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 #include <linux/sched/task.h>
  18
  19 #include "util.h"
  20
  21 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
  22 {
  23         return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
  24 }
  25
  26 static void dec_ipc_namespaces(struct ucounts *ucounts)
  27 {
  28         dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
  29 }
  30
  31 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
  32                                            struct ipc_namespace *old_ns)
  33 {
  34         struct ipc_namespace *ns;
  35         struct ucounts *ucounts;
  36         int err;
  37
  38         err = -ENOSPC;
  39         ucounts = inc_ipc_namespaces(user_ns);
  40         if (!ucounts)
  41                 goto fail;
  42
  43         err = -ENOMEM;
  44         ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
  45         if (ns == NULL)
  46                 goto fail_dec;
  47
  48         err = ns_alloc_inum(&ns->ns);
  49         if (err)
  50                 goto fail_free;
  51         ns->ns.ops = &ipcns_operations;
  52
  53         refcount_set(&ns->count, 1);
  54         ns->user_ns = get_user_ns(user_ns);
  55         ns->ucounts = ucounts;
  56
  57         err = sem_init_ns(ns);
  58         if (err)
  59                 goto fail_put;
  60         err = msg_init_ns(ns);
  61         if (err)
  62                 goto fail_destroy_sem;
  63         err = shm_init_ns(ns);
  64         if (err)
  65                 goto fail_destroy_msg;
  66
  67         err = mq_init_ns(ns);
  68         if (err)
  69                 goto fail_destroy_shm;
  70
  71         return ns;
  72
  73 fail_destroy_shm:
  74         shm_exit_ns(ns);
  75 fail_destroy_msg:
  76         msg_exit_ns(ns);
  77 fail_destroy_sem:
  78         sem_exit_ns(ns);
  79 fail_put:
  80         put_user_ns(ns->user_ns);
  81         ns_free_inum(&ns->ns);
  82 fail_free:
  83         kfree(ns);
  84 fail_dec:
  85         dec_ipc_namespaces(ucounts);
  86 fail:
  87         return ERR_PTR(err);
  88 }
  89
  90 struct ipc_namespace *copy_ipcs(unsigned long flags,
  91         struct user_namespace *user_ns, struct ipc_namespace *ns)
  92 {
  93         if (!(flags & CLONE_NEWIPC))
  94                 return get_ipc_ns(ns);
  95         return create_ipc_ns(user_ns, ns);
  96 }
  97
  98 /*
  99  * free_ipcs - free all ipcs of one type
 100  * @ns:   the namespace to remove the ipcs from
 101  * @ids:  the table of ipcs to free
 102  * @free: the function called to free each individual ipc
 103  *
 104  * Called for each kind of ipc when an ipc_namespace exits.
 105  */
 106 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
 107                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
 108 {
 109         struct kern_ipc_perm *perm;
 110         int next_id;
 111         int total, in_use;
 112
 113         down_write(&ids->rwsem);
 114
 115         in_use = ids->in_use;
 116
 117         for (total = 0, next_id = 0; total < in_use; next_id++) {
 118                 perm = idr_find(&ids->ipcs_idr, next_id);
 119                 if (perm == NULL)
 120                         continue;
 121                 rcu_read_lock();
 122                 ipc_lock_object(perm);
 123                 free(ns, perm);
 124                 total++;
 125         }
 126         up_write(&ids->rwsem);
 127 }
 128
 129 static void free_ipc_ns(struct ipc_namespace *ns)
 130 {
 131         sem_exit_ns(ns);
 132         msg_exit_ns(ns);
 133         shm_exit_ns(ns);
 134
 135         dec_ipc_namespaces(ns->ucounts);
 136         put_user_ns(ns->user_ns);
 137         ns_free_inum(&ns->ns);
 138         kfree(ns);
 139 }
 140
 141 /*
 142  * put_ipc_ns - drop a reference to an ipc namespace.
 143  * @ns: the namespace to put
 144  *
 145  * If this is the last task in the namespace exiting, and
 146  * it is dropping the refcount to 0, then it can race with
 147  * a task in another ipc namespace but in a mounts namespace
 148  * which has this ipcns's mqueuefs mounted, doing some action
 149  * with one of the mqueuefs files.  That can raise the refcount.
 150  * So dropping the refcount, and raising the refcount when
 151  * accessing it through the VFS, are protected with mq_lock.
 152  *
 153  * (Clearly, a task raising the refcount on its own ipc_ns
 154  * needn't take mq_lock since it can't race with the last task
 155  * in the ipcns exiting).
 156  */
 157 void put_ipc_ns(struct ipc_namespace *ns)
 158 {
 159         if (refcount_dec_and_lock(&ns->count, &mq_lock)) {
 160                 mq_clear_sbinfo(ns);
 161                 spin_unlock(&mq_lock);
 162                 mq_put_mnt(ns);
 163                 free_ipc_ns(ns);
 164         }
 165 }
 166
 167 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 168 {
 169         return container_of(ns, struct ipc_namespace, ns);
 170 }
 171
 172 static struct ns_common *ipcns_get(struct task_struct *task)
 173 {
 174         struct ipc_namespace *ns = NULL;
 175         struct nsproxy *nsproxy;
 176
 177         task_lock(task);
 178         nsproxy = task->nsproxy;
 179         if (nsproxy)
 180                 ns = get_ipc_ns(nsproxy->ipc_ns);
 181         task_unlock(task);
 182
 183         return ns ? &ns->ns : NULL;
 184 }
 185
 186 static void ipcns_put(struct ns_common *ns)
 187 {
 188         return put_ipc_ns(to_ipc_ns(ns));
 189 }
 190
 191 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
 192 {
 193         struct ipc_namespace *ns = to_ipc_ns(new);
 194         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 195             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 196                 return -EPERM;
 197
 198         /* Ditch state from the old ipc namespace */
 199         exit_sem(current);
 200         put_ipc_ns(nsproxy->ipc_ns);
 201         nsproxy->ipc_ns = get_ipc_ns(ns);
 202         return 0;
 203 }
 204
 205 static struct user_namespace *ipcns_owner(struct ns_common *ns)
 206 {
 207         return to_ipc_ns(ns)->user_ns;
 208 }
 209
 210 const struct proc_ns_operations ipcns_operations = {
 211         .name           = "ipc",
 212         .type           = CLONE_NEWIPC,
 213         .get            = ipcns_get,
 214         .put            = ipcns_put,
 215         .install        = ipcns_install,
 216         .owner          = ipcns_owner,
 217 };