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,int (* filter)(struct sock * dsk,struct sk_buff * skb,void * data),void * filter_data)61 int 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 }
121 EXPORT_SYMBOL_GPL(cn_netlink_send_mult);
122
123 /* 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)124 int 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 }
130 EXPORT_SYMBOL_GPL(cn_netlink_send);
131
132 /*
133 * Callback helper - queues work and setup destructor for given data.
134 */
cn_call_callback(struct sk_buff * skb)135 static 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 */
cn_bind(struct net * net,int group)173 static 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
cn_release(struct sock * sk,unsigned long * groups)186 static 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 */
cn_rx_skb(struct sk_buff * skb)199 static 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 */
cn_add_callback(const struct cb_id * id,const char * name,void (* callback)(struct cn_msg *,struct netlink_skb_parms *))225 int 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 }
236 EXPORT_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 */
cn_del_callback(const struct cb_id * id)246 void 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 }
252 EXPORT_SYMBOL_GPL(cn_del_callback);
253
cn_proc_show(struct seq_file * m,void * v)254 static 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
cn_init(void)275 static 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
cn_fini(void)303 static 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
315 subsys_initcall(cn_init);
316 module_exit(cn_fini);
317