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