namespace.c revision 0050ee05
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 ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
20					   struct ipc_namespace *old_ns)
21{
22	struct ipc_namespace *ns;
23	int err;
24
25	ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
26	if (ns == NULL)
27		return ERR_PTR(-ENOMEM);
28
29	err = proc_alloc_inum(&ns->proc_inum);
30	if (err) {
31		kfree(ns);
32		return ERR_PTR(err);
33	}
34
35	atomic_set(&ns->count, 1);
36	err = mq_init_ns(ns);
37	if (err) {
38		proc_free_inum(ns->proc_inum);
39		kfree(ns);
40		return ERR_PTR(err);
41	}
42	atomic_inc(&nr_ipc_ns);
43
44	sem_init_ns(ns);
45	msg_init_ns(ns);
46	shm_init_ns(ns);
47
48	ns->user_ns = get_user_ns(user_ns);
49
50	return ns;
51}
52
53struct ipc_namespace *copy_ipcs(unsigned long flags,
54	struct user_namespace *user_ns, struct ipc_namespace *ns)
55{
56	if (!(flags & CLONE_NEWIPC))
57		return get_ipc_ns(ns);
58	return create_ipc_ns(user_ns, ns);
59}
60
61/*
62 * free_ipcs - free all ipcs of one type
63 * @ns:   the namespace to remove the ipcs from
64 * @ids:  the table of ipcs to free
65 * @free: the function called to free each individual ipc
66 *
67 * Called for each kind of ipc when an ipc_namespace exits.
68 */
69void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
70	       void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
71{
72	struct kern_ipc_perm *perm;
73	int next_id;
74	int total, in_use;
75
76	down_write(&ids->rwsem);
77
78	in_use = ids->in_use;
79
80	for (total = 0, next_id = 0; total < in_use; next_id++) {
81		perm = idr_find(&ids->ipcs_idr, next_id);
82		if (perm == NULL)
83			continue;
84		rcu_read_lock();
85		ipc_lock_object(perm);
86		free(ns, perm);
87		total++;
88	}
89	up_write(&ids->rwsem);
90}
91
92static void free_ipc_ns(struct ipc_namespace *ns)
93{
94	sem_exit_ns(ns);
95	msg_exit_ns(ns);
96	shm_exit_ns(ns);
97	atomic_dec(&nr_ipc_ns);
98
99	put_user_ns(ns->user_ns);
100	proc_free_inum(ns->proc_inum);
101	kfree(ns);
102}
103
104/*
105 * put_ipc_ns - drop a reference to an ipc namespace.
106 * @ns: the namespace to put
107 *
108 * If this is the last task in the namespace exiting, and
109 * it is dropping the refcount to 0, then it can race with
110 * a task in another ipc namespace but in a mounts namespace
111 * which has this ipcns's mqueuefs mounted, doing some action
112 * with one of the mqueuefs files.  That can raise the refcount.
113 * So dropping the refcount, and raising the refcount when
114 * accessing it through the VFS, are protected with mq_lock.
115 *
116 * (Clearly, a task raising the refcount on its own ipc_ns
117 * needn't take mq_lock since it can't race with the last task
118 * in the ipcns exiting).
119 */
120void put_ipc_ns(struct ipc_namespace *ns)
121{
122	if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
123		mq_clear_sbinfo(ns);
124		spin_unlock(&mq_lock);
125		mq_put_mnt(ns);
126		free_ipc_ns(ns);
127	}
128}
129
130static void *ipcns_get(struct task_struct *task)
131{
132	struct ipc_namespace *ns = NULL;
133	struct nsproxy *nsproxy;
134
135	task_lock(task);
136	nsproxy = task->nsproxy;
137	if (nsproxy)
138		ns = get_ipc_ns(nsproxy->ipc_ns);
139	task_unlock(task);
140
141	return ns;
142}
143
144static void ipcns_put(void *ns)
145{
146	return put_ipc_ns(ns);
147}
148
149static int ipcns_install(struct nsproxy *nsproxy, void *new)
150{
151	struct ipc_namespace *ns = new;
152	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
153	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
154		return -EPERM;
155
156	/* Ditch state from the old ipc namespace */
157	exit_sem(current);
158	put_ipc_ns(nsproxy->ipc_ns);
159	nsproxy->ipc_ns = get_ipc_ns(ns);
160	return 0;
161}
162
163static unsigned int ipcns_inum(void *vp)
164{
165	struct ipc_namespace *ns = vp;
166
167	return ns->proc_inum;
168}
169
170const struct proc_ns_operations ipcns_operations = {
171	.name		= "ipc",
172	.type		= CLONE_NEWIPC,
173	.get		= ipcns_get,
174	.put		= ipcns_put,
175	.install	= ipcns_install,
176	.inum		= ipcns_inum,
177};
178