xref: /openbmc/linux/net/netfilter/nfnetlink.c (revision 3c6a73cc) 
1 /* Netfilter messages via netlink socket. Allows for user space
2  * protocol helpers and general trouble making from userspace.
3  *
4  * (C) 2001 by Jay Schulist <jschlst@samba.org>,
5  * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org>
6  * (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org>
7  *
8  * Initial netfilter messages via netlink development funded and
9  * generally made possible by Network Robots, Inc. (www.networkrobots.com)
10  *
11  * Further development of this code funded by Astaro AG (http://www.astaro.com)
12  *
13  * This software may be used and distributed according to the terms
14  * of the GNU General Public License, incorporated herein by reference.
15  */
16 
17 #include <linux/module.h>
18 #include <linux/types.h>
19 #include <linux/socket.h>
20 #include <linux/kernel.h>
21 #include <linux/string.h>
22 #include <linux/sockios.h>
23 #include <linux/net.h>
24 #include <linux/skbuff.h>
25 #include <asm/uaccess.h>
26 #include <net/sock.h>
27 #include <linux/init.h>
28 
29 #include <net/netlink.h>
30 #include <linux/netfilter/nfnetlink.h>
31 
32 MODULE_LICENSE("GPL");
33 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
34 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER);
35 
36 static char __initdata nfversion[] = "0.30";
37 
38 static struct {
39 	struct mutex				mutex;
40 	const struct nfnetlink_subsystem __rcu	*subsys;
41 } table[NFNL_SUBSYS_COUNT];
42 
43 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
44 	[NFNLGRP_CONNTRACK_NEW]		= NFNL_SUBSYS_CTNETLINK,
45 	[NFNLGRP_CONNTRACK_UPDATE]	= NFNL_SUBSYS_CTNETLINK,
46 	[NFNLGRP_CONNTRACK_DESTROY]	= NFNL_SUBSYS_CTNETLINK,
47 	[NFNLGRP_CONNTRACK_EXP_NEW]	= NFNL_SUBSYS_CTNETLINK_EXP,
48 	[NFNLGRP_CONNTRACK_EXP_UPDATE]	= NFNL_SUBSYS_CTNETLINK_EXP,
49 	[NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
50 };
51 
52 void nfnl_lock(__u8 subsys_id)
53 {
54 	mutex_lock(&table[subsys_id].mutex);
55 }
56 EXPORT_SYMBOL_GPL(nfnl_lock);
57 
58 void nfnl_unlock(__u8 subsys_id)
59 {
60 	mutex_unlock(&table[subsys_id].mutex);
61 }
62 EXPORT_SYMBOL_GPL(nfnl_unlock);
63 
64 #ifdef CONFIG_PROVE_LOCKING
65 int lockdep_nfnl_is_held(u8 subsys_id)
66 {
67 	return lockdep_is_held(&table[subsys_id].mutex);
68 }
69 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
70 #endif
71 
72 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
73 {
74 	nfnl_lock(n->subsys_id);
75 	if (table[n->subsys_id].subsys) {
76 		nfnl_unlock(n->subsys_id);
77 		return -EBUSY;
78 	}
79 	rcu_assign_pointer(table[n->subsys_id].subsys, n);
80 	nfnl_unlock(n->subsys_id);
81 
82 	return 0;
83 }
84 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
85 
86 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
87 {
88 	nfnl_lock(n->subsys_id);
89 	table[n->subsys_id].subsys = NULL;
90 	nfnl_unlock(n->subsys_id);
91 	synchronize_rcu();
92 	return 0;
93 }
94 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
95 
96 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
97 {
98 	u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
99 
100 	if (subsys_id >= NFNL_SUBSYS_COUNT)
101 		return NULL;
102 
103 	return rcu_dereference(table[subsys_id].subsys);
104 }
105 
106 static inline const struct nfnl_callback *
107 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
108 {
109 	u_int8_t cb_id = NFNL_MSG_TYPE(type);
110 
111 	if (cb_id >= ss->cb_count)
112 		return NULL;
113 
114 	return &ss->cb[cb_id];
115 }
116 
117 int nfnetlink_has_listeners(struct net *net, unsigned int group)
118 {
119 	return netlink_has_listeners(net->nfnl, group);
120 }
121 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
122 
123 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size,
124 				    u32 dst_portid, gfp_t gfp_mask)
125 {
126 	return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask);
127 }
128 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb);
129 
130 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
131 		   unsigned int group, int echo, gfp_t flags)
132 {
133 	return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
134 }
135 EXPORT_SYMBOL_GPL(nfnetlink_send);
136 
137 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
138 {
139 	return netlink_set_err(net->nfnl, portid, group, error);
140 }
141 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
142 
143 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
144 		      int flags)
145 {
146 	return netlink_unicast(net->nfnl, skb, portid, flags);
147 }
148 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
149 
150 /* Process one complete nfnetlink message. */
151 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
152 {
153 	struct net *net = sock_net(skb->sk);
154 	const struct nfnl_callback *nc;
155 	const struct nfnetlink_subsystem *ss;
156 	int type, err;
157 
158 	/* All the messages must at least contain nfgenmsg */
159 	if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
160 		return 0;
161 
162 	type = nlh->nlmsg_type;
163 replay:
164 	rcu_read_lock();
165 	ss = nfnetlink_get_subsys(type);
166 	if (!ss) {
167 #ifdef CONFIG_MODULES
168 		rcu_read_unlock();
169 		request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
170 		rcu_read_lock();
171 		ss = nfnetlink_get_subsys(type);
172 		if (!ss)
173 #endif
174 		{
175 			rcu_read_unlock();
176 			return -EINVAL;
177 		}
178 	}
179 
180 	nc = nfnetlink_find_client(type, ss);
181 	if (!nc) {
182 		rcu_read_unlock();
183 		return -EINVAL;
184 	}
185 
186 	{
187 		int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
188 		u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
189 		struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
190 		struct nlattr *attr = (void *)nlh + min_len;
191 		int attrlen = nlh->nlmsg_len - min_len;
192 		__u8 subsys_id = NFNL_SUBSYS_ID(type);
193 
194 		err = nla_parse(cda, ss->cb[cb_id].attr_count,
195 				attr, attrlen, ss->cb[cb_id].policy);
196 		if (err < 0) {
197 			rcu_read_unlock();
198 			return err;
199 		}
200 
201 		if (nc->call_rcu) {
202 			err = nc->call_rcu(net->nfnl, skb, nlh,
203 					   (const struct nlattr **)cda);
204 			rcu_read_unlock();
205 		} else {
206 			rcu_read_unlock();
207 			nfnl_lock(subsys_id);
208 			if (rcu_dereference_protected(table[subsys_id].subsys,
209 				lockdep_is_held(&table[subsys_id].mutex)) != ss ||
210 			    nfnetlink_find_client(type, ss) != nc)
211 				err = -EAGAIN;
212 			else if (nc->call)
213 				err = nc->call(net->nfnl, skb, nlh,
214 						   (const struct nlattr **)cda);
215 			else
216 				err = -EINVAL;
217 			nfnl_unlock(subsys_id);
218 		}
219 		if (err == -EAGAIN)
220 			goto replay;
221 		return err;
222 	}
223 }
224 
225 struct nfnl_err {
226 	struct list_head	head;
227 	struct nlmsghdr		*nlh;
228 	int			err;
229 };
230 
231 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err)
232 {
233 	struct nfnl_err *nfnl_err;
234 
235 	nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
236 	if (nfnl_err == NULL)
237 		return -ENOMEM;
238 
239 	nfnl_err->nlh = nlh;
240 	nfnl_err->err = err;
241 	list_add_tail(&nfnl_err->head, list);
242 
243 	return 0;
244 }
245 
246 static void nfnl_err_del(struct nfnl_err *nfnl_err)
247 {
248 	list_del(&nfnl_err->head);
249 	kfree(nfnl_err);
250 }
251 
252 static void nfnl_err_reset(struct list_head *err_list)
253 {
254 	struct nfnl_err *nfnl_err, *next;
255 
256 	list_for_each_entry_safe(nfnl_err, next, err_list, head)
257 		nfnl_err_del(nfnl_err);
258 }
259 
260 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
261 {
262 	struct nfnl_err *nfnl_err, *next;
263 
264 	list_for_each_entry_safe(nfnl_err, next, err_list, head) {
265 		netlink_ack(skb, nfnl_err->nlh, nfnl_err->err);
266 		nfnl_err_del(nfnl_err);
267 	}
268 }
269 
270 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
271 				u_int16_t subsys_id)
272 {
273 	struct sk_buff *nskb, *oskb = skb;
274 	struct net *net = sock_net(skb->sk);
275 	const struct nfnetlink_subsystem *ss;
276 	const struct nfnl_callback *nc;
277 	bool success = true, done = false;
278 	static LIST_HEAD(err_list);
279 	int err;
280 
281 	if (subsys_id >= NFNL_SUBSYS_COUNT)
282 		return netlink_ack(skb, nlh, -EINVAL);
283 replay:
284 	nskb = netlink_skb_clone(oskb, GFP_KERNEL);
285 	if (!nskb)
286 		return netlink_ack(oskb, nlh, -ENOMEM);
287 
288 	nskb->sk = oskb->sk;
289 	skb = nskb;
290 
291 	nfnl_lock(subsys_id);
292 	ss = rcu_dereference_protected(table[subsys_id].subsys,
293 				       lockdep_is_held(&table[subsys_id].mutex));
294 	if (!ss) {
295 #ifdef CONFIG_MODULES
296 		nfnl_unlock(subsys_id);
297 		request_module("nfnetlink-subsys-%d", subsys_id);
298 		nfnl_lock(subsys_id);
299 		ss = rcu_dereference_protected(table[subsys_id].subsys,
300 					       lockdep_is_held(&table[subsys_id].mutex));
301 		if (!ss)
302 #endif
303 		{
304 			nfnl_unlock(subsys_id);
305 			netlink_ack(skb, nlh, -EOPNOTSUPP);
306 			return kfree_skb(nskb);
307 		}
308 	}
309 
310 	if (!ss->commit || !ss->abort) {
311 		nfnl_unlock(subsys_id);
312 		netlink_ack(skb, nlh, -EOPNOTSUPP);
313 		return kfree_skb(skb);
314 	}
315 
316 	while (skb->len >= nlmsg_total_size(0)) {
317 		int msglen, type;
318 
319 		nlh = nlmsg_hdr(skb);
320 		err = 0;
321 
322 		if (nlh->nlmsg_len < NLMSG_HDRLEN) {
323 			err = -EINVAL;
324 			goto ack;
325 		}
326 
327 		/* Only requests are handled by the kernel */
328 		if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
329 			err = -EINVAL;
330 			goto ack;
331 		}
332 
333 		type = nlh->nlmsg_type;
334 		if (type == NFNL_MSG_BATCH_BEGIN) {
335 			/* Malformed: Batch begin twice */
336 			nfnl_err_reset(&err_list);
337 			success = false;
338 			goto done;
339 		} else if (type == NFNL_MSG_BATCH_END) {
340 			done = true;
341 			goto done;
342 		} else if (type < NLMSG_MIN_TYPE) {
343 			err = -EINVAL;
344 			goto ack;
345 		}
346 
347 		/* We only accept a batch with messages for the same
348 		 * subsystem.
349 		 */
350 		if (NFNL_SUBSYS_ID(type) != subsys_id) {
351 			err = -EINVAL;
352 			goto ack;
353 		}
354 
355 		nc = nfnetlink_find_client(type, ss);
356 		if (!nc) {
357 			err = -EINVAL;
358 			goto ack;
359 		}
360 
361 		{
362 			int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
363 			u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
364 			struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
365 			struct nlattr *attr = (void *)nlh + min_len;
366 			int attrlen = nlh->nlmsg_len - min_len;
367 
368 			err = nla_parse(cda, ss->cb[cb_id].attr_count,
369 					attr, attrlen, ss->cb[cb_id].policy);
370 			if (err < 0)
371 				goto ack;
372 
373 			if (nc->call_batch) {
374 				err = nc->call_batch(net->nfnl, skb, nlh,
375 						     (const struct nlattr **)cda);
376 			}
377 
378 			/* The lock was released to autoload some module, we
379 			 * have to abort and start from scratch using the
380 			 * original skb.
381 			 */
382 			if (err == -EAGAIN) {
383 				nfnl_err_reset(&err_list);
384 				ss->abort(oskb);
385 				nfnl_unlock(subsys_id);
386 				kfree_skb(nskb);
387 				goto replay;
388 			}
389 		}
390 ack:
391 		if (nlh->nlmsg_flags & NLM_F_ACK || err) {
392 			/* Errors are delivered once the full batch has been
393 			 * processed, this avoids that the same error is
394 			 * reported several times when replaying the batch.
395 			 */
396 			if (nfnl_err_add(&err_list, nlh, err) < 0) {
397 				/* We failed to enqueue an error, reset the
398 				 * list of errors and send OOM to userspace
399 				 * pointing to the batch header.
400 				 */
401 				nfnl_err_reset(&err_list);
402 				netlink_ack(skb, nlmsg_hdr(oskb), -ENOMEM);
403 				success = false;
404 				goto done;
405 			}
406 			/* We don't stop processing the batch on errors, thus,
407 			 * userspace gets all the errors that the batch
408 			 * triggers.
409 			 */
410 			if (err)
411 				success = false;
412 		}
413 
414 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
415 		if (msglen > skb->len)
416 			msglen = skb->len;
417 		skb_pull(skb, msglen);
418 	}
419 done:
420 	if (success && done)
421 		ss->commit(oskb);
422 	else
423 		ss->abort(oskb);
424 
425 	nfnl_err_deliver(&err_list, oskb);
426 	nfnl_unlock(subsys_id);
427 	kfree_skb(nskb);
428 }
429 
430 static void nfnetlink_rcv(struct sk_buff *skb)
431 {
432 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
433 	int msglen;
434 
435 	if (nlh->nlmsg_len < NLMSG_HDRLEN ||
436 	    skb->len < nlh->nlmsg_len)
437 		return;
438 
439 	if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
440 		netlink_ack(skb, nlh, -EPERM);
441 		return;
442 	}
443 
444 	if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) {
445 		struct nfgenmsg *nfgenmsg;
446 
447 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
448 		if (msglen > skb->len)
449 			msglen = skb->len;
450 
451 		if (nlh->nlmsg_len < NLMSG_HDRLEN ||
452 		    skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
453 			return;
454 
455 		nfgenmsg = nlmsg_data(nlh);
456 		skb_pull(skb, msglen);
457 		nfnetlink_rcv_batch(skb, nlh, nfgenmsg->res_id);
458 	} else {
459 		netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
460 	}
461 }
462 
463 #ifdef CONFIG_MODULES
464 static int nfnetlink_bind(int group)
465 {
466 	const struct nfnetlink_subsystem *ss;
467 	int type = nfnl_group2type[group];
468 
469 	rcu_read_lock();
470 	ss = nfnetlink_get_subsys(type);
471 	rcu_read_unlock();
472 	if (!ss)
473 		request_module("nfnetlink-subsys-%d", type);
474 	return 0;
475 }
476 #endif
477 
478 static int __net_init nfnetlink_net_init(struct net *net)
479 {
480 	struct sock *nfnl;
481 	struct netlink_kernel_cfg cfg = {
482 		.groups	= NFNLGRP_MAX,
483 		.input	= nfnetlink_rcv,
484 #ifdef CONFIG_MODULES
485 		.bind	= nfnetlink_bind,
486 #endif
487 	};
488 
489 	nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
490 	if (!nfnl)
491 		return -ENOMEM;
492 	net->nfnl_stash = nfnl;
493 	rcu_assign_pointer(net->nfnl, nfnl);
494 	return 0;
495 }
496 
497 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
498 {
499 	struct net *net;
500 
501 	list_for_each_entry(net, net_exit_list, exit_list)
502 		RCU_INIT_POINTER(net->nfnl, NULL);
503 	synchronize_net();
504 	list_for_each_entry(net, net_exit_list, exit_list)
505 		netlink_kernel_release(net->nfnl_stash);
506 }
507 
508 static struct pernet_operations nfnetlink_net_ops = {
509 	.init		= nfnetlink_net_init,
510 	.exit_batch	= nfnetlink_net_exit_batch,
511 };
512 
513 static int __init nfnetlink_init(void)
514 {
515 	int i;
516 
517 	for (i=0; i<NFNL_SUBSYS_COUNT; i++)
518 		mutex_init(&table[i].mutex);
519 
520 	pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
521 	return register_pernet_subsys(&nfnetlink_net_ops);
522 }
523 
524 static void __exit nfnetlink_exit(void)
525 {
526 	pr_info("Removing netfilter NETLINK layer.\n");
527 	unregister_pernet_subsys(&nfnetlink_net_ops);
528 }
529 module_init(nfnetlink_init);
530 module_exit(nfnetlink_exit);
531