path: root/ipc/namespace.c (plain)
blob: 0abdea496493da66166db5a8b8a24780ade4fc2c

1	/*
2	* linux/ipc/namespace.c
3	* Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
4	*/
5
6	#include <linux/ipc.h>
7	#include <linux/msg.h>
8	#include <linux/ipc_namespace.h>
9	#include <linux/rcupdate.h>
10	#include <linux/nsproxy.h>
11	#include <linux/slab.h>
12	#include <linux/fs.h>
13	#include <linux/mount.h>
14	#include <linux/user_namespace.h>
15	#include <linux/proc_ns.h>
16
17	#include "util.h"
18
19	static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
20	{
21	return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
22	}
23
24	static void dec_ipc_namespaces(struct ucounts *ucounts)
25	{
26	dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
27	}
28
29	static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
30	struct ipc_namespace *old_ns)
31	{
32	struct ipc_namespace *ns;
33	struct ucounts *ucounts;
34	int err;
35
36	err = -ENOSPC;
37	ucounts = inc_ipc_namespaces(user_ns);
38	if (!ucounts)
39	goto fail;
40
41	err = -ENOMEM;
42	ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
43	if (ns == NULL)
44	goto fail_dec;
45
46	err = ns_alloc_inum(&ns->ns);
47	if (err)
48	goto fail_free;
49	ns->ns.ops = &ipcns_operations;
50
51	atomic_set(&ns->count, 1);
52	ns->user_ns = get_user_ns(user_ns);
53	ns->ucounts = ucounts;
54
55	err = mq_init_ns(ns);
56	if (err)
57	goto fail_put;
58
59	sem_init_ns(ns);
60	msg_init_ns(ns);
61	shm_init_ns(ns);
62
63	return ns;
64
65	fail_put:
66	put_user_ns(ns->user_ns);
67	ns_free_inum(&ns->ns);
68	fail_free:
69	kfree(ns);
70	fail_dec:
71	dec_ipc_namespaces(ucounts);
72	fail:
73	return ERR_PTR(err);
74	}
75
76	struct ipc_namespace *copy_ipcs(unsigned long flags,
77	struct user_namespace *user_ns, struct ipc_namespace *ns)
78	{
79	if (!(flags & CLONE_NEWIPC))
80	return get_ipc_ns(ns);
81	return create_ipc_ns(user_ns, ns);
82	}
83
84	/*
85	* free_ipcs - free all ipcs of one type
86	* @ns: the namespace to remove the ipcs from
87	* @ids: the table of ipcs to free
88	* @free: the function called to free each individual ipc
89	*
90	* Called for each kind of ipc when an ipc_namespace exits.
91	*/
92	void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
93	void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
94	{
95	struct kern_ipc_perm *perm;
96	int next_id;
97	int total, in_use;
98
99	down_write(&ids->rwsem);
100
101	in_use = ids->in_use;
102
103	for (total = 0, next_id = 0; total < in_use; next_id++) {
104	perm = idr_find(&ids->ipcs_idr, next_id);
105	if (perm == NULL)
106	continue;
107	rcu_read_lock();
108	ipc_lock_object(perm);
109	free(ns, perm);
110	total++;
111	}
112	up_write(&ids->rwsem);
113	}
114
115	static void free_ipc_ns(struct ipc_namespace *ns)
116	{
117	sem_exit_ns(ns);
118	msg_exit_ns(ns);
119	shm_exit_ns(ns);
120
121	dec_ipc_namespaces(ns->ucounts);
122	put_user_ns(ns->user_ns);
123	ns_free_inum(&ns->ns);
124	kfree(ns);
125	}
126
127	/*
128	* put_ipc_ns - drop a reference to an ipc namespace.
129	* @ns: the namespace to put
130	*
131	* If this is the last task in the namespace exiting, and
132	* it is dropping the refcount to 0, then it can race with
133	* a task in another ipc namespace but in a mounts namespace
134	* which has this ipcns's mqueuefs mounted, doing some action
135	* with one of the mqueuefs files. That can raise the refcount.
136	* So dropping the refcount, and raising the refcount when
137	* accessing it through the VFS, are protected with mq_lock.
138	*
139	* (Clearly, a task raising the refcount on its own ipc_ns
140	* needn't take mq_lock since it can't race with the last task
141	* in the ipcns exiting).
142	*/
143	void put_ipc_ns(struct ipc_namespace *ns)
144	{
145	if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
146	mq_clear_sbinfo(ns);
147	spin_unlock(&mq_lock);
148	mq_put_mnt(ns);
149	free_ipc_ns(ns);
150	}
151	}
152
153	static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
154	{
155	return container_of(ns, struct ipc_namespace, ns);
156	}
157
158	static struct ns_common *ipcns_get(struct task_struct *task)
159	{
160	struct ipc_namespace *ns = NULL;
161	struct nsproxy *nsproxy;
162
163	task_lock(task);
164	nsproxy = task->nsproxy;
165	if (nsproxy)
166	ns = get_ipc_ns(nsproxy->ipc_ns);
167	task_unlock(task);
168
169	return ns ? &ns->ns : NULL;
170	}
171
172	static void ipcns_put(struct ns_common *ns)
173	{
174	return put_ipc_ns(to_ipc_ns(ns));
175	}
176
177	static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
178	{
179	struct ipc_namespace *ns = to_ipc_ns(new);
180	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
181	!ns_capable(current_user_ns(), CAP_SYS_ADMIN))
182	return -EPERM;
183
184	/* Ditch state from the old ipc namespace */
185	exit_sem(current);
186	put_ipc_ns(nsproxy->ipc_ns);
187	nsproxy->ipc_ns = get_ipc_ns(ns);
188	return 0;
189	}
190
191	static struct user_namespace *ipcns_owner(struct ns_common *ns)
192	{
193	return to_ipc_ns(ns)->user_ns;
194	}
195
196	const struct proc_ns_operations ipcns_operations = {
197	.name = "ipc",
198	.type = CLONE_NEWIPC,
199	.get = ipcns_get,
200	.put = ipcns_put,
201	.install = ipcns_install,
202	.owner = ipcns_owner,
203	};
204