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                kref_init(&uts_ns->kref);
  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 kref *kref)
 107{
 108        struct uts_namespace *ns;
 109
 110        ns = container_of(kref, struct uts_namespace, kref);
 111        dec_uts_namespaces(ns->ucounts);
 112        put_user_ns(ns->user_ns);
 113        ns_free_inum(&ns->ns);
 114        kmem_cache_free(uts_ns_cache, ns);
 115}
 116
 117static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)
 118{
 119        return container_of(ns, struct uts_namespace, ns);
 120}
 121
 122static struct ns_common *utsns_get(struct task_struct *task)
 123{
 124        struct uts_namespace *ns = NULL;
 125        struct nsproxy *nsproxy;
 126
 127        task_lock(task);
 128        nsproxy = task->nsproxy;
 129        if (nsproxy) {
 130                ns = nsproxy->uts_ns;
 131                get_uts_ns(ns);
 132        }
 133        task_unlock(task);
 134
 135        return ns ? &ns->ns : NULL;
 136}
 137
 138static void utsns_put(struct ns_common *ns)
 139{
 140        put_uts_ns(to_uts_ns(ns));
 141}
 142
 143static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new)
 144{
 145        struct uts_namespace *ns = to_uts_ns(new);
 146
 147        if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
 148            !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 149                return -EPERM;
 150
 151        get_uts_ns(ns);
 152        put_uts_ns(nsproxy->uts_ns);
 153        nsproxy->uts_ns = ns;
 154        return 0;
 155}
 156
 157static struct user_namespace *utsns_owner(struct ns_common *ns)
 158{
 159        return to_uts_ns(ns)->user_ns;
 160}
 161
 162const struct proc_ns_operations utsns_operations = {
 163        .name           = "uts",
 164        .type           = CLONE_NEWUTS,
 165        .get            = utsns_get,
 166        .put            = utsns_put,
 167        .install        = utsns_install,
 168        .owner          = utsns_owner,
 169};
 170
 171void __init uts_ns_init(void)
 172{
 173        uts_ns_cache = kmem_cache_create_usercopy(
 174                        "uts_namespace", sizeof(struct uts_namespace), 0,
 175                        SLAB_PANIC|SLAB_ACCOUNT,
 176                        offsetof(struct uts_namespace, name),
 177                        sizeof_field(struct uts_namespace, name),
 178                        NULL);
 179}
 180