ipc/namespace.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/ipc/namespace.c
   4  * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
   5  */
   6
   7 #include <linux/ipc.h>
   8 #include <linux/msg.h>
   9 #include <linux/ipc_namespace.h>
  10 #include <linux/rcupdate.h>
  11 #include <linux/nsproxy.h>
  12 #include <linux/slab.h>
  13 #include <linux/cred.h>
  14 #include <linux/fs.h>
  15 #include <linux/mount.h>
  16 #include <linux/user_namespace.h>
  17 #include <linux/proc_ns.h>
  18 #include <linux/sched/task.h>
  19
  20 #include "util.h"
  21
  22 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
  23 {
  24         return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
  25 }
  26
  27 static void dec_ipc_namespaces(struct ucounts *ucounts)
  28 {
  29         dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
  30 }
  31
  32 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
  33                                            struct ipc_namespace *old_ns)
  34 {
  35         struct ipc_namespace *ns;
  36         struct ucounts *ucounts;
  37         int err;
  38
  39         err = -ENOSPC;
  40         ucounts = inc_ipc_namespaces(user_ns);
  41         if (!ucounts)
  42                 goto fail;
  43
  44         err = -ENOMEM;
  45         ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
  46         if (ns == NULL)
  47                 goto fail_dec;
  48
  49         err = ns_alloc_inum(&ns->ns);
  50         if (err)
  51                 goto fail_free;
  52         ns->ns.ops = &ipcns_operations;
  53
  54         refcount_set(&ns->count, 1);
  55         ns->user_ns = get_user_ns(user_ns);
  56         ns->ucounts = ucounts;
  57
  58         err = sem_init_ns(ns);
  59         if (err)
  60                 goto fail_put;
  61         err = msg_init_ns(ns);
  62         if (err)
  63                 goto fail_destroy_sem;
  64         err = shm_init_ns(ns);
  65         if (err)
  66                 goto fail_destroy_msg;
  67
  68         err = mq_init_ns(ns);
  69         if (err)
  70                 goto fail_destroy_shm;
  71
  72         return ns;
  73
  74 fail_destroy_shm:
  75         shm_exit_ns(ns);
  76 fail_destroy_msg:
  77         msg_exit_ns(ns);
  78 fail_destroy_sem:
  79         sem_exit_ns(ns);
  80 fail_put:
  81         put_user_ns(ns->user_ns);
  82         ns_free_inum(&ns->ns);
  83 fail_free:
  84         kfree(ns);
  85 fail_dec:
  86         dec_ipc_namespaces(ucounts);
  87 fail:
  88         return ERR_PTR(err);
  89 }
  90
  91 struct ipc_namespace *copy_ipcs(unsigned long flags,
  92         struct user_namespace *user_ns, struct ipc_namespace *ns)
  93 {
  94         if (!(flags & CLONE_NEWIPC))
  95                 return get_ipc_ns(ns);
  96         return create_ipc_ns(user_ns, ns);
  97 }
  98
  99 /*
 100  * free_ipcs - free all ipcs of one type
 101  * @ns:   the namespace to remove the ipcs from
 102  * @ids:  the table of ipcs to free
 103  * @free: the function called to free each individual ipc
 104  *
 105  * Called for each kind of ipc when an ipc_namespace exits.
 106  */
 107 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
 108                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
 109 {
 110         struct kern_ipc_perm *perm;
 111         int next_id;
 112         int total, in_use;
 113
 114         down_write(&ids->rwsem);
 115
 116         in_use = ids->in_use;
 117
 118         for (total = 0, next_id = 0; total < in_use; next_id++) {
 119                 perm = idr_find(&ids->ipcs_idr, next_id);
 120                 if (perm == NULL)
 121                         continue;
 122                 rcu_read_lock();
 123                 ipc_lock_object(perm);
 124                 free(ns, perm);
 125                 total++;
 126         }
 127         up_write(&ids->rwsem);
 128 }
 129
 130 static void free_ipc_ns(struct ipc_namespace *ns)
 131 {
 132         sem_exit_ns(ns);
 133         msg_exit_ns(ns);
 134         shm_exit_ns(ns);
 135
 136         dec_ipc_namespaces(ns->ucounts);
 137         put_user_ns(ns->user_ns);
 138         ns_free_inum(&ns->ns);
 139         kfree(ns);
 140 }
 141
 142 /*
 143  * put_ipc_ns - drop a reference to an ipc namespace.
 144  * @ns: the namespace to put
 145  *
 146  * If this is the last task in the namespace exiting, and
 147  * it is dropping the refcount to 0, then it can race with
 148  * a task in another ipc namespace but in a mounts namespace
 149  * which has this ipcns's mqueuefs mounted, doing some action
 150  * with one of the mqueuefs files.  That can raise the refcount.
 151  * So dropping the refcount, and raising the refcount when
 152  * accessing it through the VFS, are protected with mq_lock.
 153  *
 154  * (Clearly, a task raising the refcount on its own ipc_ns
 155  * needn't take mq_lock since it can't race with the last task
 156  * in the ipcns exiting).
 157  */
 158 void put_ipc_ns(struct ipc_namespace *ns)
 159 {
 160         if (refcount_dec_and_lock(&ns->count, &mq_lock)) {
 161                 mq_clear_sbinfo(ns);
 162                 spin_unlock(&mq_lock);
 163                 mq_put_mnt(ns);
 164                 free_ipc_ns(ns);
 165         }
 166 }
 167
 168 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 169 {
 170         return container_of(ns, struct ipc_namespace, ns);
 171 }
 172
 173 static struct ns_common *ipcns_get(struct task_struct *task)
 174 {
 175         struct ipc_namespace *ns = NULL;
 176         struct nsproxy *nsproxy;
 177
 178         task_lock(task);
 179         nsproxy = task->nsproxy;
 180         if (nsproxy)
 181                 ns = get_ipc_ns(nsproxy->ipc_ns);
 182         task_unlock(task);
 183
 184         return ns ? &ns->ns : NULL;
 185 }
 186
 187 static void ipcns_put(struct ns_common *ns)
 188 {
 189         return put_ipc_ns(to_ipc_ns(ns));
 190 }
 191
 192 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
 193 {
 194         struct ipc_namespace *ns = to_ipc_ns(new);
 195         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 196             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 197                 return -EPERM;
 198
 199         /* Ditch state from the old ipc namespace */
 200         exit_sem(current);
 201         put_ipc_ns(nsproxy->ipc_ns);
 202         nsproxy->ipc_ns = get_ipc_ns(ns);
 203         return 0;
 204 }
 205
 206 static struct user_namespace *ipcns_owner(struct ns_common *ns)
 207 {
 208         return to_ipc_ns(ns)->user_ns;
 209 }
 210
 211 const struct proc_ns_operations ipcns_operations = {
 212         .name           = "ipc",
 213         .type           = CLONE_NEWIPC,
 214         .get            = ipcns_get,
 215         .put            = ipcns_put,
 216         .install        = ipcns_install,
 217         .owner          = ipcns_owner,
 218 };