namespace.c revision 64964528
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->ns.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->ns.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	/*
49	 * msgmni has already been computed for the new ipc ns.
50	 * Thus, do the ipcns creation notification before registering that
51	 * new ipcns in the chain.
52	 */
53	ipcns_notify(IPCNS_CREATED);
54	register_ipcns_notifier(ns);
55
56	ns->user_ns = get_user_ns(user_ns);
57
58	return ns;
59}
60
61struct ipc_namespace *copy_ipcs(unsigned long flags,
62	struct user_namespace *user_ns, struct ipc_namespace *ns)
63{
64	if (!(flags & CLONE_NEWIPC))
65		return get_ipc_ns(ns);
66	return create_ipc_ns(user_ns, ns);
67}
68
69/*
70 * free_ipcs - free all ipcs of one type
71 * @ns:   the namespace to remove the ipcs from
72 * @ids:  the table of ipcs to free
73 * @free: the function called to free each individual ipc
74 *
75 * Called for each kind of ipc when an ipc_namespace exits.
76 */
77void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
78	       void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
79{
80	struct kern_ipc_perm *perm;
81	int next_id;
82	int total, in_use;
83
84	down_write(&ids->rwsem);
85
86	in_use = ids->in_use;
87
88	for (total = 0, next_id = 0; total < in_use; next_id++) {
89		perm = idr_find(&ids->ipcs_idr, next_id);
90		if (perm == NULL)
91			continue;
92		rcu_read_lock();
93		ipc_lock_object(perm);
94		free(ns, perm);
95		total++;
96	}
97	up_write(&ids->rwsem);
98}
99
100static void free_ipc_ns(struct ipc_namespace *ns)
101{
102	/*
103	 * Unregistering the hotplug notifier at the beginning guarantees
104	 * that the ipc namespace won't be freed while we are inside the
105	 * callback routine. Since the blocking_notifier_chain_XXX routines
106	 * hold a rw lock on the notifier list, unregister_ipcns_notifier()
107	 * won't take the rw lock before blocking_notifier_call_chain() has
108	 * released the rd lock.
109	 */
110	unregister_ipcns_notifier(ns);
111	sem_exit_ns(ns);
112	msg_exit_ns(ns);
113	shm_exit_ns(ns);
114	atomic_dec(&nr_ipc_ns);
115
116	/*
117	 * Do the ipcns removal notification after decrementing nr_ipc_ns in
118	 * order to have a correct value when recomputing msgmni.
119	 */
120	ipcns_notify(IPCNS_REMOVED);
121	put_user_ns(ns->user_ns);
122	proc_free_inum(ns->ns.inum);
123	kfree(ns);
124}
125
126/*
127 * put_ipc_ns - drop a reference to an ipc namespace.
128 * @ns: the namespace to put
129 *
130 * If this is the last task in the namespace exiting, and
131 * it is dropping the refcount to 0, then it can race with
132 * a task in another ipc namespace but in a mounts namespace
133 * which has this ipcns's mqueuefs mounted, doing some action
134 * with one of the mqueuefs files.  That can raise the refcount.
135 * So dropping the refcount, and raising the refcount when
136 * accessing it through the VFS, are protected with mq_lock.
137 *
138 * (Clearly, a task raising the refcount on its own ipc_ns
139 * needn't take mq_lock since it can't race with the last task
140 * in the ipcns exiting).
141 */
142void put_ipc_ns(struct ipc_namespace *ns)
143{
144	if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
145		mq_clear_sbinfo(ns);
146		spin_unlock(&mq_lock);
147		mq_put_mnt(ns);
148		free_ipc_ns(ns);
149	}
150}
151
152static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
153{
154	return container_of(ns, struct ipc_namespace, ns);
155}
156
157static struct ns_common *ipcns_get(struct task_struct *task)
158{
159	struct ipc_namespace *ns = NULL;
160	struct nsproxy *nsproxy;
161
162	task_lock(task);
163	nsproxy = task->nsproxy;
164	if (nsproxy)
165		ns = get_ipc_ns(nsproxy->ipc_ns);
166	task_unlock(task);
167
168	return ns ? &ns->ns : NULL;
169}
170
171static void ipcns_put(struct ns_common *ns)
172{
173	return put_ipc_ns(to_ipc_ns(ns));
174}
175
176static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
177{
178	struct ipc_namespace *ns = to_ipc_ns(new);
179	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
180	    !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
181		return -EPERM;
182
183	/* Ditch state from the old ipc namespace */
184	exit_sem(current);
185	put_ipc_ns(nsproxy->ipc_ns);
186	nsproxy->ipc_ns = get_ipc_ns(ns);
187	return 0;
188}
189
190const struct proc_ns_operations ipcns_operations = {
191	.name		= "ipc",
192	.type		= CLONE_NEWIPC,
193	.get		= ipcns_get,
194	.put		= ipcns_put,
195	.install	= ipcns_install,
196};
197