1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * linux/ipc/namespace.c |
4 | * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc. |
5 | */ |
6 | |
7 | #include <linux/ipc.h> |
8 | #include <linux/msg.h> |
9 | #include <linux/ipc_namespace.h> |
10 | #include <linux/rcupdate.h> |
11 | #include <linux/nsproxy.h> |
12 | #include <linux/slab.h> |
13 | #include <linux/cred.h> |
14 | #include <linux/fs.h> |
15 | #include <linux/mount.h> |
16 | #include <linux/user_namespace.h> |
17 | #include <linux/proc_ns.h> |
18 | #include <linux/sched/task.h> |
19 | |
20 | #include "util.h" |
21 | |
22 | /* |
23 | * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount. |
24 | */ |
25 | static void free_ipc(struct work_struct *unused); |
26 | static DECLARE_WORK(free_ipc_work, free_ipc); |
27 | |
28 | static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns) |
29 | { |
30 | return inc_ucount(ns, current_euid(), type: UCOUNT_IPC_NAMESPACES); |
31 | } |
32 | |
33 | static void dec_ipc_namespaces(struct ucounts *ucounts) |
34 | { |
35 | dec_ucount(ucounts, type: UCOUNT_IPC_NAMESPACES); |
36 | } |
37 | |
38 | static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns, |
39 | struct ipc_namespace *old_ns) |
40 | { |
41 | struct ipc_namespace *ns; |
42 | struct ucounts *ucounts; |
43 | int err; |
44 | |
45 | err = -ENOSPC; |
46 | again: |
47 | ucounts = inc_ipc_namespaces(ns: user_ns); |
48 | if (!ucounts) { |
49 | /* |
50 | * IPC namespaces are freed asynchronously, by free_ipc_work. |
51 | * If frees were pending, flush_work will wait, and |
52 | * return true. Fail the allocation if no frees are pending. |
53 | */ |
54 | if (flush_work(work: &free_ipc_work)) |
55 | goto again; |
56 | goto fail; |
57 | } |
58 | |
59 | err = -ENOMEM; |
60 | ns = kzalloc(size: sizeof(struct ipc_namespace), GFP_KERNEL_ACCOUNT); |
61 | if (ns == NULL) |
62 | goto fail_dec; |
63 | |
64 | err = ns_alloc_inum(ns: &ns->ns); |
65 | if (err) |
66 | goto fail_free; |
67 | ns->ns.ops = &ipcns_operations; |
68 | |
69 | refcount_set(r: &ns->ns.count, n: 1); |
70 | ns->user_ns = get_user_ns(ns: user_ns); |
71 | ns->ucounts = ucounts; |
72 | |
73 | err = mq_init_ns(ns); |
74 | if (err) |
75 | goto fail_put; |
76 | |
77 | err = -ENOMEM; |
78 | if (!setup_mq_sysctls(ns)) |
79 | goto fail_put; |
80 | |
81 | if (!setup_ipc_sysctls(ns)) |
82 | goto fail_mq; |
83 | |
84 | err = msg_init_ns(ns); |
85 | if (err) |
86 | goto fail_put; |
87 | |
88 | sem_init_ns(ns); |
89 | shm_init_ns(ns); |
90 | |
91 | return ns; |
92 | |
93 | fail_mq: |
94 | retire_mq_sysctls(ns); |
95 | |
96 | fail_put: |
97 | put_user_ns(ns: ns->user_ns); |
98 | ns_free_inum(&ns->ns); |
99 | fail_free: |
100 | kfree(objp: ns); |
101 | fail_dec: |
102 | dec_ipc_namespaces(ucounts); |
103 | fail: |
104 | return ERR_PTR(error: err); |
105 | } |
106 | |
107 | struct ipc_namespace *copy_ipcs(unsigned long flags, |
108 | struct user_namespace *user_ns, struct ipc_namespace *ns) |
109 | { |
110 | if (!(flags & CLONE_NEWIPC)) |
111 | return get_ipc_ns(ns); |
112 | return create_ipc_ns(user_ns, old_ns: ns); |
113 | } |
114 | |
115 | /* |
116 | * free_ipcs - free all ipcs of one type |
117 | * @ns: the namespace to remove the ipcs from |
118 | * @ids: the table of ipcs to free |
119 | * @free: the function called to free each individual ipc |
120 | * |
121 | * Called for each kind of ipc when an ipc_namespace exits. |
122 | */ |
123 | void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, |
124 | void (*free)(struct ipc_namespace *, struct kern_ipc_perm *)) |
125 | { |
126 | struct kern_ipc_perm *perm; |
127 | int next_id; |
128 | int total, in_use; |
129 | |
130 | down_write(sem: &ids->rwsem); |
131 | |
132 | in_use = ids->in_use; |
133 | |
134 | for (total = 0, next_id = 0; total < in_use; next_id++) { |
135 | perm = idr_find(&ids->ipcs_idr, id: next_id); |
136 | if (perm == NULL) |
137 | continue; |
138 | rcu_read_lock(); |
139 | ipc_lock_object(perm); |
140 | free(ns, perm); |
141 | total++; |
142 | } |
143 | up_write(sem: &ids->rwsem); |
144 | } |
145 | |
146 | static void free_ipc_ns(struct ipc_namespace *ns) |
147 | { |
148 | /* |
149 | * Caller needs to wait for an RCU grace period to have passed |
150 | * after making the mount point inaccessible to new accesses. |
151 | */ |
152 | mntput(mnt: ns->mq_mnt); |
153 | sem_exit_ns(ns); |
154 | msg_exit_ns(ns); |
155 | shm_exit_ns(ns); |
156 | |
157 | retire_mq_sysctls(ns); |
158 | retire_ipc_sysctls(ns); |
159 | |
160 | dec_ipc_namespaces(ucounts: ns->ucounts); |
161 | put_user_ns(ns: ns->user_ns); |
162 | ns_free_inum(&ns->ns); |
163 | kfree(objp: ns); |
164 | } |
165 | |
166 | static LLIST_HEAD(free_ipc_list); |
167 | static void free_ipc(struct work_struct *unused) |
168 | { |
169 | struct llist_node *node = llist_del_all(head: &free_ipc_list); |
170 | struct ipc_namespace *n, *t; |
171 | |
172 | llist_for_each_entry_safe(n, t, node, mnt_llist) |
173 | mnt_make_shortterm(mnt: n->mq_mnt); |
174 | |
175 | /* Wait for any last users to have gone away. */ |
176 | synchronize_rcu(); |
177 | |
178 | llist_for_each_entry_safe(n, t, node, mnt_llist) |
179 | free_ipc_ns(ns: n); |
180 | } |
181 | |
182 | /* |
183 | * put_ipc_ns - drop a reference to an ipc namespace. |
184 | * @ns: the namespace to put |
185 | * |
186 | * If this is the last task in the namespace exiting, and |
187 | * it is dropping the refcount to 0, then it can race with |
188 | * a task in another ipc namespace but in a mounts namespace |
189 | * which has this ipcns's mqueuefs mounted, doing some action |
190 | * with one of the mqueuefs files. That can raise the refcount. |
191 | * So dropping the refcount, and raising the refcount when |
192 | * accessing it through the VFS, are protected with mq_lock. |
193 | * |
194 | * (Clearly, a task raising the refcount on its own ipc_ns |
195 | * needn't take mq_lock since it can't race with the last task |
196 | * in the ipcns exiting). |
197 | */ |
198 | void put_ipc_ns(struct ipc_namespace *ns) |
199 | { |
200 | if (refcount_dec_and_lock(r: &ns->ns.count, lock: &mq_lock)) { |
201 | mq_clear_sbinfo(ns); |
202 | spin_unlock(lock: &mq_lock); |
203 | |
204 | if (llist_add(new: &ns->mnt_llist, head: &free_ipc_list)) |
205 | schedule_work(work: &free_ipc_work); |
206 | } |
207 | } |
208 | |
209 | static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns) |
210 | { |
211 | return container_of(ns, struct ipc_namespace, ns); |
212 | } |
213 | |
214 | static struct ns_common *ipcns_get(struct task_struct *task) |
215 | { |
216 | struct ipc_namespace *ns = NULL; |
217 | struct nsproxy *nsproxy; |
218 | |
219 | task_lock(p: task); |
220 | nsproxy = task->nsproxy; |
221 | if (nsproxy) |
222 | ns = get_ipc_ns(ns: nsproxy->ipc_ns); |
223 | task_unlock(p: task); |
224 | |
225 | return ns ? &ns->ns : NULL; |
226 | } |
227 | |
228 | static void ipcns_put(struct ns_common *ns) |
229 | { |
230 | return put_ipc_ns(ns: to_ipc_ns(ns)); |
231 | } |
232 | |
233 | static int ipcns_install(struct nsset *nsset, struct ns_common *new) |
234 | { |
235 | struct nsproxy *nsproxy = nsset->nsproxy; |
236 | struct ipc_namespace *ns = to_ipc_ns(ns: new); |
237 | if (!ns_capable(ns: ns->user_ns, CAP_SYS_ADMIN) || |
238 | !ns_capable(ns: nsset->cred->user_ns, CAP_SYS_ADMIN)) |
239 | return -EPERM; |
240 | |
241 | put_ipc_ns(ns: nsproxy->ipc_ns); |
242 | nsproxy->ipc_ns = get_ipc_ns(ns); |
243 | return 0; |
244 | } |
245 | |
246 | static struct user_namespace *ipcns_owner(struct ns_common *ns) |
247 | { |
248 | return to_ipc_ns(ns)->user_ns; |
249 | } |
250 | |
251 | const struct proc_ns_operations ipcns_operations = { |
252 | .name = "ipc" , |
253 | .type = CLONE_NEWIPC, |
254 | .get = ipcns_get, |
255 | .put = ipcns_put, |
256 | .install = ipcns_install, |
257 | .owner = ipcns_owner, |
258 | }; |
259 | |