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 = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL_ACCOUNT);
  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->ns.count, 1);
  55         ns->user_ns = get_user_ns(user_ns);
  56         ns->ucounts = ucounts;
  57
  58         err = mq_init_ns(ns);
  59         if (err)
  60                 goto fail_put;
  61
  62         err = -ENOMEM;
  63         if (!setup_mq_sysctls(ns))
  64                 goto fail_put;
  65
  66         if (!setup_ipc_sysctls(ns))
  67                 goto fail_put;
  68
  69         sem_init_ns(ns);
  70         msg_init_ns(ns);
  71         shm_init_ns(ns);
  72
  73         return ns;
  74
  75 fail_put:
  76         put_user_ns(ns->user_ns);
  77         ns_free_inum(&ns->ns);
  78 fail_free:
  79         kfree(ns);
  80 fail_dec:
  81         dec_ipc_namespaces(ucounts);
  82 fail:
  83         return ERR_PTR(err);
  84 }
  85
  86 struct ipc_namespace *copy_ipcs(unsigned long flags,
  87         struct user_namespace *user_ns, struct ipc_namespace *ns)
  88 {
  89         if (!(flags & CLONE_NEWIPC))
  90                 return get_ipc_ns(ns);
  91         return create_ipc_ns(user_ns, ns);
  92 }
  93
  94 /*
  95  * free_ipcs - free all ipcs of one type
  96  * @ns:   the namespace to remove the ipcs from
  97  * @ids:  the table of ipcs to free
  98  * @free: the function called to free each individual ipc
  99  *
 100  * Called for each kind of ipc when an ipc_namespace exits.
 101  */
 102 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
 103                void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
 104 {
 105         struct kern_ipc_perm *perm;
 106         int next_id;
 107         int total, in_use;
 108
 109         down_write(&ids->rwsem);
 110
 111         in_use = ids->in_use;
 112
 113         for (total = 0, next_id = 0; total < in_use; next_id++) {
 114                 perm = idr_find(&ids->ipcs_idr, next_id);
 115                 if (perm == NULL)
 116                         continue;
 117                 rcu_read_lock();
 118                 ipc_lock_object(perm);
 119                 free(ns, perm);
 120                 total++;
 121         }
 122         up_write(&ids->rwsem);
 123 }
 124
 125 static void free_ipc_ns(struct ipc_namespace *ns)
 126 {
 127         /* mq_put_mnt() waits for a grace period as kern_unmount()
 128          * uses synchronize_rcu().
 129          */
 130         mq_put_mnt(ns);
 131         sem_exit_ns(ns);
 132         msg_exit_ns(ns);
 133         shm_exit_ns(ns);
 134
 135         retire_mq_sysctls(ns);
 136         retire_ipc_sysctls(ns);
 137
 138         dec_ipc_namespaces(ns->ucounts);
 139         put_user_ns(ns->user_ns);
 140         ns_free_inum(&ns->ns);
 141         kfree(ns);
 142 }
 143
 144 static LLIST_HEAD(free_ipc_list);
 145 static void free_ipc(struct work_struct *unused)
 146 {
 147         struct llist_node *node = llist_del_all(&free_ipc_list);
 148         struct ipc_namespace *n, *t;
 149
 150         llist_for_each_entry_safe(n, t, node, mnt_llist)
 151                 free_ipc_ns(n);
 152 }
 153
 154 /*
 155  * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
 156  */
 157 static DECLARE_WORK(free_ipc_work, free_ipc);
 158
 159 /*
 160  * put_ipc_ns - drop a reference to an ipc namespace.
 161  * @ns: the namespace to put
 162  *
 163  * If this is the last task in the namespace exiting, and
 164  * it is dropping the refcount to 0, then it can race with
 165  * a task in another ipc namespace but in a mounts namespace
 166  * which has this ipcns's mqueuefs mounted, doing some action
 167  * with one of the mqueuefs files.  That can raise the refcount.
 168  * So dropping the refcount, and raising the refcount when
 169  * accessing it through the VFS, are protected with mq_lock.
 170  *
 171  * (Clearly, a task raising the refcount on its own ipc_ns
 172  * needn't take mq_lock since it can't race with the last task
 173  * in the ipcns exiting).
 174  */
 175 void put_ipc_ns(struct ipc_namespace *ns)
 176 {
 177         if (refcount_dec_and_lock(&ns->ns.count, &mq_lock)) {
 178                 mq_clear_sbinfo(ns);
 179                 spin_unlock(&mq_lock);
 180
 181                 if (llist_add(&ns->mnt_llist, &free_ipc_list))
 182                         schedule_work(&free_ipc_work);
 183         }
 184 }
 185
 186 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
 187 {
 188         return container_of(ns, struct ipc_namespace, ns);
 189 }
 190
 191 static struct ns_common *ipcns_get(struct task_struct *task)
 192 {
 193         struct ipc_namespace *ns = NULL;
 194         struct nsproxy *nsproxy;
 195
 196         task_lock(task);
 197         nsproxy = task->nsproxy;
 198         if (nsproxy)
 199                 ns = get_ipc_ns(nsproxy->ipc_ns);
 200         task_unlock(task);
 201
 202         return ns ? &ns->ns : NULL;
 203 }
 204
 205 static void ipcns_put(struct ns_common *ns)
 206 {
 207         return put_ipc_ns(to_ipc_ns(ns));
 208 }
 209
 210 static int ipcns_install(struct nsset *nsset, struct ns_common *new)
 211 {
 212         struct nsproxy *nsproxy = nsset->nsproxy;
 213         struct ipc_namespace *ns = to_ipc_ns(new);
 214         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 215             !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
 216                 return -EPERM;
 217
 218         put_ipc_ns(nsproxy->ipc_ns);
 219         nsproxy->ipc_ns = get_ipc_ns(ns);
 220         return 0;
 221 }
 222
 223 static struct user_namespace *ipcns_owner(struct ns_common *ns)
 224 {
 225         return to_ipc_ns(ns)->user_ns;
 226 }
 227
 228 const struct proc_ns_operations ipcns_operations = {
 229         .name           = "ipc",
 230         .type           = CLONE_NEWIPC,
 231         .get            = ipcns_get,
 232         .put            = ipcns_put,
 233         .install        = ipcns_install,
 234         .owner          = ipcns_owner,
 235 };