| 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 | |
| 18 | static struct kmem_cache *uts_ns_cache __ro_after_init; |
| 19 | |
| 20 | static struct ucounts *inc_uts_namespaces(struct user_namespace *ns) |
| 21 | { |
| 22 | return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES); |
| 23 | } |
| 24 | |
| 25 | static void dec_uts_namespaces(struct ucounts *ucounts) |
| 26 | { |
| 27 | dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES); |
| 28 | } |
| 29 | |
| 30 | static 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 | */ |
| 45 | static 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 | |
| 75 | fail_free: |
| 76 | kmem_cache_free(uts_ns_cache, ns); |
| 77 | fail_dec: |
| 78 | dec_uts_namespaces(ucounts); |
| 79 | fail: |
| 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 | */ |
| 89 | struct 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 | |
| 106 | void 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 | |
| 114 | static inline struct uts_namespace *to_uts_ns(struct ns_common *ns) |
| 115 | { |
| 116 | return container_of(ns, struct uts_namespace, ns); |
| 117 | } |
| 118 | |
| 119 | static 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 | |
| 135 | static void utsns_put(struct ns_common *ns) |
| 136 | { |
| 137 | put_uts_ns(to_uts_ns(ns)); |
| 138 | } |
| 139 | |
| 140 | static 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 | |
| 155 | static struct user_namespace *utsns_owner(struct ns_common *ns) |
| 156 | { |
| 157 | return to_uts_ns(ns)->user_ns; |
| 158 | } |
| 159 | |
| 160 | const 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 | |
| 169 | void __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 | } |