/* * Copyright (C) 2004 IBM Corporation * * Author: Serge Hallyn <serue@us.ibm.com> * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation, version 2 of the * License. */ #include <linux/export.h> #include <linux/uts.h> #include <linux/utsname.h> #include <linux/err.h> #include <linux/slab.h> #include <linux/cred.h> #include <linux/user_namespace.h> #include <linux/proc_ns.h> #include <linux/sched/task.h> static struct kmem_cache *uts_ns_cache __ro_after_init; static struct ucounts *inc_uts_namespaces(struct user_namespace *ns) { return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES); } static void dec_uts_namespaces(struct ucounts *ucounts) { dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES); } static struct uts_namespace *create_uts_ns(void) { struct uts_namespace *uts_ns; uts_ns = kmem_cache_alloc(uts_ns_cache, GFP_KERNEL); if (uts_ns) kref_init(&uts_ns->kref); return uts_ns; } /* * Clone a new ns copying an original utsname, setting refcount to 1 * @old_ns: namespace to clone * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise */ static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns, struct uts_namespace *old_ns) { struct uts_namespace *ns; struct ucounts *ucounts; int err; err = -ENOSPC; ucounts = inc_uts_namespaces(user_ns); if (!ucounts) goto fail; err = -ENOMEM; ns = create_uts_ns(); if (!ns) goto fail_dec; err = ns_alloc_inum(&ns->ns); if (err) goto fail_free; ns->ucounts = ucounts; ns->ns.ops = &utsns_operations; down_read(&uts_sem); memcpy(&ns->name, &old_ns->name, sizeof(ns->name)); ns->user_ns = get_user_ns(user_ns); up_read(&uts_sem); return ns; fail_free: kmem_cache_free(uts_ns_cache, ns); fail_dec: dec_uts_namespaces(ucounts); fail: return ERR_PTR(err); } /* * Copy task tsk's utsname namespace, or clone it if flags * specifies CLONE_NEWUTS. In latter case, changes to the * utsname of this process won't be seen by parent, and vice * versa. */ struct uts_namespace *copy_utsname(unsigned long flags, struct user_namespace *user_ns, struct uts_namespace *old_ns) { struct uts_namespace *new_ns; BUG_ON(!old_ns); get_uts_ns(old_ns); if (!(flags & CLONE_NEWUTS)) return old_ns; new_ns = clone_uts_ns(user_ns, old_ns); put_uts_ns(old_ns); return new_ns; } void free_uts_ns(struct kref *kref) { struct uts_namespace *ns; ns = container_of(kref, struct uts_namespace, kref); dec_uts_namespaces(ns->ucounts); put_user_ns(ns->user_ns); ns_free_inum(&ns->ns); kmem_cache_free(uts_ns_cache, ns); } static inline struct uts_namespace *to_uts_ns(struct ns_common *ns) { return container_of(ns, struct uts_namespace, ns); } static struct ns_common *utsns_get(struct task_struct *task) { struct uts_namespace *ns = NULL; struct nsproxy *nsproxy; task_lock(task); nsproxy = task->nsproxy; if (nsproxy) { ns = nsproxy->uts_ns; get_uts_ns(ns); } task_unlock(task); return ns ? &ns->ns : NULL; } static void utsns_put(struct ns_common *ns) { put_uts_ns(to_uts_ns(ns)); } static int utsns_install(struct nsproxy *nsproxy, struct ns_common *new) { struct uts_namespace *ns = to_uts_ns(new); if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) || !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) return -EPERM; get_uts_ns(ns); put_uts_ns(nsproxy->uts_ns); nsproxy->uts_ns = ns; return 0; } static struct user_namespace *utsns_owner(struct ns_common *ns) { return to_uts_ns(ns)->user_ns; } const struct proc_ns_operations utsns_operations = { .name = "uts", .type = CLONE_NEWUTS, .get = utsns_get, .put = utsns_put, .install = utsns_install, .owner = utsns_owner, }; void __init uts_ns_init(void) { uts_ns_cache = kmem_cache_create_usercopy( "uts_namespace", sizeof(struct uts_namespace), 0, SLAB_PANIC|SLAB_ACCOUNT, offsetof(struct uts_namespace, name), sizeof_field(struct uts_namespace, name), NULL); }