linux/kernel/utsname.c
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   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 = proc_alloc_inum(&ns->proc_inum);
  46        if (err) {
  47                kfree(ns);
  48                return ERR_PTR(err);
  49        }
  50
  51        down_read(&uts_sem);
  52        memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  53        ns->user_ns = get_user_ns(user_ns);
  54        up_read(&uts_sem);
  55        return ns;
  56}
  57
  58/*
  59 * Copy task tsk's utsname namespace, or clone it if flags
  60 * specifies CLONE_NEWUTS.  In latter case, changes to the
  61 * utsname of this process won't be seen by parent, and vice
  62 * versa.
  63 */
  64struct uts_namespace *copy_utsname(unsigned long flags,
  65        struct user_namespace *user_ns, struct uts_namespace *old_ns)
  66{
  67        struct uts_namespace *new_ns;
  68
  69        BUG_ON(!old_ns);
  70        get_uts_ns(old_ns);
  71
  72        if (!(flags & CLONE_NEWUTS))
  73                return old_ns;
  74
  75        new_ns = clone_uts_ns(user_ns, old_ns);
  76
  77        put_uts_ns(old_ns);
  78        return new_ns;
  79}
  80
  81void free_uts_ns(struct kref *kref)
  82{
  83        struct uts_namespace *ns;
  84
  85        ns = container_of(kref, struct uts_namespace, kref);
  86        put_user_ns(ns->user_ns);
  87        proc_free_inum(ns->proc_inum);
  88        kfree(ns);
  89}
  90
  91static void *utsns_get(struct task_struct *task)
  92{
  93        struct uts_namespace *ns = NULL;
  94        struct nsproxy *nsproxy;
  95
  96        rcu_read_lock();
  97        nsproxy = task_nsproxy(task);
  98        if (nsproxy) {
  99                ns = nsproxy->uts_ns;
 100                get_uts_ns(ns);
 101        }
 102        rcu_read_unlock();
 103
 104        return ns;
 105}
 106
 107static void utsns_put(void *ns)
 108{
 109        put_uts_ns(ns);
 110}
 111
 112static int utsns_install(struct nsproxy *nsproxy, void *new)
 113{
 114        struct uts_namespace *ns = new;
 115
 116        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 117            !nsown_capable(CAP_SYS_ADMIN))
 118                return -EPERM;
 119
 120        get_uts_ns(ns);
 121        put_uts_ns(nsproxy->uts_ns);
 122        nsproxy->uts_ns = ns;
 123        return 0;
 124}
 125
 126static unsigned int utsns_inum(void *vp)
 127{
 128        struct uts_namespace *ns = vp;
 129
 130        return ns->proc_inum;
 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        .inum           = utsns_inum,
 140};
 141
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