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