net/netfilter/nfnetlink.c

   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                         rcu_read_unlock();
 206                 } else {
 207                         rcu_read_unlock();
 208                         nfnl_lock(subsys_id);
 209                         if (nfnl_dereference_protected(subsys_id) != ss ||
 210                             nfnetlink_find_client(type, ss) != nc)
 211                                 err = -EAGAIN;
 212                         else if (nc->call)
 213                                 err = nc->call(net, 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, NULL);
 266                 nfnl_err_del(nfnl_err);
 267         }
 268 }
 269
 270 enum {
 271         NFNL_BATCH_FAILURE      = (1 << 0),
 272         NFNL_BATCH_DONE         = (1 << 1),
 273         NFNL_BATCH_REPLAY       = (1 << 2),
 274 };
 275
 276 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 277                                 u16 subsys_id, u32 genid)
 278 {
 279         struct sk_buff *oskb = skb;
 280         struct net *net = sock_net(skb->sk);
 281         const struct nfnetlink_subsystem *ss;
 282         const struct nfnl_callback *nc;
 283         LIST_HEAD(err_list);
 284         u32 status;
 285         int err;
 286
 287         if (subsys_id >= NFNL_SUBSYS_COUNT)
 288                 return netlink_ack(skb, nlh, -EINVAL, NULL);
 289 replay:
 290         status = 0;
 291
 292         skb = netlink_skb_clone(oskb, GFP_KERNEL);
 293         if (!skb)
 294                 return netlink_ack(oskb, nlh, -ENOMEM, NULL);
 295
 296         nfnl_lock(subsys_id);
 297         ss = nfnl_dereference_protected(subsys_id);
 298         if (!ss) {
 299 #ifdef CONFIG_MODULES
 300                 nfnl_unlock(subsys_id);
 301                 request_module("nfnetlink-subsys-%d", subsys_id);
 302                 nfnl_lock(subsys_id);
 303                 ss = nfnl_dereference_protected(subsys_id);
 304                 if (!ss)
 305 #endif
 306                 {
 307                         nfnl_unlock(subsys_id);
 308                         netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
 309                         return kfree_skb(skb);
 310                 }
 311         }
 312
 313         if (!ss->commit || !ss->abort) {
 314                 nfnl_unlock(subsys_id);
 315                 netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
 316                 return kfree_skb(skb);
 317         }
 318
 319         if (genid && ss->valid_genid && !ss->valid_genid(net, genid)) {
 320                 nfnl_unlock(subsys_id);
 321                 netlink_ack(oskb, nlh, -ERESTART, NULL);
 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                         u8 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, attr,
 381                                         attrlen, ss->cb[cb_id].policy, NULL);
 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                                             NULL);
 413                                 status |= NFNL_BATCH_FAILURE;
 414                                 goto done;
 415                         }
 416                         /* We don't stop processing the batch on errors, thus,
 417                          * userspace gets all the errors that the batch
 418                          * triggers.
 419                          */
 420                         if (err)
 421                                 status |= NFNL_BATCH_FAILURE;
 422                 }
 423 next:
 424                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 425                 if (msglen > skb->len)
 426                         msglen = skb->len;
 427                 skb_pull(skb, msglen);
 428         }
 429 done:
 430         if (status & NFNL_BATCH_REPLAY) {
 431                 ss->abort(net, oskb);
 432                 nfnl_err_reset(&err_list);
 433                 nfnl_unlock(subsys_id);
 434                 kfree_skb(skb);
 435                 goto replay;
 436         } else if (status == NFNL_BATCH_DONE) {
 437                 ss->commit(net, oskb);
 438         } else {
 439                 ss->abort(net, oskb);
 440         }
 441
 442         nfnl_err_deliver(&err_list, oskb);
 443         nfnl_unlock(subsys_id);
 444         kfree_skb(skb);
 445 }
 446
 447 static const struct nla_policy nfnl_batch_policy[NFNL_BATCH_MAX + 1] = {
 448         [NFNL_BATCH_GENID]      = { .type = NLA_U32 },
 449 };
 450
 451 static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh)
 452 {
 453         int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 454         struct nlattr *attr = (void *)nlh + min_len;
 455         struct nlattr *cda[NFNL_BATCH_MAX + 1];
 456         int attrlen = nlh->nlmsg_len - min_len;
 457         struct nfgenmsg *nfgenmsg;
 458         int msglen, err;
 459         u32 gen_id = 0;
 460         u16 res_id;
 461
 462         msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 463         if (msglen > skb->len)
 464                 msglen = skb->len;
 465
 466         if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 467             skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
 468                 return;
 469
 470         err = nla_parse(cda, NFNL_BATCH_MAX, attr, attrlen, nfnl_batch_policy,
 471                         NULL);
 472         if (err < 0) {
 473                 netlink_ack(skb, nlh, err, NULL);
 474                 return;
 475         }
 476         if (cda[NFNL_BATCH_GENID])
 477                 gen_id = ntohl(nla_get_be32(cda[NFNL_BATCH_GENID]));
 478
 479         nfgenmsg = nlmsg_data(nlh);
 480         skb_pull(skb, msglen);
 481         /* Work around old nft using host byte order */
 482         if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
 483                 res_id = NFNL_SUBSYS_NFTABLES;
 484         else
 485                 res_id = ntohs(nfgenmsg->res_id);
 486
 487         nfnetlink_rcv_batch(skb, nlh, res_id, gen_id);
 488 }
 489
 490 static void nfnetlink_rcv(struct sk_buff *skb)
 491 {
 492         struct nlmsghdr *nlh = nlmsg_hdr(skb);
 493
 494         if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 495             skb->len < nlh->nlmsg_len)
 496                 return;
 497
 498         if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
 499                 netlink_ack(skb, nlh, -EPERM, NULL);
 500                 return;
 501         }
 502
 503         if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN)
 504                 nfnetlink_rcv_skb_batch(skb, nlh);
 505         else
 506                 netlink_rcv_skb(skb, nfnetlink_rcv_msg);
 507 }
 508
 509 #ifdef CONFIG_MODULES
 510 static int nfnetlink_bind(struct net *net, int group)
 511 {
 512         const struct nfnetlink_subsystem *ss;
 513         int type;
 514
 515         if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
 516                 return 0;
 517
 518         type = nfnl_group2type[group];
 519
 520         rcu_read_lock();
 521         ss = nfnetlink_get_subsys(type << 8);
 522         rcu_read_unlock();
 523         if (!ss)
 524                 request_module("nfnetlink-subsys-%d", type);
 525         return 0;
 526 }
 527 #endif
 528
 529 static int __net_init nfnetlink_net_init(struct net *net)
 530 {
 531         struct sock *nfnl;
 532         struct netlink_kernel_cfg cfg = {
 533                 .groups = NFNLGRP_MAX,
 534                 .input  = nfnetlink_rcv,
 535 #ifdef CONFIG_MODULES
 536                 .bind   = nfnetlink_bind,
 537 #endif
 538         };
 539
 540         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 541         if (!nfnl)
 542                 return -ENOMEM;
 543         net->nfnl_stash = nfnl;
 544         rcu_assign_pointer(net->nfnl, nfnl);
 545         return 0;
 546 }
 547
 548 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 549 {
 550         struct net *net;
 551
 552         list_for_each_entry(net, net_exit_list, exit_list)
 553                 RCU_INIT_POINTER(net->nfnl, NULL);
 554         synchronize_net();
 555         list_for_each_entry(net, net_exit_list, exit_list)
 556                 netlink_kernel_release(net->nfnl_stash);
 557 }
 558
 559 static struct pernet_operations nfnetlink_net_ops = {
 560         .init           = nfnetlink_net_init,
 561         .exit_batch     = nfnetlink_net_exit_batch,
 562 };
 563
 564 static int __init nfnetlink_init(void)
 565 {
 566         int i;
 567
 568         for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
 569                 BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
 570
 571         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 572                 mutex_init(&table[i].mutex);
 573
 574         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 575         return register_pernet_subsys(&nfnetlink_net_ops);
 576 }
 577
 578 static void __exit nfnetlink_exit(void)
 579 {
 580         pr_info("Removing netfilter NETLINK layer.\n");
 581         unregister_pernet_subsys(&nfnetlink_net_ops);
 582 }
 583 module_init(nfnetlink_init);
 584 module_exit(nfnetlink_exit);