LXR linux/kernel/utsname.c

   1/*
   2 *  Copyright (C) 2004 IBM Corporation
   3 *
   4 *  Author: Serge Hallyn <serue@us.ibm.com>
   5 *
   6 *  This program is free software; you can redistribute it and/or
   7 *  modify it under the terms of the GNU General Public License as
   8 *  published by the Free Software Foundation, version 2 of the
   9 *  License.
  10 */
  11
  12#include <linux/export.h>
  13#include <linux/uts.h>
  14#include <linux/utsname.h>
  15#include <linux/err.h>
  16#include <linux/slab.h>
  17#include <linux/user_namespace.h>
  18#include <linux/proc_ns.h>
  19
  20static struct uts_namespace *create_uts_ns(void)
  21{
  22        struct uts_namespace *uts_ns;
  23
  24        uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  25        if (uts_ns)
  26                kref_init(&uts_ns->kref);
  27        return uts_ns;
  28}
  29
  30/*
  31 * Clone a new ns copying an original utsname, setting refcount to 1
  32 * @old_ns: namespace to clone
  33 * Return ERR_PTR(-ENOMEM) on error (failure to kmalloc), new ns otherwise
  34 */
  35static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
  36                                          struct uts_namespace *old_ns)
  37{
  38        struct uts_namespace *ns;
  39        int err;
  40
  41        ns = create_uts_ns();
  42        if (!ns)
  43                return ERR_PTR(-ENOMEM);
  44
  45        err = ns_alloc_inum(&ns->ns);
  46        if (err) {
  47                kfree(ns);
  48                return ERR_PTR(err);
  49        }
  50
  51        ns->ns.ops = &utsns_operations;
  52
  53        down_read(&uts_sem);
  54        memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  55        ns->user_ns = get_user_ns(user_ns);
  56        up_read(&uts_sem);
  57        return ns;
  58}
  59
  60/*
  61 * Copy task tsk's utsname namespace, or clone it if flags
  62 * specifies CLONE_NEWUTS.  In latter case, changes to the
  63 * utsname of this process won't be seen by parent, and vice
  64 * versa.
  65 */
  66struct uts_namespace *copy_utsname(unsigned long flags,
  67        struct user_namespace *user_ns, struct uts_namespace *old_ns)
  68{
  69        struct uts_namespace *new_ns;
  70
  71        BUG_ON(!old_ns);
  72        get_uts_ns(old_ns);
  73
  74        if (!(flags & CLONE_NEWUTS))
  75                return old_ns;
  76
  77        new_ns = clone_uts_ns(user_ns, old_ns);
  78
  79        put_uts_ns(old_ns);
  80        return new_ns;
  81}
  82
  83void free_uts_ns(struct kref *kref)
  84{
  85        struct uts_namespace *ns;
  86
  87        ns = container_of(kref, struct uts_namespace, kref);
  88        put_user_ns(ns->user_ns);
  89        ns_free_inum(&ns->ns);
  90        kfree(ns);
  91}
  92
  93static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
  94{
  95        return container_of(ns, struct uts_namespace, ns);
  96}
  97
  98static struct ns_common *utsns_get(struct task_struct *task)
  99{
 100        struct uts_namespace *ns = NULL;
 101        struct nsproxy *nsproxy;
 102
 103        task_lock(task);
 104        nsproxy = task->nsproxy;
 105        if (nsproxy) {
 106                ns = nsproxy->uts_ns;
 107                get_uts_ns(ns);
 108        }
 109        task_unlock(task);
 110
 111        return ns ? &ns->ns : NULL;
 112}
 113
 114static void utsns_put(struct ns_common *ns)
 115{
 116        put_uts_ns(to_uts_ns(ns));
 117}
 118
 119static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
 120{
 121        struct uts_namespace *ns = to_uts_ns(new);
 122
 123        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 124            !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 125                return -EPERM;
 126
 127        get_uts_ns(ns);
 128        put_uts_ns(nsproxy->uts_ns);
 129        nsproxy->uts_ns = ns;
 130        return 0;
 131}
 132
 133const struct proc_ns_operations utsns_operations = {
 134        .name           = "uts",
 135        .type           = CLONE_NEWUTS,
 136        .get            = utsns_get,
 137        .put            = utsns_put,
 138        .install        = utsns_install,
 139};
 140