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 ucounts *inc_uts_namespaces(struct user_namespace *ns)
  21{
  22        return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
  23}
  24
  25static void dec_uts_namespaces(struct ucounts *ucounts)
  26{
  27        dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
  28}
  29
  30static struct uts_namespace *create_uts_ns(void)
  31{
  32        struct uts_namespace *uts_ns;
  33
  34        uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  35        if (uts_ns)
  36                kref_init(&uts_ns->kref);
  37        return uts_ns;
  38}
  39
  40/*
  41 * Clone a new ns copying an original utsname, setting refcount to 1
  42 * @old_ns: namespace to clone
  43 * Return ERR_PTR(-ENOMEM) on error (failure to kmalloc), new ns otherwise
  44 */
  45static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
  46                                          struct uts_namespace *old_ns)
  47{
  48        struct uts_namespace *ns;
  49        struct ucounts *ucounts;
  50        int err;
  51
  52        err = -ENOSPC;
  53        ucounts = inc_uts_namespaces(user_ns);
  54        if (!ucounts)
  55                goto fail;
  56
  57        err = -ENOMEM;
  58        ns = create_uts_ns();
  59        if (!ns)
  60                goto fail_dec;
  61
  62        err = proc_alloc_inum(&ns->proc_inum);
  63        if (err)
  64                goto fail_free;
  65
  66        ns->ucounts = ucounts;
  67
  68        down_read(&uts_sem);
  69        memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  70        ns->user_ns = get_user_ns(user_ns);
  71        up_read(&uts_sem);
  72        return ns;
  73
  74fail_free:
  75        kfree(ns);
  76fail_dec:
  77        dec_uts_namespaces(ucounts);
  78fail:
  79        return ERR_PTR(err);
  80}
  81
  82/*
  83 * Copy task tsk's utsname namespace, or clone it if flags
  84 * specifies CLONE_NEWUTS.  In latter case, changes to the
  85 * utsname of this process won't be seen by parent, and vice
  86 * versa.
  87 */
  88struct uts_namespace *copy_utsname(unsigned long flags,
  89        struct user_namespace *user_ns, struct uts_namespace *old_ns)
  90{
  91        struct uts_namespace *new_ns;
  92
  93        BUG_ON(!old_ns);
  94        get_uts_ns(old_ns);
  95
  96        if (!(flags & CLONE_NEWUTS))
  97                return old_ns;
  98
  99        new_ns = clone_uts_ns(user_ns, old_ns);
 100
 101        put_uts_ns(old_ns);
 102        return new_ns;
 103}
 104
 105void free_uts_ns(struct kref *kref)
 106{
 107        struct uts_namespace *ns;
 108
 109        ns = container_of(kref, struct uts_namespace, kref);
 110        dec_uts_namespaces(ns->ucounts);
 111        put_user_ns(ns->user_ns);
 112        proc_free_inum(ns->proc_inum);
 113        kfree(ns);
 114}
 115
 116static void *utsns_get(struct task_struct *task)
 117{
 118        struct uts_namespace *ns = NULL;
 119        struct nsproxy *nsproxy;
 120
 121        task_lock(task);
 122        nsproxy = task->nsproxy;
 123        if (nsproxy) {
 124                ns = nsproxy->uts_ns;
 125                get_uts_ns(ns);
 126        }
 127        task_unlock(task);
 128
 129        return ns;
 130}
 131
 132static void utsns_put(void *ns)
 133{
 134        put_uts_ns(ns);
 135}
 136
 137static int utsns_install(struct nsproxy *nsproxy, void *new)
 138{
 139        struct uts_namespace *ns = new;
 140
 141        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 142            !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 143                return -EPERM;
 144
 145        get_uts_ns(ns);
 146        put_uts_ns(nsproxy->uts_ns);
 147        nsproxy->uts_ns = ns;
 148        return 0;
 149}
 150
 151static unsigned int utsns_inum(void *vp)
 152{
 153        struct uts_namespace *ns = vp;
 154
 155        return ns->proc_inum;
 156}
 157
 158const struct proc_ns_operations utsns_operations = {
 159        .name           = "uts",
 160        .type           = CLONE_NEWUTS,
 161        .get            = utsns_get,
 162        .put            = utsns_put,
 163        .install        = utsns_install,
 164        .inum           = utsns_inum,
 165};
 166