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 
24 MODULE_LICENSE("GPL");
25 MODULE_AUTHOR("Evgeniy Polyakov <zbr@ioremap.net>");
26 MODULE_DESCRIPTION("Generic userspace <-> kernelspace connector.");
27 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_CONNECTOR);
28 
29 static struct cn_dev cdev;
30 
31 static 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  */
cn_netlink_send_mult(struct cn_msg * msg,u16 len,u32 portid,u32 __group,gfp_t gfp_mask)61 int cn_netlink_send_mult(struct cn_msg *msg, u16 len, u32 portid, u32 __group,
62 	gfp_t gfp_mask)
63 {
64 	struct cn_callback_entry *__cbq;
65 	unsigned int size;
66 	struct sk_buff *skb;
67 	struct nlmsghdr *nlh;
68 	struct cn_msg *data;
69 	struct cn_dev *dev = &cdev;
70 	u32 group = 0;
71 	int found = 0;
72 
73 	if (portid || __group) {
74 		group = __group;
75 	} else {
76 		spin_lock_bh(&dev->cbdev->queue_lock);
77 		list_for_each_entry(__cbq, &dev->cbdev->queue_list,
78 				    callback_entry) {
79 			if (cn_cb_equal(&__cbq->id.id, &msg->id)) {
80 				found = 1;
81 				group = __cbq->group;
82 				break;
83 			}
84 		}
85 		spin_unlock_bh(&dev->cbdev->queue_lock);
86 
87 		if (!found)
88 			return -ENODEV;
89 	}
90 
91 	if (!portid && !netlink_has_listeners(dev->nls, group))
92 		return -ESRCH;
93 
94 	size = sizeof(*msg) + len;
95 
96 	skb = nlmsg_new(size, gfp_mask);
97 	if (!skb)
98 		return -ENOMEM;
99 
100 	nlh = nlmsg_put(skb, 0, msg->seq, NLMSG_DONE, size, 0);
101 	if (!nlh) {
102 		kfree_skb(skb);
103 		return -EMSGSIZE;
104 	}
105 
106 	data = nlmsg_data(nlh);
107 
108 	memcpy(data, msg, size);
109 
110 	NETLINK_CB(skb).dst_group = group;
111 
112 	if (group)
113 		return netlink_broadcast(dev->nls, skb, portid, group,
114 					 gfp_mask);
115 	return netlink_unicast(dev->nls, skb, portid,
116 			!gfpflags_allow_blocking(gfp_mask));
117 }
118 EXPORT_SYMBOL_GPL(cn_netlink_send_mult);
119 
120 /* same as cn_netlink_send_mult except msg->len is used for len */
cn_netlink_send(struct cn_msg * msg,u32 portid,u32 __group,gfp_t gfp_mask)121 int cn_netlink_send(struct cn_msg *msg, u32 portid, u32 __group,
122 	gfp_t gfp_mask)
123 {
124 	return cn_netlink_send_mult(msg, msg->len, portid, __group, gfp_mask);
125 }
126 EXPORT_SYMBOL_GPL(cn_netlink_send);
127 
128 /*
129  * Callback helper - queues work and setup destructor for given data.
130  */
cn_call_callback(struct sk_buff * skb)131 static int cn_call_callback(struct sk_buff *skb)
132 {
133 	struct nlmsghdr *nlh;
134 	struct cn_callback_entry *i, *cbq = NULL;
135 	struct cn_dev *dev = &cdev;
136 	struct cn_msg *msg = nlmsg_data(nlmsg_hdr(skb));
137 	struct netlink_skb_parms *nsp = &NETLINK_CB(skb);
138 	int err = -ENODEV;
139 
140 	/* verify msg->len is within skb */
141 	nlh = nlmsg_hdr(skb);
142 	if (nlh->nlmsg_len < NLMSG_HDRLEN + sizeof(struct cn_msg) + msg->len)
143 		return -EINVAL;
144 
145 	spin_lock_bh(&dev->cbdev->queue_lock);
146 	list_for_each_entry(i, &dev->cbdev->queue_list, callback_entry) {
147 		if (cn_cb_equal(&i->id.id, &msg->id)) {
148 			refcount_inc(&i->refcnt);
149 			cbq = i;
150 			break;
151 		}
152 	}
153 	spin_unlock_bh(&dev->cbdev->queue_lock);
154 
155 	if (cbq != NULL) {
156 		cbq->callback(msg, nsp);
157 		kfree_skb(skb);
158 		cn_queue_release_callback(cbq);
159 		err = 0;
160 	}
161 
162 	return err;
163 }
164 
165 /*
166  * Main netlink receiving function.
167  *
168  * It checks skb, netlink header and msg sizes, and calls callback helper.
169  */
cn_rx_skb(struct sk_buff * skb)170 static void cn_rx_skb(struct sk_buff *skb)
171 {
172 	struct nlmsghdr *nlh;
173 	int len, err;
174 
175 	if (skb->len >= NLMSG_HDRLEN) {
176 		nlh = nlmsg_hdr(skb);
177 		len = nlmsg_len(nlh);
178 
179 		if (len < (int)sizeof(struct cn_msg) ||
180 		    skb->len < nlh->nlmsg_len ||
181 		    len > CONNECTOR_MAX_MSG_SIZE)
182 			return;
183 
184 		err = cn_call_callback(skb_get(skb));
185 		if (err < 0)
186 			kfree_skb(skb);
187 	}
188 }
189 
190 /*
191  * Callback add routing - adds callback with given ID and name.
192  * If there is registered callback with the same ID it will not be added.
193  *
194  * May sleep.
195  */
cn_add_callback(const struct cb_id * id,const char * name,void (* callback)(struct cn_msg *,struct netlink_skb_parms *))196 int cn_add_callback(const struct cb_id *id, const char *name,
197 		    void (*callback)(struct cn_msg *,
198 				     struct netlink_skb_parms *))
199 {
200 	struct cn_dev *dev = &cdev;
201 
202 	if (!cn_already_initialized)
203 		return -EAGAIN;
204 
205 	return cn_queue_add_callback(dev->cbdev, name, id, callback);
206 }
207 EXPORT_SYMBOL_GPL(cn_add_callback);
208 
209 /*
210  * Callback remove routing - removes callback
211  * with given ID.
212  * If there is no registered callback with given
213  * ID nothing happens.
214  *
215  * May sleep while waiting for reference counter to become zero.
216  */
cn_del_callback(const struct cb_id * id)217 void cn_del_callback(const struct cb_id *id)
218 {
219 	struct cn_dev *dev = &cdev;
220 
221 	cn_queue_del_callback(dev->cbdev, id);
222 }
223 EXPORT_SYMBOL_GPL(cn_del_callback);
224 
cn_proc_show(struct seq_file * m,void * v)225 static int __maybe_unused cn_proc_show(struct seq_file *m, void *v)
226 {
227 	struct cn_queue_dev *dev = cdev.cbdev;
228 	struct cn_callback_entry *cbq;
229 
230 	seq_printf(m, "Name            ID\n");
231 
232 	spin_lock_bh(&dev->queue_lock);
233 
234 	list_for_each_entry(cbq, &dev->queue_list, callback_entry) {
235 		seq_printf(m, "%-15s %u:%u\n",
236 			   cbq->id.name,
237 			   cbq->id.id.idx,
238 			   cbq->id.id.val);
239 	}
240 
241 	spin_unlock_bh(&dev->queue_lock);
242 
243 	return 0;
244 }
245 
cn_init(void)246 static int cn_init(void)
247 {
248 	struct cn_dev *dev = &cdev;
249 	struct netlink_kernel_cfg cfg = {
250 		.groups	= CN_NETLINK_USERS + 0xf,
251 		.input	= cn_rx_skb,
252 	};
253 
254 	dev->nls = netlink_kernel_create(&init_net, NETLINK_CONNECTOR, &cfg);
255 	if (!dev->nls)
256 		return -EIO;
257 
258 	dev->cbdev = cn_queue_alloc_dev("cqueue", dev->nls);
259 	if (!dev->cbdev) {
260 		netlink_kernel_release(dev->nls);
261 		return -EINVAL;
262 	}
263 
264 	cn_already_initialized = 1;
265 
266 	proc_create_single("connector", S_IRUGO, init_net.proc_net, cn_proc_show);
267 
268 	return 0;
269 }
270 
cn_fini(void)271 static void cn_fini(void)
272 {
273 	struct cn_dev *dev = &cdev;
274 
275 	cn_already_initialized = 0;
276 
277 	remove_proc_entry("connector", init_net.proc_net);
278 
279 	cn_queue_free_dev(dev->cbdev);
280 	netlink_kernel_release(dev->nls);
281 }
282 
283 subsys_initcall(cn_init);
284 module_exit(cn_fini);
285