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_ns.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 ERR_PTR(-ENOMEM) 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 = ns_alloc_inum(&ns->ns);
  46         if (err) {
  47                 kfree(ns);
  48                 return ERR_PTR(err);
  49         }
  50
  51         ns->ns.ops = &utsns_operations;
  52
  53         down_read(&uts_sem);
  54         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  55         ns->user_ns = get_user_ns(user_ns);
  56         up_read(&uts_sem);
  57         return ns;
  58 }
  59
  60 /*
  61  * Copy task tsk's utsname namespace, or clone it if flags
  62  * specifies CLONE_NEWUTS.  In latter case, changes to the
  63  * utsname of this process won't be seen by parent, and vice
  64  * versa.
  65  */
  66 struct uts_namespace *copy_utsname(unsigned long flags,
  67         struct user_namespace *user_ns, struct uts_namespace *old_ns)
  68 {
  69         struct uts_namespace *new_ns;
  70
  71         BUG_ON(!old_ns);
  72         get_uts_ns(old_ns);
  73
  74         if (!(flags & CLONE_NEWUTS))
  75                 return old_ns;
  76
  77         new_ns = clone_uts_ns(user_ns, old_ns);
  78
  79         put_uts_ns(old_ns);
  80         return new_ns;
  81 }
  82
  83 void free_uts_ns(struct kref *kref)
  84 {
  85         struct uts_namespace *ns;
  86
  87         ns = container_of(kref, struct uts_namespace, kref);
  88         put_user_ns(ns->user_ns);
  89         ns_free_inum(&ns->ns);
  90         kfree(ns);
  91 }
  92
  93 static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
  94 {
  95         return container_of(ns, struct uts_namespace, ns);
  96 }
  97
  98 static struct ns_common *utsns_get(struct task_struct *task)
  99 {
 100         struct uts_namespace *ns = NULL;
 101         struct nsproxy *nsproxy;
 102
 103         task_lock(task);
 104         nsproxy = task->nsproxy;
 105         if (nsproxy) {
 106                 ns = nsproxy->uts_ns;
 107                 get_uts_ns(ns);
 108         }
 109         task_unlock(task);
 110
 111         return ns ? &ns->ns : NULL;
 112 }
 113
 114 static void utsns_put(struct ns_common *ns)
 115 {
 116         put_uts_ns(to_uts_ns(ns));
 117 }
 118
 119 static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
 120 {
 121         struct uts_namespace *ns = to_uts_ns(new);
 122
 123         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 124             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 125                 return -EPERM;
 126
 127         get_uts_ns(ns);
 128         put_uts_ns(nsproxy->uts_ns);
 129         nsproxy->uts_ns = ns;
 130         return 0;
 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 };