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         ns->user_ns = get_user_ns(user_ns);
  38
  39         err = mq_init_ns(ns);
  40         if (err) {
  41                 put_user_ns(ns->user_ns);
  42                 ns_free_inum(&ns->ns);
  43                 kfree(ns);
  44                 return ERR_PTR(err);
  45         }
  46         atomic_inc(&nr_ipc_ns);
  47
  48         sem_init_ns(ns);
  49         msg_init_ns(ns);
  50         shm_init_ns(ns);
  51
  52         return ns;
  53 }
  54
  55 struct ipc_namespace *copy_ipcs(unsigned long flags,
  56         struct user_namespace *user_ns, struct ipc_namespace *ns)
  57 {
  58         if (!(flags & CLONE_NEWIPC))
  59                 return get_ipc_ns(ns);
  60         return create_ipc_ns(user_ns, ns);
  61 }
  62
  63 /*
  64  * free_ipcs - free all ipcs of one type
  65  * @ns:   the namespace to remove the ipcs from
  66  * @ids:  the table of ipcs to free
  67  * @free: the function called to free each individual ipc
  68  *
  69  * Called for each kind of ipc when an ipc_namespace exits.
  70  */
  71 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
  72                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
  73 {
  74         struct kern_ipc_perm *perm;
  75         int next_id;
  76         int total, in_use;
  77
  78         down_write(&ids->rwsem);
  79
  80         in_use = ids->in_use;
  81
  82         for (total = 0, next_id = 0; total < in_use; next_id++) {
  83                 perm = idr_find(&ids->ipcs_idr, next_id);
  84                 if (perm == NULL)
  85                         continue;
  86                 rcu_read_lock();
  87                 ipc_lock_object(perm);
  88                 free(ns, perm);
  89                 total++;
  90         }
  91         up_write(&ids->rwsem);
  92 }
  93
  94 static void free_ipc_ns(struct ipc_namespace *ns)
  95 {
  96         sem_exit_ns(ns);
  97         msg_exit_ns(ns);
  98         shm_exit_ns(ns);
  99         atomic_dec(&nr_ipc_ns);
 100
 101         put_user_ns(ns->user_ns);
 102         ns_free_inum(&ns->ns);
 103         kfree(ns);
 104 }
 105
 106 /*
 107  * put_ipc_ns - drop a reference to an ipc namespace.
 108  * @ns: the namespace to put
 109  *
 110  * If this is the last task in the namespace exiting, and
 111  * it is dropping the refcount to 0, then it can race with
 112  * a task in another ipc namespace but in a mounts namespace
 113  * which has this ipcns's mqueuefs mounted, doing some action
 114  * with one of the mqueuefs files.  That can raise the refcount.
 115  * So dropping the refcount, and raising the refcount when
 116  * accessing it through the VFS, are protected with mq_lock.
 117  *
 118  * (Clearly, a task raising the refcount on its own ipc_ns
 119  * needn't take mq_lock since it can't race with the last task
 120  * in the ipcns exiting).
 121  */
 122 void put_ipc_ns(struct ipc_namespace *ns)
 123 {
 124         if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
 125                 mq_clear_sbinfo(ns);
 126                 spin_unlock(&mq_lock);
 127                 mq_put_mnt(ns);
 128                 free_ipc_ns(ns);
 129         }
 130 }
 131
 132 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 133 {
 134         return container_of(ns, struct ipc_namespace, ns);
 135 }
 136
 137 static struct ns_common *ipcns_get(struct task_struct *task)
 138 {
 139         struct ipc_namespace *ns = NULL;
 140         struct nsproxy *nsproxy;
 141
 142         task_lock(task);
 143         nsproxy = task->nsproxy;
 144         if (nsproxy)
 145                 ns = get_ipc_ns(nsproxy->ipc_ns);
 146         task_unlock(task);
 147
 148         return ns ? &ns->ns : NULL;
 149 }
 150
 151 static void ipcns_put(struct ns_common *ns)
 152 {
 153         return put_ipc_ns(to_ipc_ns(ns));
 154 }
 155
 156 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
 157 {
 158         struct ipc_namespace *ns = to_ipc_ns(new);
 159         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 160             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 161                 return -EPERM;
 162
 163         /* Ditch state from the old ipc namespace */
 164         exit_sem(current);
 165         put_ipc_ns(nsproxy->ipc_ns);
 166         nsproxy->ipc_ns = get_ipc_ns(ns);
 167         return 0;
 168 }
 169
 170 const struct proc_ns_operations ipcns_operations = {
 171         .name           = "ipc",
 172         .type           = CLONE_NEWIPC,
 173         .get            = ipcns_get,
 174         .put            = ipcns_put,
 175         .install        = ipcns_install,
 176 };