1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2019 Facebook */
3 #include <linux/rculist.h>
4 #include <linux/list.h>
5 #include <linux/hash.h>
6 #include <linux/types.h>
7 #include <linux/spinlock.h>
8 #include <linux/bpf.h>
9 #include <linux/btf_ids.h>
10 #include <linux/bpf_local_storage.h>
11 #include <net/sock.h>
12 #include <uapi/linux/sock_diag.h>
13 #include <uapi/linux/btf.h>
14 #include <linux/rcupdate.h>
15 #include <linux/rcupdate_trace.h>
16 #include <linux/rcupdate_wait.h>
17
18 #define BPF_LOCAL_STORAGE_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_CLONE)
19
20 static struct bpf_local_storage_map_bucket *
21 select_bucket(struct bpf_local_storage_map *smap,
22 struct bpf_local_storage_elem *selem)
23 {
24 return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
25 }
26
27 static int mem_charge(struct bpf_local_storage_map *smap, void *owner, u32 size)
28 {
29 struct bpf_map *map = &smap->map;
30
31 if (!map->ops->map_local_storage_charge)
32 return 0;
33
34 return map->ops->map_local_storage_charge(smap, owner, size);
35 }
36
37 static void mem_uncharge(struct bpf_local_storage_map *smap, void *owner,
38 u32 size)
39 {
40 struct bpf_map *map = &smap->map;
41
42 if (map->ops->map_local_storage_uncharge)
43 map->ops->map_local_storage_uncharge(smap, owner, size);
44 }
45
46 static struct bpf_local_storage __rcu **
47 owner_storage(struct bpf_local_storage_map *smap, void *owner)
48 {
49 struct bpf_map *map = &smap->map;
50
51 return map->ops->map_owner_storage_ptr(owner);
52 }
53
54 static bool selem_linked_to_storage_lockless(const struct bpf_local_storage_elem *selem)
55 {
56 return !hlist_unhashed_lockless(&selem->snode);
57 }
58
59 static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem)
60 {
61 return !hlist_unhashed(&selem->snode);
62 }
63
64 static bool selem_linked_to_map_lockless(const struct bpf_local_storage_elem *selem)
65 {
66 return !hlist_unhashed_lockless(&selem->map_node);
67 }
68
69 static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem)
70 {
71 return !hlist_unhashed(&selem->map_node);
72 }
73
74 struct bpf_local_storage_elem *
75 bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner,
76 void *value, bool charge_mem, gfp_t gfp_flags)
77 {
78 struct bpf_local_storage_elem *selem;
79
80 if (charge_mem && mem_charge(smap, owner, smap->elem_size))
81 return NULL;
82
83 if (smap->bpf_ma) {
84 migrate_disable();
85 selem = bpf_mem_cache_alloc_flags(&smap->selem_ma, gfp_flags);
86 migrate_enable();
87 if (selem)
88 /* Keep the original bpf_map_kzalloc behavior
89 * before started using the bpf_mem_cache_alloc.
90 *
91 * No need to use zero_map_value. The bpf_selem_free()
92 * only does bpf_mem_cache_free when there is
93 * no other bpf prog is using the selem.
94 */
95 memset(SDATA(selem)->data, 0, smap->map.value_size);
96 } else {
97 selem = bpf_map_kzalloc(&smap->map, smap->elem_size,
98 gfp_flags | __GFP_NOWARN);
99 }
100
101 if (selem) {
102 if (value)
103 copy_map_value(&smap->map, SDATA(selem)->data, value);
104 /* No need to call check_and_init_map_value as memory is zero init */
105 return selem;
106 }
107
108 if (charge_mem)
109 mem_uncharge(smap, owner, smap->elem_size);
110
111 return NULL;
112 }
113
114 /* rcu tasks trace callback for bpf_ma == false */
115 static void __bpf_local_storage_free_trace_rcu(struct rcu_head *rcu)
116 {
117 struct bpf_local_storage *local_storage;
118
119 /* If RCU Tasks Trace grace period implies RCU grace period, do
120 * kfree(), else do kfree_rcu().
121 */
122 local_storage = container_of(rcu, struct bpf_local_storage, rcu);
123 if (rcu_trace_implies_rcu_gp())
124 kfree(local_storage);
125 else
126 kfree_rcu(local_storage, rcu);
127 }
128
129 static void bpf_local_storage_free_rcu(struct rcu_head *rcu)
130 {
131 struct bpf_local_storage *local_storage;
132
133 local_storage = container_of(rcu, struct bpf_local_storage, rcu);
134 bpf_mem_cache_raw_free(local_storage);
135 }
136
137 static void bpf_local_storage_free_trace_rcu(struct rcu_head *rcu)
138 {
139 if (rcu_trace_implies_rcu_gp())
140 bpf_local_storage_free_rcu(rcu);
141 else
142 call_rcu(rcu, bpf_local_storage_free_rcu);
143 }
144
145 /* Handle bpf_ma == false */
146 static void __bpf_local_storage_free(struct bpf_local_storage *local_storage,
147 bool vanilla_rcu)
148 {
149 if (vanilla_rcu)
150 kfree_rcu(local_storage, rcu);
151 else
152 call_rcu_tasks_trace(&local_storage->rcu,
153 __bpf_local_storage_free_trace_rcu);
154 }
155
156 static void bpf_local_storage_free(struct bpf_local_storage *local_storage,
157 struct bpf_local_storage_map *smap,
158 bool bpf_ma, bool reuse_now)
159 {
160 if (!local_storage)
161 return;
162
163 if (!bpf_ma) {
164 __bpf_local_storage_free(local_storage, reuse_now);
165 return;
166 }
167
168 if (!reuse_now) {
169 call_rcu_tasks_trace(&local_storage->rcu,
170 bpf_local_storage_free_trace_rcu);
171 return;
172 }
173
174 if (smap) {
175 migrate_disable();
176 bpf_mem_cache_free(&smap->storage_ma, local_storage);
177 migrate_enable();
178 } else {
179 /* smap could be NULL if the selem that triggered
180 * this 'local_storage' creation had been long gone.
181 * In this case, directly do call_rcu().
182 */
183 call_rcu(&local_storage->rcu, bpf_local_storage_free_rcu);
184 }
185 }
186
187 /* rcu tasks trace callback for bpf_ma == false */
188 static void __bpf_selem_free_trace_rcu(struct rcu_head *rcu)
189 {
190 struct bpf_local_storage_elem *selem;
191
192 selem = container_of(rcu, struct bpf_local_storage_elem, rcu);
193 if (rcu_trace_implies_rcu_gp())
194 kfree(selem);
195 else
196 kfree_rcu(selem, rcu);
197 }
198
199 /* Handle bpf_ma == false */
200 static void __bpf_selem_free(struct bpf_local_storage_elem *selem,
201 bool vanilla_rcu)
202 {
203 if (vanilla_rcu)
204 kfree_rcu(selem, rcu);
205 else
206 call_rcu_tasks_trace(&selem->rcu, __bpf_selem_free_trace_rcu);
207 }
208
209 static void bpf_selem_free_rcu(struct rcu_head *rcu)
210 {
211 struct bpf_local_storage_elem *selem;
212
213 selem = container_of(rcu, struct bpf_local_storage_elem, rcu);
214 bpf_mem_cache_raw_free(selem);
215 }
216
217 static void bpf_selem_free_trace_rcu(struct rcu_head *rcu)
218 {
219 if (rcu_trace_implies_rcu_gp())
220 bpf_selem_free_rcu(rcu);
221 else
222 call_rcu(rcu, bpf_selem_free_rcu);
223 }
224
225 void bpf_selem_free(struct bpf_local_storage_elem *selem,
226 struct bpf_local_storage_map *smap,
227 bool reuse_now)
228 {
229 bpf_obj_free_fields(smap->map.record, SDATA(selem)->data);
230
231 if (!smap->bpf_ma) {
232 __bpf_selem_free(selem, reuse_now);
233 return;
234 }
235
236 if (!reuse_now) {
237 call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu);
238 } else {
239 /* Instead of using the vanilla call_rcu(),
240 * bpf_mem_cache_free will be able to reuse selem
241 * immediately.
242 */
243 migrate_disable();
244 bpf_mem_cache_free(&smap->selem_ma, selem);
245 migrate_enable();
246 }
247 }
248
249 /* local_storage->lock must be held and selem->local_storage == local_storage.
250 * The caller must ensure selem->smap is still valid to be
251 * dereferenced for its smap->elem_size and smap->cache_idx.
252 */
253 static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
254 struct bpf_local_storage_elem *selem,
255 bool uncharge_mem, bool reuse_now)
256 {
257 struct bpf_local_storage_map *smap;
258 bool free_local_storage;
259 void *owner;
260
261 smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
262 owner = local_storage->owner;
263
264 /* All uncharging on the owner must be done first.
265 * The owner may be freed once the last selem is unlinked
266 * from local_storage.
267 */
268 if (uncharge_mem)
269 mem_uncharge(smap, owner, smap->elem_size);
270
271 free_local_storage = hlist_is_singular_node(&selem->snode,
272 &local_storage->list);
273 if (free_local_storage) {
274 mem_uncharge(smap, owner, sizeof(struct bpf_local_storage));
275 local_storage->owner = NULL;
276
277 /* After this RCU_INIT, owner may be freed and cannot be used */
278 RCU_INIT_POINTER(*owner_storage(smap, owner), NULL);
279
280 /* local_storage is not freed now. local_storage->lock is
281 * still held and raw_spin_unlock_bh(&local_storage->lock)
282 * will be done by the caller.
283 *
284 * Although the unlock will be done under
285 * rcu_read_lock(), it is more intuitive to
286 * read if the freeing of the storage is done
287 * after the raw_spin_unlock_bh(&local_storage->lock).
288 *
289 * Hence, a "bool free_local_storage" is returned
290 * to the caller which then calls then frees the storage after
291 * all the RCU grace periods have expired.
292 */
293 }
294 hlist_del_init_rcu(&selem->snode);
295 if (rcu_access_pointer(local_storage->cache[smap->cache_idx]) ==
296 SDATA(selem))
297 RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
298
299 bpf_selem_free(selem, smap, reuse_now);
300
301 if (rcu_access_pointer(local_storage->smap) == smap)
302 RCU_INIT_POINTER(local_storage->smap, NULL);
303
304 return free_local_storage;
305 }
306
307 static bool check_storage_bpf_ma(struct bpf_local_storage *local_storage,
308 struct bpf_local_storage_map *storage_smap,
309 struct bpf_local_storage_elem *selem)
310 {
311
312 struct bpf_local_storage_map *selem_smap;
313
314 /* local_storage->smap may be NULL. If it is, get the bpf_ma
315 * from any selem in the local_storage->list. The bpf_ma of all
316 * local_storage and selem should have the same value
317 * for the same map type.
318 *
319 * If the local_storage->list is already empty, the caller will not
320 * care about the bpf_ma value also because the caller is not
321 * responsible to free the local_storage.
322 */
323
324 if (storage_smap)
325 return storage_smap->bpf_ma;
326
327 if (!selem) {
328 struct hlist_node *n;
329
330 n = rcu_dereference_check(hlist_first_rcu(&local_storage->list),
331 bpf_rcu_lock_held());
332 if (!n)
333 return false;
334
335 selem = hlist_entry(n, struct bpf_local_storage_elem, snode);
336 }
337 selem_smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
338
339 return selem_smap->bpf_ma;
340 }
341
342 static void bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem,
343 bool reuse_now)
344 {
345 struct bpf_local_storage_map *storage_smap;
346 struct bpf_local_storage *local_storage;
347 bool bpf_ma, free_local_storage = false;
348 unsigned long flags;
349
350 if (unlikely(!selem_linked_to_storage_lockless(selem)))
351 /* selem has already been unlinked from sk */
352 return;
353
354 local_storage = rcu_dereference_check(selem->local_storage,
355 bpf_rcu_lock_held());
356 storage_smap = rcu_dereference_check(local_storage->smap,
357 bpf_rcu_lock_held());
358 bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, selem);
359
360 raw_spin_lock_irqsave(&local_storage->lock, flags);
361 if (likely(selem_linked_to_storage(selem)))
362 free_local_storage = bpf_selem_unlink_storage_nolock(
363 local_storage, selem, true, reuse_now);
364 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
365
366 if (free_local_storage)
367 bpf_local_storage_free(local_storage, storage_smap, bpf_ma, reuse_now);
368 }
369
370 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
371 struct bpf_local_storage_elem *selem)
372 {
373 RCU_INIT_POINTER(selem->local_storage, local_storage);
374 hlist_add_head_rcu(&selem->snode, &local_storage->list);
375 }
376
377 static void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
378 {
379 struct bpf_local_storage_map *smap;
380 struct bpf_local_storage_map_bucket *b;
381 unsigned long flags;
382
383 if (unlikely(!selem_linked_to_map_lockless(selem)))
384 /* selem has already be unlinked from smap */
385 return;
386
387 smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held());
388 b = select_bucket(smap, selem);
389 raw_spin_lock_irqsave(&b->lock, flags);
390 if (likely(selem_linked_to_map(selem)))
391 hlist_del_init_rcu(&selem->map_node);
392 raw_spin_unlock_irqrestore(&b->lock, flags);
393 }
394
395 void bpf_selem_link_map(struct bpf_local_storage_map *smap,
396 struct bpf_local_storage_elem *selem)
397 {
398 struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem);
399 unsigned long flags;
400
401 raw_spin_lock_irqsave(&b->lock, flags);
402 RCU_INIT_POINTER(SDATA(selem)->smap, smap);
403 hlist_add_head_rcu(&selem->map_node, &b->list);
404 raw_spin_unlock_irqrestore(&b->lock, flags);
405 }
406
407 void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool reuse_now)
408 {
409 /* Always unlink from map before unlinking from local_storage
410 * because selem will be freed after successfully unlinked from
411 * the local_storage.
412 */
413 bpf_selem_unlink_map(selem);
414 bpf_selem_unlink_storage(selem, reuse_now);
415 }
416
417 void __bpf_local_storage_insert_cache(struct bpf_local_storage *local_storage,
418 struct bpf_local_storage_map *smap,
419 struct bpf_local_storage_elem *selem)
420 {
421 unsigned long flags;
422
423 /* spinlock is needed to avoid racing with the
424 * parallel delete. Otherwise, publishing an already
425 * deleted sdata to the cache will become a use-after-free
426 * problem in the next bpf_local_storage_lookup().
427 */
428 raw_spin_lock_irqsave(&local_storage->lock, flags);
429 if (selem_linked_to_storage(selem))
430 rcu_assign_pointer(local_storage->cache[smap->cache_idx], SDATA(selem));
431 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
432 }
433
434 static int check_flags(const struct bpf_local_storage_data *old_sdata,
435 u64 map_flags)
436 {
437 if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
438 /* elem already exists */
439 return -EEXIST;
440
441 if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
442 /* elem doesn't exist, cannot update it */
443 return -ENOENT;
444
445 return 0;
446 }
447
448 int bpf_local_storage_alloc(void *owner,
449 struct bpf_local_storage_map *smap,
450 struct bpf_local_storage_elem *first_selem,
451 gfp_t gfp_flags)
452 {
453 struct bpf_local_storage *prev_storage, *storage;
454 struct bpf_local_storage **owner_storage_ptr;
455 int err;
456
457 err = mem_charge(smap, owner, sizeof(*storage));
458 if (err)
459 return err;
460
461 if (smap->bpf_ma) {
462 migrate_disable();
463 storage = bpf_mem_cache_alloc_flags(&smap->storage_ma, gfp_flags);
464 migrate_enable();
465 } else {
466 storage = bpf_map_kzalloc(&smap->map, sizeof(*storage),
467 gfp_flags | __GFP_NOWARN);
468 }
469
470 if (!storage) {
471 err = -ENOMEM;
472 goto uncharge;
473 }
474
475 RCU_INIT_POINTER(storage->smap, smap);
476 INIT_HLIST_HEAD(&storage->list);
477 raw_spin_lock_init(&storage->lock);
478 storage->owner = owner;
479
480 bpf_selem_link_storage_nolock(storage, first_selem);
481 bpf_selem_link_map(smap, first_selem);
482
483 owner_storage_ptr =
484 (struct bpf_local_storage **)owner_storage(smap, owner);
485 /* Publish storage to the owner.
486 * Instead of using any lock of the kernel object (i.e. owner),
487 * cmpxchg will work with any kernel object regardless what
488 * the running context is, bh, irq...etc.
489 *
490 * From now on, the owner->storage pointer (e.g. sk->sk_bpf_storage)
491 * is protected by the storage->lock. Hence, when freeing
492 * the owner->storage, the storage->lock must be held before
493 * setting owner->storage ptr to NULL.
494 */
495 prev_storage = cmpxchg(owner_storage_ptr, NULL, storage);
496 if (unlikely(prev_storage)) {
497 bpf_selem_unlink_map(first_selem);
498 err = -EAGAIN;
499 goto uncharge;
500
501 /* Note that even first_selem was linked to smap's
502 * bucket->list, first_selem can be freed immediately
503 * (instead of kfree_rcu) because
504 * bpf_local_storage_map_free() does a
505 * synchronize_rcu_mult (waiting for both sleepable and
506 * normal programs) before walking the bucket->list.
507 * Hence, no one is accessing selem from the
508 * bucket->list under rcu_read_lock().
509 */
510 }
511
512 return 0;
513
514 uncharge:
515 bpf_local_storage_free(storage, smap, smap->bpf_ma, true);
516 mem_uncharge(smap, owner, sizeof(*storage));
517 return err;
518 }
519
520 /* sk cannot be going away because it is linking new elem
521 * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0).
522 * Otherwise, it will become a leak (and other memory issues
523 * during map destruction).
524 */
525 struct bpf_local_storage_data *
526 bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
527 void *value, u64 map_flags, gfp_t gfp_flags)
528 {
529 struct bpf_local_storage_data *old_sdata = NULL;
530 struct bpf_local_storage_elem *alloc_selem, *selem = NULL;
531 struct bpf_local_storage *local_storage;
532 unsigned long flags;
533 int err;
534
535 /* BPF_EXIST and BPF_NOEXIST cannot be both set */
536 if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
537 /* BPF_F_LOCK can only be used in a value with spin_lock */
538 unlikely((map_flags & BPF_F_LOCK) &&
539 !btf_record_has_field(smap->map.record, BPF_SPIN_LOCK)))
540 return ERR_PTR(-EINVAL);
541
542 if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST)
543 return ERR_PTR(-EINVAL);
544
545 local_storage = rcu_dereference_check(*owner_storage(smap, owner),
546 bpf_rcu_lock_held());
547 if (!local_storage || hlist_empty(&local_storage->list)) {
548 /* Very first elem for the owner */
549 err = check_flags(NULL, map_flags);
550 if (err)
551 return ERR_PTR(err);
552
553 selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags);
554 if (!selem)
555 return ERR_PTR(-ENOMEM);
556
557 err = bpf_local_storage_alloc(owner, smap, selem, gfp_flags);
558 if (err) {
559 bpf_selem_free(selem, smap, true);
560 mem_uncharge(smap, owner, smap->elem_size);
561 return ERR_PTR(err);
562 }
563
564 return SDATA(selem);
565 }
566
567 if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) {
568 /* Hoping to find an old_sdata to do inline update
569 * such that it can avoid taking the local_storage->lock
570 * and changing the lists.
571 */
572 old_sdata =
573 bpf_local_storage_lookup(local_storage, smap, false);
574 err = check_flags(old_sdata, map_flags);
575 if (err)
576 return ERR_PTR(err);
577 if (old_sdata && selem_linked_to_storage_lockless(SELEM(old_sdata))) {
578 copy_map_value_locked(&smap->map, old_sdata->data,
579 value, false);
580 return old_sdata;
581 }
582 }
583
584 /* A lookup has just been done before and concluded a new selem is
585 * needed. The chance of an unnecessary alloc is unlikely.
586 */
587 alloc_selem = selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags);
588 if (!alloc_selem)
589 return ERR_PTR(-ENOMEM);
590
591 raw_spin_lock_irqsave(&local_storage->lock, flags);
592
593 /* Recheck local_storage->list under local_storage->lock */
594 if (unlikely(hlist_empty(&local_storage->list))) {
595 /* A parallel del is happening and local_storage is going
596 * away. It has just been checked before, so very
597 * unlikely. Return instead of retry to keep things
598 * simple.
599 */
600 err = -EAGAIN;
601 goto unlock;
602 }
603
604 old_sdata = bpf_local_storage_lookup(local_storage, smap, false);
605 err = check_flags(old_sdata, map_flags);
606 if (err)
607 goto unlock;
608
609 if (old_sdata && (map_flags & BPF_F_LOCK)) {
610 copy_map_value_locked(&smap->map, old_sdata->data, value,
611 false);
612 selem = SELEM(old_sdata);
613 goto unlock;
614 }
615
616 alloc_selem = NULL;
617 /* First, link the new selem to the map */
618 bpf_selem_link_map(smap, selem);
619
620 /* Second, link (and publish) the new selem to local_storage */
621 bpf_selem_link_storage_nolock(local_storage, selem);
622
623 /* Third, remove old selem, SELEM(old_sdata) */
624 if (old_sdata) {
625 bpf_selem_unlink_map(SELEM(old_sdata));
626 bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata),
627 true, false);
628 }
629
630 unlock:
631 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
632 if (alloc_selem) {
633 mem_uncharge(smap, owner, smap->elem_size);
634 bpf_selem_free(alloc_selem, smap, true);
635 }
636 return err ? ERR_PTR(err) : SDATA(selem);
637 }
638
639 static u16 bpf_local_storage_cache_idx_get(struct bpf_local_storage_cache *cache)
640 {
641 u64 min_usage = U64_MAX;
642 u16 i, res = 0;
643
644 spin_lock(&cache->idx_lock);
645
646 for (i = 0; i < BPF_LOCAL_STORAGE_CACHE_SIZE; i++) {
647 if (cache->idx_usage_counts[i] < min_usage) {
648 min_usage = cache->idx_usage_counts[i];
649 res = i;
650
651 /* Found a free cache_idx */
652 if (!min_usage)
653 break;
654 }
655 }
656 cache->idx_usage_counts[res]++;
657
658 spin_unlock(&cache->idx_lock);
659
660 return res;
661 }
662
663 static void bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache *cache,
664 u16 idx)
665 {
666 spin_lock(&cache->idx_lock);
667 cache->idx_usage_counts[idx]--;
668 spin_unlock(&cache->idx_lock);
669 }
670
671 int bpf_local_storage_map_alloc_check(union bpf_attr *attr)
672 {
673 if (attr->map_flags & ~BPF_LOCAL_STORAGE_CREATE_FLAG_MASK ||
674 !(attr->map_flags & BPF_F_NO_PREALLOC) ||
675 attr->max_entries ||
676 attr->key_size != sizeof(int) || !attr->value_size ||
677 /* Enforce BTF for userspace sk dumping */
678 !attr->btf_key_type_id || !attr->btf_value_type_id)
679 return -EINVAL;
680
681 if (attr->value_size > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE)
682 return -E2BIG;
683
684 return 0;
685 }
686
687 int bpf_local_storage_map_check_btf(const struct bpf_map *map,
688 const struct btf *btf,
689 const struct btf_type *key_type,
690 const struct btf_type *value_type)
691 {
692 u32 int_data;
693
694 if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
695 return -EINVAL;
696
697 int_data = *(u32 *)(key_type + 1);
698 if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))
699 return -EINVAL;
700
701 return 0;
702 }
703
704 void bpf_local_storage_destroy(struct bpf_local_storage *local_storage)
705 {
706 struct bpf_local_storage_map *storage_smap;
707 struct bpf_local_storage_elem *selem;
708 bool bpf_ma, free_storage = false;
709 struct hlist_node *n;
710 unsigned long flags;
711
712 storage_smap = rcu_dereference_check(local_storage->smap, bpf_rcu_lock_held());
713 bpf_ma = check_storage_bpf_ma(local_storage, storage_smap, NULL);
714
715 /* Neither the bpf_prog nor the bpf_map's syscall
716 * could be modifying the local_storage->list now.
717 * Thus, no elem can be added to or deleted from the
718 * local_storage->list by the bpf_prog or by the bpf_map's syscall.
719 *
720 * It is racing with bpf_local_storage_map_free() alone
721 * when unlinking elem from the local_storage->list and
722 * the map's bucket->list.
723 */
724 raw_spin_lock_irqsave(&local_storage->lock, flags);
725 hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) {
726 /* Always unlink from map before unlinking from
727 * local_storage.
728 */
729 bpf_selem_unlink_map(selem);
730 /* If local_storage list has only one element, the
731 * bpf_selem_unlink_storage_nolock() will return true.
732 * Otherwise, it will return false. The current loop iteration
733 * intends to remove all local storage. So the last iteration
734 * of the loop will set the free_cgroup_storage to true.
735 */
736 free_storage = bpf_selem_unlink_storage_nolock(
737 local_storage, selem, true, true);
738 }
739 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
740
741 if (free_storage)
742 bpf_local_storage_free(local_storage, storage_smap, bpf_ma, true);
743 }
744
745 u64 bpf_local_storage_map_mem_usage(const struct bpf_map *map)
746 {
747 struct bpf_local_storage_map *smap = (struct bpf_local_storage_map *)map;
748 u64 usage = sizeof(*smap);
749
750 /* The dynamically callocated selems are not counted currently. */
751 usage += sizeof(*smap->buckets) * (1ULL << smap->bucket_log);
752 return usage;
753 }
754
755 /* When bpf_ma == true, the bpf_mem_alloc is used to allocate and free memory.
756 * A deadlock free allocator is useful for storage that the bpf prog can easily
757 * get a hold of the owner PTR_TO_BTF_ID in any context. eg. bpf_get_current_task_btf.
758 * The task and cgroup storage fall into this case. The bpf_mem_alloc reuses
759 * memory immediately. To be reuse-immediate safe, the owner destruction
760 * code path needs to go through a rcu grace period before calling
761 * bpf_local_storage_destroy().
762 *
763 * When bpf_ma == false, the kmalloc and kfree are used.
764 */
765 struct bpf_map *
766 bpf_local_storage_map_alloc(union bpf_attr *attr,
767 struct bpf_local_storage_cache *cache,
768 bool bpf_ma)
769 {
770 struct bpf_local_storage_map *smap;
771 unsigned int i;
772 u32 nbuckets;
773 int err;
774
775 smap = bpf_map_area_alloc(sizeof(*smap), NUMA_NO_NODE);
776 if (!smap)
777 return ERR_PTR(-ENOMEM);
778 bpf_map_init_from_attr(&smap->map, attr);
779
780 nbuckets = roundup_pow_of_two(num_possible_cpus());
781 /* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */
782 nbuckets = max_t(u32, 2, nbuckets);
783 smap->bucket_log = ilog2(nbuckets);
784
785 smap->buckets = bpf_map_kvcalloc(&smap->map, nbuckets,
786 sizeof(*smap->buckets), GFP_USER | __GFP_NOWARN);
787 if (!smap->buckets) {
788 err = -ENOMEM;
789 goto free_smap;
790 }
791
792 for (i = 0; i < nbuckets; i++) {
793 INIT_HLIST_HEAD(&smap->buckets[i].list);
794 raw_spin_lock_init(&smap->buckets[i].lock);
795 }
796
797 smap->elem_size = offsetof(struct bpf_local_storage_elem,
798 sdata.data[attr->value_size]);
799
800 smap->bpf_ma = bpf_ma;
801 if (bpf_ma) {
802 err = bpf_mem_alloc_init(&smap->selem_ma, smap->elem_size, false);
803 if (err)
804 goto free_smap;
805
806 err = bpf_mem_alloc_init(&smap->storage_ma, sizeof(struct bpf_local_storage), false);
807 if (err) {
808 bpf_mem_alloc_destroy(&smap->selem_ma);
809 goto free_smap;
810 }
811 }
812
813 smap->cache_idx = bpf_local_storage_cache_idx_get(cache);
814 return &smap->map;
815
816 free_smap:
817 kvfree(smap->buckets);
818 bpf_map_area_free(smap);
819 return ERR_PTR(err);
820 }
821
822 void bpf_local_storage_map_free(struct bpf_map *map,
823 struct bpf_local_storage_cache *cache,
824 int __percpu *busy_counter)
825 {
826 struct bpf_local_storage_map_bucket *b;
827 struct bpf_local_storage_elem *selem;
828 struct bpf_local_storage_map *smap;
829 unsigned int i;
830
831 smap = (struct bpf_local_storage_map *)map;
832 bpf_local_storage_cache_idx_free(cache, smap->cache_idx);
833
834 /* Note that this map might be concurrently cloned from
835 * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
836 * RCU read section to finish before proceeding. New RCU
837 * read sections should be prevented via bpf_map_inc_not_zero.
838 */
839 synchronize_rcu();
840
841 /* bpf prog and the userspace can no longer access this map
842 * now. No new selem (of this map) can be added
843 * to the owner->storage or to the map bucket's list.
844 *
845 * The elem of this map can be cleaned up here
846 * or when the storage is freed e.g.
847 * by bpf_sk_storage_free() during __sk_destruct().
848 */
849 for (i = 0; i < (1U << smap->bucket_log); i++) {
850 b = &smap->buckets[i];
851
852 rcu_read_lock();
853 /* No one is adding to b->list now */
854 while ((selem = hlist_entry_safe(
855 rcu_dereference_raw(hlist_first_rcu(&b->list)),
856 struct bpf_local_storage_elem, map_node))) {
857 if (busy_counter) {
858 migrate_disable();
859 this_cpu_inc(*busy_counter);
860 }
861 bpf_selem_unlink(selem, true);
862 if (busy_counter) {
863 this_cpu_dec(*busy_counter);
864 migrate_enable();
865 }
866 cond_resched_rcu();
867 }
868 rcu_read_unlock();
869 }
870
871 /* While freeing the storage we may still need to access the map.
872 *
873 * e.g. when bpf_sk_storage_free() has unlinked selem from the map
874 * which then made the above while((selem = ...)) loop
875 * exit immediately.
876 *
877 * However, while freeing the storage one still needs to access the
878 * smap->elem_size to do the uncharging in
879 * bpf_selem_unlink_storage_nolock().
880 *
881 * Hence, wait another rcu grace period for the storage to be freed.
882 */
883 synchronize_rcu();
884
885 if (smap->bpf_ma) {
886 bpf_mem_alloc_destroy(&smap->selem_ma);
887 bpf_mem_alloc_destroy(&smap->storage_ma);
888 }
889 kvfree(smap->buckets);
890 bpf_map_area_free(smap);
891 }
892
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