kernel/bpf/bpf_local_storage.c

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