net/strparser/strparser.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Stream Parser
   4  *
   5  * Copyright (c) 2016 Tom Herbert <tom@herbertland.com>
   6  */
   7
   8 #include <linux/bpf.h>
   9 #include <linux/errno.h>
  10 #include <linux/errqueue.h>
  11 #include <linux/file.h>
  12 #include <linux/in.h>
  13 #include <linux/kernel.h>
  14 #include <linux/export.h>
  15 #include <linux/init.h>
  16 #include <linux/net.h>
  17 #include <linux/netdevice.h>
  18 #include <linux/poll.h>
  19 #include <linux/rculist.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/socket.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/workqueue.h>
  24 #include <net/strparser.h>
  25 #include <net/netns/generic.h>
  26 #include <net/sock.h>
  27
  28 static struct workqueue_struct *strp_wq;
  29
  30 struct _strp_msg {
  31         /* Internal cb structure. struct strp_msg must be first for passing
  32          * to upper layer.
  33          */
  34         struct strp_msg strp;
  35         int accum_len;
  36 };
  37
  38 static inline struct _strp_msg *_strp_msg(struct sk_buff *skb)
  39 {
  40         return (struct _strp_msg *)((void *)skb->cb +
  41                 offsetof(struct qdisc_skb_cb, data));
  42 }
  43
  44 /* Lower lock held */
  45 static void strp_abort_strp(struct strparser *strp, int err)
  46 {
  47         /* Unrecoverable error in receive */
  48
  49         cancel_delayed_work(&strp->msg_timer_work);
  50
  51         if (strp->stopped)
  52                 return;
  53
  54         strp->stopped = 1;
  55
  56         if (strp->sk) {
  57                 struct sock *sk = strp->sk;
  58
  59                 /* Report an error on the lower socket */
  60                 sk->sk_err = -err;
  61                 sk->sk_error_report(sk);
  62         }
  63 }
  64
  65 static void strp_start_timer(struct strparser *strp, long timeo)
  66 {
  67         if (timeo && timeo != LONG_MAX)
  68                 mod_delayed_work(strp_wq, &strp->msg_timer_work, timeo);
  69 }
  70
  71 /* Lower lock held */
  72 static void strp_parser_err(struct strparser *strp, int err,
  73                             read_descriptor_t *desc)
  74 {
  75         desc->error = err;
  76         kfree_skb(strp->skb_head);
  77         strp->skb_head = NULL;
  78         strp->cb.abort_parser(strp, err);
  79 }
  80
  81 static inline int strp_peek_len(struct strparser *strp)
  82 {
  83         if (strp->sk) {
  84                 struct socket *sock = strp->sk->sk_socket;
  85
  86                 return sock->ops->peek_len(sock);
  87         }
  88
  89         /* If we don't have an associated socket there's nothing to peek.
  90          * Return int max to avoid stopping the strparser.
  91          */
  92
  93         return INT_MAX;
  94 }
  95
  96 /* Lower socket lock held */
  97 static int __strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
  98                        unsigned int orig_offset, size_t orig_len,
  99                        size_t max_msg_size, long timeo)
 100 {
 101         struct strparser *strp = (struct strparser *)desc->arg.data;
 102         struct _strp_msg *stm;
 103         struct sk_buff *head, *skb;
 104         size_t eaten = 0, cand_len;
 105         ssize_t extra;
 106         int err;
 107         bool cloned_orig = false;
 108
 109         if (strp->paused)
 110                 return 0;
 111
 112         head = strp->skb_head;
 113         if (head) {
 114                 /* Message already in progress */
 115                 if (unlikely(orig_offset)) {
 116                         /* Getting data with a non-zero offset when a message is
 117                          * in progress is not expected. If it does happen, we
 118                          * need to clone and pull since we can't deal with
 119                          * offsets in the skbs for a message expect in the head.
 120                          */
 121                         orig_skb = skb_clone(orig_skb, GFP_ATOMIC);
 122                         if (!orig_skb) {
 123                                 STRP_STATS_INCR(strp->stats.mem_fail);
 124                                 desc->error = -ENOMEM;
 125                                 return 0;
 126                         }
 127                         if (!pskb_pull(orig_skb, orig_offset)) {
 128                                 STRP_STATS_INCR(strp->stats.mem_fail);
 129                                 kfree_skb(orig_skb);
 130                                 desc->error = -ENOMEM;
 131                                 return 0;
 132                         }
 133                         cloned_orig = true;
 134                         orig_offset = 0;
 135                 }
 136
 137                 if (!strp->skb_nextp) {
 138                         /* We are going to append to the frags_list of head.
 139                          * Need to unshare the frag_list.
 140                          */
 141                         err = skb_unclone(head, GFP_ATOMIC);
 142                         if (err) {
 143                                 STRP_STATS_INCR(strp->stats.mem_fail);
 144                                 desc->error = err;
 145                                 return 0;
 146                         }
 147
 148                         if (unlikely(skb_shinfo(head)->frag_list)) {
 149                                 /* We can't append to an sk_buff that already
 150                                  * has a frag_list. We create a new head, point
 151                                  * the frag_list of that to the old head, and
 152                                  * then are able to use the old head->next for
 153                                  * appending to the message.
 154                                  */
 155                                 if (WARN_ON(head->next)) {
 156                                         desc->error = -EINVAL;
 157                                         return 0;
 158                                 }
 159
 160                                 skb = alloc_skb_for_msg(head);
 161                                 if (!skb) {
 162                                         STRP_STATS_INCR(strp->stats.mem_fail);
 163                                         desc->error = -ENOMEM;
 164                                         return 0;
 165                                 }
 166
 167                                 strp->skb_nextp = &head->next;
 168                                 strp->skb_head = skb;
 169                                 head = skb;
 170                         } else {
 171                                 strp->skb_nextp =
 172                                     &skb_shinfo(head)->frag_list;
 173                         }
 174                 }
 175         }
 176
 177         while (eaten < orig_len) {
 178                 /* Always clone since we will consume something */
 179                 skb = skb_clone(orig_skb, GFP_ATOMIC);
 180                 if (!skb) {
 181                         STRP_STATS_INCR(strp->stats.mem_fail);
 182                         desc->error = -ENOMEM;
 183                         break;
 184                 }
 185
 186                 cand_len = orig_len - eaten;
 187
 188                 head = strp->skb_head;
 189                 if (!head) {
 190                         head = skb;
 191                         strp->skb_head = head;
 192                         /* Will set skb_nextp on next packet if needed */
 193                         strp->skb_nextp = NULL;
 194                         stm = _strp_msg(head);
 195                         memset(stm, 0, sizeof(*stm));
 196                         stm->strp.offset = orig_offset + eaten;
 197                 } else {
 198                         /* Unclone if we are appending to an skb that we
 199                          * already share a frag_list with.
 200                          */
 201                         if (skb_has_frag_list(skb)) {
 202                                 err = skb_unclone(skb, GFP_ATOMIC);
 203                                 if (err) {
 204                                         STRP_STATS_INCR(strp->stats.mem_fail);
 205                                         desc->error = err;
 206                                         break;
 207                                 }
 208                         }
 209
 210                         stm = _strp_msg(head);
 211                         *strp->skb_nextp = skb;
 212                         strp->skb_nextp = &skb->next;
 213                         head->data_len += skb->len;
 214                         head->len += skb->len;
 215                         head->truesize += skb->truesize;
 216                 }
 217
 218                 if (!stm->strp.full_len) {
 219                         ssize_t len;
 220
 221                         len = (*strp->cb.parse_msg)(strp, head);
 222
 223                         if (!len) {
 224                                 /* Need more header to determine length */
 225                                 if (!stm->accum_len) {
 226                                         /* Start RX timer for new message */
 227                                         strp_start_timer(strp, timeo);
 228                                 }
 229                                 stm->accum_len += cand_len;
 230                                 eaten += cand_len;
 231                                 STRP_STATS_INCR(strp->stats.need_more_hdr);
 232                                 WARN_ON(eaten != orig_len);
 233                                 break;
 234                         } else if (len < 0) {
 235                                 if (len == -ESTRPIPE && stm->accum_len) {
 236                                         len = -ENODATA;
 237                                         strp->unrecov_intr = 1;
 238                                 } else {
 239                                         strp->interrupted = 1;
 240                                 }
 241                                 strp_parser_err(strp, len, desc);
 242                                 break;
 243                         } else if (len > max_msg_size) {
 244                                 /* Message length exceeds maximum allowed */
 245                                 STRP_STATS_INCR(strp->stats.msg_too_big);
 246                                 strp_parser_err(strp, -EMSGSIZE, desc);
 247                                 break;
 248                         } else if (len <= (ssize_t)head->len -
 249                                           skb->len - stm->strp.offset) {
 250                                 /* Length must be into new skb (and also
 251                                  * greater than zero)
 252                                  */
 253                                 STRP_STATS_INCR(strp->stats.bad_hdr_len);
 254                                 strp_parser_err(strp, -EPROTO, desc);
 255                                 break;
 256                         }
 257
 258                         stm->strp.full_len = len;
 259                 }
 260
 261                 extra = (ssize_t)(stm->accum_len + cand_len) -
 262                         stm->strp.full_len;
 263
 264                 if (extra < 0) {
 265                         /* Message not complete yet. */
 266                         if (stm->strp.full_len - stm->accum_len >
 267                             strp_peek_len(strp)) {
 268                                 /* Don't have the whole message in the socket
 269                                  * buffer. Set strp->need_bytes to wait for
 270                                  * the rest of the message. Also, set "early
 271                                  * eaten" since we've already buffered the skb
 272                                  * but don't consume yet per strp_read_sock.
 273                                  */
 274
 275                                 if (!stm->accum_len) {
 276                                         /* Start RX timer for new message */
 277                                         strp_start_timer(strp, timeo);
 278                                 }
 279
 280                                 stm->accum_len += cand_len;
 281                                 eaten += cand_len;
 282                                 strp->need_bytes = stm->strp.full_len -
 283                                                        stm->accum_len;
 284                                 STRP_STATS_ADD(strp->stats.bytes, cand_len);
 285                                 desc->count = 0; /* Stop reading socket */
 286                                 break;
 287                         }
 288                         stm->accum_len += cand_len;
 289                         eaten += cand_len;
 290                         WARN_ON(eaten != orig_len);
 291                         break;
 292                 }
 293
 294                 /* Positive extra indicates more bytes than needed for the
 295                  * message
 296                  */
 297
 298                 WARN_ON(extra > cand_len);
 299
 300                 eaten += (cand_len - extra);
 301
 302                 /* Hurray, we have a new message! */
 303                 cancel_delayed_work(&strp->msg_timer_work);
 304                 strp->skb_head = NULL;
 305                 strp->need_bytes = 0;
 306                 STRP_STATS_INCR(strp->stats.msgs);
 307
 308                 /* Give skb to upper layer */
 309                 strp->cb.rcv_msg(strp, head);
 310
 311                 if (unlikely(strp->paused)) {
 312                         /* Upper layer paused strp */
 313                         break;
 314                 }
 315         }
 316
 317         if (cloned_orig)
 318                 kfree_skb(orig_skb);
 319
 320         STRP_STATS_ADD(strp->stats.bytes, eaten);
 321
 322         return eaten;
 323 }
 324
 325 int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
 326                  unsigned int orig_offset, size_t orig_len,
 327                  size_t max_msg_size, long timeo)
 328 {
 329         read_descriptor_t desc; /* Dummy arg to strp_recv */
 330
 331         desc.arg.data = strp;
 332
 333         return __strp_recv(&desc, orig_skb, orig_offset, orig_len,
 334                            max_msg_size, timeo);
 335 }
 336 EXPORT_SYMBOL_GPL(strp_process);
 337
 338 static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
 339                      unsigned int orig_offset, size_t orig_len)
 340 {
 341         struct strparser *strp = (struct strparser *)desc->arg.data;
 342
 343         return __strp_recv(desc, orig_skb, orig_offset, orig_len,
 344                            strp->sk->sk_rcvbuf, strp->sk->sk_rcvtimeo);
 345 }
 346
 347 static int default_read_sock_done(struct strparser *strp, int err)
 348 {
 349         return err;
 350 }
 351
 352 /* Called with lock held on lower socket */
 353 static int strp_read_sock(struct strparser *strp)
 354 {
 355         struct socket *sock = strp->sk->sk_socket;
 356         read_descriptor_t desc;
 357
 358         if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
 359                 return -EBUSY;
 360
 361         desc.arg.data = strp;
 362         desc.error = 0;
 363         desc.count = 1; /* give more than one skb per call */
 364
 365         /* sk should be locked here, so okay to do read_sock */
 366         sock->ops->read_sock(strp->sk, &desc, strp_recv);
 367
 368         desc.error = strp->cb.read_sock_done(strp, desc.error);
 369
 370         return desc.error;
 371 }
 372
 373 /* Lower sock lock held */
 374 void strp_data_ready(struct strparser *strp)
 375 {
 376         if (unlikely(strp->stopped) || strp->paused)
 377                 return;
 378
 379         /* This check is needed to synchronize with do_strp_work.
 380          * do_strp_work acquires a process lock (lock_sock) whereas
 381          * the lock held here is bh_lock_sock. The two locks can be
 382          * held by different threads at the same time, but bh_lock_sock
 383          * allows a thread in BH context to safely check if the process
 384          * lock is held. In this case, if the lock is held, queue work.
 385          */
 386         if (sock_owned_by_user_nocheck(strp->sk)) {
 387                 queue_work(strp_wq, &strp->work);
 388                 return;
 389         }
 390
 391         if (strp->need_bytes) {
 392                 if (strp_peek_len(strp) < strp->need_bytes)
 393                         return;
 394         }
 395
 396         if (strp_read_sock(strp) == -ENOMEM)
 397                 queue_work(strp_wq, &strp->work);
 398 }
 399 EXPORT_SYMBOL_GPL(strp_data_ready);
 400
 401 static void do_strp_work(struct strparser *strp)
 402 {
 403         /* We need the read lock to synchronize with strp_data_ready. We
 404          * need the socket lock for calling strp_read_sock.
 405          */
 406         strp->cb.lock(strp);
 407
 408         if (unlikely(strp->stopped))
 409                 goto out;
 410
 411         if (strp->paused)
 412                 goto out;
 413
 414         if (strp_read_sock(strp) == -ENOMEM)
 415                 queue_work(strp_wq, &strp->work);
 416
 417 out:
 418         strp->cb.unlock(strp);
 419 }
 420
 421 static void strp_work(struct work_struct *w)
 422 {
 423         do_strp_work(container_of(w, struct strparser, work));
 424 }
 425
 426 static void strp_msg_timeout(struct work_struct *w)
 427 {
 428         struct strparser *strp = container_of(w, struct strparser,
 429                                               msg_timer_work.work);
 430
 431         /* Message assembly timed out */
 432         STRP_STATS_INCR(strp->stats.msg_timeouts);
 433         strp->cb.lock(strp);
 434         strp->cb.abort_parser(strp, -ETIMEDOUT);
 435         strp->cb.unlock(strp);
 436 }
 437
 438 static void strp_sock_lock(struct strparser *strp)
 439 {
 440         lock_sock(strp->sk);
 441 }
 442
 443 static void strp_sock_unlock(struct strparser *strp)
 444 {
 445         release_sock(strp->sk);
 446 }
 447
 448 int strp_init(struct strparser *strp, struct sock *sk,
 449               const struct strp_callbacks *cb)
 450 {
 451
 452         if (!cb || !cb->rcv_msg || !cb->parse_msg)
 453                 return -EINVAL;
 454
 455         /* The sk (sock) arg determines the mode of the stream parser.
 456          *
 457          * If the sock is set then the strparser is in receive callback mode.
 458          * The upper layer calls strp_data_ready to kick receive processing
 459          * and strparser calls the read_sock function on the socket to
 460          * get packets.
 461          *
 462          * If the sock is not set then the strparser is in general mode.
 463          * The upper layer calls strp_process for each skb to be parsed.
 464          */
 465
 466         if (!sk) {
 467                 if (!cb->lock || !cb->unlock)
 468                         return -EINVAL;
 469         }
 470
 471         memset(strp, 0, sizeof(*strp));
 472
 473         strp->sk = sk;
 474
 475         strp->cb.lock = cb->lock ? : strp_sock_lock;
 476         strp->cb.unlock = cb->unlock ? : strp_sock_unlock;
 477         strp->cb.rcv_msg = cb->rcv_msg;
 478         strp->cb.parse_msg = cb->parse_msg;
 479         strp->cb.read_sock_done = cb->read_sock_done ? : default_read_sock_done;
 480         strp->cb.abort_parser = cb->abort_parser ? : strp_abort_strp;
 481
 482         INIT_DELAYED_WORK(&strp->msg_timer_work, strp_msg_timeout);
 483         INIT_WORK(&strp->work, strp_work);
 484
 485         return 0;
 486 }
 487 EXPORT_SYMBOL_GPL(strp_init);
 488
 489 /* Sock process lock held (lock_sock) */
 490 void __strp_unpause(struct strparser *strp)
 491 {
 492         strp->paused = 0;
 493
 494         if (strp->need_bytes) {
 495                 if (strp_peek_len(strp) < strp->need_bytes)
 496                         return;
 497         }
 498         strp_read_sock(strp);
 499 }
 500 EXPORT_SYMBOL_GPL(__strp_unpause);
 501
 502 void strp_unpause(struct strparser *strp)
 503 {
 504         strp->paused = 0;
 505
 506         /* Sync setting paused with RX work */
 507         smp_mb();
 508
 509         queue_work(strp_wq, &strp->work);
 510 }
 511 EXPORT_SYMBOL_GPL(strp_unpause);
 512
 513 /* strp must already be stopped so that strp_recv will no longer be called.
 514  * Note that strp_done is not called with the lower socket held.
 515  */
 516 void strp_done(struct strparser *strp)
 517 {
 518         WARN_ON(!strp->stopped);
 519
 520         cancel_delayed_work_sync(&strp->msg_timer_work);
 521         cancel_work_sync(&strp->work);
 522
 523         if (strp->skb_head) {
 524                 kfree_skb(strp->skb_head);
 525                 strp->skb_head = NULL;
 526         }
 527 }
 528 EXPORT_SYMBOL_GPL(strp_done);
 529
 530 void strp_stop(struct strparser *strp)
 531 {
 532         strp->stopped = 1;
 533 }
 534 EXPORT_SYMBOL_GPL(strp_stop);
 535
 536 void strp_check_rcv(struct strparser *strp)
 537 {
 538         queue_work(strp_wq, &strp->work);
 539 }
 540 EXPORT_SYMBOL_GPL(strp_check_rcv);
 541
 542 static int __init strp_dev_init(void)
 543 {
 544         strp_wq = create_singlethread_workqueue("kstrp");
 545         if (unlikely(!strp_wq))
 546                 return -ENOMEM;
 547
 548         return 0;
 549 }
 550 device_initcall(strp_dev_init);