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 = proc_alloc_inum(&ns->proc_inum);
  30         if (err) {
  31                 kfree(ns);
  32                 return ERR_PTR(err);
  33         }
  34
  35         atomic_set(&ns->count, 1);
  36         err = mq_init_ns(ns);
  37         if (err) {
  38                 proc_free_inum(ns->proc_inum);
  39                 kfree(ns);
  40                 return ERR_PTR(err);
  41         }
  42         atomic_inc(&nr_ipc_ns);
  43
  44         sem_init_ns(ns);
  45         msg_init_ns(ns);
  46         shm_init_ns(ns);
  47
  48         /*
  49          * msgmni has already been computed for the new ipc ns.
  50          * Thus, do the ipcns creation notification before registering that
  51          * new ipcns in the chain.
  52          */
  53         ipcns_notify(IPCNS_CREATED);
  54         register_ipcns_notifier(ns);
  55
  56         ns->user_ns = get_user_ns(user_ns);
  57
  58         return ns;
  59 }
  60
  61 struct ipc_namespace *copy_ipcs(unsigned long flags,
  62         struct user_namespace *user_ns, struct ipc_namespace *ns)
  63 {
  64         if (!(flags & CLONE_NEWIPC))
  65                 return get_ipc_ns(ns);
  66         return create_ipc_ns(user_ns, ns);
  67 }
  68
  69 /*
  70  * free_ipcs - free all ipcs of one type
  71  * @ns:   the namespace to remove the ipcs from
  72  * @ids:  the table of ipcs to free
  73  * @free: the function called to free each individual ipc
  74  *
  75  * Called for each kind of ipc when an ipc_namespace exits.
  76  */
  77 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  78                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  79 {
  80         struct kern_ipc_perm *perm;
  81         int next_id;
  82         int total, in_use;
  83
  84         down_write(&ids->rwsem);
  85
  86         in_use = ids->in_use;
  87
  88         for (total = 0, next_id = 0; total < in_use; next_id++) {
  89                 perm = idr_find(&ids->ipcs_idr, next_id);
  90                 if (perm == NULL)
  91                         continue;
  92                 rcu_read_lock();
  93                 ipc_lock_object(perm);
  94                 free(ns, perm);
  95                 total++;
  96         }
  97         up_write(&ids->rwsem);
  98 }
  99
 100 static void free_ipc_ns(struct ipc_namespace *ns)
 101 {
 102         /*
 103          * Unregistering the hotplug notifier at the beginning guarantees
 104          * that the ipc namespace won't be freed while we are inside the
 105          * callback routine. Since the blocking_notifier_chain_XXX routines
 106          * hold a rw lock on the notifier list, unregister_ipcns_notifier()
 107          * won't take the rw lock before blocking_notifier_call_chain() has
 108          * released the rd lock.
 109          */
 110         unregister_ipcns_notifier(ns);
 111         sem_exit_ns(ns);
 112         msg_exit_ns(ns);
 113         shm_exit_ns(ns);
 114         atomic_dec(&nr_ipc_ns);
 115
 116         /*
 117          * Do the ipcns removal notification after decrementing nr_ipc_ns in
 118          * order to have a correct value when recomputing msgmni.
 119          */
 120         ipcns_notify(IPCNS_REMOVED);
 121         put_user_ns(ns->user_ns);
 122         proc_free_inum(ns->proc_inum);
 123         kfree(ns);
 124 }
 125
 126 /*
 127  * put_ipc_ns - drop a reference to an ipc namespace.
 128  * @ns: the namespace to put
 129  *
 130  * If this is the last task in the namespace exiting, and
 131  * it is dropping the refcount to 0, then it can race with
 132  * a task in another ipc namespace but in a mounts namespace
 133  * which has this ipcns's mqueuefs mounted, doing some action
 134  * with one of the mqueuefs files.  That can raise the refcount.
 135  * So dropping the refcount, and raising the refcount when
 136  * accessing it through the VFS, are protected with mq_lock.
 137  *
 138  * (Clearly, a task raising the refcount on its own ipc_ns
 139  * needn't take mq_lock since it can't race with the last task
 140  * in the ipcns exiting).
 141  */
 142 void put_ipc_ns(struct ipc_namespace *ns)
 143 {
 144         if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 145                 mq_clear_sbinfo(ns);
 146                 spin_unlock(&mq_lock);
 147                 mq_put_mnt(ns);
 148                 free_ipc_ns(ns);
 149         }
 150 }
 151
 152 static void *ipcns_get(struct task_struct *task)
 153 {
 154         struct ipc_namespace *ns = NULL;
 155         struct nsproxy *nsproxy;
 156
 157         rcu_read_lock();
 158         nsproxy = task_nsproxy(task);
 159         if (nsproxy)
 160                 ns = get_ipc_ns(nsproxy->ipc_ns);
 161         rcu_read_unlock();
 162
 163         return ns;
 164 }
 165
 166 static void ipcns_put(void *ns)
 167 {
 168         return put_ipc_ns(ns);
 169 }
 170
 171 static int ipcns_install(struct nsproxy *nsproxy, void *new)
 172 {
 173         struct ipc_namespace *ns = new;
 174         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 175             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 176                 return -EPERM;
 177
 178         /* Ditch state from the old ipc namespace */
 179         exit_sem(current);
 180         put_ipc_ns(nsproxy->ipc_ns);
 181         nsproxy->ipc_ns = get_ipc_ns(ns);
 182         return 0;
 183 }
 184
 185 static unsigned int ipcns_inum(void *vp)
 186 {
 187         struct ipc_namespace *ns = vp;
 188
 189         return ns->proc_inum;
 190 }
 191
 192 const struct proc_ns_operations ipcns_operations = {
 193         .name           = "ipc",
 194         .type           = CLONE_NEWIPC,
 195         .get            = ipcns_get,
 196         .put            = ipcns_put,
 197         .install        = ipcns_install,
 198         .inum           = ipcns_inum,
 199 };