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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
15#define BPF_LOCAL_STORAGE_CREATE_FLAG_MASK (BPF_F_NO_PREALLOC | BPF_F_CLONE)
16
17static struct bpf_local_storage_map_bucket *
18select_bucket(struct bpf_local_storage_map *smap,
19 struct bpf_local_storage_elem *selem)
20{
21 return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
22}
23
24static int mem_charge(struct bpf_local_storage_map *smap, void *owner, u32 size)
25{
26 struct bpf_map *map = &smap->map;
27
28 if (!map->ops->map_local_storage_charge)
29 return 0;
30
31 return map->ops->map_local_storage_charge(smap, owner, size);
32}
33
34static void mem_uncharge(struct bpf_local_storage_map *smap, void *owner,
35 u32 size)
36{
37 struct bpf_map *map = &smap->map;
38
39 if (map->ops->map_local_storage_uncharge)
40 map->ops->map_local_storage_uncharge(smap, owner, size);
41}
42
43static struct bpf_local_storage __rcu **
44owner_storage(struct bpf_local_storage_map *smap, void *owner)
45{
46 struct bpf_map *map = &smap->map;
47
48 return map->ops->map_owner_storage_ptr(owner);
49}
50
51static bool selem_linked_to_storage(const struct bpf_local_storage_elem *selem)
52{
53 return !hlist_unhashed(&selem->snode);
54}
55
56static bool selem_linked_to_map(const struct bpf_local_storage_elem *selem)
57{
58 return !hlist_unhashed(&selem->map_node);
59}
60
61struct bpf_local_storage_elem *
62bpf_selem_alloc(struct bpf_local_storage_map *smap, void *owner,
63 void *value, bool charge_mem)
64{
65 struct bpf_local_storage_elem *selem;
66
67 if (charge_mem && mem_charge(smap, owner, smap->elem_size))
68 return NULL;
69
70 selem = bpf_map_kzalloc(&smap->map, smap->elem_size,
71 GFP_ATOMIC | __GFP_NOWARN);
72 if (selem) {
73 if (value)
74 memcpy(SDATA(selem)->data, value, smap->map.value_size);
75 return selem;
76 }
77
78 if (charge_mem)
79 mem_uncharge(smap, owner, smap->elem_size);
80
81 return NULL;
82}
83
84/* local_storage->lock must be held and selem->local_storage == local_storage.
85 * The caller must ensure selem->smap is still valid to be
86 * dereferenced for its smap->elem_size and smap->cache_idx.
87 */
88bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage,
89 struct bpf_local_storage_elem *selem,
90 bool uncharge_mem)
91{
92 struct bpf_local_storage_map *smap;
93 bool free_local_storage;
94 void *owner;
95
96 smap = rcu_dereference(SDATA(selem)->smap);
97 owner = local_storage->owner;
98
99 /* All uncharging on the owner must be done first.
100 * The owner may be freed once the last selem is unlinked
101 * from local_storage.
102 */
103 if (uncharge_mem)
104 mem_uncharge(smap, owner, smap->elem_size);
105
106 free_local_storage = hlist_is_singular_node(&selem->snode,
107 &local_storage->list);
108 if (free_local_storage) {
109 mem_uncharge(smap, owner, sizeof(struct bpf_local_storage));
110 local_storage->owner = NULL;
111
112 /* After this RCU_INIT, owner may be freed and cannot be used */
113 RCU_INIT_POINTER(*owner_storage(smap, owner), NULL);
114
115 /* local_storage is not freed now. local_storage->lock is
116 * still held and raw_spin_unlock_bh(&local_storage->lock)
117 * will be done by the caller.
118 *
119 * Although the unlock will be done under
120 * rcu_read_lock(), it is more intutivie to
121 * read if kfree_rcu(local_storage, rcu) is done
122 * after the raw_spin_unlock_bh(&local_storage->lock).
123 *
124 * Hence, a "bool free_local_storage" is returned
125 * to the caller which then calls the kfree_rcu()
126 * after unlock.
127 */
128 }
129 hlist_del_init_rcu(&selem->snode);
130 if (rcu_access_pointer(local_storage->cache[smap->cache_idx]) ==
131 SDATA(selem))
132 RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL);
133
134 kfree_rcu(selem, rcu);
135
136 return free_local_storage;
137}
138
139static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem)
140{
141 struct bpf_local_storage *local_storage;
142 bool free_local_storage = false;
143 unsigned long flags;
144
145 if (unlikely(!selem_linked_to_storage(selem)))
146 /* selem has already been unlinked from sk */
147 return;
148
149 local_storage = rcu_dereference(selem->local_storage);
150 raw_spin_lock_irqsave(&local_storage->lock, flags);
151 if (likely(selem_linked_to_storage(selem)))
152 free_local_storage = bpf_selem_unlink_storage_nolock(
153 local_storage, selem, true);
154 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
155
156 if (free_local_storage)
157 kfree_rcu(local_storage, rcu);
158}
159
160void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage,
161 struct bpf_local_storage_elem *selem)
162{
163 RCU_INIT_POINTER(selem->local_storage, local_storage);
164 hlist_add_head_rcu(&selem->snode, &local_storage->list);
165}
166
167void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem)
168{
169 struct bpf_local_storage_map *smap;
170 struct bpf_local_storage_map_bucket *b;
171 unsigned long flags;
172
173 if (unlikely(!selem_linked_to_map(selem)))
174 /* selem has already be unlinked from smap */
175 return;
176
177 smap = rcu_dereference(SDATA(selem)->smap);
178 b = select_bucket(smap, selem);
179 raw_spin_lock_irqsave(&b->lock, flags);
180 if (likely(selem_linked_to_map(selem)))
181 hlist_del_init_rcu(&selem->map_node);
182 raw_spin_unlock_irqrestore(&b->lock, flags);
183}
184
185void bpf_selem_link_map(struct bpf_local_storage_map *smap,
186 struct bpf_local_storage_elem *selem)
187{
188 struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem);
189 unsigned long flags;
190
191 raw_spin_lock_irqsave(&b->lock, flags);
192 RCU_INIT_POINTER(SDATA(selem)->smap, smap);
193 hlist_add_head_rcu(&selem->map_node, &b->list);
194 raw_spin_unlock_irqrestore(&b->lock, flags);
195}
196
197void bpf_selem_unlink(struct bpf_local_storage_elem *selem)
198{
199 /* Always unlink from map before unlinking from local_storage
200 * because selem will be freed after successfully unlinked from
201 * the local_storage.
202 */
203 bpf_selem_unlink_map(selem);
204 __bpf_selem_unlink_storage(selem);
205}
206
207struct bpf_local_storage_data *
208bpf_local_storage_lookup(struct bpf_local_storage *local_storage,
209 struct bpf_local_storage_map *smap,
210 bool cacheit_lockit)
211{
212 struct bpf_local_storage_data *sdata;
213 struct bpf_local_storage_elem *selem;
214
215 /* Fast path (cache hit) */
216 sdata = rcu_dereference(local_storage->cache[smap->cache_idx]);
217 if (sdata && rcu_access_pointer(sdata->smap) == smap)
218 return sdata;
219
220 /* Slow path (cache miss) */
221 hlist_for_each_entry_rcu(selem, &local_storage->list, snode)
222 if (rcu_access_pointer(SDATA(selem)->smap) == smap)
223 break;
224
225 if (!selem)
226 return NULL;
227
228 sdata = SDATA(selem);
229 if (cacheit_lockit) {
230 unsigned long flags;
231
232 /* spinlock is needed to avoid racing with the
233 * parallel delete. Otherwise, publishing an already
234 * deleted sdata to the cache will become a use-after-free
235 * problem in the next bpf_local_storage_lookup().
236 */
237 raw_spin_lock_irqsave(&local_storage->lock, flags);
238 if (selem_linked_to_storage(selem))
239 rcu_assign_pointer(local_storage->cache[smap->cache_idx],
240 sdata);
241 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
242 }
243
244 return sdata;
245}
246
247static int check_flags(const struct bpf_local_storage_data *old_sdata,
248 u64 map_flags)
249{
250 if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
251 /* elem already exists */
252 return -EEXIST;
253
254 if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
255 /* elem doesn't exist, cannot update it */
256 return -ENOENT;
257
258 return 0;
259}
260
261int bpf_local_storage_alloc(void *owner,
262 struct bpf_local_storage_map *smap,
263 struct bpf_local_storage_elem *first_selem)
264{
265 struct bpf_local_storage *prev_storage, *storage;
266 struct bpf_local_storage **owner_storage_ptr;
267 int err;
268
269 err = mem_charge(smap, owner, sizeof(*storage));
270 if (err)
271 return err;
272
273 storage = bpf_map_kzalloc(&smap->map, sizeof(*storage),
274 GFP_ATOMIC | __GFP_NOWARN);
275 if (!storage) {
276 err = -ENOMEM;
277 goto uncharge;
278 }
279
280 INIT_HLIST_HEAD(&storage->list);
281 raw_spin_lock_init(&storage->lock);
282 storage->owner = owner;
283
284 bpf_selem_link_storage_nolock(storage, first_selem);
285 bpf_selem_link_map(smap, first_selem);
286
287 owner_storage_ptr =
288 (struct bpf_local_storage **)owner_storage(smap, owner);
289 /* Publish storage to the owner.
290 * Instead of using any lock of the kernel object (i.e. owner),
291 * cmpxchg will work with any kernel object regardless what
292 * the running context is, bh, irq...etc.
293 *
294 * From now on, the owner->storage pointer (e.g. sk->sk_bpf_storage)
295 * is protected by the storage->lock. Hence, when freeing
296 * the owner->storage, the storage->lock must be held before
297 * setting owner->storage ptr to NULL.
298 */
299 prev_storage = cmpxchg(owner_storage_ptr, NULL, storage);
300 if (unlikely(prev_storage)) {
301 bpf_selem_unlink_map(first_selem);
302 err = -EAGAIN;
303 goto uncharge;
304
305 /* Note that even first_selem was linked to smap's
306 * bucket->list, first_selem can be freed immediately
307 * (instead of kfree_rcu) because
308 * bpf_local_storage_map_free() does a
309 * synchronize_rcu() before walking the bucket->list.
310 * Hence, no one is accessing selem from the
311 * bucket->list under rcu_read_lock().
312 */
313 }
314
315 return 0;
316
317uncharge:
318 kfree(storage);
319 mem_uncharge(smap, owner, sizeof(*storage));
320 return err;
321}
322
323/* sk cannot be going away because it is linking new elem
324 * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0).
325 * Otherwise, it will become a leak (and other memory issues
326 * during map destruction).
327 */
328struct bpf_local_storage_data *
329bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap,
330 void *value, u64 map_flags)
331{
332 struct bpf_local_storage_data *old_sdata = NULL;
333 struct bpf_local_storage_elem *selem;
334 struct bpf_local_storage *local_storage;
335 unsigned long flags;
336 int err;
337
338 /* BPF_EXIST and BPF_NOEXIST cannot be both set */
339 if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
340 /* BPF_F_LOCK can only be used in a value with spin_lock */
341 unlikely((map_flags & BPF_F_LOCK) &&
342 !map_value_has_spin_lock(&smap->map)))
343 return ERR_PTR(-EINVAL);
344
345 local_storage = rcu_dereference(*owner_storage(smap, owner));
346 if (!local_storage || hlist_empty(&local_storage->list)) {
347 /* Very first elem for the owner */
348 err = check_flags(NULL, map_flags);
349 if (err)
350 return ERR_PTR(err);
351
352 selem = bpf_selem_alloc(smap, owner, value, true);
353 if (!selem)
354 return ERR_PTR(-ENOMEM);
355
356 err = bpf_local_storage_alloc(owner, smap, selem);
357 if (err) {
358 kfree(selem);
359 mem_uncharge(smap, owner, smap->elem_size);
360 return ERR_PTR(err);
361 }
362
363 return SDATA(selem);
364 }
365
366 if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) {
367 /* Hoping to find an old_sdata to do inline update
368 * such that it can avoid taking the local_storage->lock
369 * and changing the lists.
370 */
371 old_sdata =
372 bpf_local_storage_lookup(local_storage, smap, false);
373 err = check_flags(old_sdata, map_flags);
374 if (err)
375 return ERR_PTR(err);
376 if (old_sdata && selem_linked_to_storage(SELEM(old_sdata))) {
377 copy_map_value_locked(&smap->map, old_sdata->data,
378 value, false);
379 return old_sdata;
380 }
381 }
382
383 raw_spin_lock_irqsave(&local_storage->lock, flags);
384
385 /* Recheck local_storage->list under local_storage->lock */
386 if (unlikely(hlist_empty(&local_storage->list))) {
387 /* A parallel del is happening and local_storage is going
388 * away. It has just been checked before, so very
389 * unlikely. Return instead of retry to keep things
390 * simple.
391 */
392 err = -EAGAIN;
393 goto unlock_err;
394 }
395
396 old_sdata = bpf_local_storage_lookup(local_storage, smap, false);
397 err = check_flags(old_sdata, map_flags);
398 if (err)
399 goto unlock_err;
400
401 if (old_sdata && (map_flags & BPF_F_LOCK)) {
402 copy_map_value_locked(&smap->map, old_sdata->data, value,
403 false);
404 selem = SELEM(old_sdata);
405 goto unlock;
406 }
407
408 /* local_storage->lock is held. Hence, we are sure
409 * we can unlink and uncharge the old_sdata successfully
410 * later. Hence, instead of charging the new selem now
411 * and then uncharge the old selem later (which may cause
412 * a potential but unnecessary charge failure), avoid taking
413 * a charge at all here (the "!old_sdata" check) and the
414 * old_sdata will not be uncharged later during
415 * bpf_selem_unlink_storage_nolock().
416 */
417 selem = bpf_selem_alloc(smap, owner, value, !old_sdata);
418 if (!selem) {
419 err = -ENOMEM;
420 goto unlock_err;
421 }
422
423 /* First, link the new selem to the map */
424 bpf_selem_link_map(smap, selem);
425
426 /* Second, link (and publish) the new selem to local_storage */
427 bpf_selem_link_storage_nolock(local_storage, selem);
428
429 /* Third, remove old selem, SELEM(old_sdata) */
430 if (old_sdata) {
431 bpf_selem_unlink_map(SELEM(old_sdata));
432 bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata),
433 false);
434 }
435
436unlock:
437 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
438 return SDATA(selem);
439
440unlock_err:
441 raw_spin_unlock_irqrestore(&local_storage->lock, flags);
442 return ERR_PTR(err);
443}
444
445u16 bpf_local_storage_cache_idx_get(struct bpf_local_storage_cache *cache)
446{
447 u64 min_usage = U64_MAX;
448 u16 i, res = 0;
449
450 spin_lock(&cache->idx_lock);
451
452 for (i = 0; i < BPF_LOCAL_STORAGE_CACHE_SIZE; i++) {
453 if (cache->idx_usage_counts[i] < min_usage) {
454 min_usage = cache->idx_usage_counts[i];
455 res = i;
456
457 /* Found a free cache_idx */
458 if (!min_usage)
459 break;
460 }
461 }
462 cache->idx_usage_counts[res]++;
463
464 spin_unlock(&cache->idx_lock);
465
466 return res;
467}
468
469void bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache *cache,
470 u16 idx)
471{
472 spin_lock(&cache->idx_lock);
473 cache->idx_usage_counts[idx]--;
474 spin_unlock(&cache->idx_lock);
475}
476
477void bpf_local_storage_map_free(struct bpf_local_storage_map *smap,
478 int __percpu *busy_counter)
479{
480 struct bpf_local_storage_elem *selem;
481 struct bpf_local_storage_map_bucket *b;
482 unsigned int i;
483
484 /* Note that this map might be concurrently cloned from
485 * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
486 * RCU read section to finish before proceeding. New RCU
487 * read sections should be prevented via bpf_map_inc_not_zero.
488 */
489 synchronize_rcu();
490
491 /* bpf prog and the userspace can no longer access this map
492 * now. No new selem (of this map) can be added
493 * to the owner->storage or to the map bucket's list.
494 *
495 * The elem of this map can be cleaned up here
496 * or when the storage is freed e.g.
497 * by bpf_sk_storage_free() during __sk_destruct().
498 */
499 for (i = 0; i < (1U << smap->bucket_log); i++) {
500 b = &smap->buckets[i];
501
502 rcu_read_lock();
503 /* No one is adding to b->list now */
504 while ((selem = hlist_entry_safe(
505 rcu_dereference_raw(hlist_first_rcu(&b->list)),
506 struct bpf_local_storage_elem, map_node))) {
507 if (busy_counter) {
508 migrate_disable();
509 __this_cpu_inc(*busy_counter);
510 }
511 bpf_selem_unlink(selem);
512 if (busy_counter) {
513 __this_cpu_dec(*busy_counter);
514 migrate_enable();
515 }
516 cond_resched_rcu();
517 }
518 rcu_read_unlock();
519 }
520
521 /* While freeing the storage we may still need to access the map.
522 *
523 * e.g. when bpf_sk_storage_free() has unlinked selem from the map
524 * which then made the above while((selem = ...)) loop
525 * exit immediately.
526 *
527 * However, while freeing the storage one still needs to access the
528 * smap->elem_size to do the uncharging in
529 * bpf_selem_unlink_storage_nolock().
530 *
531 * Hence, wait another rcu grace period for the storage to be freed.
532 */
533 synchronize_rcu();
534
535 kvfree(smap->buckets);
536 kfree(smap);
537}
538
539int bpf_local_storage_map_alloc_check(union bpf_attr *attr)
540{
541 if (attr->map_flags & ~BPF_LOCAL_STORAGE_CREATE_FLAG_MASK ||
542 !(attr->map_flags & BPF_F_NO_PREALLOC) ||
543 attr->max_entries ||
544 attr->key_size != sizeof(int) || !attr->value_size ||
545 /* Enforce BTF for userspace sk dumping */
546 !attr->btf_key_type_id || !attr->btf_value_type_id)
547 return -EINVAL;
548
549 if (!bpf_capable())
550 return -EPERM;
551
552 if (attr->value_size > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE)
553 return -E2BIG;
554
555 return 0;
556}
557
558struct bpf_local_storage_map *bpf_local_storage_map_alloc(union bpf_attr *attr)
559{
560 struct bpf_local_storage_map *smap;
561 unsigned int i;
562 u32 nbuckets;
563
564 smap = kzalloc(sizeof(*smap), GFP_USER | __GFP_NOWARN | __GFP_ACCOUNT);
565 if (!smap)
566 return ERR_PTR(-ENOMEM);
567 bpf_map_init_from_attr(&smap->map, attr);
568
569 nbuckets = roundup_pow_of_two(num_possible_cpus());
570 /* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */
571 nbuckets = max_t(u32, 2, nbuckets);
572 smap->bucket_log = ilog2(nbuckets);
573
574 smap->buckets = kvcalloc(sizeof(*smap->buckets), nbuckets,
575 GFP_USER | __GFP_NOWARN | __GFP_ACCOUNT);
576 if (!smap->buckets) {
577 kfree(smap);
578 return ERR_PTR(-ENOMEM);
579 }
580
581 for (i = 0; i < nbuckets; i++) {
582 INIT_HLIST_HEAD(&smap->buckets[i].list);
583 raw_spin_lock_init(&smap->buckets[i].lock);
584 }
585
586 smap->elem_size =
587 sizeof(struct bpf_local_storage_elem) + attr->value_size;
588
589 return smap;
590}
591
592int bpf_local_storage_map_check_btf(const struct bpf_map *map,
593 const struct btf *btf,
594 const struct btf_type *key_type,
595 const struct btf_type *value_type)
596{
597 u32 int_data;
598
599 if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
600 return -EINVAL;
601
602 int_data = *(u32 *)(key_type + 1);
603 if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))
604 return -EINVAL;
605
606 return 0;
607}