1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	connector.c
4 *
5 * 2004+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
6 * All rights reserved.
7 */
8
9#include <linux/compiler.h>
10#include <linux/kernel.h>
11#include <linux/module.h>
12#include <linux/list.h>
13#include <linux/skbuff.h>
14#include <net/netlink.h>
15#include <linux/moduleparam.h>
16#include <linux/connector.h>
17#include <linux/slab.h>
18#include <linux/mutex.h>
19#include <linux/proc_fs.h>
20#include <linux/spinlock.h>
21
22#include <net/sock.h>
23
24MODULE_LICENSE("GPL");
25MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
26MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
27MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_CONNECTOR);
28
29static struct cn_dev cdev;
30
31static int cn_already_initialized;
32
33/*
34 * Sends mult (multiple) cn_msg at a time.
35 *
36 * msg->seq and msg->ack are used to determine message genealogy.
37 * When someone sends message it puts there locally unique sequence
38 * and random acknowledge numbers.  Sequence number may be copied into
39 * nlmsghdr->nlmsg_seq too.
40 *
41 * Sequence number is incremented with each message to be sent.
42 *
43 * If we expect a reply to our message then the sequence number in
44 * received message MUST be the same as in original message, and
45 * acknowledge number MUST be the same + 1.
46 *
47 * If we receive a message and its sequence number is not equal to the
48 * one we are expecting then it is a new message.
49 *
50 * If we receive a message and its sequence number is the same as one
51 * we are expecting but it's acknowledgement number is not equal to
52 * the acknowledgement number in the original message + 1, then it is
53 * a new message.
54 *
55 * If msg->len != len, then additional cn_msg messages are expected following
56 * the first msg.
57 *
58 * The message is sent to, the portid if given, the group if given, both if
59 * both, or if both are zero then the group is looked up and sent there.
60 */
61int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid, u32 __group,
62	gfp_t gfp_mask,
63	int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
64	void *filter_data)
65{
66	struct cn_callback_entry *__cbq;
67	unsigned int size;
68	struct sk_buff *skb;
69	struct nlmsghdr *nlh;
70	struct cn_msg *data;
71	struct cn_dev *dev = &cdev;
72	u32 group = 0;
73	int found = 0;
74
75	if (portid || __group) {
76		group = __group;
77	} else {
78		spin_lock_bh(&dev->cbdev->queue_lock);
79		list_for_each_entry(__cbq, &dev->cbdev->queue_list,
80				    callback_entry) {
81			if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
82				found = 1;
83				group = __cbq->group;
84				break;
85			}
86		}
87		spin_unlock_bh(&dev->cbdev->queue_lock);
88
89		if (!found)
90			return -ENODEV;
91	}
92
93	if (!portid && !netlink_has_listeners(dev->nls, group))
94		return -ESRCH;
95
96	size = sizeof(*msg) + len;
97
98	skb = nlmsg_new(size, gfp_mask);
99	if (!skb)
100		return -ENOMEM;
101
102	nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 0);
103	if (!nlh) {
104		kfree_skb(skb);
105		return -EMSGSIZE;
106	}
107
108	data = nlmsg_data(nlh);
109
110	memcpy(data, msg, size);
111
112	NETLINK_CB(skb).dst_group = group;
113
114	if (group)
115		return netlink_broadcast_filtered(dev->nls, skb, portid, group,
116						  gfp_mask, filter,
117						  (void *)filter_data);
118	return netlink_unicast(dev->nls, skb, portid,
119			!gfpflags_allow_blocking(gfp_mask));
120}
121EXPORT_SYMBOL_GPL(cn_netlink_send_mult);
122
123/* same as cn_netlink_send_mult except msg->len is used for len */
124int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
125	gfp_t gfp_mask)
126{
127	return cn_netlink_send_mult(msg, msg->len, portid, __group, gfp_mask,
128				    NULL, NULL);
129}
130EXPORT_SYMBOL_GPL(cn_netlink_send);
131
132/*
133 * Callback helper - queues work and setup destructor for given data.
134 */
135static int cn_call_callback(struct sk_buff *skb)
136{
137	struct nlmsghdr *nlh;
138	struct cn_callback_entry *i, *cbq = NULL;
139	struct cn_dev *dev = &cdev;
140	struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb));
141	struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
142	int err = -ENODEV;
143
144	/* verify msg->len is within skb */
145	nlh = nlmsg_hdr(skb);
146	if (nlh->nlmsg_len < NLMSG_HDRLEN + sizeof(struct cn_msg) + msg->len)
147		return -EINVAL;
148
149	spin_lock_bh(&dev->cbdev->queue_lock);
150	list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
151		if (cn_cb_equal(&i->id.id, &msg->id)) {
152			refcount_inc(&i->refcnt);
153			cbq = i;
154			break;
155		}
156	}
157	spin_unlock_bh(&dev->cbdev->queue_lock);
158
159	if (cbq != NULL) {
160		cbq->callback(msg, nsp);
161		kfree_skb(skb);
162		cn_queue_release_callback(cbq);
163		err = 0;
164	}
165
166	return err;
167}
168
169/*
170 * Allow non-root access for NETLINK_CONNECTOR family having CN_IDX_PROC
171 * multicast group.
172 */
173static int cn_bind(struct net *net, int group)
174{
175	unsigned long groups = (unsigned long) group;
176
177	if (ns_capable(net->user_ns, CAP_NET_ADMIN))
178		return 0;
179
180	if (test_bit(CN_IDX_PROC - 1, &groups))
181		return 0;
182
183	return -EPERM;
184}
185
186static void cn_release(struct sock *sk, unsigned long *groups)
187{
188	if (groups && test_bit(CN_IDX_PROC - 1, groups)) {
189		kfree(sk->sk_user_data);
190		sk->sk_user_data = NULL;
191	}
192}
193
194/*
195 * Main netlink receiving function.
196 *
197 * It checks skb, netlink header and msg sizes, and calls callback helper.
198 */
199static void cn_rx_skb(struct sk_buff *skb)
200{
201	struct nlmsghdr *nlh;
202	int len, err;
203
204	if (skb->len >= NLMSG_HDRLEN) {
205		nlh = nlmsg_hdr(skb);
206		len = nlmsg_len(nlh);
207
208		if (len < (int)sizeof(struct cn_msg) ||
209		    skb->len < nlh->nlmsg_len ||
210		    len > CONNECTOR_MAX_MSG_SIZE)
211			return;
212
213		err = cn_call_callback(skb_get(skb));
214		if (err < 0)
215			kfree_skb(skb);
216	}
217}
218
219/*
220 * Callback add routing - adds callback with given ID and name.
221 * If there is registered callback with the same ID it will not be added.
222 *
223 * May sleep.
224 */
225int cn_add_callback(const struct cb_id *id, const char *name,
226		    void (*callback)(struct cn_msg *,
227				     struct netlink_skb_parms *))
228{
229	struct cn_dev *dev = &cdev;
230
231	if (!cn_already_initialized)
232		return -EAGAIN;
233
234	return cn_queue_add_callback(dev->cbdev, name, id, callback);
235}
236EXPORT_SYMBOL_GPL(cn_add_callback);
237
238/*
239 * Callback remove routing - removes callback
240 * with given ID.
241 * If there is no registered callback with given
242 * ID nothing happens.
243 *
244 * May sleep while waiting for reference counter to become zero.
245 */
246void cn_del_callback(const struct cb_id *id)
247{
248	struct cn_dev *dev = &cdev;
249
250	cn_queue_del_callback(dev->cbdev, id);
251}
252EXPORT_SYMBOL_GPL(cn_del_callback);
253
254static int __maybe_unused cn_proc_show(struct seq_file *m, void *v)
255{
256	struct cn_queue_dev *dev = cdev.cbdev;
257	struct cn_callback_entry *cbq;
258
259	seq_printf(m, "Name            ID\n");
260
261	spin_lock_bh(&dev->queue_lock);
262
263	list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
264		seq_printf(m, "%-15s %u:%u\n",
265			   cbq->id.name,
266			   cbq->id.id.idx,
267			   cbq->id.id.val);
268	}
269
270	spin_unlock_bh(&dev->queue_lock);
271
272	return 0;
273}
274
275static int cn_init(void)
276{
277	struct cn_dev *dev = &cdev;
278	struct netlink_kernel_cfg cfg = {
279		.groups	= CN_NETLINK_USERS + 0xf,
280		.input	= cn_rx_skb,
281		.flags  = NL_CFG_F_NONROOT_RECV,
282		.bind   = cn_bind,
283		.release = cn_release,
284	};
285
286	dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
287	if (!dev->nls)
288		return -EIO;
289
290	dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
291	if (!dev->cbdev) {
292		netlink_kernel_release(dev->nls);
293		return -EINVAL;
294	}
295
296	cn_already_initialized = 1;
297
298	proc_create_single("connector", S_IRUGO, init_net.proc_net, cn_proc_show);
299
300	return 0;
301}
302
303static void cn_fini(void)
304{
305	struct cn_dev *dev = &cdev;
306
307	cn_already_initialized = 0;
308
309	remove_proc_entry("connector", init_net.proc_net);
310
311	cn_queue_free_dev(dev->cbdev);
312	netlink_kernel_release(dev->nls);
313}
314
315subsys_initcall(cn_init);
316module_exit(cn_fini);
317