namespace.c revision aba35661
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
19static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
20{
21	return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
22}
23
24static void dec_ipc_namespaces(struct ucounts *ucounts)
25{
26	dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
27}
28
29static 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 = -ENFILE;
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
65fail_put:
66	put_user_ns(ns->user_ns);
67	ns_free_inum(&ns->ns);
68fail_free:
69	kfree(ns);
70fail_dec:
71	dec_ipc_namespaces(ucounts);
72fail:
73	return ERR_PTR(err);
74}
75
76struct 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 */
92void 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
115static 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 */
143void 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
153static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
154{
155	return container_of(ns, struct ipc_namespace, ns);
156}
157
158static 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
172static void ipcns_put(struct ns_common *ns)
173{
174	return put_ipc_ns(to_ipc_ns(ns));
175}
176
177static 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
191const struct proc_ns_operations ipcns_operations = {
192	.name		= "ipc",
193	.type		= CLONE_NEWIPC,
194	.get		= ipcns_get,
195	.put		= ipcns_put,
196	.install	= ipcns_install,
197};
198