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 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  */
  64 struct 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
  81 void 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
  91 static 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
 107 static void utsns_put(void *ns)
 108 {
 109         put_uts_ns(ns);
 110 }
 111
 112 static 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
 126 static unsigned int utsns_inum(void *vp)
 127 {
 128         struct uts_namespace *ns = vp;
 129
 130         return ns->proc_inum;
 131 }
 132
 133 const 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 };