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/cred.h>
  18 #include <linux/user_namespace.h>
  19 #include <linux/proc_ns.h>
  20 #include <linux/sched/task.h>
  21
  22 static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
  23 {
  24         return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
  25 }
  26
  27 static void dec_uts_namespaces(struct ucounts *ucounts)
  28 {
  29         dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
  30 }
  31
  32 static struct uts_namespace *create_uts_ns(void)
  33 {
  34         struct uts_namespace *uts_ns;
  35
  36         uts_ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
  37         if (uts_ns)
  38                 kref_init(&uts_ns->kref);
  39         return uts_ns;
  40 }
  41
  42 /*
  43  * Clone a new ns copying an original utsname, setting refcount to 1
  44  * @old_ns: namespace to clone
  45  * Return ERR_PTR(-ENOMEM) on error (failure to kmalloc), new ns otherwise
  46  */
  47 static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
  48                                           struct uts_namespace *old_ns)
  49 {
  50         struct uts_namespace *ns;
  51         struct ucounts *ucounts;
  52         int err;
  53
  54         err = -ENOSPC;
  55         ucounts = inc_uts_namespaces(user_ns);
  56         if (!ucounts)
  57                 goto fail;
  58
  59         err = -ENOMEM;
  60         ns = create_uts_ns();
  61         if (!ns)
  62                 goto fail_dec;
  63
  64         err = ns_alloc_inum(&ns->ns);
  65         if (err)
  66                 goto fail_free;
  67
  68         ns->ucounts = ucounts;
  69         ns->ns.ops = &utsns_operations;
  70
  71         down_read(&uts_sem);
  72         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  73         ns->user_ns = get_user_ns(user_ns);
  74         up_read(&uts_sem);
  75         return ns;
  76
  77 fail_free:
  78         kfree(ns);
  79 fail_dec:
  80         dec_uts_namespaces(ucounts);
  81 fail:
  82         return ERR_PTR(err);
  83 }
  84
  85 /*
  86  * Copy task tsk's utsname namespace, or clone it if flags
  87  * specifies CLONE_NEWUTS.  In latter case, changes to the
  88  * utsname of this process won't be seen by parent, and vice
  89  * versa.
  90  */
  91 struct uts_namespace *copy_utsname(unsigned long flags,
  92         struct user_namespace *user_ns, struct uts_namespace *old_ns)
  93 {
  94         struct uts_namespace *new_ns;
  95
  96         BUG_ON(!old_ns);
  97         get_uts_ns(old_ns);
  98
  99         if (!(flags & CLONE_NEWUTS))
 100                 return old_ns;
 101
 102         new_ns = clone_uts_ns(user_ns, old_ns);
 103
 104         put_uts_ns(old_ns);
 105         return new_ns;
 106 }
 107
 108 void free_uts_ns(struct kref *kref)
 109 {
 110         struct uts_namespace *ns;
 111
 112         ns = container_of(kref, struct uts_namespace, kref);
 113         dec_uts_namespaces(ns->ucounts);
 114         put_user_ns(ns->user_ns);
 115         ns_free_inum(&ns->ns);
 116         kfree(ns);
 117 }
 118
 119 static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
 120 {
 121         return container_of(ns, struct uts_namespace, ns);
 122 }
 123
 124 static struct ns_common *utsns_get(struct task_struct *task)
 125 {
 126         struct uts_namespace *ns = NULL;
 127         struct nsproxy *nsproxy;
 128
 129         task_lock(task);
 130         nsproxy = task->nsproxy;
 131         if (nsproxy) {
 132                 ns = nsproxy->uts_ns;
 133                 get_uts_ns(ns);
 134         }
 135         task_unlock(task);
 136
 137         return ns ? &ns->ns : NULL;
 138 }
 139
 140 static void utsns_put(struct ns_common *ns)
 141 {
 142         put_uts_ns(to_uts_ns(ns));
 143 }
 144
 145 static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
 146 {
 147         struct uts_namespace *ns = to_uts_ns(new);
 148
 149         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 150             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 151                 return -EPERM;
 152
 153         get_uts_ns(ns);
 154         put_uts_ns(nsproxy->uts_ns);
 155         nsproxy->uts_ns = ns;
 156         return 0;
 157 }
 158
 159 static struct user_namespace *utsns_owner(struct ns_common *ns)
 160 {
 161         return to_uts_ns(ns)->user_ns;
 162 }
 163
 164 const struct proc_ns_operations utsns_operations = {
 165         .name           = "uts",
 166         .type           = CLONE_NEWUTS,
 167         .get            = utsns_get,
 168         .put            = utsns_put,
 169         .install        = utsns_install,
 170         .owner          = utsns_owner,
 171 };