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1 | /* Copyright (c) 2017 Covalent IO, Inc. http://covalent.io |
2 | * | |
3 | * This program is free software; you can redistribute it and/or | |
4 | * modify it under the terms of version 2 of the GNU General Public | |
5 | * License as published by the Free Software Foundation. | |
6 | * | |
7 | * This program is distributed in the hope that it will be useful, but | |
8 | * WITHOUT ANY WARRANTY; without even the implied warranty of | |
9 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
10 | * General Public License for more details. | |
11 | */ | |
12 | ||
13 | /* A BPF sock_map is used to store sock objects. This is primarly used | |
14 | * for doing socket redirect with BPF helper routines. | |
15 | * | |
16 | * A sock map may have two BPF programs attached to it, a program used | |
17 | * to parse packets and a program to provide a verdict and redirect | |
18 | * decision on the packet. If no BPF parse program is provided it is | |
19 | * assumed that every skb is a "message" (skb->len). Otherwise the | |
20 | * parse program is attached to strparser and used to build messages | |
21 | * that may span multiple skbs. The verdict program will either select | |
22 | * a socket to send/receive the skb on or provide the drop code indicating | |
23 | * the skb should be dropped. More actions may be added later as needed. | |
24 | * The default program will drop packets. | |
25 | * | |
26 | * For reference this program is similar to devmap used in XDP context | |
27 | * reviewing these together may be useful. For an example please review | |
28 | * ./samples/bpf/sockmap/. | |
29 | */ | |
30 | #include <linux/bpf.h> | |
31 | #include <net/sock.h> | |
32 | #include <linux/filter.h> | |
33 | #include <linux/errno.h> | |
34 | #include <linux/file.h> | |
35 | #include <linux/kernel.h> | |
36 | #include <linux/net.h> | |
37 | #include <linux/skbuff.h> | |
38 | #include <linux/workqueue.h> | |
39 | #include <linux/list.h> | |
40 | #include <net/strparser.h> | |
41 | ||
42 | struct bpf_stab { | |
43 | struct bpf_map map; | |
44 | struct sock **sock_map; | |
45 | struct bpf_prog *bpf_parse; | |
46 | struct bpf_prog *bpf_verdict; | |
47 | refcount_t refcnt; | |
48 | }; | |
49 | ||
50 | enum smap_psock_state { | |
51 | SMAP_TX_RUNNING, | |
52 | }; | |
53 | ||
54 | struct smap_psock { | |
55 | struct rcu_head rcu; | |
56 | ||
57 | /* datapath variables */ | |
58 | struct sk_buff_head rxqueue; | |
59 | bool strp_enabled; | |
60 | ||
61 | /* datapath error path cache across tx work invocations */ | |
62 | int save_rem; | |
63 | int save_off; | |
64 | struct sk_buff *save_skb; | |
65 | ||
66 | struct strparser strp; | |
67 | struct bpf_prog *bpf_parse; | |
68 | struct bpf_prog *bpf_verdict; | |
69 | struct bpf_stab *stab; | |
70 | ||
71 | /* Back reference used when sock callback trigger sockmap operations */ | |
72 | int key; | |
73 | struct sock *sock; | |
74 | unsigned long state; | |
75 | ||
76 | struct work_struct tx_work; | |
77 | struct work_struct gc_work; | |
78 | ||
79 | void (*save_data_ready)(struct sock *sk); | |
80 | void (*save_write_space)(struct sock *sk); | |
81 | void (*save_state_change)(struct sock *sk); | |
82 | }; | |
83 | ||
84 | static inline struct smap_psock *smap_psock_sk(const struct sock *sk) | |
85 | { | |
86 | return (struct smap_psock *)rcu_dereference_sk_user_data(sk); | |
87 | } | |
88 | ||
89 | static int smap_verdict_func(struct smap_psock *psock, struct sk_buff *skb) | |
90 | { | |
91 | struct bpf_prog *prog = READ_ONCE(psock->bpf_verdict); | |
92 | int rc; | |
93 | ||
94 | if (unlikely(!prog)) | |
95 | return SK_DROP; | |
96 | ||
97 | skb_orphan(skb); | |
98 | skb->sk = psock->sock; | |
99 | bpf_compute_data_end(skb); | |
100 | rc = (*prog->bpf_func)(skb, prog->insnsi); | |
101 | skb->sk = NULL; | |
102 | ||
103 | return rc; | |
104 | } | |
105 | ||
106 | static void smap_do_verdict(struct smap_psock *psock, struct sk_buff *skb) | |
107 | { | |
108 | struct sock *sock; | |
109 | int rc; | |
110 | ||
111 | /* Because we use per cpu values to feed input from sock redirect | |
112 | * in BPF program to do_sk_redirect_map() call we need to ensure we | |
113 | * are not preempted. RCU read lock is not sufficient in this case | |
114 | * with CONFIG_PREEMPT_RCU enabled so we must be explicit here. | |
115 | */ | |
116 | preempt_disable(); | |
117 | rc = smap_verdict_func(psock, skb); | |
118 | switch (rc) { | |
119 | case SK_REDIRECT: | |
120 | sock = do_sk_redirect_map(); | |
121 | preempt_enable(); | |
122 | if (likely(sock)) { | |
123 | struct smap_psock *peer = smap_psock_sk(sock); | |
124 | ||
125 | if (likely(peer && | |
126 | test_bit(SMAP_TX_RUNNING, &peer->state) && | |
127 | sk_stream_memory_free(peer->sock))) { | |
128 | peer->sock->sk_wmem_queued += skb->truesize; | |
129 | sk_mem_charge(peer->sock, skb->truesize); | |
130 | skb_queue_tail(&peer->rxqueue, skb); | |
131 | schedule_work(&peer->tx_work); | |
132 | break; | |
133 | } | |
134 | } | |
135 | /* Fall through and free skb otherwise */ | |
136 | case SK_DROP: | |
137 | default: | |
138 | preempt_enable(); | |
139 | kfree_skb(skb); | |
140 | } | |
141 | } | |
142 | ||
143 | static void smap_report_sk_error(struct smap_psock *psock, int err) | |
144 | { | |
145 | struct sock *sk = psock->sock; | |
146 | ||
147 | sk->sk_err = err; | |
148 | sk->sk_error_report(sk); | |
149 | } | |
150 | ||
151 | static void smap_release_sock(struct sock *sock); | |
152 | ||
153 | /* Called with lock_sock(sk) held */ | |
154 | static void smap_state_change(struct sock *sk) | |
155 | { | |
156 | struct smap_psock *psock; | |
157 | struct sock *osk; | |
158 | ||
159 | rcu_read_lock(); | |
160 | ||
161 | /* Allowing transitions into an established syn_recv states allows | |
162 | * for early binding sockets to a smap object before the connection | |
163 | * is established. | |
164 | */ | |
165 | switch (sk->sk_state) { | |
166 | case TCP_SYN_RECV: | |
167 | case TCP_ESTABLISHED: | |
168 | break; | |
169 | case TCP_CLOSE_WAIT: | |
170 | case TCP_CLOSING: | |
171 | case TCP_LAST_ACK: | |
172 | case TCP_FIN_WAIT1: | |
173 | case TCP_FIN_WAIT2: | |
174 | case TCP_LISTEN: | |
175 | break; | |
176 | case TCP_CLOSE: | |
177 | /* Only release if the map entry is in fact the sock in | |
178 | * question. There is a case where the operator deletes | |
179 | * the sock from the map, but the TCP sock is closed before | |
180 | * the psock is detached. Use cmpxchg to verify correct | |
181 | * sock is removed. | |
182 | */ | |
183 | psock = smap_psock_sk(sk); | |
184 | if (unlikely(!psock)) | |
185 | break; | |
186 | osk = cmpxchg(&psock->stab->sock_map[psock->key], sk, NULL); | |
187 | if (osk == sk) | |
188 | smap_release_sock(sk); | |
189 | break; | |
190 | default: | |
191 | smap_report_sk_error(psock, EPIPE); | |
192 | break; | |
193 | } | |
194 | rcu_read_unlock(); | |
195 | } | |
196 | ||
197 | static void smap_read_sock_strparser(struct strparser *strp, | |
198 | struct sk_buff *skb) | |
199 | { | |
200 | struct smap_psock *psock; | |
201 | ||
202 | rcu_read_lock(); | |
203 | psock = container_of(strp, struct smap_psock, strp); | |
204 | smap_do_verdict(psock, skb); | |
205 | rcu_read_unlock(); | |
206 | } | |
207 | ||
208 | /* Called with lock held on socket */ | |
209 | static void smap_data_ready(struct sock *sk) | |
210 | { | |
211 | struct smap_psock *psock; | |
212 | ||
213 | write_lock_bh(&sk->sk_callback_lock); | |
214 | psock = smap_psock_sk(sk); | |
215 | if (likely(psock)) | |
216 | strp_data_ready(&psock->strp); | |
217 | write_unlock_bh(&sk->sk_callback_lock); | |
218 | } | |
219 | ||
220 | static void smap_tx_work(struct work_struct *w) | |
221 | { | |
222 | struct smap_psock *psock; | |
223 | struct sk_buff *skb; | |
224 | int rem, off, n; | |
225 | ||
226 | psock = container_of(w, struct smap_psock, tx_work); | |
227 | ||
228 | /* lock sock to avoid losing sk_socket at some point during loop */ | |
229 | lock_sock(psock->sock); | |
230 | if (psock->save_skb) { | |
231 | skb = psock->save_skb; | |
232 | rem = psock->save_rem; | |
233 | off = psock->save_off; | |
234 | psock->save_skb = NULL; | |
235 | goto start; | |
236 | } | |
237 | ||
238 | while ((skb = skb_dequeue(&psock->rxqueue))) { | |
239 | rem = skb->len; | |
240 | off = 0; | |
241 | start: | |
242 | do { | |
243 | if (likely(psock->sock->sk_socket)) | |
244 | n = skb_send_sock_locked(psock->sock, | |
245 | skb, off, rem); | |
246 | else | |
247 | n = -EINVAL; | |
248 | if (n <= 0) { | |
249 | if (n == -EAGAIN) { | |
250 | /* Retry when space is available */ | |
251 | psock->save_skb = skb; | |
252 | psock->save_rem = rem; | |
253 | psock->save_off = off; | |
254 | goto out; | |
255 | } | |
256 | /* Hard errors break pipe and stop xmit */ | |
257 | smap_report_sk_error(psock, n ? -n : EPIPE); | |
258 | clear_bit(SMAP_TX_RUNNING, &psock->state); | |
259 | sk_mem_uncharge(psock->sock, skb->truesize); | |
260 | psock->sock->sk_wmem_queued -= skb->truesize; | |
261 | kfree_skb(skb); | |
262 | goto out; | |
263 | } | |
264 | rem -= n; | |
265 | off += n; | |
266 | } while (rem); | |
267 | sk_mem_uncharge(psock->sock, skb->truesize); | |
268 | psock->sock->sk_wmem_queued -= skb->truesize; | |
269 | kfree_skb(skb); | |
270 | } | |
271 | out: | |
272 | release_sock(psock->sock); | |
273 | } | |
274 | ||
275 | static void smap_write_space(struct sock *sk) | |
276 | { | |
277 | struct smap_psock *psock; | |
278 | ||
279 | rcu_read_lock(); | |
280 | psock = smap_psock_sk(sk); | |
281 | if (likely(psock && test_bit(SMAP_TX_RUNNING, &psock->state))) | |
282 | schedule_work(&psock->tx_work); | |
283 | rcu_read_unlock(); | |
284 | } | |
285 | ||
286 | static void smap_stop_sock(struct smap_psock *psock, struct sock *sk) | |
287 | { | |
288 | write_lock_bh(&sk->sk_callback_lock); | |
289 | if (!psock->strp_enabled) | |
290 | goto out; | |
291 | sk->sk_data_ready = psock->save_data_ready; | |
292 | sk->sk_write_space = psock->save_write_space; | |
293 | sk->sk_state_change = psock->save_state_change; | |
294 | psock->save_data_ready = NULL; | |
295 | psock->save_write_space = NULL; | |
296 | psock->save_state_change = NULL; | |
297 | strp_stop(&psock->strp); | |
298 | psock->strp_enabled = false; | |
299 | out: | |
300 | write_unlock_bh(&sk->sk_callback_lock); | |
301 | } | |
302 | ||
303 | static void smap_destroy_psock(struct rcu_head *rcu) | |
304 | { | |
305 | struct smap_psock *psock = container_of(rcu, | |
306 | struct smap_psock, rcu); | |
307 | ||
308 | /* Now that a grace period has passed there is no longer | |
309 | * any reference to this sock in the sockmap so we can | |
310 | * destroy the psock, strparser, and bpf programs. But, | |
311 | * because we use workqueue sync operations we can not | |
312 | * do it in rcu context | |
313 | */ | |
314 | schedule_work(&psock->gc_work); | |
315 | } | |
316 | ||
317 | static void smap_release_sock(struct sock *sock) | |
318 | { | |
319 | struct smap_psock *psock = smap_psock_sk(sock); | |
320 | ||
321 | smap_stop_sock(psock, sock); | |
322 | clear_bit(SMAP_TX_RUNNING, &psock->state); | |
323 | rcu_assign_sk_user_data(sock, NULL); | |
324 | call_rcu_sched(&psock->rcu, smap_destroy_psock); | |
325 | } | |
326 | ||
327 | static int smap_parse_func_strparser(struct strparser *strp, | |
328 | struct sk_buff *skb) | |
329 | { | |
330 | struct smap_psock *psock; | |
331 | struct bpf_prog *prog; | |
332 | int rc; | |
333 | ||
334 | rcu_read_lock(); | |
335 | psock = container_of(strp, struct smap_psock, strp); | |
336 | prog = READ_ONCE(psock->bpf_parse); | |
337 | ||
338 | if (unlikely(!prog)) { | |
339 | rcu_read_unlock(); | |
340 | return skb->len; | |
341 | } | |
342 | ||
343 | /* Attach socket for bpf program to use if needed we can do this | |
344 | * because strparser clones the skb before handing it to a upper | |
345 | * layer, meaning skb_orphan has been called. We NULL sk on the | |
346 | * way out to ensure we don't trigger a BUG_ON in skb/sk operations | |
347 | * later and because we are not charging the memory of this skb to | |
348 | * any socket yet. | |
349 | */ | |
350 | skb->sk = psock->sock; | |
351 | bpf_compute_data_end(skb); | |
352 | rc = (*prog->bpf_func)(skb, prog->insnsi); | |
353 | skb->sk = NULL; | |
354 | rcu_read_unlock(); | |
355 | return rc; | |
356 | } | |
357 | ||
358 | ||
359 | static int smap_read_sock_done(struct strparser *strp, int err) | |
360 | { | |
361 | return err; | |
362 | } | |
363 | ||
364 | static int smap_init_sock(struct smap_psock *psock, | |
365 | struct sock *sk) | |
366 | { | |
367 | struct strp_callbacks cb; | |
368 | ||
369 | memset(&cb, 0, sizeof(cb)); | |
370 | cb.rcv_msg = smap_read_sock_strparser; | |
371 | cb.parse_msg = smap_parse_func_strparser; | |
372 | cb.read_sock_done = smap_read_sock_done; | |
373 | return strp_init(&psock->strp, sk, &cb); | |
374 | } | |
375 | ||
376 | static void smap_init_progs(struct smap_psock *psock, | |
377 | struct bpf_stab *stab, | |
378 | struct bpf_prog *verdict, | |
379 | struct bpf_prog *parse) | |
380 | { | |
381 | struct bpf_prog *orig_parse, *orig_verdict; | |
382 | ||
383 | orig_parse = xchg(&psock->bpf_parse, parse); | |
384 | orig_verdict = xchg(&psock->bpf_verdict, verdict); | |
385 | ||
386 | if (orig_verdict) | |
387 | bpf_prog_put(orig_verdict); | |
388 | if (orig_parse) | |
389 | bpf_prog_put(orig_parse); | |
390 | } | |
391 | ||
392 | static void smap_start_sock(struct smap_psock *psock, struct sock *sk) | |
393 | { | |
394 | if (sk->sk_data_ready == smap_data_ready) | |
395 | return; | |
396 | psock->save_data_ready = sk->sk_data_ready; | |
397 | psock->save_write_space = sk->sk_write_space; | |
398 | psock->save_state_change = sk->sk_state_change; | |
399 | sk->sk_data_ready = smap_data_ready; | |
400 | sk->sk_write_space = smap_write_space; | |
401 | sk->sk_state_change = smap_state_change; | |
402 | psock->strp_enabled = true; | |
403 | } | |
404 | ||
405 | static void sock_map_remove_complete(struct bpf_stab *stab) | |
406 | { | |
407 | bpf_map_area_free(stab->sock_map); | |
408 | kfree(stab); | |
409 | } | |
410 | ||
411 | static void smap_gc_work(struct work_struct *w) | |
412 | { | |
413 | struct smap_psock *psock; | |
414 | ||
415 | psock = container_of(w, struct smap_psock, gc_work); | |
416 | ||
417 | /* no callback lock needed because we already detached sockmap ops */ | |
418 | if (psock->strp_enabled) | |
419 | strp_done(&psock->strp); | |
420 | ||
421 | cancel_work_sync(&psock->tx_work); | |
422 | __skb_queue_purge(&psock->rxqueue); | |
423 | ||
424 | /* At this point all strparser and xmit work must be complete */ | |
425 | if (psock->bpf_parse) | |
426 | bpf_prog_put(psock->bpf_parse); | |
427 | if (psock->bpf_verdict) | |
428 | bpf_prog_put(psock->bpf_verdict); | |
429 | ||
430 | if (refcount_dec_and_test(&psock->stab->refcnt)) | |
431 | sock_map_remove_complete(psock->stab); | |
432 | ||
433 | sock_put(psock->sock); | |
434 | kfree(psock); | |
435 | } | |
436 | ||
437 | static struct smap_psock *smap_init_psock(struct sock *sock, | |
438 | struct bpf_stab *stab) | |
439 | { | |
440 | struct smap_psock *psock; | |
441 | ||
442 | psock = kzalloc(sizeof(struct smap_psock), GFP_ATOMIC | __GFP_NOWARN); | |
443 | if (!psock) | |
444 | return ERR_PTR(-ENOMEM); | |
445 | ||
446 | psock->sock = sock; | |
447 | skb_queue_head_init(&psock->rxqueue); | |
448 | INIT_WORK(&psock->tx_work, smap_tx_work); | |
449 | INIT_WORK(&psock->gc_work, smap_gc_work); | |
450 | ||
451 | rcu_assign_sk_user_data(sock, psock); | |
452 | sock_hold(sock); | |
453 | return psock; | |
454 | } | |
455 | ||
456 | static struct bpf_map *sock_map_alloc(union bpf_attr *attr) | |
457 | { | |
458 | struct bpf_stab *stab; | |
459 | int err = -EINVAL; | |
460 | u64 cost; | |
461 | ||
462 | /* check sanity of attributes */ | |
463 | if (attr->max_entries == 0 || attr->key_size != 4 || | |
464 | attr->value_size != 4 || attr->map_flags) | |
465 | return ERR_PTR(-EINVAL); | |
466 | ||
467 | if (attr->value_size > KMALLOC_MAX_SIZE) | |
468 | return ERR_PTR(-E2BIG); | |
469 | ||
470 | stab = kzalloc(sizeof(*stab), GFP_USER); | |
471 | if (!stab) | |
472 | return ERR_PTR(-ENOMEM); | |
473 | ||
474 | /* mandatory map attributes */ | |
475 | stab->map.map_type = attr->map_type; | |
476 | stab->map.key_size = attr->key_size; | |
477 | stab->map.value_size = attr->value_size; | |
478 | stab->map.max_entries = attr->max_entries; | |
479 | stab->map.map_flags = attr->map_flags; | |
480 | ||
481 | /* make sure page count doesn't overflow */ | |
482 | cost = (u64) stab->map.max_entries * sizeof(struct sock *); | |
483 | if (cost >= U32_MAX - PAGE_SIZE) | |
484 | goto free_stab; | |
485 | ||
486 | stab->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT; | |
487 | ||
488 | /* if map size is larger than memlock limit, reject it early */ | |
489 | err = bpf_map_precharge_memlock(stab->map.pages); | |
490 | if (err) | |
491 | goto free_stab; | |
492 | ||
493 | stab->sock_map = bpf_map_area_alloc(stab->map.max_entries * | |
494 | sizeof(struct sock *)); | |
495 | if (!stab->sock_map) | |
496 | goto free_stab; | |
497 | ||
498 | refcount_set(&stab->refcnt, 1); | |
499 | return &stab->map; | |
500 | free_stab: | |
501 | kfree(stab); | |
502 | return ERR_PTR(err); | |
503 | } | |
504 | ||
505 | static void sock_map_free(struct bpf_map *map) | |
506 | { | |
507 | struct bpf_stab *stab = container_of(map, struct bpf_stab, map); | |
508 | int i; | |
509 | ||
510 | synchronize_rcu(); | |
511 | ||
512 | /* At this point no update, lookup or delete operations can happen. | |
513 | * However, be aware we can still get a socket state event updates, | |
514 | * and data ready callabacks that reference the psock from sk_user_data | |
515 | * Also psock worker threads are still in-flight. So smap_release_sock | |
516 | * will only free the psock after cancel_sync on the worker threads | |
517 | * and a grace period expire to ensure psock is really safe to remove. | |
518 | */ | |
519 | rcu_read_lock(); | |
520 | for (i = 0; i < stab->map.max_entries; i++) { | |
521 | struct sock *sock; | |
522 | ||
523 | sock = xchg(&stab->sock_map[i], NULL); | |
524 | if (!sock) | |
525 | continue; | |
526 | ||
527 | smap_release_sock(sock); | |
528 | } | |
529 | rcu_read_unlock(); | |
530 | ||
531 | if (stab->bpf_verdict) | |
532 | bpf_prog_put(stab->bpf_verdict); | |
533 | if (stab->bpf_parse) | |
534 | bpf_prog_put(stab->bpf_parse); | |
535 | ||
536 | if (refcount_dec_and_test(&stab->refcnt)) | |
537 | sock_map_remove_complete(stab); | |
538 | } | |
539 | ||
540 | static int sock_map_get_next_key(struct bpf_map *map, void *key, void *next_key) | |
541 | { | |
542 | struct bpf_stab *stab = container_of(map, struct bpf_stab, map); | |
543 | u32 i = key ? *(u32 *)key : U32_MAX; | |
544 | u32 *next = (u32 *)next_key; | |
545 | ||
546 | if (i >= stab->map.max_entries) { | |
547 | *next = 0; | |
548 | return 0; | |
549 | } | |
550 | ||
551 | if (i == stab->map.max_entries - 1) | |
552 | return -ENOENT; | |
553 | ||
554 | *next = i + 1; | |
555 | return 0; | |
556 | } | |
557 | ||
558 | struct sock *__sock_map_lookup_elem(struct bpf_map *map, u32 key) | |
559 | { | |
560 | struct bpf_stab *stab = container_of(map, struct bpf_stab, map); | |
561 | ||
562 | if (key >= map->max_entries) | |
563 | return NULL; | |
564 | ||
565 | return READ_ONCE(stab->sock_map[key]); | |
566 | } | |
567 | ||
568 | static int sock_map_delete_elem(struct bpf_map *map, void *key) | |
569 | { | |
570 | struct bpf_stab *stab = container_of(map, struct bpf_stab, map); | |
571 | int k = *(u32 *)key; | |
572 | struct sock *sock; | |
573 | ||
574 | if (k >= map->max_entries) | |
575 | return -EINVAL; | |
576 | ||
577 | sock = xchg(&stab->sock_map[k], NULL); | |
578 | if (!sock) | |
579 | return -EINVAL; | |
580 | ||
581 | smap_release_sock(sock); | |
582 | return 0; | |
583 | } | |
584 | ||
585 | /* Locking notes: Concurrent updates, deletes, and lookups are allowed and are | |
586 | * done inside rcu critical sections. This ensures on updates that the psock | |
587 | * will not be released via smap_release_sock() until concurrent updates/deletes | |
588 | * complete. All operations operate on sock_map using cmpxchg and xchg | |
589 | * operations to ensure we do not get stale references. Any reads into the | |
590 | * map must be done with READ_ONCE() because of this. | |
591 | * | |
592 | * A psock is destroyed via call_rcu and after any worker threads are cancelled | |
593 | * and syncd so we are certain all references from the update/lookup/delete | |
594 | * operations as well as references in the data path are no longer in use. | |
595 | * | |
596 | * A psock object holds a refcnt on the sockmap it is attached to and this is | |
597 | * not decremented until after a RCU grace period and garbage collection occurs. | |
598 | * This ensures the map is not free'd until psocks linked to it are removed. The | |
599 | * map link is used when the independent sock events trigger map deletion. | |
600 | * | |
601 | * Psocks may only participate in one sockmap at a time. Users that try to | |
602 | * join a single sock to multiple maps will get an error. | |
603 | * | |
604 | * Last, but not least, it is possible the socket is closed while running | |
605 | * an update on an existing psock. This will release the psock, but again | |
606 | * not until the update has completed due to rcu grace period rules. | |
607 | */ | |
608 | static int sock_map_ctx_update_elem(struct bpf_sock_ops_kern *skops, | |
609 | struct bpf_map *map, | |
610 | void *key, u64 flags, u64 map_flags) | |
611 | { | |
612 | struct bpf_stab *stab = container_of(map, struct bpf_stab, map); | |
613 | struct bpf_prog *verdict, *parse; | |
614 | struct smap_psock *psock = NULL; | |
615 | struct sock *old_sock, *sock; | |
616 | u32 i = *(u32 *)key; | |
617 | bool update = false; | |
618 | int err = 0; | |
619 | ||
620 | if (unlikely(flags > BPF_EXIST)) | |
621 | return -EINVAL; | |
622 | ||
623 | if (unlikely(i >= stab->map.max_entries)) | |
624 | return -E2BIG; | |
625 | ||
626 | if (unlikely(map_flags > BPF_SOCKMAP_STRPARSER)) | |
627 | return -EINVAL; | |
628 | ||
629 | verdict = parse = NULL; | |
630 | sock = READ_ONCE(stab->sock_map[i]); | |
631 | ||
632 | if (flags == BPF_EXIST || flags == BPF_ANY) { | |
633 | if (!sock && flags == BPF_EXIST) { | |
634 | return -ENOENT; | |
635 | } else if (sock && sock != skops->sk) { | |
636 | return -EINVAL; | |
637 | } else if (sock) { | |
638 | psock = smap_psock_sk(sock); | |
639 | if (unlikely(!psock)) | |
640 | return -EBUSY; | |
641 | update = true; | |
642 | } | |
643 | } else if (sock && BPF_NOEXIST) { | |
644 | return -EEXIST; | |
645 | } | |
646 | ||
647 | /* reserve BPF programs early so can abort easily on failures */ | |
648 | if (map_flags & BPF_SOCKMAP_STRPARSER) { | |
649 | verdict = READ_ONCE(stab->bpf_verdict); | |
650 | parse = READ_ONCE(stab->bpf_parse); | |
651 | ||
652 | if (!verdict || !parse) | |
653 | return -ENOENT; | |
654 | ||
655 | /* bpf prog refcnt may be zero if a concurrent attach operation | |
656 | * removes the program after the above READ_ONCE() but before | |
657 | * we increment the refcnt. If this is the case abort with an | |
658 | * error. | |
659 | */ | |
660 | verdict = bpf_prog_inc_not_zero(stab->bpf_verdict); | |
661 | if (IS_ERR(verdict)) | |
662 | return PTR_ERR(verdict); | |
663 | ||
664 | parse = bpf_prog_inc_not_zero(stab->bpf_parse); | |
665 | if (IS_ERR(parse)) { | |
666 | bpf_prog_put(verdict); | |
667 | return PTR_ERR(parse); | |
668 | } | |
669 | } | |
670 | ||
671 | if (!psock) { | |
672 | sock = skops->sk; | |
673 | if (rcu_dereference_sk_user_data(sock)) | |
674 | return -EEXIST; | |
675 | psock = smap_init_psock(sock, stab); | |
676 | if (IS_ERR(psock)) { | |
677 | if (verdict) | |
678 | bpf_prog_put(verdict); | |
679 | if (parse) | |
680 | bpf_prog_put(parse); | |
681 | return PTR_ERR(psock); | |
682 | } | |
683 | psock->key = i; | |
684 | psock->stab = stab; | |
685 | refcount_inc(&stab->refcnt); | |
686 | set_bit(SMAP_TX_RUNNING, &psock->state); | |
687 | } | |
688 | ||
689 | if (map_flags & BPF_SOCKMAP_STRPARSER) { | |
690 | write_lock_bh(&sock->sk_callback_lock); | |
691 | if (psock->strp_enabled) | |
692 | goto start_done; | |
693 | err = smap_init_sock(psock, sock); | |
694 | if (err) | |
695 | goto out; | |
696 | smap_init_progs(psock, stab, verdict, parse); | |
697 | smap_start_sock(psock, sock); | |
698 | start_done: | |
699 | write_unlock_bh(&sock->sk_callback_lock); | |
700 | } else if (update) { | |
701 | smap_stop_sock(psock, sock); | |
702 | } | |
703 | ||
704 | if (!update) { | |
705 | old_sock = xchg(&stab->sock_map[i], skops->sk); | |
706 | if (old_sock) | |
707 | smap_release_sock(old_sock); | |
708 | } | |
709 | ||
710 | return 0; | |
711 | out: | |
712 | write_unlock_bh(&sock->sk_callback_lock); | |
713 | if (!update) | |
714 | smap_release_sock(sock); | |
715 | return err; | |
716 | } | |
717 | ||
718 | static int sock_map_attach_prog(struct bpf_map *map, | |
719 | struct bpf_prog *parse, | |
720 | struct bpf_prog *verdict) | |
721 | { | |
722 | struct bpf_stab *stab = container_of(map, struct bpf_stab, map); | |
723 | struct bpf_prog *_parse, *_verdict; | |
724 | ||
725 | _parse = xchg(&stab->bpf_parse, parse); | |
726 | _verdict = xchg(&stab->bpf_verdict, verdict); | |
727 | ||
728 | if (_parse) | |
729 | bpf_prog_put(_parse); | |
730 | if (_verdict) | |
731 | bpf_prog_put(_verdict); | |
732 | ||
733 | return 0; | |
734 | } | |
735 | ||
736 | static void *sock_map_lookup(struct bpf_map *map, void *key) | |
737 | { | |
738 | return NULL; | |
739 | } | |
740 | ||
741 | static int sock_map_update_elem(struct bpf_map *map, | |
742 | void *key, void *value, u64 flags) | |
743 | { | |
744 | struct bpf_sock_ops_kern skops; | |
745 | u32 fd = *(u32 *)value; | |
746 | struct socket *socket; | |
747 | int err; | |
748 | ||
749 | socket = sockfd_lookup(fd, &err); | |
750 | if (!socket) | |
751 | return err; | |
752 | ||
753 | skops.sk = socket->sk; | |
754 | if (!skops.sk) { | |
755 | fput(socket->file); | |
756 | return -EINVAL; | |
757 | } | |
758 | ||
759 | err = sock_map_ctx_update_elem(&skops, map, key, | |
760 | flags, BPF_SOCKMAP_STRPARSER); | |
761 | fput(socket->file); | |
762 | return err; | |
763 | } | |
764 | ||
765 | const struct bpf_map_ops sock_map_ops = { | |
766 | .map_alloc = sock_map_alloc, | |
767 | .map_free = sock_map_free, | |
768 | .map_lookup_elem = sock_map_lookup, | |
769 | .map_get_next_key = sock_map_get_next_key, | |
770 | .map_update_elem = sock_map_update_elem, | |
771 | .map_delete_elem = sock_map_delete_elem, | |
772 | .map_attach = sock_map_attach_prog, | |
773 | }; | |
774 | ||
775 | BPF_CALL_5(bpf_sock_map_update, struct bpf_sock_ops_kern *, bpf_sock, | |
776 | struct bpf_map *, map, void *, key, u64, flags, u64, map_flags) | |
777 | { | |
778 | WARN_ON_ONCE(!rcu_read_lock_held()); | |
779 | return sock_map_ctx_update_elem(bpf_sock, map, key, flags, map_flags); | |
780 | } | |
781 | ||
782 | const struct bpf_func_proto bpf_sock_map_update_proto = { | |
783 | .func = bpf_sock_map_update, | |
784 | .gpl_only = false, | |
785 | .pkt_access = true, | |
786 | .ret_type = RET_INTEGER, | |
787 | .arg1_type = ARG_PTR_TO_CTX, | |
788 | .arg2_type = ARG_CONST_MAP_PTR, | |
789 | .arg3_type = ARG_PTR_TO_MAP_KEY, | |
790 | .arg4_type = ARG_ANYTHING, | |
791 | .arg5_type = ARG_ANYTHING, | |
792 | }; |