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 selem = bpf_map_kzalloc(&smap->map, smap->elem_size, 84 gfp_flags | __GFP_NOWARN); 85 if (selem) { 86 if (value) 87 copy_map_value(&smap->map, SDATA(selem)->data, value); 88 /* No need to call check_and_init_map_value as memory is zero init */ 89 return selem; 90 } 91 92 if (charge_mem) 93 mem_uncharge(smap, owner, smap->elem_size); 94 95 return NULL; 96 } 97 98 void bpf_local_storage_free_rcu(struct rcu_head *rcu) 99 { 100 struct bpf_local_storage *local_storage; 101 102 /* If RCU Tasks Trace grace period implies RCU grace period, do 103 * kfree(), else do kfree_rcu(). 104 */ 105 local_storage = container_of(rcu, struct bpf_local_storage, rcu); 106 if (rcu_trace_implies_rcu_gp()) 107 kfree(local_storage); 108 else 109 kfree_rcu(local_storage, rcu); 110 } 111 112 static void bpf_selem_free_fields_rcu(struct rcu_head *rcu) 113 { 114 struct bpf_local_storage_elem *selem; 115 struct bpf_local_storage_map *smap; 116 117 selem = container_of(rcu, struct bpf_local_storage_elem, rcu); 118 /* protected by the rcu_barrier*() */ 119 smap = rcu_dereference_protected(SDATA(selem)->smap, true); 120 bpf_obj_free_fields(smap->map.record, SDATA(selem)->data); 121 kfree(selem); 122 } 123 124 static void bpf_selem_free_fields_trace_rcu(struct rcu_head *rcu) 125 { 126 /* Free directly if Tasks Trace RCU GP also implies RCU GP */ 127 if (rcu_trace_implies_rcu_gp()) 128 bpf_selem_free_fields_rcu(rcu); 129 else 130 call_rcu(rcu, bpf_selem_free_fields_rcu); 131 } 132 133 static void bpf_selem_free_trace_rcu(struct rcu_head *rcu) 134 { 135 struct bpf_local_storage_elem *selem; 136 137 selem = container_of(rcu, struct bpf_local_storage_elem, rcu); 138 if (rcu_trace_implies_rcu_gp()) 139 kfree(selem); 140 else 141 kfree_rcu(selem, rcu); 142 } 143 144 /* local_storage->lock must be held and selem->local_storage == local_storage. 145 * The caller must ensure selem->smap is still valid to be 146 * dereferenced for its smap->elem_size and smap->cache_idx. 147 */ 148 static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_storage, 149 struct bpf_local_storage_elem *selem, 150 bool uncharge_mem, bool use_trace_rcu) 151 { 152 struct bpf_local_storage_map *smap; 153 bool free_local_storage; 154 struct btf_record *rec; 155 void *owner; 156 157 smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); 158 owner = local_storage->owner; 159 160 /* All uncharging on the owner must be done first. 161 * The owner may be freed once the last selem is unlinked 162 * from local_storage. 163 */ 164 if (uncharge_mem) 165 mem_uncharge(smap, owner, smap->elem_size); 166 167 free_local_storage = hlist_is_singular_node(&selem->snode, 168 &local_storage->list); 169 if (free_local_storage) { 170 mem_uncharge(smap, owner, sizeof(struct bpf_local_storage)); 171 local_storage->owner = NULL; 172 173 /* After this RCU_INIT, owner may be freed and cannot be used */ 174 RCU_INIT_POINTER(*owner_storage(smap, owner), NULL); 175 176 /* local_storage is not freed now. local_storage->lock is 177 * still held and raw_spin_unlock_bh(&local_storage->lock) 178 * will be done by the caller. 179 * 180 * Although the unlock will be done under 181 * rcu_read_lock(), it is more intuitive to 182 * read if the freeing of the storage is done 183 * after the raw_spin_unlock_bh(&local_storage->lock). 184 * 185 * Hence, a "bool free_local_storage" is returned 186 * to the caller which then calls then frees the storage after 187 * all the RCU grace periods have expired. 188 */ 189 } 190 hlist_del_init_rcu(&selem->snode); 191 if (rcu_access_pointer(local_storage->cache[smap->cache_idx]) == 192 SDATA(selem)) 193 RCU_INIT_POINTER(local_storage->cache[smap->cache_idx], NULL); 194 195 /* A different RCU callback is chosen whenever we need to free 196 * additional fields in selem data before freeing selem. 197 * bpf_local_storage_map_free only executes rcu_barrier to wait for RCU 198 * callbacks when it has special fields, hence we can only conditionally 199 * dereference smap, as by this time the map might have already been 200 * freed without waiting for our call_rcu callback if it did not have 201 * any special fields. 202 */ 203 rec = smap->map.record; 204 if (use_trace_rcu) { 205 if (!IS_ERR_OR_NULL(rec)) 206 call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_fields_trace_rcu); 207 else 208 call_rcu_tasks_trace(&selem->rcu, bpf_selem_free_trace_rcu); 209 } else { 210 if (!IS_ERR_OR_NULL(rec)) 211 call_rcu(&selem->rcu, bpf_selem_free_fields_rcu); 212 else 213 kfree_rcu(selem, rcu); 214 } 215 216 return free_local_storage; 217 } 218 219 static void __bpf_selem_unlink_storage(struct bpf_local_storage_elem *selem, 220 bool use_trace_rcu) 221 { 222 struct bpf_local_storage *local_storage; 223 bool free_local_storage = false; 224 unsigned long flags; 225 226 if (unlikely(!selem_linked_to_storage_lockless(selem))) 227 /* selem has already been unlinked from sk */ 228 return; 229 230 local_storage = rcu_dereference_check(selem->local_storage, 231 bpf_rcu_lock_held()); 232 raw_spin_lock_irqsave(&local_storage->lock, flags); 233 if (likely(selem_linked_to_storage(selem))) 234 free_local_storage = bpf_selem_unlink_storage_nolock( 235 local_storage, selem, true, use_trace_rcu); 236 raw_spin_unlock_irqrestore(&local_storage->lock, flags); 237 238 if (free_local_storage) { 239 if (use_trace_rcu) 240 call_rcu_tasks_trace(&local_storage->rcu, 241 bpf_local_storage_free_rcu); 242 else 243 kfree_rcu(local_storage, rcu); 244 } 245 } 246 247 void bpf_selem_link_storage_nolock(struct bpf_local_storage *local_storage, 248 struct bpf_local_storage_elem *selem) 249 { 250 RCU_INIT_POINTER(selem->local_storage, local_storage); 251 hlist_add_head_rcu(&selem->snode, &local_storage->list); 252 } 253 254 void bpf_selem_unlink_map(struct bpf_local_storage_elem *selem) 255 { 256 struct bpf_local_storage_map *smap; 257 struct bpf_local_storage_map_bucket *b; 258 unsigned long flags; 259 260 if (unlikely(!selem_linked_to_map_lockless(selem))) 261 /* selem has already be unlinked from smap */ 262 return; 263 264 smap = rcu_dereference_check(SDATA(selem)->smap, bpf_rcu_lock_held()); 265 b = select_bucket(smap, selem); 266 raw_spin_lock_irqsave(&b->lock, flags); 267 if (likely(selem_linked_to_map(selem))) 268 hlist_del_init_rcu(&selem->map_node); 269 raw_spin_unlock_irqrestore(&b->lock, flags); 270 } 271 272 void bpf_selem_link_map(struct bpf_local_storage_map *smap, 273 struct bpf_local_storage_elem *selem) 274 { 275 struct bpf_local_storage_map_bucket *b = select_bucket(smap, selem); 276 unsigned long flags; 277 278 raw_spin_lock_irqsave(&b->lock, flags); 279 RCU_INIT_POINTER(SDATA(selem)->smap, smap); 280 hlist_add_head_rcu(&selem->map_node, &b->list); 281 raw_spin_unlock_irqrestore(&b->lock, flags); 282 } 283 284 void bpf_selem_unlink(struct bpf_local_storage_elem *selem, bool use_trace_rcu) 285 { 286 /* Always unlink from map before unlinking from local_storage 287 * because selem will be freed after successfully unlinked from 288 * the local_storage. 289 */ 290 bpf_selem_unlink_map(selem); 291 __bpf_selem_unlink_storage(selem, use_trace_rcu); 292 } 293 294 /* If cacheit_lockit is false, this lookup function is lockless */ 295 struct bpf_local_storage_data * 296 bpf_local_storage_lookup(struct bpf_local_storage *local_storage, 297 struct bpf_local_storage_map *smap, 298 bool cacheit_lockit) 299 { 300 struct bpf_local_storage_data *sdata; 301 struct bpf_local_storage_elem *selem; 302 303 /* Fast path (cache hit) */ 304 sdata = rcu_dereference_check(local_storage->cache[smap->cache_idx], 305 bpf_rcu_lock_held()); 306 if (sdata && rcu_access_pointer(sdata->smap) == smap) 307 return sdata; 308 309 /* Slow path (cache miss) */ 310 hlist_for_each_entry_rcu(selem, &local_storage->list, snode, 311 rcu_read_lock_trace_held()) 312 if (rcu_access_pointer(SDATA(selem)->smap) == smap) 313 break; 314 315 if (!selem) 316 return NULL; 317 318 sdata = SDATA(selem); 319 if (cacheit_lockit) { 320 unsigned long flags; 321 322 /* spinlock is needed to avoid racing with the 323 * parallel delete. Otherwise, publishing an already 324 * deleted sdata to the cache will become a use-after-free 325 * problem in the next bpf_local_storage_lookup(). 326 */ 327 raw_spin_lock_irqsave(&local_storage->lock, flags); 328 if (selem_linked_to_storage(selem)) 329 rcu_assign_pointer(local_storage->cache[smap->cache_idx], 330 sdata); 331 raw_spin_unlock_irqrestore(&local_storage->lock, flags); 332 } 333 334 return sdata; 335 } 336 337 static int check_flags(const struct bpf_local_storage_data *old_sdata, 338 u64 map_flags) 339 { 340 if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST) 341 /* elem already exists */ 342 return -EEXIST; 343 344 if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST) 345 /* elem doesn't exist, cannot update it */ 346 return -ENOENT; 347 348 return 0; 349 } 350 351 int bpf_local_storage_alloc(void *owner, 352 struct bpf_local_storage_map *smap, 353 struct bpf_local_storage_elem *first_selem, 354 gfp_t gfp_flags) 355 { 356 struct bpf_local_storage *prev_storage, *storage; 357 struct bpf_local_storage **owner_storage_ptr; 358 int err; 359 360 err = mem_charge(smap, owner, sizeof(*storage)); 361 if (err) 362 return err; 363 364 storage = bpf_map_kzalloc(&smap->map, sizeof(*storage), 365 gfp_flags | __GFP_NOWARN); 366 if (!storage) { 367 err = -ENOMEM; 368 goto uncharge; 369 } 370 371 INIT_HLIST_HEAD(&storage->list); 372 raw_spin_lock_init(&storage->lock); 373 storage->owner = owner; 374 375 bpf_selem_link_storage_nolock(storage, first_selem); 376 bpf_selem_link_map(smap, first_selem); 377 378 owner_storage_ptr = 379 (struct bpf_local_storage **)owner_storage(smap, owner); 380 /* Publish storage to the owner. 381 * Instead of using any lock of the kernel object (i.e. owner), 382 * cmpxchg will work with any kernel object regardless what 383 * the running context is, bh, irq...etc. 384 * 385 * From now on, the owner->storage pointer (e.g. sk->sk_bpf_storage) 386 * is protected by the storage->lock. Hence, when freeing 387 * the owner->storage, the storage->lock must be held before 388 * setting owner->storage ptr to NULL. 389 */ 390 prev_storage = cmpxchg(owner_storage_ptr, NULL, storage); 391 if (unlikely(prev_storage)) { 392 bpf_selem_unlink_map(first_selem); 393 err = -EAGAIN; 394 goto uncharge; 395 396 /* Note that even first_selem was linked to smap's 397 * bucket->list, first_selem can be freed immediately 398 * (instead of kfree_rcu) because 399 * bpf_local_storage_map_free() does a 400 * synchronize_rcu_mult (waiting for both sleepable and 401 * normal programs) before walking the bucket->list. 402 * Hence, no one is accessing selem from the 403 * bucket->list under rcu_read_lock(). 404 */ 405 } 406 407 return 0; 408 409 uncharge: 410 kfree(storage); 411 mem_uncharge(smap, owner, sizeof(*storage)); 412 return err; 413 } 414 415 /* sk cannot be going away because it is linking new elem 416 * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0). 417 * Otherwise, it will become a leak (and other memory issues 418 * during map destruction). 419 */ 420 struct bpf_local_storage_data * 421 bpf_local_storage_update(void *owner, struct bpf_local_storage_map *smap, 422 void *value, u64 map_flags, gfp_t gfp_flags) 423 { 424 struct bpf_local_storage_data *old_sdata = NULL; 425 struct bpf_local_storage_elem *selem = NULL; 426 struct bpf_local_storage *local_storage; 427 unsigned long flags; 428 int err; 429 430 /* BPF_EXIST and BPF_NOEXIST cannot be both set */ 431 if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) || 432 /* BPF_F_LOCK can only be used in a value with spin_lock */ 433 unlikely((map_flags & BPF_F_LOCK) && 434 !btf_record_has_field(smap->map.record, BPF_SPIN_LOCK))) 435 return ERR_PTR(-EINVAL); 436 437 if (gfp_flags == GFP_KERNEL && (map_flags & ~BPF_F_LOCK) != BPF_NOEXIST) 438 return ERR_PTR(-EINVAL); 439 440 local_storage = rcu_dereference_check(*owner_storage(smap, owner), 441 bpf_rcu_lock_held()); 442 if (!local_storage || hlist_empty(&local_storage->list)) { 443 /* Very first elem for the owner */ 444 err = check_flags(NULL, map_flags); 445 if (err) 446 return ERR_PTR(err); 447 448 selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags); 449 if (!selem) 450 return ERR_PTR(-ENOMEM); 451 452 err = bpf_local_storage_alloc(owner, smap, selem, gfp_flags); 453 if (err) { 454 kfree(selem); 455 mem_uncharge(smap, owner, smap->elem_size); 456 return ERR_PTR(err); 457 } 458 459 return SDATA(selem); 460 } 461 462 if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) { 463 /* Hoping to find an old_sdata to do inline update 464 * such that it can avoid taking the local_storage->lock 465 * and changing the lists. 466 */ 467 old_sdata = 468 bpf_local_storage_lookup(local_storage, smap, false); 469 err = check_flags(old_sdata, map_flags); 470 if (err) 471 return ERR_PTR(err); 472 if (old_sdata && selem_linked_to_storage_lockless(SELEM(old_sdata))) { 473 copy_map_value_locked(&smap->map, old_sdata->data, 474 value, false); 475 return old_sdata; 476 } 477 } 478 479 if (gfp_flags == GFP_KERNEL) { 480 selem = bpf_selem_alloc(smap, owner, value, true, gfp_flags); 481 if (!selem) 482 return ERR_PTR(-ENOMEM); 483 } 484 485 raw_spin_lock_irqsave(&local_storage->lock, flags); 486 487 /* Recheck local_storage->list under local_storage->lock */ 488 if (unlikely(hlist_empty(&local_storage->list))) { 489 /* A parallel del is happening and local_storage is going 490 * away. It has just been checked before, so very 491 * unlikely. Return instead of retry to keep things 492 * simple. 493 */ 494 err = -EAGAIN; 495 goto unlock_err; 496 } 497 498 old_sdata = bpf_local_storage_lookup(local_storage, smap, false); 499 err = check_flags(old_sdata, map_flags); 500 if (err) 501 goto unlock_err; 502 503 if (old_sdata && (map_flags & BPF_F_LOCK)) { 504 copy_map_value_locked(&smap->map, old_sdata->data, value, 505 false); 506 selem = SELEM(old_sdata); 507 goto unlock; 508 } 509 510 if (gfp_flags != GFP_KERNEL) { 511 /* local_storage->lock is held. Hence, we are sure 512 * we can unlink and uncharge the old_sdata successfully 513 * later. Hence, instead of charging the new selem now 514 * and then uncharge the old selem later (which may cause 515 * a potential but unnecessary charge failure), avoid taking 516 * a charge at all here (the "!old_sdata" check) and the 517 * old_sdata will not be uncharged later during 518 * bpf_selem_unlink_storage_nolock(). 519 */ 520 selem = bpf_selem_alloc(smap, owner, value, !old_sdata, gfp_flags); 521 if (!selem) { 522 err = -ENOMEM; 523 goto unlock_err; 524 } 525 } 526 527 /* First, link the new selem to the map */ 528 bpf_selem_link_map(smap, selem); 529 530 /* Second, link (and publish) the new selem to local_storage */ 531 bpf_selem_link_storage_nolock(local_storage, selem); 532 533 /* Third, remove old selem, SELEM(old_sdata) */ 534 if (old_sdata) { 535 bpf_selem_unlink_map(SELEM(old_sdata)); 536 bpf_selem_unlink_storage_nolock(local_storage, SELEM(old_sdata), 537 false, true); 538 } 539 540 unlock: 541 raw_spin_unlock_irqrestore(&local_storage->lock, flags); 542 return SDATA(selem); 543 544 unlock_err: 545 raw_spin_unlock_irqrestore(&local_storage->lock, flags); 546 if (selem) { 547 mem_uncharge(smap, owner, smap->elem_size); 548 kfree(selem); 549 } 550 return ERR_PTR(err); 551 } 552 553 static u16 bpf_local_storage_cache_idx_get(struct bpf_local_storage_cache *cache) 554 { 555 u64 min_usage = U64_MAX; 556 u16 i, res = 0; 557 558 spin_lock(&cache->idx_lock); 559 560 for (i = 0; i < BPF_LOCAL_STORAGE_CACHE_SIZE; i++) { 561 if (cache->idx_usage_counts[i] < min_usage) { 562 min_usage = cache->idx_usage_counts[i]; 563 res = i; 564 565 /* Found a free cache_idx */ 566 if (!min_usage) 567 break; 568 } 569 } 570 cache->idx_usage_counts[res]++; 571 572 spin_unlock(&cache->idx_lock); 573 574 return res; 575 } 576 577 static void bpf_local_storage_cache_idx_free(struct bpf_local_storage_cache *cache, 578 u16 idx) 579 { 580 spin_lock(&cache->idx_lock); 581 cache->idx_usage_counts[idx]--; 582 spin_unlock(&cache->idx_lock); 583 } 584 585 int bpf_local_storage_map_alloc_check(union bpf_attr *attr) 586 { 587 if (attr->map_flags & ~BPF_LOCAL_STORAGE_CREATE_FLAG_MASK || 588 !(attr->map_flags & BPF_F_NO_PREALLOC) || 589 attr->max_entries || 590 attr->key_size != sizeof(int) || !attr->value_size || 591 /* Enforce BTF for userspace sk dumping */ 592 !attr->btf_key_type_id || !attr->btf_value_type_id) 593 return -EINVAL; 594 595 if (!bpf_capable()) 596 return -EPERM; 597 598 if (attr->value_size > BPF_LOCAL_STORAGE_MAX_VALUE_SIZE) 599 return -E2BIG; 600 601 return 0; 602 } 603 604 static struct bpf_local_storage_map *__bpf_local_storage_map_alloc(union bpf_attr *attr) 605 { 606 struct bpf_local_storage_map *smap; 607 unsigned int i; 608 u32 nbuckets; 609 610 smap = bpf_map_area_alloc(sizeof(*smap), NUMA_NO_NODE); 611 if (!smap) 612 return ERR_PTR(-ENOMEM); 613 bpf_map_init_from_attr(&smap->map, attr); 614 615 nbuckets = roundup_pow_of_two(num_possible_cpus()); 616 /* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */ 617 nbuckets = max_t(u32, 2, nbuckets); 618 smap->bucket_log = ilog2(nbuckets); 619 620 smap->buckets = bpf_map_kvcalloc(&smap->map, sizeof(*smap->buckets), 621 nbuckets, GFP_USER | __GFP_NOWARN); 622 if (!smap->buckets) { 623 bpf_map_area_free(smap); 624 return ERR_PTR(-ENOMEM); 625 } 626 627 for (i = 0; i < nbuckets; i++) { 628 INIT_HLIST_HEAD(&smap->buckets[i].list); 629 raw_spin_lock_init(&smap->buckets[i].lock); 630 } 631 632 smap->elem_size = offsetof(struct bpf_local_storage_elem, 633 sdata.data[attr->value_size]); 634 635 return smap; 636 } 637 638 int bpf_local_storage_map_check_btf(const struct bpf_map *map, 639 const struct btf *btf, 640 const struct btf_type *key_type, 641 const struct btf_type *value_type) 642 { 643 u32 int_data; 644 645 if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT) 646 return -EINVAL; 647 648 int_data = *(u32 *)(key_type + 1); 649 if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data)) 650 return -EINVAL; 651 652 return 0; 653 } 654 655 bool bpf_local_storage_unlink_nolock(struct bpf_local_storage *local_storage) 656 { 657 struct bpf_local_storage_elem *selem; 658 bool free_storage = false; 659 struct hlist_node *n; 660 661 /* Neither the bpf_prog nor the bpf_map's syscall 662 * could be modifying the local_storage->list now. 663 * Thus, no elem can be added to or deleted from the 664 * local_storage->list by the bpf_prog or by the bpf_map's syscall. 665 * 666 * It is racing with bpf_local_storage_map_free() alone 667 * when unlinking elem from the local_storage->list and 668 * the map's bucket->list. 669 */ 670 hlist_for_each_entry_safe(selem, n, &local_storage->list, snode) { 671 /* Always unlink from map before unlinking from 672 * local_storage. 673 */ 674 bpf_selem_unlink_map(selem); 675 /* If local_storage list has only one element, the 676 * bpf_selem_unlink_storage_nolock() will return true. 677 * Otherwise, it will return false. The current loop iteration 678 * intends to remove all local storage. So the last iteration 679 * of the loop will set the free_cgroup_storage to true. 680 */ 681 free_storage = bpf_selem_unlink_storage_nolock( 682 local_storage, selem, false, false); 683 } 684 685 return free_storage; 686 } 687 688 u64 bpf_local_storage_map_mem_usage(const struct bpf_map *map) 689 { 690 struct bpf_local_storage_map *smap = (struct bpf_local_storage_map *)map; 691 u64 usage = sizeof(*smap); 692 693 /* The dynamically callocated selems are not counted currently. */ 694 usage += sizeof(*smap->buckets) * (1ULL << smap->bucket_log); 695 return usage; 696 } 697 698 struct bpf_map * 699 bpf_local_storage_map_alloc(union bpf_attr *attr, 700 struct bpf_local_storage_cache *cache) 701 { 702 struct bpf_local_storage_map *smap; 703 704 smap = __bpf_local_storage_map_alloc(attr); 705 if (IS_ERR(smap)) 706 return ERR_CAST(smap); 707 708 smap->cache_idx = bpf_local_storage_cache_idx_get(cache); 709 return &smap->map; 710 } 711 712 void bpf_local_storage_map_free(struct bpf_map *map, 713 struct bpf_local_storage_cache *cache, 714 int __percpu *busy_counter) 715 { 716 struct bpf_local_storage_map_bucket *b; 717 struct bpf_local_storage_elem *selem; 718 struct bpf_local_storage_map *smap; 719 unsigned int i; 720 721 smap = (struct bpf_local_storage_map *)map; 722 bpf_local_storage_cache_idx_free(cache, smap->cache_idx); 723 724 /* Note that this map might be concurrently cloned from 725 * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone 726 * RCU read section to finish before proceeding. New RCU 727 * read sections should be prevented via bpf_map_inc_not_zero. 728 */ 729 synchronize_rcu(); 730 731 /* bpf prog and the userspace can no longer access this map 732 * now. No new selem (of this map) can be added 733 * to the owner->storage or to the map bucket's list. 734 * 735 * The elem of this map can be cleaned up here 736 * or when the storage is freed e.g. 737 * by bpf_sk_storage_free() during __sk_destruct(). 738 */ 739 for (i = 0; i < (1U << smap->bucket_log); i++) { 740 b = &smap->buckets[i]; 741 742 rcu_read_lock(); 743 /* No one is adding to b->list now */ 744 while ((selem = hlist_entry_safe( 745 rcu_dereference_raw(hlist_first_rcu(&b->list)), 746 struct bpf_local_storage_elem, map_node))) { 747 if (busy_counter) { 748 migrate_disable(); 749 this_cpu_inc(*busy_counter); 750 } 751 bpf_selem_unlink(selem, false); 752 if (busy_counter) { 753 this_cpu_dec(*busy_counter); 754 migrate_enable(); 755 } 756 cond_resched_rcu(); 757 } 758 rcu_read_unlock(); 759 } 760 761 /* While freeing the storage we may still need to access the map. 762 * 763 * e.g. when bpf_sk_storage_free() has unlinked selem from the map 764 * which then made the above while((selem = ...)) loop 765 * exit immediately. 766 * 767 * However, while freeing the storage one still needs to access the 768 * smap->elem_size to do the uncharging in 769 * bpf_selem_unlink_storage_nolock(). 770 * 771 * Hence, wait another rcu grace period for the storage to be freed. 772 */ 773 synchronize_rcu(); 774 775 /* Only delay freeing of smap, buckets are not needed anymore */ 776 kvfree(smap->buckets); 777 778 /* When local storage has special fields, callbacks for 779 * bpf_selem_free_fields_rcu and bpf_selem_free_fields_trace_rcu will 780 * keep using the map BTF record, we need to execute an RCU barrier to 781 * wait for them as the record will be freed right after our map_free 782 * callback. 783 */ 784 if (!IS_ERR_OR_NULL(smap->map.record)) { 785 rcu_barrier_tasks_trace(); 786 /* We cannot skip rcu_barrier() when rcu_trace_implies_rcu_gp() 787 * is true, because while call_rcu invocation is skipped in that 788 * case in bpf_selem_free_fields_trace_rcu (and all local 789 * storage maps pass use_trace_rcu = true), there can be 790 * call_rcu callbacks based on use_trace_rcu = false in the 791 * while ((selem = ...)) loop above or when owner's free path 792 * calls bpf_local_storage_unlink_nolock. 793 */ 794 rcu_barrier(); 795 } 796 bpf_map_area_free(smap); 797 } 798