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 uts_namespace *old_ns)
  35 {
  36         struct uts_namespace *ns;
  37
  38         ns = create_uts_ns();
  39         if (!ns)
  40                 return ERR_PTR(-ENOMEM);
  41
  42         down_read(&uts_sem);
  43         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  44         ns->user_ns = old_ns->user_ns;
  45         get_user_ns(ns->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, struct uts_namespace *old_ns)
  57 {
  58         struct uts_namespace *new_ns;
  59
  60         BUG_ON(!old_ns);
  61         get_uts_ns(old_ns);
  62
  63         if (!(flags & CLONE_NEWUTS))
  64                 return old_ns;
  65
  66         new_ns = clone_uts_ns(old_ns);
  67
  68         put_uts_ns(old_ns);
  69         return new_ns;
  70 }
  71
  72 void free_uts_ns(struct kref *kref)
  73 {
  74         struct uts_namespace *ns;
  75
  76         ns = container_of(kref, struct uts_namespace, kref);
  77         put_user_ns(ns->user_ns);
  78         kfree(ns);
  79 }