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Linux/net/netfilter/nfnetlink.c

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  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 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, 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 (nfnl_dereference_protected(subsys_id) != ss ||
209                             nfnetlink_find_client(type, ss) != nc)
210                                 err = -EAGAIN;
211                         else if (nc->call)
212                                 err = nc->call(net, net->nfnl, skb, nlh,
213                                                (const struct nlattr **)cda);
214                         else
215                                 err = -EINVAL;
216                         nfnl_unlock(subsys_id);
217                 }
218                 if (err == -EAGAIN)
219                         goto replay;
220                 return err;
221         }
222 }
223 
224 struct nfnl_err {
225         struct list_head        head;
226         struct nlmsghdr         *nlh;
227         int                     err;
228 };
229 
230 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err)
231 {
232         struct nfnl_err *nfnl_err;
233 
234         nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
235         if (nfnl_err == NULL)
236                 return -ENOMEM;
237 
238         nfnl_err->nlh = nlh;
239         nfnl_err->err = err;
240         list_add_tail(&nfnl_err->head, list);
241 
242         return 0;
243 }
244 
245 static void nfnl_err_del(struct nfnl_err *nfnl_err)
246 {
247         list_del(&nfnl_err->head);
248         kfree(nfnl_err);
249 }
250 
251 static void nfnl_err_reset(struct list_head *err_list)
252 {
253         struct nfnl_err *nfnl_err, *next;
254 
255         list_for_each_entry_safe(nfnl_err, next, err_list, head)
256                 nfnl_err_del(nfnl_err);
257 }
258 
259 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
260 {
261         struct nfnl_err *nfnl_err, *next;
262 
263         list_for_each_entry_safe(nfnl_err, next, err_list, head) {
264                 netlink_ack(skb, nfnl_err->nlh, nfnl_err->err);
265                 nfnl_err_del(nfnl_err);
266         }
267 }
268 
269 enum {
270         NFNL_BATCH_FAILURE      = (1 << 0),
271         NFNL_BATCH_DONE         = (1 << 1),
272         NFNL_BATCH_REPLAY       = (1 << 2),
273 };
274 
275 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
276                                 u_int16_t subsys_id)
277 {
278         struct sk_buff *oskb = skb;
279         struct net *net = sock_net(skb->sk);
280         const struct nfnetlink_subsystem *ss;
281         const struct nfnl_callback *nc;
282         static LIST_HEAD(err_list);
283         u32 status;
284         int err;
285 
286         if (subsys_id >= NFNL_SUBSYS_COUNT)
287                 return netlink_ack(skb, nlh, -EINVAL);
288 replay:
289         status = 0;
290 
291         skb = netlink_skb_clone(oskb, GFP_KERNEL);
292         if (!skb)
293                 return netlink_ack(oskb, nlh, -ENOMEM);
294 
295         nfnl_lock(subsys_id);
296         ss = nfnl_dereference_protected(subsys_id);
297         if (!ss) {
298 #ifdef CONFIG_MODULES
299                 nfnl_unlock(subsys_id);
300                 request_module("nfnetlink-subsys-%d", subsys_id);
301                 nfnl_lock(subsys_id);
302                 ss = nfnl_dereference_protected(subsys_id);
303                 if (!ss)
304 #endif
305                 {
306                         nfnl_unlock(subsys_id);
307                         netlink_ack(oskb, nlh, -EOPNOTSUPP);
308                         return kfree_skb(skb);
309                 }
310         }
311 
312         if (!ss->commit || !ss->abort) {
313                 nfnl_unlock(subsys_id);
314                 netlink_ack(oskb, nlh, -EOPNOTSUPP);
315                 return kfree_skb(skb);
316         }
317 
318         while (skb->len >= nlmsg_total_size(0)) {
319                 int msglen, type;
320 
321                 nlh = nlmsg_hdr(skb);
322                 err = 0;
323 
324                 if (nlh->nlmsg_len < NLMSG_HDRLEN ||
325                     skb->len < nlh->nlmsg_len ||
326                     nlmsg_len(nlh) < sizeof(struct nfgenmsg)) {
327                         nfnl_err_reset(&err_list);
328                         status |= NFNL_BATCH_FAILURE;
329                         goto done;
330                 }
331 
332                 /* Only requests are handled by the kernel */
333                 if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
334                         err = -EINVAL;
335                         goto ack;
336                 }
337 
338                 type = nlh->nlmsg_type;
339                 if (type == NFNL_MSG_BATCH_BEGIN) {
340                         /* Malformed: Batch begin twice */
341                         nfnl_err_reset(&err_list);
342                         status |= NFNL_BATCH_FAILURE;
343                         goto done;
344                 } else if (type == NFNL_MSG_BATCH_END) {
345                         status |= NFNL_BATCH_DONE;
346                         goto done;
347                 } else if (type < NLMSG_MIN_TYPE) {
348                         err = -EINVAL;
349                         goto ack;
350                 }
351 
352                 /* We only accept a batch with messages for the same
353                  * subsystem.
354                  */
355                 if (NFNL_SUBSYS_ID(type) != subsys_id) {
356                         err = -EINVAL;
357                         goto ack;
358                 }
359 
360                 nc = nfnetlink_find_client(type, ss);
361                 if (!nc) {
362                         err = -EINVAL;
363                         goto ack;
364                 }
365 
366                 {
367                         int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
368                         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
369                         struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
370                         struct nlattr *attr = (void *)nlh + min_len;
371                         int attrlen = nlh->nlmsg_len - min_len;
372 
373                         err = nla_parse(cda, ss->cb[cb_id].attr_count,
374                                         attr, attrlen, ss->cb[cb_id].policy);
375                         if (err < 0)
376                                 goto ack;
377 
378                         if (nc->call_batch) {
379                                 err = nc->call_batch(net, net->nfnl, skb, nlh,
380                                                      (const struct nlattr **)cda);
381                         }
382 
383                         /* The lock was released to autoload some module, we
384                          * have to abort and start from scratch using the
385                          * original skb.
386                          */
387                         if (err == -EAGAIN) {
388                                 status |= NFNL_BATCH_REPLAY;
389                                 goto next;
390                         }
391                 }
392 ack:
393                 if (nlh->nlmsg_flags & NLM_F_ACK || err) {
394                         /* Errors are delivered once the full batch has been
395                          * processed, this avoids that the same error is
396                          * reported several times when replaying the batch.
397                          */
398                         if (nfnl_err_add(&err_list, nlh, err) < 0) {
399                                 /* We failed to enqueue an error, reset the
400                                  * list of errors and send OOM to userspace
401                                  * pointing to the batch header.
402                                  */
403                                 nfnl_err_reset(&err_list);
404                                 netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM);
405                                 status |= NFNL_BATCH_FAILURE;
406                                 goto done;
407                         }
408                         /* We don't stop processing the batch on errors, thus,
409                          * userspace gets all the errors that the batch
410                          * triggers.
411                          */
412                         if (err)
413                                 status |= NFNL_BATCH_FAILURE;
414                 }
415 next:
416                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
417                 if (msglen > skb->len)
418                         msglen = skb->len;
419                 skb_pull(skb, msglen);
420         }
421 done:
422         if (status & NFNL_BATCH_REPLAY) {
423                 ss->abort(net, oskb);
424                 nfnl_err_reset(&err_list);
425                 nfnl_unlock(subsys_id);
426                 kfree_skb(skb);
427                 goto replay;
428         } else if (status == NFNL_BATCH_DONE) {
429                 ss->commit(net, oskb);
430         } else {
431                 ss->abort(net, oskb);
432         }
433 
434         nfnl_err_deliver(&err_list, oskb);
435         nfnl_unlock(subsys_id);
436         kfree_skb(skb);
437 }
438 
439 static void nfnetlink_rcv(struct sk_buff *skb)
440 {
441         struct nlmsghdr *nlh = nlmsg_hdr(skb);
442         u_int16_t res_id;
443         int msglen;
444 
445         if (nlh->nlmsg_len < NLMSG_HDRLEN ||
446             skb->len < nlh->nlmsg_len)
447                 return;
448 
449         if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
450                 netlink_ack(skb, nlh, -EPERM);
451                 return;
452         }
453 
454         if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) {
455                 struct nfgenmsg *nfgenmsg;
456 
457                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
458                 if (msglen > skb->len)
459                         msglen = skb->len;
460 
461                 if (nlh->nlmsg_len < NLMSG_HDRLEN ||
462                     skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
463                         return;
464 
465                 nfgenmsg = nlmsg_data(nlh);
466                 skb_pull(skb, msglen);
467                 /* Work around old nft using host byte order */
468                 if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
469                         res_id = NFNL_SUBSYS_NFTABLES;
470                 else
471                         res_id = ntohs(nfgenmsg->res_id);
472                 nfnetlink_rcv_batch(skb, nlh, res_id);
473         } else {
474                 netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
475         }
476 }
477 
478 #ifdef CONFIG_MODULES
479 static int nfnetlink_bind(struct net *net, int group)
480 {
481         const struct nfnetlink_subsystem *ss;
482         int type;
483 
484         if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
485                 return 0;
486 
487         type = nfnl_group2type[group];
488 
489         rcu_read_lock();
490         ss = nfnetlink_get_subsys(type << 8);
491         rcu_read_unlock();
492         if (!ss)
493                 request_module("nfnetlink-subsys-%d", type);
494         return 0;
495 }
496 #endif
497 
498 static int __net_init nfnetlink_net_init(struct net *net)
499 {
500         struct sock *nfnl;
501         struct netlink_kernel_cfg cfg = {
502                 .groups = NFNLGRP_MAX,
503                 .input  = nfnetlink_rcv,
504 #ifdef CONFIG_MODULES
505                 .bind   = nfnetlink_bind,
506 #endif
507         };
508 
509         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
510         if (!nfnl)
511                 return -ENOMEM;
512         net->nfnl_stash = nfnl;
513         rcu_assign_pointer(net->nfnl, nfnl);
514         return 0;
515 }
516 
517 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
518 {
519         struct net *net;
520 
521         list_for_each_entry(net, net_exit_list, exit_list)
522                 RCU_INIT_POINTER(net->nfnl, NULL);
523         synchronize_net();
524         list_for_each_entry(net, net_exit_list, exit_list)
525                 netlink_kernel_release(net->nfnl_stash);
526 }
527 
528 static struct pernet_operations nfnetlink_net_ops = {
529         .init           = nfnetlink_net_init,
530         .exit_batch     = nfnetlink_net_exit_batch,
531 };
532 
533 static int __init nfnetlink_init(void)
534 {
535         int i;
536 
537         for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
538                 BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
539 
540         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
541                 mutex_init(&table[i].mutex);
542 
543         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
544         return register_pernet_subsys(&nfnetlink_net_ops);
545 }
546 
547 static void __exit nfnetlink_exit(void)
548 {
549         pr_info("Removing netfilter NETLINK layer.\n");
550         unregister_pernet_subsys(&nfnetlink_net_ops);
551 }
552 module_init(nfnetlink_init);
553 module_exit(nfnetlink_exit);
554 

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