns;
 195 }
 196
 197 const struct proc_ns_operations ipcns_operations = {
 198         .name           = "ipc",
 199         .type           = CLONE_NEWIPC,
 200         .get            = ipcns_get,
 201         .put            = ipcns_put,
 202         .install        = ipcns_install,
 203         .owner          = ipcns_owner,
 204 };