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_fs.h>
  19
  20 static 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 NULL on error (failure to kmalloc), new ns otherwise
  34  */
  35 static struct uts_namespace *clone_uts_ns(struct task_struct *tsk,
  36                                           struct uts_namespace *old_ns)
  37 {
  38         struct uts_namespace *ns;
  39
  40         ns = create_uts_ns();
  41         if (!ns)
  42                 return ERR_PTR(-ENOMEM);
  43
  44         down_read(&uts_sem);
  45         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  46         ns->user_ns = get_user_ns(task_cred_xxx(tsk, user_ns));
  47         up_read(&uts_sem);
  48         return ns;
  49 }
  50
  51 /*
  52  * Copy task tsk's utsname namespace, or clone it if flags
  53  * specifies CLONE_NEWUTS.  In latter case, changes to the
  54  * utsname of this process won't be seen by parent, and vice
  55  * versa.
  56  */
  57 struct uts_namespace *copy_utsname(unsigned long flags,
  58                                    struct task_struct *tsk)
  59 {
  60         struct uts_namespace *old_ns = tsk->nsproxy->uts_ns;
  61         struct uts_namespace *new_ns;
  62
  63         BUG_ON(!old_ns);
  64         get_uts_ns(old_ns);
  65
  66         if (!(flags & CLONE_NEWUTS))
  67                 return old_ns;
  68
  69         new_ns = clone_uts_ns(tsk, old_ns);
  70
  71         put_uts_ns(old_ns);
  72         return new_ns;
  73 }
  74
  75 void free_uts_ns(struct kref *kref)
  76 {
  77         struct uts_namespace *ns;
  78
  79         ns = container_of(kref, struct uts_namespace, kref);
  80         put_user_ns(ns->user_ns);
  81         kfree(ns);
  82 }
  83
  84 static void *utsns_get(struct task_struct *task)
  85 {
  86         struct uts_namespace *ns = NULL;
  87         struct nsproxy *nsproxy;
  88
  89         rcu_read_lock();
  90         nsproxy = task_nsproxy(task);
  91         if (nsproxy) {
  92                 ns = nsproxy->uts_ns;
  93                 get_uts_ns(ns);
  94         }
  95         rcu_read_unlock();
  96
  97         return ns;
  98 }
  99
 100 static void utsns_put(void *ns)
 101 {
 102         put_uts_ns(ns);
 103 }
 104
 105 static int utsns_install(struct nsproxy *nsproxy, void *ns)
 106 {
 107         get_uts_ns(ns);
 108         put_uts_ns(nsproxy->uts_ns);
 109         nsproxy->uts_ns = ns;
 110         return 0;
 111 }
 112
 113 const struct proc_ns_operations utsns_operations = {
 114         .name           = "uts",
 115         .type           = CLONE_NEWUTS,
 116         .get            = utsns_get,
 117         .put            = utsns_put,
 118         .install        = utsns_install,
 119 };
 120