xref: /openbmc/linux/net/netfilter/nfnetlink.c (revision b24413180f5600bcb3bb70fbed5cf186b60864bd) 
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) 2005-2017 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 <linux/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(u16 type)
104 {
105 	u8 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(u16 type, const struct nfnetlink_subsystem *ss)
115 {
116 	u8 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 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 			     struct netlink_ext_ack *extack)
153 {
154 	struct net *net = sock_net(skb->sk);
155 	const struct nfnl_callback *nc;
156 	const struct nfnetlink_subsystem *ss;
157 	int type, err;
158 
159 	/* All the messages must at least contain nfgenmsg */
160 	if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
161 		return 0;
162 
163 	type = nlh->nlmsg_type;
164 replay:
165 	rcu_read_lock();
166 	ss = nfnetlink_get_subsys(type);
167 	if (!ss) {
168 #ifdef CONFIG_MODULES
169 		rcu_read_unlock();
170 		request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
171 		rcu_read_lock();
172 		ss = nfnetlink_get_subsys(type);
173 		if (!ss)
174 #endif
175 		{
176 			rcu_read_unlock();
177 			return -EINVAL;
178 		}
179 	}
180 
181 	nc = nfnetlink_find_client(type, ss);
182 	if (!nc) {
183 		rcu_read_unlock();
184 		return -EINVAL;
185 	}
186 
187 	{
188 		int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
189 		u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
190 		struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
191 		struct nlattr *attr = (void *)nlh + min_len;
192 		int attrlen = nlh->nlmsg_len - min_len;
193 		__u8 subsys_id = NFNL_SUBSYS_ID(type);
194 
195 		err = nla_parse(cda, ss->cb[cb_id].attr_count, attr, attrlen,
196 				ss->cb[cb_id].policy, extack);
197 		if (err < 0) {
198 			rcu_read_unlock();
199 			return err;
200 		}
201 
202 		if (nc->call_rcu) {
203 			err = nc->call_rcu(net, net->nfnl, skb, nlh,
204 					   (const struct nlattr **)cda,
205 					   extack);
206 			rcu_read_unlock();
207 		} else {
208 			rcu_read_unlock();
209 			nfnl_lock(subsys_id);
210 			if (nfnl_dereference_protected(subsys_id) != ss ||
211 			    nfnetlink_find_client(type, ss) != nc)
212 				err = -EAGAIN;
213 			else if (nc->call)
214 				err = nc->call(net, net->nfnl, skb, nlh,
215 					       (const struct nlattr **)cda,
216 					       extack);
217 			else
218 				err = -EINVAL;
219 			nfnl_unlock(subsys_id);
220 		}
221 		if (err == -EAGAIN)
222 			goto replay;
223 		return err;
224 	}
225 }
226 
227 struct nfnl_err {
228 	struct list_head	head;
229 	struct nlmsghdr		*nlh;
230 	int			err;
231 	struct netlink_ext_ack	extack;
232 };
233 
234 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err,
235 			const struct netlink_ext_ack *extack)
236 {
237 	struct nfnl_err *nfnl_err;
238 
239 	nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
240 	if (nfnl_err == NULL)
241 		return -ENOMEM;
242 
243 	nfnl_err->nlh = nlh;
244 	nfnl_err->err = err;
245 	nfnl_err->extack = *extack;
246 	list_add_tail(&nfnl_err->head, list);
247 
248 	return 0;
249 }
250 
251 static void nfnl_err_del(struct nfnl_err *nfnl_err)
252 {
253 	list_del(&nfnl_err->head);
254 	kfree(nfnl_err);
255 }
256 
257 static void nfnl_err_reset(struct list_head *err_list)
258 {
259 	struct nfnl_err *nfnl_err, *next;
260 
261 	list_for_each_entry_safe(nfnl_err, next, err_list, head)
262 		nfnl_err_del(nfnl_err);
263 }
264 
265 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
266 {
267 	struct nfnl_err *nfnl_err, *next;
268 
269 	list_for_each_entry_safe(nfnl_err, next, err_list, head) {
270 		netlink_ack(skb, nfnl_err->nlh, nfnl_err->err,
271 			    &nfnl_err->extack);
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 				u16 subsys_id, u32 genid)
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 	struct netlink_ext_ack extack;
290 	LIST_HEAD(err_list);
291 	u32 status;
292 	int err;
293 
294 	if (subsys_id >= NFNL_SUBSYS_COUNT)
295 		return netlink_ack(skb, nlh, -EINVAL, NULL);
296 replay:
297 	status = 0;
298 
299 	skb = netlink_skb_clone(oskb, GFP_KERNEL);
300 	if (!skb)
301 		return netlink_ack(oskb, nlh, -ENOMEM, NULL);
302 
303 	nfnl_lock(subsys_id);
304 	ss = nfnl_dereference_protected(subsys_id);
305 	if (!ss) {
306 #ifdef CONFIG_MODULES
307 		nfnl_unlock(subsys_id);
308 		request_module("nfnetlink-subsys-%d", subsys_id);
309 		nfnl_lock(subsys_id);
310 		ss = nfnl_dereference_protected(subsys_id);
311 		if (!ss)
312 #endif
313 		{
314 			nfnl_unlock(subsys_id);
315 			netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
316 			return kfree_skb(skb);
317 		}
318 	}
319 
320 	if (!ss->commit || !ss->abort) {
321 		nfnl_unlock(subsys_id);
322 		netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
323 		return kfree_skb(skb);
324 	}
325 
326 	if (genid && ss->valid_genid && !ss->valid_genid(net, genid)) {
327 		nfnl_unlock(subsys_id);
328 		netlink_ack(oskb, nlh, -ERESTART, NULL);
329 		return kfree_skb(skb);
330 	}
331 
332 	while (skb->len >= nlmsg_total_size(0)) {
333 		int msglen, type;
334 
335 		memset(&extack, 0, sizeof(extack));
336 		nlh = nlmsg_hdr(skb);
337 		err = 0;
338 
339 		if (nlh->nlmsg_len < NLMSG_HDRLEN ||
340 		    skb->len < nlh->nlmsg_len ||
341 		    nlmsg_len(nlh) < sizeof(struct nfgenmsg)) {
342 			nfnl_err_reset(&err_list);
343 			status |= NFNL_BATCH_FAILURE;
344 			goto done;
345 		}
346 
347 		/* Only requests are handled by the kernel */
348 		if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
349 			err = -EINVAL;
350 			goto ack;
351 		}
352 
353 		type = nlh->nlmsg_type;
354 		if (type == NFNL_MSG_BATCH_BEGIN) {
355 			/* Malformed: Batch begin twice */
356 			nfnl_err_reset(&err_list);
357 			status |= NFNL_BATCH_FAILURE;
358 			goto done;
359 		} else if (type == NFNL_MSG_BATCH_END) {
360 			status |= NFNL_BATCH_DONE;
361 			goto done;
362 		} else if (type < NLMSG_MIN_TYPE) {
363 			err = -EINVAL;
364 			goto ack;
365 		}
366 
367 		/* We only accept a batch with messages for the same
368 		 * subsystem.
369 		 */
370 		if (NFNL_SUBSYS_ID(type) != subsys_id) {
371 			err = -EINVAL;
372 			goto ack;
373 		}
374 
375 		nc = nfnetlink_find_client(type, ss);
376 		if (!nc) {
377 			err = -EINVAL;
378 			goto ack;
379 		}
380 
381 		{
382 			int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
383 			u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
384 			struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
385 			struct nlattr *attr = (void *)nlh + min_len;
386 			int attrlen = nlh->nlmsg_len - min_len;
387 
388 			err = nla_parse(cda, ss->cb[cb_id].attr_count, attr,
389 					attrlen, ss->cb[cb_id].policy, NULL);
390 			if (err < 0)
391 				goto ack;
392 
393 			if (nc->call_batch) {
394 				err = nc->call_batch(net, net->nfnl, skb, nlh,
395 						     (const struct nlattr **)cda,
396 						     &extack);
397 			}
398 
399 			/* The lock was released to autoload some module, we
400 			 * have to abort and start from scratch using the
401 			 * original skb.
402 			 */
403 			if (err == -EAGAIN) {
404 				status |= NFNL_BATCH_REPLAY;
405 				goto next;
406 			}
407 		}
408 ack:
409 		if (nlh->nlmsg_flags & NLM_F_ACK || err) {
410 			/* Errors are delivered once the full batch has been
411 			 * processed, this avoids that the same error is
412 			 * reported several times when replaying the batch.
413 			 */
414 			if (nfnl_err_add(&err_list, nlh, err, &extack) < 0) {
415 				/* We failed to enqueue an error, reset the
416 				 * list of errors and send OOM to userspace
417 				 * pointing to the batch header.
418 				 */
419 				nfnl_err_reset(&err_list);
420 				netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM,
421 					    NULL);
422 				status |= NFNL_BATCH_FAILURE;
423 				goto done;
424 			}
425 			/* We don't stop processing the batch on errors, thus,
426 			 * userspace gets all the errors that the batch
427 			 * triggers.
428 			 */
429 			if (err)
430 				status |= NFNL_BATCH_FAILURE;
431 		}
432 next:
433 		msglen = NLMSG_ALIGN(nlh->nlmsg_len);
434 		if (msglen > skb->len)
435 			msglen = skb->len;
436 		skb_pull(skb, msglen);
437 	}
438 done:
439 	if (status & NFNL_BATCH_REPLAY) {
440 		ss->abort(net, oskb);
441 		nfnl_err_reset(&err_list);
442 		nfnl_unlock(subsys_id);
443 		kfree_skb(skb);
444 		goto replay;
445 	} else if (status == NFNL_BATCH_DONE) {
446 		ss->commit(net, oskb);
447 	} else {
448 		ss->abort(net, oskb);
449 	}
450 
451 	nfnl_err_deliver(&err_list, oskb);
452 	nfnl_unlock(subsys_id);
453 	kfree_skb(skb);
454 }
455 
456 static const struct nla_policy nfnl_batch_policy[NFNL_BATCH_MAX + 1] = {
457 	[NFNL_BATCH_GENID]	= { .type = NLA_U32 },
458 };
459 
460 static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh)
461 {
462 	int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
463 	struct nlattr *attr = (void *)nlh + min_len;
464 	struct nlattr *cda[NFNL_BATCH_MAX + 1];
465 	int attrlen = nlh->nlmsg_len - min_len;
466 	struct nfgenmsg *nfgenmsg;
467 	int msglen, err;
468 	u32 gen_id = 0;
469 	u16 res_id;
470 
471 	msglen = NLMSG_ALIGN(nlh->nlmsg_len);
472 	if (msglen > skb->len)
473 		msglen = skb->len;
474 
475 	if (skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
476 		return;
477 
478 	err = nla_parse(cda, NFNL_BATCH_MAX, attr, attrlen, nfnl_batch_policy,
479 			NULL);
480 	if (err < 0) {
481 		netlink_ack(skb, nlh, err, NULL);
482 		return;
483 	}
484 	if (cda[NFNL_BATCH_GENID])
485 		gen_id = ntohl(nla_get_be32(cda[NFNL_BATCH_GENID]));
486 
487 	nfgenmsg = nlmsg_data(nlh);
488 	skb_pull(skb, msglen);
489 	/* Work around old nft using host byte order */
490 	if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
491 		res_id = NFNL_SUBSYS_NFTABLES;
492 	else
493 		res_id = ntohs(nfgenmsg->res_id);
494 
495 	nfnetlink_rcv_batch(skb, nlh, res_id, gen_id);
496 }
497 
498 static void nfnetlink_rcv(struct sk_buff *skb)
499 {
500 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
501 
502 	if (skb->len < NLMSG_HDRLEN ||
503 	    nlh->nlmsg_len < NLMSG_HDRLEN ||
504 	    skb->len < nlh->nlmsg_len)
505 		return;
506 
507 	if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
508 		netlink_ack(skb, nlh, -EPERM, NULL);
509 		return;
510 	}
511 
512 	if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN)
513 		nfnetlink_rcv_skb_batch(skb, nlh);
514 	else
515 		netlink_rcv_skb(skb, nfnetlink_rcv_msg);
516 }
517 
518 #ifdef CONFIG_MODULES
519 static int nfnetlink_bind(struct net *net, int group)
520 {
521 	const struct nfnetlink_subsystem *ss;
522 	int type;
523 
524 	if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
525 		return 0;
526 
527 	type = nfnl_group2type[group];
528 
529 	rcu_read_lock();
530 	ss = nfnetlink_get_subsys(type << 8);
531 	rcu_read_unlock();
532 	if (!ss)
533 		request_module("nfnetlink-subsys-%d", type);
534 	return 0;
535 }
536 #endif
537 
538 static int __net_init nfnetlink_net_init(struct net *net)
539 {
540 	struct sock *nfnl;
541 	struct netlink_kernel_cfg cfg = {
542 		.groups	= NFNLGRP_MAX,
543 		.input	= nfnetlink_rcv,
544 #ifdef CONFIG_MODULES
545 		.bind	= nfnetlink_bind,
546 #endif
547 	};
548 
549 	nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
550 	if (!nfnl)
551 		return -ENOMEM;
552 	net->nfnl_stash = nfnl;
553 	rcu_assign_pointer(net->nfnl, nfnl);
554 	return 0;
555 }
556 
557 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
558 {
559 	struct net *net;
560 
561 	list_for_each_entry(net, net_exit_list, exit_list)
562 		RCU_INIT_POINTER(net->nfnl, NULL);
563 	synchronize_net();
564 	list_for_each_entry(net, net_exit_list, exit_list)
565 		netlink_kernel_release(net->nfnl_stash);
566 }
567 
568 static struct pernet_operations nfnetlink_net_ops = {
569 	.init		= nfnetlink_net_init,
570 	.exit_batch	= nfnetlink_net_exit_batch,
571 };
572 
573 static int __init nfnetlink_init(void)
574 {
575 	int i;
576 
577 	for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
578 		BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
579 
580 	for (i=0; i<NFNL_SUBSYS_COUNT; i++)
581 		mutex_init(&table[i].mutex);
582 
583 	pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
584 	return register_pernet_subsys(&nfnetlink_net_ops);
585 }
586 
587 static void __exit nfnetlink_exit(void)
588 {
589 	pr_info("Removing netfilter NETLINK layer.\n");
590 	unregister_pernet_subsys(&nfnetlink_net_ops);
591 }
592 module_init(nfnetlink_init);
593 module_exit(nfnetlink_exit);
594