LXR linux/kernel/utsname.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  Copyright (C) 2004 IBM Corporation
   4 *
   5 *  Author: Serge Hallyn <serue@us.ibm.com>
   6 */
   7
   8#include <linux/export.h>
   9#include <linux/uts.h>
  10#include <linux/utsname.h>
  11#include <linux/err.h>
  12#include <linux/slab.h>
  13#include <linux/cred.h>
  14#include <linux/user_namespace.h>
  15#include <linux/proc_ns.h>
  16#include <linux/sched/task.h>
  17
  18static struct kmem_cache *uts_ns_cache __ro_after_init;
  19
  20static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
  21{
  22        return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
  23}
  24
  25static void dec_uts_namespaces(struct ucounts *ucounts)
  26{
  27        dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
  28}
  29
  30static struct uts_namespace *create_uts_ns(void)
  31{
  32        struct uts_namespace *uts_ns;
  33
  34        uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL);
  35        if (uts_ns)
  36                refcount_set(&uts_ns->ns.count, 1);
  37        return uts_ns;
  38}
  39
  40/*
  41 * Clone a new ns copying an original utsname, setting refcount to 1
  42 * @old_ns: namespace to clone
  43 * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise
  44 */
  45static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
  46                                          struct uts_namespace *old_ns)
  47{
  48        struct uts_namespace *ns;
  49        struct ucounts *ucounts;
  50        int err;
  51
  52        err = -ENOSPC;
  53        ucounts = inc_uts_namespaces(user_ns);
  54        if (!ucounts)
  55                goto fail;
  56
  57        err = -ENOMEM;
  58        ns = create_uts_ns();
  59        if (!ns)
  60                goto fail_dec;
  61
  62        err = ns_alloc_inum(&ns->ns);
  63        if (err)
  64                goto fail_free;
  65
  66        ns->ucounts = ucounts;
  67        ns->ns.ops = &utsns_operations;
  68
  69        down_read(&uts_sem);
  70        memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
  71        ns->user_ns = get_user_ns(user_ns);
  72        up_read(&uts_sem);
  73        return ns;
  74
  75fail_free:
  76        kmem_cache_free(uts_ns_cache, ns);
  77fail_dec:
  78        dec_uts_namespaces(ucounts);
  79fail:
  80        return ERR_PTR(err);
  81}
  82
  83/*
  84 * Copy task tsk's utsname namespace, or clone it if flags
  85 * specifies CLONE_NEWUTS.  In latter case, changes to the
  86 * utsname of this process won't be seen by parent, and vice
  87 * versa.
  88 */
  89struct uts_namespace *copy_utsname(unsigned long flags,
  90        struct user_namespace *user_ns, struct uts_namespace *old_ns)
  91{
  92        struct uts_namespace *new_ns;
  93
  94        BUG_ON(!old_ns);
  95        get_uts_ns(old_ns);
  96
  97        if (!(flags & CLONE_NEWUTS))
  98                return old_ns;
  99
 100        new_ns = clone_uts_ns(user_ns, old_ns);
 101
 102        put_uts_ns(old_ns);
 103        return new_ns;
 104}
 105
 106void free_uts_ns(struct uts_namespace *ns)
 107{
 108        dec_uts_namespaces(ns->ucounts);
 109        put_user_ns(ns->user_ns);
 110        ns_free_inum(&ns->ns);
 111        kmem_cache_free(uts_ns_cache, ns);
 112}
 113
 114static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
 115{
 116        return container_of(ns, struct uts_namespace, ns);
 117}
 118
 119static struct ns_common *utsns_get(struct task_struct *task)
 120{
 121        struct uts_namespace *ns = NULL;
 122        struct nsproxy *nsproxy;
 123
 124        task_lock(task);
 125        nsproxy = task->nsproxy;
 126        if (nsproxy) {
 127                ns = nsproxy->uts_ns;
 128                get_uts_ns(ns);
 129        }
 130        task_unlock(task);
 131
 132        return ns ? &ns->ns : NULL;
 133}
 134
 135static void utsns_put(struct ns_common *ns)
 136{
 137        put_uts_ns(to_uts_ns(ns));
 138}
 139
 140static int utsns_install(struct nsset *nsset, struct ns_common *new)
 141{
 142        struct nsproxy *nsproxy = nsset->nsproxy;
 143        struct uts_namespace *ns = to_uts_ns(new);
 144
 145        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 146            !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
 147                return -EPERM;
 148
 149        get_uts_ns(ns);
 150        put_uts_ns(nsproxy->uts_ns);
 151        nsproxy->uts_ns = ns;
 152        return 0;
 153}
 154
 155static struct user_namespace *utsns_owner(struct ns_common *ns)
 156{
 157        return to_uts_ns(ns)->user_ns;
 158}
 159
 160const struct proc_ns_operations utsns_operations = {
 161        .name           = "uts",
 162        .type           = CLONE_NEWUTS,
 163        .get            = utsns_get,
 164        .put            = utsns_put,
 165        .install        = utsns_install,
 166        .owner          = utsns_owner,
 167};
 168
 169void __init uts_ns_init(void)
 170{
 171        uts_ns_cache = kmem_cache_create_usercopy(
 172                        "uts_namespace", sizeof(struct uts_namespace), 0,
 173                        SLAB_PANIC|SLAB_ACCOUNT,
 174                        offsetof(struct uts_namespace, name),
 175                        sizeof_field(struct uts_namespace, name),
 176                        NULL);
 177}
 178