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 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         /*
  50          * msgmni has already been computed for the new ipc ns.
  51          * Thus, do the ipcns creation notification before registering that
  52          * new ipcns in the chain.
  53          */
  54         ipcns_notify(IPCNS_CREATED);
  55         register_ipcns_notifier(ns);
  56
  57         ns->user_ns = get_user_ns(user_ns);
  58
  59         return ns;
  60 }
  61
  62 struct ipc_namespace *copy_ipcs(unsigned long flags,
  63         struct user_namespace *user_ns, struct ipc_namespace *ns)
  64 {
  65         if (!(flags & CLONE_NEWIPC))
  66                 return get_ipc_ns(ns);
  67         return create_ipc_ns(user_ns, ns);
  68 }
  69
  70 /*
  71  * free_ipcs - free all ipcs of one type
  72  * @ns:   the namespace to remove the ipcs from
  73  * @ids:  the table of ipcs to free
  74  * @free: the function called to free each individual ipc
  75  *
  76  * Called for each kind of ipc when an ipc_namespace exits.
  77  */
  78 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  79                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  80 {
  81         struct kern_ipc_perm *perm;
  82         int next_id;
  83         int total, in_use;
  84
  85         down_write(&ids->rwsem);
  86
  87         in_use = ids->in_use;
  88
  89         for (total = 0, next_id = 0; total < in_use; next_id++) {
  90                 perm = idr_find(&ids->ipcs_idr, next_id);
  91                 if (perm == NULL)
  92                         continue;
  93                 rcu_read_lock();
  94                 ipc_lock_object(perm);
  95                 free(ns, perm);
  96                 total++;
  97         }
  98         up_write(&ids->rwsem);
  99 }
 100
 101 static void free_ipc_ns(struct ipc_namespace *ns)
 102 {
 103         /*
 104          * Unregistering the hotplug notifier at the beginning guarantees
 105          * that the ipc namespace won't be freed while we are inside the
 106          * callback routine. Since the blocking_notifier_chain_XXX routines
 107          * hold a rw lock on the notifier list, unregister_ipcns_notifier()
 108          * won't take the rw lock before blocking_notifier_call_chain() has
 109          * released the rd lock.
 110          */
 111         unregister_ipcns_notifier(ns);
 112         sem_exit_ns(ns);
 113         msg_exit_ns(ns);
 114         shm_exit_ns(ns);
 115         atomic_dec(&nr_ipc_ns);
 116
 117         /*
 118          * Do the ipcns removal notification after decrementing nr_ipc_ns in
 119          * order to have a correct value when recomputing msgmni.
 120          */
 121         ipcns_notify(IPCNS_REMOVED);
 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 const struct proc_ns_operations ipcns_operations = {
 192         .name           = "ipc",
 193         .type           = CLONE_NEWIPC,
 194         .get            = ipcns_get,
 195         .put            = ipcns_put,
 196         .install        = ipcns_install,
 197 };