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 kmem_cache *uts_ns_cache __ro_after_init;
  23
  24 static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
  25 {
  26         return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
  27 }
  28
  29 static void dec_uts_namespaces(struct ucounts *ucounts)
  30 {
  31         dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
  32 }
  33
  34 static struct uts_namespace *create_uts_ns(void)
  35 {
  36         struct uts_namespace *uts_ns;
  37
  38         uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL);
  39         if (uts_ns)
  40                 kref_init(&uts_ns->kref);
  41         return uts_ns;
  42 }
  43
  44 /*
  45  * Clone a new ns copying an original utsname, setting refcount to 1
  46  * @old_ns: namespace to clone
  47  * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise
  48  */
  49 static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
  50                                           struct uts_namespace *old_ns)
  51 {
  52         struct uts_namespace *ns;
  53         struct ucounts *ucounts;
  54         int err;
  55
  56         err = -ENOSPC;
  57         ucounts = inc_uts_namespaces(user_ns);
  58         if (!ucounts)
  59                 goto fail;
  60
  61         err = -ENOMEM;
  62         ns = create_uts_ns();
  63         if (!ns)
  64                 goto fail_dec;
  65
  66         err = ns_alloc_inum(&ns->ns);
  67         if (err)
  68                 goto fail_free;
  69
  70         ns->ucounts = ucounts;
  71         ns->ns.ops = &utsns_operations;
  72
  73         down_read(&uts_sem);
  74         memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  75         ns->user_ns = get_user_ns(user_ns);
  76         up_read(&uts_sem);
  77         return ns;
  78
  79 fail_free:
  80         kmem_cache_free(uts_ns_cache, ns);
  81 fail_dec:
  82         dec_uts_namespaces(ucounts);
  83 fail:
  84         return ERR_PTR(err);
  85 }
  86
  87 /*
  88  * Copy task tsk's utsname namespace, or clone it if flags
  89  * specifies CLONE_NEWUTS.  In latter case, changes to the
  90  * utsname of this process won't be seen by parent, and vice
  91  * versa.
  92  */
  93 struct uts_namespace *copy_utsname(unsigned long flags,
  94         struct user_namespace *user_ns, struct uts_namespace *old_ns)
  95 {
  96         struct uts_namespace *new_ns;
  97
  98         BUG_ON(!old_ns);
  99         get_uts_ns(old_ns);
 100
 101         if (!(flags & CLONE_NEWUTS))
 102                 return old_ns;
 103
 104         new_ns = clone_uts_ns(user_ns, old_ns);
 105
 106         put_uts_ns(old_ns);
 107         return new_ns;
 108 }
 109
 110 void free_uts_ns(struct kref *kref)
 111 {
 112         struct uts_namespace *ns;
 113
 114         ns = container_of(kref, struct uts_namespace, kref);
 115         dec_uts_namespaces(ns->ucounts);
 116         put_user_ns(ns->user_ns);
 117         ns_free_inum(&ns->ns);
 118         kmem_cache_free(uts_ns_cache, ns);
 119 }
 120
 121 static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
 122 {
 123         return container_of(ns, struct uts_namespace, ns);
 124 }
 125
 126 static struct ns_common *utsns_get(struct task_struct *task)
 127 {
 128         struct uts_namespace *ns = NULL;
 129         struct nsproxy *nsproxy;
 130
 131         task_lock(task);
 132         nsproxy = task->nsproxy;
 133         if (nsproxy) {
 134                 ns = nsproxy->uts_ns;
 135                 get_uts_ns(ns);
 136         }
 137         task_unlock(task);
 138
 139         return ns ? &ns->ns : NULL;
 140 }
 141
 142 static void utsns_put(struct ns_common *ns)
 143 {
 144         put_uts_ns(to_uts_ns(ns));
 145 }
 146
 147 static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
 148 {
 149         struct uts_namespace *ns = to_uts_ns(new);
 150
 151         if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 152             !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 153                 return -EPERM;
 154
 155         get_uts_ns(ns);
 156         put_uts_ns(nsproxy->uts_ns);
 157         nsproxy->uts_ns = ns;
 158         return 0;
 159 }
 160
 161 static struct user_namespace *utsns_owner(struct ns_common *ns)
 162 {
 163         return to_uts_ns(ns)->user_ns;
 164 }
 165
 166 const struct proc_ns_operations utsns_operations = {
 167         .name           = "uts",
 168         .type           = CLONE_NEWUTS,
 169         .get            = utsns_get,
 170         .put            = utsns_put,
 171         .install        = utsns_install,
 172         .owner          = utsns_owner,
 173 };
 174
 175 void __init uts_ns_init(void)
 176 {
 177         uts_ns_cache = kmem_cache_create_usercopy(
 178                         "uts_namespace", sizeof(struct uts_namespace), 0,
 179                         SLAB_PANIC|SLAB_ACCOUNT,
 180                         offsetof(struct uts_namespace, name),
 181                         sizeof_field(struct uts_namespace, name),
 182                         NULL);
 183 }