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/err.h>
  16 #include <linux/slab.h>
  17 #include <linux/user_namespace.h>
  18
  19 static struct uts_namespace *create_uts_ns(void)
  20 {
  21         struct uts_namespace *uts_ns;
  22
  23         uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  24         if (uts_ns)
  25                 kref_init(&uts_ns->kref);
  26         return uts_ns;
  27 }
  28
  29 /*
  30  * Clone a new ns copying an original utsname, setting refcount to 1
  31  * @old_ns: namespace to clone
  32  * Return NULL on error (failure to kmalloc), new ns otherwise
  33  */
  34 static struct uts_namespace *clone_uts_ns(struct task_struct *tsk,
  35                                           struct uts_namespace *old_ns)
  36 {
  37         struct uts_namespace *ns;
  38
  39         ns = create_uts_ns();
  40         if (!ns)
  41                 return ERR_PTR(-ENOMEM);
  42
  43         down_read(&uts_sem);
  44         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  45         ns->user_ns = get_user_ns(task_cred_xxx(tsk, user)->user_ns);
  46         up_read(&uts_sem);
  47         return ns;
  48 }
  49
  50 /*
  51  * Copy task tsk's utsname namespace, or clone it if flags
  52  * specifies CLONE_NEWUTS.  In latter case, changes to the
  53  * utsname of this process won't be seen by parent, and vice
  54  * versa.
  55  */
  56 struct uts_namespace *copy_utsname(unsigned long flags,
  57                                    struct task_struct *tsk)
  58 {
  59         struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
  60         struct uts_namespace *new_ns;
  61
  62         BUG_ON(!old_ns);
  63         get_uts_ns(old_ns);
  64
  65         if (!(flags & CLONE_NEWUTS))
  66                 return old_ns;
  67
  68         new_ns = clone_uts_ns(tsk, old_ns);
  69
  70         put_uts_ns(old_ns);
  71         return new_ns;
  72 }
  73
  74 void free_uts_ns(struct kref *kref)
  75 {
  76         struct uts_namespace *ns;
  77
  78         ns = container_of(kref, struct uts_namespace, kref);
  79         put_user_ns(ns->user_ns);
  80         kfree(ns);
  81 }