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/module.h>
  13 #include <linux/uts.h>
  14 #include <linux/utsname.h>
  15 #include <linux/version.h>
  16
  17 /*
  18  * Clone a new ns copying an original utsname, setting refcount to 1
  19  * @old_ns: namespace to clone
  20  * Return NULL on error (failure to kmalloc), new ns otherwise
  21  */
  22 static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
  23 {
  24         struct uts_namespace *ns;
  25
  26         ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  27         if (ns) {
  28                 memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  29                 kref_init(&ns->kref);
  30         }
  31         return ns;
  32 }
  33
  34 /*
  35  * unshare the current process' utsname namespace.
  36  * called only in sys_unshare()
  37  */
  38 int unshare_utsname(unsigned long unshare_flags, struct uts_namespace **new_uts)
  39 {
  40         if (unshare_flags & CLONE_NEWUTS) {
  41                 if (!capable(CAP_SYS_ADMIN))
  42                         return -EPERM;
  43
  44                 *new_uts = clone_uts_ns(current->nsproxy->uts_ns);
  45                 if (!*new_uts)
  46                         return -ENOMEM;
  47         }
  48
  49         return 0;
  50 }
  51
  52 /*
  53  * Copy task tsk's utsname namespace, or clone it if flags
  54  * specifies CLONE_NEWUTS.  In latter case, changes to the
  55  * utsname of this process won't be seen by parent, and vice
  56  * versa.
  57  */
  58 int copy_utsname(int flags, struct task_struct *tsk)
  59 {
  60         struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
  61         struct uts_namespace *new_ns;
  62         int err = 0;
  63
  64         if (!old_ns)
  65                 return 0;
  66
  67         get_uts_ns(old_ns);
  68
  69         if (!(flags & CLONE_NEWUTS))
  70                 return 0;
  71
  72         if (!capable(CAP_SYS_ADMIN)) {
  73                 err = -EPERM;
  74                 goto out;
  75         }
  76
  77         new_ns = clone_uts_ns(old_ns);
  78         if (!new_ns) {
  79                 err = -ENOMEM;
  80                 goto out;
  81         }
  82         tsk->nsproxy->uts_ns = new_ns;
  83
  84 out:
  85         put_uts_ns(old_ns);
  86         return err;
  87 }
  88
  89 void free_uts_ns(struct kref *kref)
  90 {
  91         struct uts_namespace *ns;
  92
  93         ns = container_of(kref, struct uts_namespace, kref);
  94         kfree(ns);
  95 }