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) 2005,2007 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 static char __initdata nfversion[] = "0.30";
  37
  38 static struct {
  39         struct mutex                            mutex;
  40         const struct nfnetlink_subsystem __rcu  *subsys;
  41 } table[NFNL_SUBSYS_COUNT];
  42
  43 static const int nfnl_group2type[NFNLGRP_MAX+1] = {
  44         [NFNLGRP_CONNTRACK_NEW]         = NFNL_SUBSYS_CTNETLINK,
  45         [NFNLGRP_CONNTRACK_UPDATE]      = NFNL_SUBSYS_CTNETLINK,
  46         [NFNLGRP_CONNTRACK_DESTROY]     = NFNL_SUBSYS_CTNETLINK,
  47         [NFNLGRP_CONNTRACK_EXP_NEW]     = NFNL_SUBSYS_CTNETLINK_EXP,
  48         [NFNLGRP_CONNTRACK_EXP_UPDATE]  = NFNL_SUBSYS_CTNETLINK_EXP,
  49         [NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP,
  50         [NFNLGRP_NFTABLES]              = NFNL_SUBSYS_NFTABLES,
  51         [NFNLGRP_ACCT_QUOTA]            = NFNL_SUBSYS_ACCT,
  52 };
  53
  54 void nfnl_lock(__u8 subsys_id)
  55 {
  56         mutex_lock(&table[subsys_id].mutex);
  57 }
  58 EXPORT_SYMBOL_GPL(nfnl_lock);
  59
  60 void nfnl_unlock(__u8 subsys_id)
  61 {
  62         mutex_unlock(&table[subsys_id].mutex);
  63 }
  64 EXPORT_SYMBOL_GPL(nfnl_unlock);
  65
  66 #ifdef CONFIG_PROVE_LOCKING
  67 int lockdep_nfnl_is_held(u8 subsys_id)
  68 {
  69         return lockdep_is_held(&table[subsys_id].mutex);
  70 }
  71 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held);
  72 #endif
  73
  74 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n)
  75 {
  76         nfnl_lock(n->subsys_id);
  77         if (table[n->subsys_id].subsys) {
  78                 nfnl_unlock(n->subsys_id);
  79                 return -EBUSY;
  80         }
  81         rcu_assign_pointer(table[n->subsys_id].subsys, n);
  82         nfnl_unlock(n->subsys_id);
  83
  84         return 0;
  85 }
  86 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register);
  87
  88 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n)
  89 {
  90         nfnl_lock(n->subsys_id);
  91         table[n->subsys_id].subsys = NULL;
  92         nfnl_unlock(n->subsys_id);
  93         synchronize_rcu();
  94         return 0;
  95 }
  96 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister);
  97
  98 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type)
  99 {
 100         u_int8_t subsys_id = NFNL_SUBSYS_ID(type);
 101
 102         if (subsys_id >= NFNL_SUBSYS_COUNT)
 103                 return NULL;
 104
 105         return rcu_dereference(table[subsys_id].subsys);
 106 }
 107
 108 static inline const struct nfnl_callback *
 109 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss)
 110 {
 111         u_int8_t cb_id = NFNL_MSG_TYPE(type);
 112
 113         if (cb_id >= ss->cb_count)
 114                 return NULL;
 115
 116         return &ss->cb[cb_id];
 117 }
 118
 119 int nfnetlink_has_listeners(struct net *net, unsigned int group)
 120 {
 121         return netlink_has_listeners(net->nfnl, group);
 122 }
 123 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners);
 124
 125 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size,
 126                                     u32 dst_portid, gfp_t gfp_mask)
 127 {
 128         return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask);
 129 }
 130 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb);
 131
 132 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
 133                    unsigned int group, int echo, gfp_t flags)
 134 {
 135         return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
 136 }
 137 EXPORT_SYMBOL_GPL(nfnetlink_send);
 138
 139 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
 140 {
 141         return netlink_set_err(net->nfnl, portid, group, error);
 142 }
 143 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 144
 145 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
 146                       int flags)
 147 {
 148         return netlink_unicast(net->nfnl, skb, portid, flags);
 149 }
 150 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 151
 152 /* Process one complete nfnetlink message. */
 153 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 154 {
 155         struct net *net = sock_net(skb->sk);
 156         const struct nfnl_callback *nc;
 157         const struct nfnetlink_subsystem *ss;
 158         int type, err;
 159
 160         /* All the messages must at least contain nfgenmsg */
 161         if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
 162                 return 0;
 163
 164         type = nlh->nlmsg_type;
 165 replay:
 166         rcu_read_lock();
 167         ss = nfnetlink_get_subsys(type);
 168         if (!ss) {
 169 #ifdef CONFIG_MODULES
 170                 rcu_read_unlock();
 171                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 172                 rcu_read_lock();
 173                 ss = nfnetlink_get_subsys(type);
 174                 if (!ss)
 175 #endif
 176                 {
 177                         rcu_read_unlock();
 178                         return -EINVAL;
 179                 }
 180         }
 181
 182         nc = nfnetlink_find_client(type, ss);
 183         if (!nc) {
 184                 rcu_read_unlock();
 185                 return -EINVAL;
 186         }
 187
 188         {
 189                 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 190                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 191                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 192                 struct nlattr *attr = (void *)nlh + min_len;
 193                 int attrlen = nlh->nlmsg_len - min_len;
 194                 __u8 subsys_id = NFNL_SUBSYS_ID(type);
 195
 196                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 197                                 attr, attrlen, ss->cb[cb_id].policy);
 198                 if (err < 0) {
 199                         rcu_read_unlock();
 200                         return err;
 201                 }
 202
 203                 if (nc->call_rcu) {
 204                         err = nc->call_rcu(net->nfnl, skb, nlh,
 205                                            (const struct nlattr **)cda);
 206                         rcu_read_unlock();
 207                 } else {
 208                         rcu_read_unlock();
 209                         nfnl_lock(subsys_id);
 210                         if (rcu_dereference_protected(table[subsys_id].subsys,
 211                                 lockdep_is_held(&table[subsys_id].mutex)) != ss ||
 212                             nfnetlink_find_client(type, ss) != nc)
 213                                 err = -EAGAIN;
 214                         else if (nc->call)
 215                                 err = nc->call(net->nfnl, skb, nlh,
 216                                                    (const struct nlattr **)cda);
 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 };
 232
 233 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err)
 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         list_add_tail(&nfnl_err->head, list);
 244
 245         return 0;
 246 }
 247
 248 static void nfnl_err_del(struct nfnl_err *nfnl_err)
 249 {
 250         list_del(&nfnl_err->head);
 251         kfree(nfnl_err);
 252 }
 253
 254 static void nfnl_err_reset(struct list_head *err_list)
 255 {
 256         struct nfnl_err *nfnl_err, *next;
 257
 258         list_for_each_entry_safe(nfnl_err, next, err_list, head)
 259                 nfnl_err_del(nfnl_err);
 260 }
 261
 262 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
 263 {
 264         struct nfnl_err *nfnl_err, *next;
 265
 266         list_for_each_entry_safe(nfnl_err, next, err_list, head) {
 267                 netlink_ack(skb, nfnl_err->nlh, nfnl_err->err);
 268                 nfnl_err_del(nfnl_err);
 269         }
 270 }
 271
 272 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 273                                 u_int16_t subsys_id)
 274 {
 275         struct sk_buff *oskb = skb;
 276         struct net *net = sock_net(skb->sk);
 277         const struct nfnetlink_subsystem *ss;
 278         const struct nfnl_callback *nc;
 279         bool success = true, done = false;
 280         static LIST_HEAD(err_list);
 281         int err;
 282
 283         if (subsys_id >= NFNL_SUBSYS_COUNT)
 284                 return netlink_ack(skb, nlh, -EINVAL);
 285 replay:
 286         skb = netlink_skb_clone(oskb, GFP_KERNEL);
 287         if (!skb)
 288                 return netlink_ack(oskb, nlh, -ENOMEM);
 289
 290         skb->sk = oskb->sk;
 291
 292         nfnl_lock(subsys_id);
 293         ss = rcu_dereference_protected(table[subsys_id].subsys,
 294                                        lockdep_is_held(&table[subsys_id].mutex));
 295         if (!ss) {
 296 #ifdef CONFIG_MODULES
 297                 nfnl_unlock(subsys_id);
 298                 request_module("nfnetlink-subsys-%d", subsys_id);
 299                 nfnl_lock(subsys_id);
 300                 ss = rcu_dereference_protected(table[subsys_id].subsys,
 301                                                lockdep_is_held(&table[subsys_id].mutex));
 302                 if (!ss)
 303 #endif
 304                 {
 305                         nfnl_unlock(subsys_id);
 306                         netlink_ack(skb, nlh, -EOPNOTSUPP);
 307                         return kfree_skb(skb);
 308                 }
 309         }
 310
 311         if (!ss->commit || !ss->abort) {
 312                 nfnl_unlock(subsys_id);
 313                 netlink_ack(skb, nlh, -EOPNOTSUPP);
 314                 return kfree_skb(skb);
 315         }
 316
 317         while (skb->len >= nlmsg_total_size(0)) {
 318                 int msglen, type;
 319
 320                 nlh = nlmsg_hdr(skb);
 321                 err = 0;
 322
 323                 if (nlmsg_len(nlh) < sizeof(struct nfgenmsg) ||
 324                     skb->len < nlh->nlmsg_len) {
 325                         err = -EINVAL;
 326                         goto ack;
 327                 }
 328
 329                 /* Only requests are handled by the kernel */
 330                 if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 331                         err = -EINVAL;
 332                         goto ack;
 333                 }
 334
 335                 type = nlh->nlmsg_type;
 336                 if (type == NFNL_MSG_BATCH_BEGIN) {
 337                         /* Malformed: Batch begin twice */
 338                         nfnl_err_reset(&err_list);
 339                         success = false;
 340                         goto done;
 341                 } else if (type == NFNL_MSG_BATCH_END) {
 342                         done = true;
 343                         goto done;
 344                 } else if (type < NLMSG_MIN_TYPE) {
 345                         err = -EINVAL;
 346                         goto ack;
 347                 }
 348
 349                 /* We only accept a batch with messages for the same
 350                  * subsystem.
 351                  */
 352                 if (NFNL_SUBSYS_ID(type) != subsys_id) {
 353                         err = -EINVAL;
 354                         goto ack;
 355                 }
 356
 357                 nc = nfnetlink_find_client(type, ss);
 358                 if (!nc) {
 359                         err = -EINVAL;
 360                         goto ack;
 361                 }
 362
 363                 {
 364                         int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 365                         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 366                         struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 367                         struct nlattr *attr = (void *)nlh + min_len;
 368                         int attrlen = nlh->nlmsg_len - min_len;
 369
 370                         err = nla_parse(cda, ss->cb[cb_id].attr_count,
 371                                         attr, attrlen, ss->cb[cb_id].policy);
 372                         if (err < 0)
 373                                 goto ack;
 374
 375                         if (nc->call_batch) {
 376                                 err = nc->call_batch(net->nfnl, skb, nlh,
 377                                                      (const struct nlattr **)cda);
 378                         }
 379
 380                         /* The lock was released to autoload some module, we
 381                          * have to abort and start from scratch using the
 382                          * original skb.
 383                          */
 384                         if (err == -EAGAIN) {
 385                                 nfnl_err_reset(&err_list);
 386                                 ss->abort(oskb);
 387                                 nfnl_unlock(subsys_id);
 388                                 kfree_skb(skb);
 389                                 goto replay;
 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(skb, nlmsg_hdr(oskb), -ENOMEM);
 405                                 success = false;
 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                                 success = false;
 414                 }
 415
 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 (success && done)
 423                 ss->commit(oskb);
 424         else
 425                 ss->abort(oskb);
 426
 427         nfnl_err_deliver(&err_list, oskb);
 428         nfnl_unlock(subsys_id);
 429         kfree_skb(skb);
 430 }
 431
 432 static void nfnetlink_rcv(struct sk_buff *skb)
 433 {
 434         struct nlmsghdr *nlh = nlmsg_hdr(skb);
 435         int msglen;
 436
 437         if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 438             skb->len < nlh->nlmsg_len)
 439                 return;
 440
 441         if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
 442                 netlink_ack(skb, nlh, -EPERM);
 443                 return;
 444         }
 445
 446         if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) {
 447                 struct nfgenmsg *nfgenmsg;
 448
 449                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 450                 if (msglen > skb->len)
 451                         msglen = skb->len;
 452
 453                 if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 454                     skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
 455                         return;
 456
 457                 nfgenmsg = nlmsg_data(nlh);
 458                 skb_pull(skb, msglen);
 459                 nfnetlink_rcv_batch(skb, nlh, nfgenmsg->res_id);
 460         } else {
 461                 netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 462         }
 463 }
 464
 465 #ifdef CONFIG_MODULES
 466 static int nfnetlink_bind(struct net *net, int group)
 467 {
 468         const struct nfnetlink_subsystem *ss;
 469         int type;
 470
 471         if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
 472                 return 0;
 473
 474         type = nfnl_group2type[group];
 475
 476         rcu_read_lock();
 477         ss = nfnetlink_get_subsys(type);
 478         rcu_read_unlock();
 479         if (!ss)
 480                 request_module("nfnetlink-subsys-%d", type);
 481         return 0;
 482 }
 483 #endif
 484
 485 static int __net_init nfnetlink_net_init(struct net *net)
 486 {
 487         struct sock *nfnl;
 488         struct netlink_kernel_cfg cfg = {
 489                 .groups = NFNLGRP_MAX,
 490                 .input  = nfnetlink_rcv,
 491 #ifdef CONFIG_MODULES
 492                 .bind   = nfnetlink_bind,
 493 #endif
 494         };
 495
 496         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 497         if (!nfnl)
 498                 return -ENOMEM;
 499         net->nfnl_stash = nfnl;
 500         rcu_assign_pointer(net->nfnl, nfnl);
 501         return 0;
 502 }
 503
 504 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 505 {
 506         struct net *net;
 507
 508         list_for_each_entry(net, net_exit_list, exit_list)
 509                 RCU_INIT_POINTER(net->nfnl, NULL);
 510         synchronize_net();
 511         list_for_each_entry(net, net_exit_list, exit_list)
 512                 netlink_kernel_release(net->nfnl_stash);
 513 }
 514
 515 static struct pernet_operations nfnetlink_net_ops = {
 516         .init           = nfnetlink_net_init,
 517         .exit_batch     = nfnetlink_net_exit_batch,
 518 };
 519
 520 static int __init nfnetlink_init(void)
 521 {
 522         int i;
 523
 524         for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
 525                 BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
 526
 527         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 528                 mutex_init(&table[i].mutex);
 529
 530         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 531         return register_pernet_subsys(&nfnetlink_net_ops);
 532 }
 533
 534 static void __exit nfnetlink_exit(void)
 535 {
 536         pr_info("Removing netfilter NETLINK layer.\n");
 537         unregister_pernet_subsys(&nfnetlink_net_ops);
 538 }
 539 module_init(nfnetlink_init);
 540 module_exit(nfnetlink_exit);