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                                            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);