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