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(), type: UCOUNT_UTS_NAMESPACES); |
23 | } |
24 | |
25 | static void dec_uts_namespaces(struct ucounts *ucounts) |
26 | { |
27 | dec_ucount(ucounts, type: 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(cachep: uts_ns_cache, GFP_KERNEL); |
35 | if (uts_ns) |
36 | refcount_set(r: &uts_ns->ns.count, n: 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(ns: 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->ns); |
63 | if (err) |
64 | goto fail_free; |
65 | |
66 | ns->ucounts = ucounts; |
67 | ns->ns.ops = &utsns_operations; |
68 | |
69 | down_read(sem: &uts_sem); |
70 | memcpy(&ns->name, &old_ns->name, sizeof(ns->name)); |
71 | ns->user_ns = get_user_ns(ns: user_ns); |
72 | up_read(sem: &uts_sem); |
73 | return ns; |
74 | |
75 | fail_free: |
76 | kmem_cache_free(s: uts_ns_cache, objp: ns); |
77 | fail_dec: |
78 | dec_uts_namespaces(ucounts); |
79 | fail: |
80 | return ERR_PTR(error: 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(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(ns: old_ns); |
103 | return new_ns; |
104 | } |
105 | |
106 | void free_uts_ns(struct uts_namespace *ns) |
107 | { |
108 | dec_uts_namespaces(ucounts: ns->ucounts); |
109 | put_user_ns(ns: ns->user_ns); |
110 | ns_free_inum(&ns->ns); |
111 | kmem_cache_free(s: uts_ns_cache, objp: 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(p: task); |
125 | nsproxy = task->nsproxy; |
126 | if (nsproxy) { |
127 | ns = nsproxy->uts_ns; |
128 | get_uts_ns(ns); |
129 | } |
130 | task_unlock(p: task); |
131 | |
132 | return ns ? &ns->ns : NULL; |
133 | } |
134 | |
135 | static void utsns_put(struct ns_common *ns) |
136 | { |
137 | put_uts_ns(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(ns: new); |
144 | |
145 | if (!ns_capable(ns: ns->user_ns, CAP_SYS_ADMIN) || |
146 | !ns_capable(ns: nsset->cred->user_ns, CAP_SYS_ADMIN)) |
147 | return -EPERM; |
148 | |
149 | get_uts_ns(ns); |
150 | put_uts_ns(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 | name: "uts_namespace" , size: sizeof(struct uts_namespace), align: 0, |
173 | SLAB_PANIC|SLAB_ACCOUNT, |
174 | offsetof(struct uts_namespace, name), |
175 | sizeof_field(struct uts_namespace, name), |
176 | NULL); |
177 | } |
178 | |