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