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