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 struct {
  41         struct mutex                            mutex;
  42         const struct nfnetlink_subsystem __rcu  *subsys;
  43 } table[NFNL_SUBSYS_COUNT];
  44
  45 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
  46         [NFNLGRP_CONNTRACK_NEW]         = NFNL_SUBSYS_CTNETLINK,
  47         [NFNLGRP_CONNTRACK_UPDATE]      = NFNL_SUBSYS_CTNETLINK,
  48         [NFNLGRP_CONNTRACK_DESTROY]     = NFNL_SUBSYS_CTNETLINK,
  49         [NFNLGRP_CONNTRACK_EXP_NEW]     = NFNL_SUBSYS_CTNETLINK_EXP,
  50         [NFNLGRP_CONNTRACK_EXP_UPDATE]  = NFNL_SUBSYS_CTNETLINK_EXP,
  51         [NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
  52         [NFNLGRP_NFTABLES]              = NFNL_SUBSYS_NFTABLES,
  53         [NFNLGRP_ACCT_QUOTA]            = NFNL_SUBSYS_ACCT,
  54         [NFNLGRP_NFTRACE]               = NFNL_SUBSYS_NFTABLES,
  55 };
  56
  57 void nfnl_lock(__u8 subsys_id)
  58 {
  59         mutex_lock(&table[subsys_id].mutex);
  60 }
  61 EXPORT_SYMBOL_GPL(nfnl_lock);
  62
  63 void nfnl_unlock(__u8 subsys_id)
  64 {
  65         mutex_unlock(&table[subsys_id].mutex);
  66 }
  67 EXPORT_SYMBOL_GPL(nfnl_unlock);
  68
  69 #ifdef CONFIG_PROVE_LOCKING
  70 bool lockdep_nfnl_is_held(u8 subsys_id)
  71 {
  72         return lockdep_is_held(&table[subsys_id].mutex);
  73 }
  74 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
  75 #endif
  76
  77 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  78 {
  79         nfnl_lock(n->subsys_id);
  80         if (table[n->subsys_id].subsys) {
  81                 nfnl_unlock(n->subsys_id);
  82                 return -EBUSY;
  83         }
  84         rcu_assign_pointer(table[n->subsys_id].subsys, n);
  85         nfnl_unlock(n->subsys_id);
  86
  87         return 0;
  88 }
  89 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  90
  91 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  92 {
  93         nfnl_lock(n->subsys_id);
  94         table[n->subsys_id].subsys = NULL;
  95         nfnl_unlock(n->subsys_id);
  96         synchronize_rcu();
  97         return 0;
  98 }
  99 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
 100
 101 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u16 type)
 102 {
 103         u8 subsys_id = NFNL_SUBSYS_ID(type);
 104
 105         if (subsys_id >= NFNL_SUBSYS_COUNT)
 106                 return NULL;
 107
 108         return rcu_dereference(table[subsys_id].subsys);
 109 }
 110
 111 static inline const struct nfnl_callback *
 112 nfnetlink_find_client(u16 type, const struct nfnetlink_subsystem *ss)
 113 {
 114         u8 cb_id = NFNL_MSG_TYPE(type);
 115
 116         if (cb_id >= ss->cb_count)
 117                 return NULL;
 118
 119         return &ss->cb[cb_id];
 120 }
 121
 122 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 123 {
 124         return netlink_has_listeners(net->nfnl, group);
 125 }
 126 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 127
 128 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
 129                    unsigned int group, int echo, gfp_t flags)
 130 {
 131         return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
 132 }
 133 EXPORT_SYMBOL_GPL(nfnetlink_send);
 134
 135 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
 136 {
 137         return netlink_set_err(net->nfnl, portid, group, error);
 138 }
 139 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 140
 141 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
 142                       int flags)
 143 {
 144         return netlink_unicast(net->nfnl, skb, portid, flags);
 145 }
 146 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 147
 148 /* Process one complete nfnetlink message. */
 149 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
 150                              struct netlink_ext_ack *extack)
 151 {
 152         struct net *net = sock_net(skb->sk);
 153         const struct nfnl_callback *nc;
 154         const struct nfnetlink_subsystem *ss;
 155         int type, err;
 156
 157         /* All the messages must at least contain nfgenmsg */
 158         if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
 159                 return 0;
 160
 161         type = nlh->nlmsg_type;
 162 replay:
 163         rcu_read_lock();
 164         ss = nfnetlink_get_subsys(type);
 165         if (!ss) {
 166 #ifdef CONFIG_MODULES
 167                 rcu_read_unlock();
 168                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 169                 rcu_read_lock();
 170                 ss = nfnetlink_get_subsys(type);
 171                 if (!ss)
 172 #endif
 173                 {
 174                         rcu_read_unlock();
 175                         return -EINVAL;
 176                 }
 177         }
 178
 179         nc = nfnetlink_find_client(type, ss);
 180         if (!nc) {
 181                 rcu_read_unlock();
 182                 return -EINVAL;
 183         }
 184
 185         {
 186                 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 187                 u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 188                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 189                 struct nlattr *attr = (void *)nlh + min_len;
 190                 int attrlen = nlh->nlmsg_len - min_len;
 191                 __u8 subsys_id = NFNL_SUBSYS_ID(type);
 192
 193                 err = nla_parse(cda, ss->cb[cb_id].attr_count, attr, attrlen,
 194                                 ss->cb[cb_id].policy, extack);
 195                 if (err < 0) {
 196                         rcu_read_unlock();
 197                         return err;
 198                 }
 199
 200                 if (nc->call_rcu) {
 201                         err = nc->call_rcu(net, net->nfnl, skb, nlh,
 202                                            (const struct nlattr **)cda,
 203                                            extack);
 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                                                extack);
 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         struct netlink_ext_ack  extack;
 230 };
 231
 232 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err,
 233                         const struct netlink_ext_ack *extack)
 234 {
 235         struct nfnl_err *nfnl_err;
 236
 237         nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
 238         if (nfnl_err == NULL)
 239                 return -ENOMEM;
 240
 241         nfnl_err->nlh = nlh;
 242         nfnl_err->err = err;
 243         nfnl_err->extack = *extack;
 244         list_add_tail(&nfnl_err->head, list);
 245
 246         return 0;
 247 }
 248
 249 static void nfnl_err_del(struct nfnl_err *nfnl_err)
 250 {
 251         list_del(&nfnl_err->head);
 252         kfree(nfnl_err);
 253 }
 254
 255 static void nfnl_err_reset(struct list_head *err_list)
 256 {
 257         struct nfnl_err *nfnl_err, *next;
 258
 259         list_for_each_entry_safe(nfnl_err, next, err_list, head)
 260                 nfnl_err_del(nfnl_err);
 261 }
 262
 263 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
 264 {
 265         struct nfnl_err *nfnl_err, *next;
 266
 267         list_for_each_entry_safe(nfnl_err, next, err_list, head) {
 268                 netlink_ack(skb, nfnl_err->nlh, nfnl_err->err,
 269                             &nfnl_err->extack);
 270                 nfnl_err_del(nfnl_err);
 271         }
 272 }
 273
 274 enum {
 275         NFNL_BATCH_FAILURE      = (1 << 0),
 276         NFNL_BATCH_DONE         = (1 << 1),
 277         NFNL_BATCH_REPLAY       = (1 << 2),
 278 };
 279
 280 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 281                                 u16 subsys_id, u32 genid)
 282 {
 283         struct sk_buff *oskb = skb;
 284         struct net *net = sock_net(skb->sk);
 285         const struct nfnetlink_subsystem *ss;
 286         const struct nfnl_callback *nc;
 287         struct netlink_ext_ack extack;
 288         LIST_HEAD(err_list);
 289         u32 status;
 290         int err;
 291
 292         if (subsys_id >= NFNL_SUBSYS_COUNT)
 293                 return netlink_ack(skb, nlh, -EINVAL, NULL);
 294 replay:
 295         status = 0;
 296
 297         skb = netlink_skb_clone(oskb, GFP_KERNEL);
 298         if (!skb)
 299                 return netlink_ack(oskb, nlh, -ENOMEM, NULL);
 300
 301         nfnl_lock(subsys_id);
 302         ss = nfnl_dereference_protected(subsys_id);
 303         if (!ss) {
 304 #ifdef CONFIG_MODULES
 305                 nfnl_unlock(subsys_id);
 306                 request_module("nfnetlink-subsys-%d", subsys_id);
 307                 nfnl_lock(subsys_id);
 308                 ss = nfnl_dereference_protected(subsys_id);
 309                 if (!ss)
 310 #endif
 311                 {
 312                         nfnl_unlock(subsys_id);
 313                         netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
 314                         return kfree_skb(skb);
 315                 }
 316         }
 317
 318         if (!ss->commit || !ss->abort) {
 319                 nfnl_unlock(subsys_id);
 320                 netlink_ack(oskb, nlh, -EOPNOTSUPP, NULL);
 321                 return kfree_skb(skb);
 322         }
 323
 324         if (genid && ss->valid_genid && !ss->valid_genid(net, genid)) {
 325                 nfnl_unlock(subsys_id);
 326                 netlink_ack(oskb, nlh, -ERESTART, NULL);
 327                 return kfree_skb(skb);
 328         }
 329
 330         while (skb->len >= nlmsg_total_size(0)) {
 331                 int msglen, type;
 332
 333                 memset(&extack, 0, sizeof(extack));
 334                 nlh = nlmsg_hdr(skb);
 335                 err = 0;
 336
 337                 if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 338                     skb->len < nlh->nlmsg_len ||
 339                     nlmsg_len(nlh) < sizeof(struct nfgenmsg)) {
 340                         nfnl_err_reset(&err_list);
 341                         status |= NFNL_BATCH_FAILURE;
 342                         goto done;
 343                 }
 344
 345                 /* Only requests are handled by the kernel */
 346                 if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 347                         err = -EINVAL;
 348                         goto ack;
 349                 }
 350
 351                 type = nlh->nlmsg_type;
 352                 if (type == NFNL_MSG_BATCH_BEGIN) {
 353                         /* Malformed: Batch begin twice */
 354                         nfnl_err_reset(&err_list);
 355                         status |= NFNL_BATCH_FAILURE;
 356                         goto done;
 357                 } else if (type == NFNL_MSG_BATCH_END) {
 358                         status |= NFNL_BATCH_DONE;
 359                         goto done;
 360                 } else if (type < NLMSG_MIN_TYPE) {
 361                         err = -EINVAL;
 362                         goto ack;
 363                 }
 364
 365                 /* We only accept a batch with messages for the same
 366                  * subsystem.
 367                  */
 368                 if (NFNL_SUBSYS_ID(type) != subsys_id) {
 369                         err = -EINVAL;
 370                         goto ack;
 371                 }
 372
 373                 nc = nfnetlink_find_client(type, ss);
 374                 if (!nc) {
 375                         err = -EINVAL;
 376                         goto ack;
 377                 }
 378
 379                 {
 380                         int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 381                         u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 382                         struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 383                         struct nlattr *attr = (void *)nlh + min_len;
 384                         int attrlen = nlh->nlmsg_len - min_len;
 385
 386                         err = nla_parse(cda, ss->cb[cb_id].attr_count, attr,
 387                                         attrlen, ss->cb[cb_id].policy, NULL);
 388                         if (err < 0)
 389                                 goto ack;
 390
 391                         if (nc->call_batch) {
 392                                 err = nc->call_batch(net, net->nfnl, skb, nlh,
 393                                                      (const struct nlattr **)cda,
 394                                                      &extack);
 395                         }
 396
 397                         /* The lock was released to autoload some module, we
 398                          * have to abort and start from scratch using the
 399                          * original skb.
 400                          */
 401                         if (err == -EAGAIN) {
 402                                 status |= NFNL_BATCH_REPLAY;
 403                                 goto next;
 404                         }
 405                 }
 406 ack:
 407                 if (nlh->nlmsg_flags & NLM_F_ACK || err) {
 408                         /* Errors are delivered once the full batch has been
 409                          * processed, this avoids that the same error is
 410                          * reported several times when replaying the batch.
 411                          */
 412                         if (nfnl_err_add(&err_list, nlh, err, &extack) < 0) {
 413                                 /* We failed to enqueue an error, reset the
 414                                  * list of errors and send OOM to userspace
 415                                  * pointing to the batch header.
 416                                  */
 417                                 nfnl_err_reset(&err_list);
 418                                 netlink_ack(oskb, nlmsg_hdr(oskb), -ENOMEM,
 419                                             NULL);
 420                                 status |= NFNL_BATCH_FAILURE;
 421                                 goto done;
 422                         }
 423                         /* We don't stop processing the batch on errors, thus,
 424                          * userspace gets all the errors that the batch
 425                          * triggers.
 426                          */
 427                         if (err)
 428                                 status |= NFNL_BATCH_FAILURE;
 429                 }
 430 next:
 431                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 432                 if (msglen > skb->len)
 433                         msglen = skb->len;
 434                 skb_pull(skb, msglen);
 435         }
 436 done:
 437         if (status & NFNL_BATCH_REPLAY) {
 438                 ss->abort(net, oskb);
 439                 nfnl_err_reset(&err_list);
 440                 nfnl_unlock(subsys_id);
 441                 kfree_skb(skb);
 442                 goto replay;
 443         } else if (status == NFNL_BATCH_DONE) {
 444                 ss->commit(net, oskb);
 445         } else {
 446                 ss->abort(net, oskb);
 447         }
 448
 449         nfnl_err_deliver(&err_list, oskb);
 450         nfnl_unlock(subsys_id);
 451         kfree_skb(skb);
 452 }
 453
 454 static const struct nla_policy nfnl_batch_policy[NFNL_BATCH_MAX + 1] = {
 455         [NFNL_BATCH_GENID]      = { .type = NLA_U32 },
 456 };
 457
 458 static void nfnetlink_rcv_skb_batch(struct sk_buff *skb, struct nlmsghdr *nlh)
 459 {
 460         int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 461         struct nlattr *attr = (void *)nlh + min_len;
 462         struct nlattr *cda[NFNL_BATCH_MAX + 1];
 463         int attrlen = nlh->nlmsg_len - min_len;
 464         struct nfgenmsg *nfgenmsg;
 465         int msglen, err;
 466         u32 gen_id = 0;
 467         u16 res_id;
 468
 469         msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 470         if (msglen > skb->len)
 471                 msglen = skb->len;
 472
 473         if (skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
 474                 return;
 475
 476         err = nla_parse(cda, NFNL_BATCH_MAX, attr, attrlen, nfnl_batch_policy,
 477                         NULL);
 478         if (err < 0) {
 479                 netlink_ack(skb, nlh, err, NULL);
 480                 return;
 481         }
 482         if (cda[NFNL_BATCH_GENID])
 483                 gen_id = ntohl(nla_get_be32(cda[NFNL_BATCH_GENID]));
 484
 485         nfgenmsg = nlmsg_data(nlh);
 486         skb_pull(skb, msglen);
 487         /* Work around old nft using host byte order */
 488         if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
 489                 res_id = NFNL_SUBSYS_NFTABLES;
 490         else
 491                 res_id = ntohs(nfgenmsg->res_id);
 492
 493         nfnetlink_rcv_batch(skb, nlh, res_id, gen_id);
 494 }
 495
 496 static void nfnetlink_rcv(struct sk_buff *skb)
 497 {
 498         struct nlmsghdr *nlh = nlmsg_hdr(skb);
 499
 500         if (skb->len < NLMSG_HDRLEN ||
 501             nlh->nlmsg_len < NLMSG_HDRLEN ||
 502             skb->len < nlh->nlmsg_len)
 503                 return;
 504
 505         if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
 506                 netlink_ack(skb, nlh, -EPERM, NULL);
 507                 return;
 508         }
 509
 510         if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN)
 511                 nfnetlink_rcv_skb_batch(skb, nlh);
 512         else
 513                 netlink_rcv_skb(skb, nfnetlink_rcv_msg);
 514 }
 515
 516 #ifdef CONFIG_MODULES
 517 static int nfnetlink_bind(struct net *net, int group)
 518 {
 519         const struct nfnetlink_subsystem *ss;
 520         int type;
 521
 522         if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
 523                 return 0;
 524
 525         type = nfnl_group2type[group];
 526
 527         rcu_read_lock();
 528         ss = nfnetlink_get_subsys(type << 8);
 529         rcu_read_unlock();
 530         if (!ss)
 531                 request_module("nfnetlink-subsys-%d", type);
 532         return 0;
 533 }
 534 #endif
 535
 536 static int __net_init nfnetlink_net_init(struct net *net)
 537 {
 538         struct sock *nfnl;
 539         struct netlink_kernel_cfg cfg = {
 540                 .groups = NFNLGRP_MAX,
 541                 .input  = nfnetlink_rcv,
 542 #ifdef CONFIG_MODULES
 543                 .bind   = nfnetlink_bind,
 544 #endif
 545         };
 546
 547         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 548         if (!nfnl)
 549                 return -ENOMEM;
 550         net->nfnl_stash = nfnl;
 551         rcu_assign_pointer(net->nfnl, nfnl);
 552         return 0;
 553 }
 554
 555 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 556 {
 557         struct net *net;
 558
 559         list_for_each_entry(net, net_exit_list, exit_list)
 560                 RCU_INIT_POINTER(net->nfnl, NULL);
 561         synchronize_net();
 562         list_for_each_entry(net, net_exit_list, exit_list)
 563                 netlink_kernel_release(net->nfnl_stash);
 564 }
 565
 566 static struct pernet_operations nfnetlink_net_ops = {
 567         .init           = nfnetlink_net_init,
 568         .exit_batch     = nfnetlink_net_exit_batch,
 569 };
 570
 571 static int __init nfnetlink_init(void)
 572 {
 573         int i;
 574
 575         for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
 576                 BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
 577
 578         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 579                 mutex_init(&table[i].mutex);
 580
 581         return register_pernet_subsys(&nfnetlink_net_ops);
 582 }
 583
 584 static void __exit nfnetlink_exit(void)
 585 {
 586         unregister_pernet_subsys(&nfnetlink_net_ops);
 587 }
 588 module_init(nfnetlink_init);
 589 module_exit(nfnetlink_exit);