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TOMOYO Linux Cross Reference
Linux/net/strparser/strparser.c

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  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(0, GFP_ATOMIC);
161                                 if (!skb) {
162                                         STRP_STATS_INCR(strp->stats.mem_fail);
163                                         desc->error = -ENOMEM;
164                                         return 0;
165                                 }
166                                 skb->len = head->len;
167                                 skb->data_len = head->len;
168                                 skb->truesize = head->truesize;
169                                 *_strp_msg(skb) = *_strp_msg(head);
170                                 strp->skb_nextp = &head->next;
171                                 skb_shinfo(skb)->frag_list = head;
172                                 strp->skb_head = skb;
173                                 head = skb;
174                         } else {
175                                 strp->skb_nextp =
176                                     &skb_shinfo(head)->frag_list;
177                         }
178                 }
179         }
180 
181         while (eaten < orig_len) {
182                 /* Always clone since we will consume something */
183                 skb = skb_clone(orig_skb, GFP_ATOMIC);
184                 if (!skb) {
185                         STRP_STATS_INCR(strp->stats.mem_fail);
186                         desc->error = -ENOMEM;
187                         break;
188                 }
189 
190                 cand_len = orig_len - eaten;
191 
192                 head = strp->skb_head;
193                 if (!head) {
194                         head = skb;
195                         strp->skb_head = head;
196                         /* Will set skb_nextp on next packet if needed */
197                         strp->skb_nextp = NULL;
198                         stm = _strp_msg(head);
199                         memset(stm, 0, sizeof(*stm));
200                         stm->strp.offset = orig_offset + eaten;
201                 } else {
202                         /* Unclone if we are appending to an skb that we
203                          * already share a frag_list with.
204                          */
205                         if (skb_has_frag_list(skb)) {
206                                 err = skb_unclone(skb, GFP_ATOMIC);
207                                 if (err) {
208                                         STRP_STATS_INCR(strp->stats.mem_fail);
209                                         desc->error = err;
210                                         break;
211                                 }
212                         }
213 
214                         stm = _strp_msg(head);
215                         *strp->skb_nextp = skb;
216                         strp->skb_nextp = &skb->next;
217                         head->data_len += skb->len;
218                         head->len += skb->len;
219                         head->truesize += skb->truesize;
220                 }
221 
222                 if (!stm->strp.full_len) {
223                         ssize_t len;
224 
225                         len = (*strp->cb.parse_msg)(strp, head);
226 
227                         if (!len) {
228                                 /* Need more header to determine length */
229                                 if (!stm->accum_len) {
230                                         /* Start RX timer for new message */
231                                         strp_start_timer(strp, timeo);
232                                 }
233                                 stm->accum_len += cand_len;
234                                 eaten += cand_len;
235                                 STRP_STATS_INCR(strp->stats.need_more_hdr);
236                                 WARN_ON(eaten != orig_len);
237                                 break;
238                         } else if (len < 0) {
239                                 if (len == -ESTRPIPE && stm->accum_len) {
240                                         len = -ENODATA;
241                                         strp->unrecov_intr = 1;
242                                 } else {
243                                         strp->interrupted = 1;
244                                 }
245                                 strp_parser_err(strp, len, desc);
246                                 break;
247                         } else if (len > max_msg_size) {
248                                 /* Message length exceeds maximum allowed */
249                                 STRP_STATS_INCR(strp->stats.msg_too_big);
250                                 strp_parser_err(strp, -EMSGSIZE, desc);
251                                 break;
252                         } else if (len <= (ssize_t)head->len -
253                                           skb->len - stm->strp.offset) {
254                                 /* Length must be into new skb (and also
255                                  * greater than zero)
256                                  */
257                                 STRP_STATS_INCR(strp->stats.bad_hdr_len);
258                                 strp_parser_err(strp, -EPROTO, desc);
259                                 break;
260                         }
261 
262                         stm->strp.full_len = len;
263                 }
264 
265                 extra = (ssize_t)(stm->accum_len + cand_len) -
266                         stm->strp.full_len;
267 
268                 if (extra < 0) {
269                         /* Message not complete yet. */
270                         if (stm->strp.full_len - stm->accum_len >
271                             strp_peek_len(strp)) {
272                                 /* Don't have the whole message in the socket
273                                  * buffer. Set strp->need_bytes to wait for
274                                  * the rest of the message. Also, set "early
275                                  * eaten" since we've already buffered the skb
276                                  * but don't consume yet per strp_read_sock.
277                                  */
278 
279                                 if (!stm->accum_len) {
280                                         /* Start RX timer for new message */
281                                         strp_start_timer(strp, timeo);
282                                 }
283 
284                                 stm->accum_len += cand_len;
285                                 eaten += cand_len;
286                                 strp->need_bytes = stm->strp.full_len -
287                                                        stm->accum_len;
288                                 STRP_STATS_ADD(strp->stats.bytes, cand_len);
289                                 desc->count = 0; /* Stop reading socket */
290                                 break;
291                         }
292                         stm->accum_len += cand_len;
293                         eaten += cand_len;
294                         WARN_ON(eaten != orig_len);
295                         break;
296                 }
297 
298                 /* Positive extra indicates more bytes than needed for the
299                  * message
300                  */
301 
302                 WARN_ON(extra > cand_len);
303 
304                 eaten += (cand_len - extra);
305 
306                 /* Hurray, we have a new message! */
307                 cancel_delayed_work(&strp->msg_timer_work);
308                 strp->skb_head = NULL;
309                 strp->need_bytes = 0;
310                 STRP_STATS_INCR(strp->stats.msgs);
311 
312                 /* Give skb to upper layer */
313                 strp->cb.rcv_msg(strp, head);
314 
315                 if (unlikely(strp->paused)) {
316                         /* Upper layer paused strp */
317                         break;
318                 }
319         }
320 
321         if (cloned_orig)
322                 kfree_skb(orig_skb);
323 
324         STRP_STATS_ADD(strp->stats.bytes, eaten);
325 
326         return eaten;
327 }
328 
329 int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
330                  unsigned int orig_offset, size_t orig_len,
331                  size_t max_msg_size, long timeo)
332 {
333         read_descriptor_t desc; /* Dummy arg to strp_recv */
334 
335         desc.arg.data = strp;
336 
337         return __strp_recv(&desc, orig_skb, orig_offset, orig_len,
338                            max_msg_size, timeo);
339 }
340 EXPORT_SYMBOL_GPL(strp_process);
341 
342 static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
343                      unsigned int orig_offset, size_t orig_len)
344 {
345         struct strparser *strp = (struct strparser *)desc->arg.data;
346 
347         return __strp_recv(desc, orig_skb, orig_offset, orig_len,
348                            strp->sk->sk_rcvbuf, strp->sk->sk_rcvtimeo);
349 }
350 
351 static int default_read_sock_done(struct strparser *strp, int err)
352 {
353         return err;
354 }
355 
356 /* Called with lock held on lower socket */
357 static int strp_read_sock(struct strparser *strp)
358 {
359         struct socket *sock = strp->sk->sk_socket;
360         read_descriptor_t desc;
361 
362         if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
363                 return -EBUSY;
364 
365         desc.arg.data = strp;
366         desc.error = 0;
367         desc.count = 1; /* give more than one skb per call */
368 
369         /* sk should be locked here, so okay to do read_sock */
370         sock->ops->read_sock(strp->sk, &desc, strp_recv);
371 
372         desc.error = strp->cb.read_sock_done(strp, desc.error);
373 
374         return desc.error;
375 }
376 
377 /* Lower sock lock held */
378 void strp_data_ready(struct strparser *strp)
379 {
380         if (unlikely(strp->stopped) || strp->paused)
381                 return;
382 
383         /* This check is needed to synchronize with do_strp_work.
384          * do_strp_work acquires a process lock (lock_sock) whereas
385          * the lock held here is bh_lock_sock. The two locks can be
386          * held by different threads at the same time, but bh_lock_sock
387          * allows a thread in BH context to safely check if the process
388          * lock is held. In this case, if the lock is held, queue work.
389          */
390         if (sock_owned_by_user_nocheck(strp->sk)) {
391                 queue_work(strp_wq, &strp->work);
392                 return;
393         }
394 
395         if (strp->need_bytes) {
396                 if (strp_peek_len(strp) < strp->need_bytes)
397                         return;
398         }
399 
400         if (strp_read_sock(strp) == -ENOMEM)
401                 queue_work(strp_wq, &strp->work);
402 }
403 EXPORT_SYMBOL_GPL(strp_data_ready);
404 
405 static void do_strp_work(struct strparser *strp)
406 {
407         /* We need the read lock to synchronize with strp_data_ready. We
408          * need the socket lock for calling strp_read_sock.
409          */
410         strp->cb.lock(strp);
411 
412         if (unlikely(strp->stopped))
413                 goto out;
414 
415         if (strp->paused)
416                 goto out;
417 
418         if (strp_read_sock(strp) == -ENOMEM)
419                 queue_work(strp_wq, &strp->work);
420 
421 out:
422         strp->cb.unlock(strp);
423 }
424 
425 static void strp_work(struct work_struct *w)
426 {
427         do_strp_work(container_of(w, struct strparser, work));
428 }
429 
430 static void strp_msg_timeout(struct work_struct *w)
431 {
432         struct strparser *strp = container_of(w, struct strparser,
433                                               msg_timer_work.work);
434 
435         /* Message assembly timed out */
436         STRP_STATS_INCR(strp->stats.msg_timeouts);
437         strp->cb.lock(strp);
438         strp->cb.abort_parser(strp, -ETIMEDOUT);
439         strp->cb.unlock(strp);
440 }
441 
442 static void strp_sock_lock(struct strparser *strp)
443 {
444         lock_sock(strp->sk);
445 }
446 
447 static void strp_sock_unlock(struct strparser *strp)
448 {
449         release_sock(strp->sk);
450 }
451 
452 int strp_init(struct strparser *strp, struct sock *sk,
453               const struct strp_callbacks *cb)
454 {
455 
456         if (!cb || !cb->rcv_msg || !cb->parse_msg)
457                 return -EINVAL;
458 
459         /* The sk (sock) arg determines the mode of the stream parser.
460          *
461          * If the sock is set then the strparser is in receive callback mode.
462          * The upper layer calls strp_data_ready to kick receive processing
463          * and strparser calls the read_sock function on the socket to
464          * get packets.
465          *
466          * If the sock is not set then the strparser is in general mode.
467          * The upper layer calls strp_process for each skb to be parsed.
468          */
469 
470         if (!sk) {
471                 if (!cb->lock || !cb->unlock)
472                         return -EINVAL;
473         }
474 
475         memset(strp, 0, sizeof(*strp));
476 
477         strp->sk = sk;
478 
479         strp->cb.lock = cb->lock ? : strp_sock_lock;
480         strp->cb.unlock = cb->unlock ? : strp_sock_unlock;
481         strp->cb.rcv_msg = cb->rcv_msg;
482         strp->cb.parse_msg = cb->parse_msg;
483         strp->cb.read_sock_done = cb->read_sock_done ? : default_read_sock_done;
484         strp->cb.abort_parser = cb->abort_parser ? : strp_abort_strp;
485 
486         INIT_DELAYED_WORK(&strp->msg_timer_work, strp_msg_timeout);
487         INIT_WORK(&strp->work, strp_work);
488 
489         return 0;
490 }
491 EXPORT_SYMBOL_GPL(strp_init);
492 
493 /* Sock process lock held (lock_sock) */
494 void __strp_unpause(struct strparser *strp)
495 {
496         strp->paused = 0;
497 
498         if (strp->need_bytes) {
499                 if (strp_peek_len(strp) < strp->need_bytes)
500                         return;
501         }
502         strp_read_sock(strp);
503 }
504 EXPORT_SYMBOL_GPL(__strp_unpause);
505 
506 void strp_unpause(struct strparser *strp)
507 {
508         strp->paused = 0;
509 
510         /* Sync setting paused with RX work */
511         smp_mb();
512 
513         queue_work(strp_wq, &strp->work);
514 }
515 EXPORT_SYMBOL_GPL(strp_unpause);
516 
517 /* strp must already be stopped so that strp_recv will no longer be called.
518  * Note that strp_done is not called with the lower socket held.
519  */
520 void strp_done(struct strparser *strp)
521 {
522         WARN_ON(!strp->stopped);
523 
524         cancel_delayed_work_sync(&strp->msg_timer_work);
525         cancel_work_sync(&strp->work);
526 
527         if (strp->skb_head) {
528                 kfree_skb(strp->skb_head);
529                 strp->skb_head = NULL;
530         }
531 }
532 EXPORT_SYMBOL_GPL(strp_done);
533 
534 void strp_stop(struct strparser *strp)
535 {
536         strp->stopped = 1;
537 }
538 EXPORT_SYMBOL_GPL(strp_stop);
539 
540 void strp_check_rcv(struct strparser *strp)
541 {
542         queue_work(strp_wq, &strp->work);
543 }
544 EXPORT_SYMBOL_GPL(strp_check_rcv);
545 
546 static int __init strp_dev_init(void)
547 {
548         strp_wq = create_singlethread_workqueue("kstrp");
549         if (unlikely(!strp_wq))
550                 return -ENOMEM;
551 
552         return 0;
553 }
554 device_initcall(strp_dev_init);
555 

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