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
inc_ipc_namespaces(struct user_namespace * ns)22 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
23 {
24 return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
25 }
26
dec_ipc_namespaces(struct ucounts * ucounts)27 static void dec_ipc_namespaces(struct ucounts *ucounts)
28 {
29 dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
30 }
31
create_ipc_ns(struct user_namespace * user_ns,struct ipc_namespace * old_ns)32 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
33 struct ipc_namespace *old_ns)
34 {
35 struct ipc_namespace *ns;
36 struct ucounts *ucounts;
37 int err;
38
39 err = -ENOSPC;
40 ucounts = inc_ipc_namespaces(user_ns);
41 if (!ucounts)
42 goto fail;
43
44 err = -ENOMEM;
45 ns = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL_ACCOUNT);
46 if (ns == NULL)
47 goto fail_dec;
48
49 err = ns_alloc_inum(&ns->ns);
50 if (err)
51 goto fail_free;
52 ns->ns.ops = &ipcns_operations;
53
54 refcount_set(&ns->ns.count, 1);
55 ns->user_ns = get_user_ns(user_ns);
56 ns->ucounts = ucounts;
57
58 err = mq_init_ns(ns);
59 if (err)
60 goto fail_put;
61
62 err = -ENOMEM;
63 if (!setup_mq_sysctls(ns))
64 goto fail_put;
65
66 if (!setup_ipc_sysctls(ns))
67 goto fail_mq;
68
69 err = msg_init_ns(ns);
70 if (err)
71 goto fail_put;
72
73 sem_init_ns(ns);
74 shm_init_ns(ns);
75
76 return ns;
77
78 fail_mq:
79 retire_mq_sysctls(ns);
80
81 fail_put:
82 put_user_ns(ns->user_ns);
83 ns_free_inum(&ns->ns);
84 fail_free:
85 kfree(ns);
86 fail_dec:
87 dec_ipc_namespaces(ucounts);
88 fail:
89 return ERR_PTR(err);
90 }
91
copy_ipcs(unsigned long flags,struct user_namespace * user_ns,struct ipc_namespace * ns)92 struct ipc_namespace *copy_ipcs(unsigned long flags,
93 struct user_namespace *user_ns, struct ipc_namespace *ns)
94 {
95 if (!(flags & CLONE_NEWIPC))
96 return get_ipc_ns(ns);
97 return create_ipc_ns(user_ns, ns);
98 }
99
100 /*
101 * free_ipcs - free all ipcs of one type
102 * @ns: the namespace to remove the ipcs from
103 * @ids: the table of ipcs to free
104 * @free: the function called to free each individual ipc
105 *
106 * Called for each kind of ipc when an ipc_namespace exits.
107 */
free_ipcs(struct ipc_namespace * ns,struct ipc_ids * ids,void (* free)(struct ipc_namespace *,struct kern_ipc_perm *))108 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
109 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
110 {
111 struct kern_ipc_perm *perm;
112 int next_id;
113 int total, in_use;
114
115 down_write(&ids->rwsem);
116
117 in_use = ids->in_use;
118
119 for (total = 0, next_id = 0; total < in_use; next_id++) {
120 perm = idr_find(&ids->ipcs_idr, next_id);
121 if (perm == NULL)
122 continue;
123 rcu_read_lock();
124 ipc_lock_object(perm);
125 free(ns, perm);
126 total++;
127 }
128 up_write(&ids->rwsem);
129 }
130
free_ipc_ns(struct ipc_namespace * ns)131 static void free_ipc_ns(struct ipc_namespace *ns)
132 {
133 /* mq_put_mnt() waits for a grace period as kern_unmount()
134 * uses synchronize_rcu().
135 */
136 mq_put_mnt(ns);
137 sem_exit_ns(ns);
138 msg_exit_ns(ns);
139 shm_exit_ns(ns);
140
141 retire_mq_sysctls(ns);
142 retire_ipc_sysctls(ns);
143
144 dec_ipc_namespaces(ns->ucounts);
145 put_user_ns(ns->user_ns);
146 ns_free_inum(&ns->ns);
147 kfree(ns);
148 }
149
150 static LLIST_HEAD(free_ipc_list);
free_ipc(struct work_struct * unused)151 static void free_ipc(struct work_struct *unused)
152 {
153 struct llist_node *node = llist_del_all(&free_ipc_list);
154 struct ipc_namespace *n, *t;
155
156 llist_for_each_entry_safe(n, t, node, mnt_llist)
157 free_ipc_ns(n);
158 }
159
160 /*
161 * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
162 */
163 static DECLARE_WORK(free_ipc_work, free_ipc);
164
165 /*
166 * put_ipc_ns - drop a reference to an ipc namespace.
167 * @ns: the namespace to put
168 *
169 * If this is the last task in the namespace exiting, and
170 * it is dropping the refcount to 0, then it can race with
171 * a task in another ipc namespace but in a mounts namespace
172 * which has this ipcns's mqueuefs mounted, doing some action
173 * with one of the mqueuefs files. That can raise the refcount.
174 * So dropping the refcount, and raising the refcount when
175 * accessing it through the VFS, are protected with mq_lock.
176 *
177 * (Clearly, a task raising the refcount on its own ipc_ns
178 * needn't take mq_lock since it can't race with the last task
179 * in the ipcns exiting).
180 */
put_ipc_ns(struct ipc_namespace * ns)181 void put_ipc_ns(struct ipc_namespace *ns)
182 {
183 if (refcount_dec_and_lock(&ns->ns.count, &mq_lock)) {
184 mq_clear_sbinfo(ns);
185 spin_unlock(&mq_lock);
186
187 if (llist_add(&ns->mnt_llist, &free_ipc_list))
188 schedule_work(&free_ipc_work);
189 }
190 }
191
to_ipc_ns(struct ns_common * ns)192 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
193 {
194 return container_of(ns, struct ipc_namespace, ns);
195 }
196
ipcns_get(struct task_struct * task)197 static struct ns_common *ipcns_get(struct task_struct *task)
198 {
199 struct ipc_namespace *ns = NULL;
200 struct nsproxy *nsproxy;
201
202 task_lock(task);
203 nsproxy = task->nsproxy;
204 if (nsproxy)
205 ns = get_ipc_ns(nsproxy->ipc_ns);
206 task_unlock(task);
207
208 return ns ? &ns->ns : NULL;
209 }
210
ipcns_put(struct ns_common * ns)211 static void ipcns_put(struct ns_common *ns)
212 {
213 return put_ipc_ns(to_ipc_ns(ns));
214 }
215
ipcns_install(struct nsset * nsset,struct ns_common * new)216 static int ipcns_install(struct nsset *nsset, struct ns_common *new)
217 {
218 struct nsproxy *nsproxy = nsset->nsproxy;
219 struct ipc_namespace *ns = to_ipc_ns(new);
220 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
221 !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
222 return -EPERM;
223
224 put_ipc_ns(nsproxy->ipc_ns);
225 nsproxy->ipc_ns = get_ipc_ns(ns);
226 return 0;
227 }
228
ipcns_owner(struct ns_common * ns)229 static struct user_namespace *ipcns_owner(struct ns_common *ns)
230 {
231 return to_ipc_ns(ns)->user_ns;
232 }
233
234 const struct proc_ns_operations ipcns_operations = {
235 .name = "ipc",
236 .type = CLONE_NEWIPC,
237 .get = ipcns_get,
238 .put = ipcns_put,
239 .install = ipcns_install,
240 .owner = ipcns_owner,
241 };
242