xref: /openbmc/linux/net/netfilter/nfnetlink.c (revision 2596e07a) 
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 #define nfnl_dereference_protected(id) \
37 	rcu_dereference_protected(table[(id)].subsys, \
38 				  lockdep_nfnl_is_held((id)))
39 
40 static char __initdata nfversion[] = "0.30";
41 
42 static struct {
43 	struct mutex				mutex;
44 	const struct nfnetlink_subsystem __rcu	*subsys;
45 } table[NFNL_SUBSYS_COUNT];
46 
47 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
48 	[NFNLGRP_CONNTRACK_NEW]		= NFNL_SUBSYS_CTNETLINK,
49 	[NFNLGRP_CONNTRACK_UPDATE]	= NFNL_SUBSYS_CTNETLINK,
50 	[NFNLGRP_CONNTRACK_DESTROY]	= NFNL_SUBSYS_CTNETLINK,
51 	[NFNLGRP_CONNTRACK_EXP_NEW]	= NFNL_SUBSYS_CTNETLINK_EXP,
52 	[NFNLGRP_CONNTRACK_EXP_UPDATE]	= NFNL_SUBSYS_CTNETLINK_EXP,
53 	[NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
54 	[NFNLGRP_NFTABLES]		= NFNL_SUBSYS_NFTABLES,
55 	[NFNLGRP_ACCT_QUOTA]		= NFNL_SUBSYS_ACCT,
56 	[NFNLGRP_NFTRACE]		= NFNL_SUBSYS_NFTABLES,
57 };
58 
59 void nfnl_lock(__u8 subsys_id)
60 {
61 	mutex_lock(&table[subsys_id].mutex);
62 }
63 EXPORT_SYMBOL_GPL(nfnl_lock);
64 
65 void nfnl_unlock(__u8 subsys_id)
66 {
67 	mutex_unlock(&table[subsys_id].mutex);
68 }
69 EXPORT_SYMBOL_GPL(nfnl_unlock);
70 
71 #ifdef CONFIG_PROVE_LOCKING
72 bool lockdep_nfnl_is_held(u8 subsys_id)
73 {
74 	return lockdep_is_held(&table[subsys_id].mutex);
75 }
76 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
77 #endif
78 
79 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
80 {
81 	nfnl_lock(n->subsys_id);
82 	if (table[n->subsys_id].subsys) {
83 		nfnl_unlock(n->subsys_id);
84 		return -EBUSY;
85 	}
86 	rcu_assign_pointer(table[n->subsys_id].subsys, n);
87 	nfnl_unlock(n->subsys_id);
88 
89 	return 0;
90 }
91 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
92 
93 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
94 {
95 	nfnl_lock(n->subsys_id);
96 	table[n->subsys_id].subsys = NULL;
97 	nfnl_unlock(n->subsys_id);
98 	synchronize_rcu();
99 	return 0;
100 }
101 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
102 
103 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
104 {
105 	u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
106 
107 	if (subsys_id >= NFNL_SUBSYS_COUNT)
108 		return NULL;
109 
110 	return rcu_dereference(table[subsys_id].subsys);
111 }
112 
113 static inline const struct nfnl_callback *
114 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
115 {
116 	u_int8_t cb_id = NFNL_MSG_TYPE(type);
117 
118 	if (cb_id >= ss->cb_count)
119 		return NULL;
120 
121 	return &ss->cb[cb_id];
122 }
123 
124 int nfnetlink_has_listeners(struct net *net, unsigned int group)
125 {
126 	return netlink_has_listeners(net->nfnl, group);
127 }
128 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
129 
130 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size,
131 				    u32 dst_portid, gfp_t gfp_mask)
132 {
133 	return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask);
134 }
135 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb);
136 
137 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
138 		   unsigned int group, int echo, gfp_t flags)
139 {
140 	return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
141 }
142 EXPORT_SYMBOL_GPL(nfnetlink_send);
143 
144 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
145 {
146 	return netlink_set_err(net->nfnl, portid, group, error);
147 }
148 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
149 
150 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
151 		      int flags)
152 {
153 	return netlink_unicast(net->nfnl, skb, portid, flags);
154 }
155 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
156 
157 /* Process one complete nfnetlink message. */
158 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
159 {
160 	struct net *net = sock_net(skb->sk);
161 	const struct nfnl_callback *nc;
162 	const struct nfnetlink_subsystem *ss;
163 	int type, err;
164 
165 	/* All the messages must at least contain nfgenmsg */
166 	if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
167 		return 0;
168 
169 	type = nlh->nlmsg_type;
170 replay:
171 	rcu_read_lock();
172 	ss = nfnetlink_get_subsys(type);
173 	if (!ss) {
174 #ifdef CONFIG_MODULES
175 		rcu_read_unlock();
176 		request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
177 		rcu_read_lock();
178 		ss = nfnetlink_get_subsys(type);
179 		if (!ss)
180 #endif
181 		{
182 			rcu_read_unlock();
183 			return -EINVAL;
184 		}
185 	}
186 
187 	nc = nfnetlink_find_client(type, ss);
188 	if (!nc) {
189 		rcu_read_unlock();
190 		return -EINVAL;
191 	}
192 
193 	{
194 		int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
195 		u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
196 		struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
197 		struct nlattr *attr = (void *)nlh + min_len;
198 		int attrlen = nlh->nlmsg_len - min_len;
199 		__u8 subsys_id = NFNL_SUBSYS_ID(type);
200 
201 		err = nla_parse(cda, ss->cb[cb_id].attr_count,
202 				attr, attrlen, ss->cb[cb_id].policy);
203 		if (err < 0) {
204 			rcu_read_unlock();
205 			return err;
206 		}
207 
208 		if (nc->call_rcu) {
209 			err = nc->call_rcu(net, net->nfnl, skb, nlh,
210 					   (const struct nlattr **)cda);
211 			rcu_read_unlock();
212 		} else {
213 			rcu_read_unlock();
214 			nfnl_lock(subsys_id);
215 			if (nfnl_dereference_protected(subsys_id) != ss ||
216 			    nfnetlink_find_client(type, ss) != nc)
217 				err = -EAGAIN;
218 			else if (nc->call)
219 				err = nc->call(net, net->nfnl, skb, nlh,
220 					       (const struct nlattr **)cda);
221 			else
222 				err = -EINVAL;
223 			nfnl_unlock(subsys_id);
224 		}
225 		if (err == -EAGAIN)
226 			goto replay;
227 		return err;
228 	}
229 }
230 
231 struct nfnl_err {
232 	struct list_head	head;
233 	struct nlmsghdr		*nlh;
234 	int			err;
235 };
236 
237 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err)
238 {
239 	struct nfnl_err *nfnl_err;
240 
241 	nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
242 	if (nfnl_err == NULL)
243 		return -ENOMEM;
244 
245 	nfnl_err->nlh = nlh;
246 	nfnl_err->err = err;
247 	list_add_tail(&nfnl_err->head, list);
248 
249 	return 0;
250 }
251 
252 static void nfnl_err_del(struct nfnl_err *nfnl_err)
253 {
254 	list_del(&nfnl_err->head);
255 	kfree(nfnl_err);
256 }
257 
258 static void nfnl_err_reset(struct list_head *err_list)
259 {
260 	struct nfnl_err *nfnl_err, *next;
261 
262 	list_for_each_entry_safe(nfnl_err, next, err_list, head)
263 		nfnl_err_del(nfnl_err);
264 }
265 
266 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
267 {
268 	struct nfnl_err *nfnl_err, *next;
269 
270 	list_for_each_entry_safe(nfnl_err, next, err_list, head) {
271 		netlink_ack(skb, nfnl_err->nlh, nfnl_err->err);
272 		nfnl_err_del(nfnl_err);
273 	}
274 }
275 
276 enum {
277 	NFNL_BATCH_FAILURE	= (1 << 0),
278 	NFNL_BATCH_DONE		= (1 << 1),
279 	NFNL_BATCH_REPLAY	= (1 << 2),
280 };
281 
282 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
283 				u_int16_t subsys_id)
284 {
285 	struct sk_buff *oskb = skb;
286 	struct net *net = sock_net(skb->sk);
287 	const struct nfnetlink_subsystem *ss;
288 	const struct nfnl_callback *nc;
289 	static LIST_HEAD(err_list);
290 	u32 status;
291 	int err;
292 
293 	if (subsys_id >= NFNL_SUBSYS_COUNT)
294 		return netlink_ack(skb, nlh, -EINVAL);
295 replay:
296 	status = 0;
297 
298 	skb = netlink_skb_clone(oskb, GFP_KERNEL);
299 	if (!skb)
300 		return netlink_ack(oskb, nlh, -ENOMEM);
301 
302 	nfnl_lock(subsys_id);
303 	ss = nfnl_dereference_protected(subsys_id);
304 	if (!ss) {
305 #ifdef CONFIG_MODULES
306 		nfnl_unlock(subsys_id);
307 		request_module("nfnetlink-subsys-%d", subsys_id);
308 		nfnl_lock(subsys_id);
309 		ss = nfnl_dereference_protected(subsys_id);
310 		if (!ss)
311 #endif
312 		{
313 			nfnl_unlock(subsys_id);
314 			netlink_ack(oskb, nlh, -EOPNOTSUPP);
315 			return kfree_skb(skb);
316 		}
317 	}
318 
319 	if (!ss->commit || !ss->abort) {
320 		nfnl_unlock(subsys_id);
321 		netlink_ack(oskb, nlh, -EOPNOTSUPP);
322 		return kfree_skb(skb);
323 	}
324 
325 	while (skb->len >= nlmsg_total_size(0)) {
326 		int msglen, type;
327 
328 		nlh = nlmsg_hdr(skb);
329 		err = 0;
330 
331 		if (nlh->nlmsg_len < NLMSG_HDRLEN ||
332 		    skb->len < nlh->nlmsg_len ||
333 		    nlmsg_len(nlh) < sizeof(struct nfgenmsg)) {
334 			nfnl_err_reset(&err_list);
335 			status |= NFNL_BATCH_FAILURE;
336 			goto done;
337 		}
338 
339 		/* Only requests are handled by the kernel */
340 		if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
341 			err = -EINVAL;
342 			goto ack;
343 		}
344 
345 		type = nlh->nlmsg_type;
346 		if (type == NFNL_MSG_BATCH_BEGIN) {
347 			/* Malformed: Batch begin twice */
348 			nfnl_err_reset(&err_list);
349 			status |= NFNL_BATCH_FAILURE;
350 			goto done;
351 		} else if (type == NFNL_MSG_BATCH_END) {
352 			status |= NFNL_BATCH_DONE;
353 			goto done;
354 		} else if (type < NLMSG_MIN_TYPE) {
355 			err = -EINVAL;
356 			goto ack;
357 		}
358 
359 		/* We only accept a batch with messages for the same
360 		 * subsystem.
361 		 */
362 		if (NFNL_SUBSYS_ID(type) != subsys_id) {
363 			err = -EINVAL;
364 			goto ack;
365 		}
366 
367 		nc = nfnetlink_find_client(type, ss);
368 		if (!nc) {
369 			err = -EINVAL;
370 			goto ack;
371 		}
372 
373 		{
374 			int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
375 			u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
376 			struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
377 			struct nlattr *attr = (void *)nlh + min_len;
378 			int attrlen = nlh->nlmsg_len - min_len;
379 
380 			err = nla_parse(cda, ss->cb[cb_id].attr_count,
381 					attr, attrlen, ss->cb[cb_id].policy);
382 			if (err < 0)
383 				goto ack;
384 
385 			if (nc->call_batch) {
386 				err = nc->call_batch(net, net->nfnl, skb, nlh,
387 						     (const struct nlattr **)cda);
388 			}
389 
390 			/* The lock was released to autoload some module, we
391 			 * have to abort and start from scratch using the
392 			 * original skb.
393 			 */
394 			if (err == -EAGAIN) {
395 				status |= NFNL_BATCH_REPLAY;
396 				goto next;
397 			}
398 		}
399 ack:
400 		if (nlh->nlmsg_flags & NLM_F_ACK || err) {
401 			/* Errors are delivered once the full batch has been
402 			 * processed, this avoids that the same error is
403 			 * reported several times when replaying the batch.
404 			 */
405 			if (nfnl_err_add(&err_list, nlh, err) < 0) {
406 				/* We failed to enqueue an error, reset the
407 				 * list of errors and send OOM to userspace
408 				 * pointing to the batch header.
409 				 */
410 				nfnl_err_reset(&err_list);
411 				netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM);
412 				status |= NFNL_BATCH_FAILURE;
413 				goto done;
414 			}
415 			/* We don't stop processing the batch on errors, thus,
416 			 * userspace gets all the errors that the batch
417 			 * triggers.
418 			 */
419 			if (err)
420 				status |= NFNL_BATCH_FAILURE;
421 		}
422 next:
423 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
424 		if (msglen > skb->len)
425 			msglen = skb->len;
426 		skb_pull(skb, msglen);
427 	}
428 done:
429 	if (status & NFNL_BATCH_REPLAY) {
430 		ss->abort(net, oskb);
431 		nfnl_err_reset(&err_list);
432 		nfnl_unlock(subsys_id);
433 		kfree_skb(skb);
434 		goto replay;
435 	} else if (status == NFNL_BATCH_DONE) {
436 		ss->commit(net, oskb);
437 	} else {
438 		ss->abort(net, oskb);
439 	}
440 
441 	nfnl_err_deliver(&err_list, oskb);
442 	nfnl_unlock(subsys_id);
443 	kfree_skb(skb);
444 }
445 
446 static void nfnetlink_rcv(struct sk_buff *skb)
447 {
448 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
449 	u_int16_t res_id;
450 	int msglen;
451 
452 	if (nlh->nlmsg_len < NLMSG_HDRLEN ||
453 	    skb->len < nlh->nlmsg_len)
454 		return;
455 
456 	if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
457 		netlink_ack(skb, nlh, -EPERM);
458 		return;
459 	}
460 
461 	if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) {
462 		struct nfgenmsg *nfgenmsg;
463 
464 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
465 		if (msglen > skb->len)
466 			msglen = skb->len;
467 
468 		if (nlh->nlmsg_len < NLMSG_HDRLEN ||
469 		    skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
470 			return;
471 
472 		nfgenmsg = nlmsg_data(nlh);
473 		skb_pull(skb, msglen);
474 		/* Work around old nft using host byte order */
475 		if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
476 			res_id = NFNL_SUBSYS_NFTABLES;
477 		else
478 			res_id = ntohs(nfgenmsg->res_id);
479 		nfnetlink_rcv_batch(skb, nlh, res_id);
480 	} else {
481 		netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
482 	}
483 }
484 
485 #ifdef CONFIG_MODULES
486 static int nfnetlink_bind(struct net *net, int group)
487 {
488 	const struct nfnetlink_subsystem *ss;
489 	int type;
490 
491 	if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
492 		return 0;
493 
494 	type = nfnl_group2type[group];
495 
496 	rcu_read_lock();
497 	ss = nfnetlink_get_subsys(type << 8);
498 	rcu_read_unlock();
499 	if (!ss)
500 		request_module("nfnetlink-subsys-%d", type);
501 	return 0;
502 }
503 #endif
504 
505 static int __net_init nfnetlink_net_init(struct net *net)
506 {
507 	struct sock *nfnl;
508 	struct netlink_kernel_cfg cfg = {
509 		.groups	= NFNLGRP_MAX,
510 		.input	= nfnetlink_rcv,
511 #ifdef CONFIG_MODULES
512 		.bind	= nfnetlink_bind,
513 #endif
514 	};
515 
516 	nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
517 	if (!nfnl)
518 		return -ENOMEM;
519 	net->nfnl_stash = nfnl;
520 	rcu_assign_pointer(net->nfnl, nfnl);
521 	return 0;
522 }
523 
524 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
525 {
526 	struct net *net;
527 
528 	list_for_each_entry(net, net_exit_list, exit_list)
529 		RCU_INIT_POINTER(net->nfnl, NULL);
530 	synchronize_net();
531 	list_for_each_entry(net, net_exit_list, exit_list)
532 		netlink_kernel_release(net->nfnl_stash);
533 }
534 
535 static struct pernet_operations nfnetlink_net_ops = {
536 	.init		= nfnetlink_net_init,
537 	.exit_batch	= nfnetlink_net_exit_batch,
538 };
539 
540 static int __init nfnetlink_init(void)
541 {
542 	int i;
543 
544 	for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
545 		BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
546 
547 	for (i=0; i<NFNL_SUBSYS_COUNT; i++)
548 		mutex_init(&table[i].mutex);
549 
550 	pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
551 	return register_pernet_subsys(&nfnetlink_net_ops);
552 }
553 
554 static void __exit nfnetlink_exit(void)
555 {
556 	pr_info("Removing netfilter NETLINK layer.\n");
557 	unregister_pernet_subsys(&nfnetlink_net_ops);
558 }
559 module_init(nfnetlink_init);
560 module_exit(nfnetlink_exit);
561