net/core/bpf_sk

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
select_bucket
omem_charge
selem_linked_to_sk
selem_linked_to_map
selem_alloc
__selem_unlink_sk
selem_unlink_sk
__selem_link_sk
selem_unlink_map
selem_link_map
selem_unlink
__sk_storage_lookup
sk_storage_lookup
check_flags
sk_storage_alloc
sk_storage_update
sk_storage_delete
bpf_sk_storage_free
bpf_sk_storage_map_free
bpf_sk_storage_map_alloc_check
bpf_sk_storage_map_alloc
notsupp_get_next_key
bpf_sk_storage_map_check_btf
bpf_fd_sk_storage_lookup_elem
bpf_fd_sk_storage_update_elem
bpf_fd_sk_storage_delete_elem
bpf_sk_storage_clone_elem
bpf_sk_storage_clone
BPF_CALL_4
BPF_CALL_2
   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 <net/bpf_sk_storage.h>
  10 #include <net/sock.h>
  11 #include <uapi/linux/btf.h>
  12 
  13 static atomic_t cache_idx;
  14 
  15 #define SK_STORAGE_CREATE_FLAG_MASK                                     \
  16         (BPF_F_NO_PREALLOC | BPF_F_CLONE)
  17 
  18 struct bucket {
  19         struct hlist_head list;
  20         raw_spinlock_t lock;
  21 };
  22 
  23 /* Thp map is not the primary owner of a bpf_sk_storage_elem.
  24  * Instead, the sk->sk_bpf_storage is.
  25  *
  26  * The map (bpf_sk_storage_map) is for two purposes
  27  * 1. Define the size of the "sk local storage".  It is
  28  *    the map's value_size.
  29  *
  30  * 2. Maintain a list to keep track of all elems such
  31  *    that they can be cleaned up during the map destruction.
  32  *
  33  * When a bpf local storage is being looked up for a
  34  * particular sk,  the "bpf_map" pointer is actually used
  35  * as the "key" to search in the list of elem in
  36  * sk->sk_bpf_storage.
  37  *
  38  * Hence, consider sk->sk_bpf_storage is the mini-map
  39  * with the "bpf_map" pointer as the searching key.
  40  */
  41 struct bpf_sk_storage_map {
  42         struct bpf_map map;
  43         /* Lookup elem does not require accessing the map.
  44          *
  45          * Updating/Deleting requires a bucket lock to
  46          * link/unlink the elem from the map.  Having
  47          * multiple buckets to improve contention.
  48          */
  49         struct bucket *buckets;
  50         u32 bucket_log;
  51         u16 elem_size;
  52         u16 cache_idx;
  53 };
  54 
  55 struct bpf_sk_storage_data {
  56         /* smap is used as the searching key when looking up
  57          * from sk->sk_bpf_storage.
  58          *
  59          * Put it in the same cacheline as the data to minimize
  60          * the number of cachelines access during the cache hit case.
  61          */
  62         struct bpf_sk_storage_map __rcu *smap;
  63         u8 data[0] __aligned(8);
  64 };
  65 
  66 /* Linked to bpf_sk_storage and bpf_sk_storage_map */
  67 struct bpf_sk_storage_elem {
  68         struct hlist_node map_node;     /* Linked to bpf_sk_storage_map */
  69         struct hlist_node snode;        /* Linked to bpf_sk_storage */
  70         struct bpf_sk_storage __rcu *sk_storage;
  71         struct rcu_head rcu;
  72         /* 8 bytes hole */
  73         /* The data is stored in aother cacheline to minimize
  74          * the number of cachelines access during a cache hit.
  75          */
  76         struct bpf_sk_storage_data sdata ____cacheline_aligned;
  77 };
  78 
  79 #define SELEM(_SDATA) container_of((_SDATA), struct bpf_sk_storage_elem, sdata)
  80 #define SDATA(_SELEM) (&(_SELEM)->sdata)
  81 #define BPF_SK_STORAGE_CACHE_SIZE       16
  82 
  83 struct bpf_sk_storage {
  84         struct bpf_sk_storage_data __rcu *cache[BPF_SK_STORAGE_CACHE_SIZE];
  85         struct hlist_head list; /* List of bpf_sk_storage_elem */
  86         struct sock *sk;        /* The sk that owns the the above "list" of
  87                                  * bpf_sk_storage_elem.
  88                                  */
  89         struct rcu_head rcu;
  90         raw_spinlock_t lock;    /* Protect adding/removing from the "list" */
  91 };
  92 
  93 static struct bucket *select_bucket(struct bpf_sk_storage_map *smap,
  94                                     struct bpf_sk_storage_elem *selem)
  95 {
  96         return &smap->buckets[hash_ptr(selem, smap->bucket_log)];
  97 }
  98 
  99 static int omem_charge(struct sock *sk, unsigned int size)
 100 {
 101         /* same check as in sock_kmalloc() */
 102         if (size <= sysctl_optmem_max &&
 103             atomic_read(&sk->sk_omem_alloc) + size < sysctl_optmem_max) {
 104                 atomic_add(size, &sk->sk_omem_alloc);
 105                 return 0;
 106         }
 107 
 108         return -ENOMEM;
 109 }
 110 
 111 static bool selem_linked_to_sk(const struct bpf_sk_storage_elem *selem)
 112 {
 113         return !hlist_unhashed(&selem->snode);
 114 }
 115 
 116 static bool selem_linked_to_map(const struct bpf_sk_storage_elem *selem)
 117 {
 118         return !hlist_unhashed(&selem->map_node);
 119 }
 120 
 121 static struct bpf_sk_storage_elem *selem_alloc(struct bpf_sk_storage_map *smap,
 122                                                struct sock *sk, void *value,
 123                                                bool charge_omem)
 124 {
 125         struct bpf_sk_storage_elem *selem;
 126 
 127         if (charge_omem && omem_charge(sk, smap->elem_size))
 128                 return NULL;
 129 
 130         selem = kzalloc(smap->elem_size, GFP_ATOMIC | __GFP_NOWARN);
 131         if (selem) {
 132                 if (value)
 133                         memcpy(SDATA(selem)->data, value, smap->map.value_size);
 134                 return selem;
 135         }
 136 
 137         if (charge_omem)
 138                 atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
 139 
 140         return NULL;
 141 }
 142 
 143 /* sk_storage->lock must be held and selem->sk_storage == sk_storage.
 144  * The caller must ensure selem->smap is still valid to be
 145  * dereferenced for its smap->elem_size and smap->cache_idx.
 146  */
 147 static bool __selem_unlink_sk(struct bpf_sk_storage *sk_storage,
 148                               struct bpf_sk_storage_elem *selem,
 149                               bool uncharge_omem)
 150 {
 151         struct bpf_sk_storage_map *smap;
 152         bool free_sk_storage;
 153         struct sock *sk;
 154 
 155         smap = rcu_dereference(SDATA(selem)->smap);
 156         sk = sk_storage->sk;
 157 
 158         /* All uncharging on sk->sk_omem_alloc must be done first.
 159          * sk may be freed once the last selem is unlinked from sk_storage.
 160          */
 161         if (uncharge_omem)
 162                 atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
 163 
 164         free_sk_storage = hlist_is_singular_node(&selem->snode,
 165                                                  &sk_storage->list);
 166         if (free_sk_storage) {
 167                 atomic_sub(sizeof(struct bpf_sk_storage), &sk->sk_omem_alloc);
 168                 sk_storage->sk = NULL;
 169                 /* After this RCU_INIT, sk may be freed and cannot be used */
 170                 RCU_INIT_POINTER(sk->sk_bpf_storage, NULL);
 171 
 172                 /* sk_storage is not freed now.  sk_storage->lock is
 173                  * still held and raw_spin_unlock_bh(&sk_storage->lock)
 174                  * will be done by the caller.
 175                  *
 176                  * Although the unlock will be done under
 177                  * rcu_read_lock(),  it is more intutivie to
 178                  * read if kfree_rcu(sk_storage, rcu) is done
 179                  * after the raw_spin_unlock_bh(&sk_storage->lock).
 180                  *
 181                  * Hence, a "bool free_sk_storage" is returned
 182                  * to the caller which then calls the kfree_rcu()
 183                  * after unlock.
 184                  */
 185         }
 186         hlist_del_init_rcu(&selem->snode);
 187         if (rcu_access_pointer(sk_storage->cache[smap->cache_idx]) ==
 188             SDATA(selem))
 189                 RCU_INIT_POINTER(sk_storage->cache[smap->cache_idx], NULL);
 190 
 191         kfree_rcu(selem, rcu);
 192 
 193         return free_sk_storage;
 194 }
 195 
 196 static void selem_unlink_sk(struct bpf_sk_storage_elem *selem)
 197 {
 198         struct bpf_sk_storage *sk_storage;
 199         bool free_sk_storage = false;
 200 
 201         if (unlikely(!selem_linked_to_sk(selem)))
 202                 /* selem has already been unlinked from sk */
 203                 return;
 204 
 205         sk_storage = rcu_dereference(selem->sk_storage);
 206         raw_spin_lock_bh(&sk_storage->lock);
 207         if (likely(selem_linked_to_sk(selem)))
 208                 free_sk_storage = __selem_unlink_sk(sk_storage, selem, true);
 209         raw_spin_unlock_bh(&sk_storage->lock);
 210 
 211         if (free_sk_storage)
 212                 kfree_rcu(sk_storage, rcu);
 213 }
 214 
 215 static void __selem_link_sk(struct bpf_sk_storage *sk_storage,
 216                             struct bpf_sk_storage_elem *selem)
 217 {
 218         RCU_INIT_POINTER(selem->sk_storage, sk_storage);
 219         hlist_add_head(&selem->snode, &sk_storage->list);
 220 }
 221 
 222 static void selem_unlink_map(struct bpf_sk_storage_elem *selem)
 223 {
 224         struct bpf_sk_storage_map *smap;
 225         struct bucket *b;
 226 
 227         if (unlikely(!selem_linked_to_map(selem)))
 228                 /* selem has already be unlinked from smap */
 229                 return;
 230 
 231         smap = rcu_dereference(SDATA(selem)->smap);
 232         b = select_bucket(smap, selem);
 233         raw_spin_lock_bh(&b->lock);
 234         if (likely(selem_linked_to_map(selem)))
 235                 hlist_del_init_rcu(&selem->map_node);
 236         raw_spin_unlock_bh(&b->lock);
 237 }
 238 
 239 static void selem_link_map(struct bpf_sk_storage_map *smap,
 240                            struct bpf_sk_storage_elem *selem)
 241 {
 242         struct bucket *b = select_bucket(smap, selem);
 243 
 244         raw_spin_lock_bh(&b->lock);
 245         RCU_INIT_POINTER(SDATA(selem)->smap, smap);
 246         hlist_add_head_rcu(&selem->map_node, &b->list);
 247         raw_spin_unlock_bh(&b->lock);
 248 }
 249 
 250 static void selem_unlink(struct bpf_sk_storage_elem *selem)
 251 {
 252         /* Always unlink from map before unlinking from sk_storage
 253          * because selem will be freed after successfully unlinked from
 254          * the sk_storage.
 255          */
 256         selem_unlink_map(selem);
 257         selem_unlink_sk(selem);
 258 }
 259 
 260 static struct bpf_sk_storage_data *
 261 __sk_storage_lookup(struct bpf_sk_storage *sk_storage,
 262                     struct bpf_sk_storage_map *smap,
 263                     bool cacheit_lockit)
 264 {
 265         struct bpf_sk_storage_data *sdata;
 266         struct bpf_sk_storage_elem *selem;
 267 
 268         /* Fast path (cache hit) */
 269         sdata = rcu_dereference(sk_storage->cache[smap->cache_idx]);
 270         if (sdata && rcu_access_pointer(sdata->smap) == smap)
 271                 return sdata;
 272 
 273         /* Slow path (cache miss) */
 274         hlist_for_each_entry_rcu(selem, &sk_storage->list, snode)
 275                 if (rcu_access_pointer(SDATA(selem)->smap) == smap)
 276                         break;
 277 
 278         if (!selem)
 279                 return NULL;
 280 
 281         sdata = SDATA(selem);
 282         if (cacheit_lockit) {
 283                 /* spinlock is needed to avoid racing with the
 284                  * parallel delete.  Otherwise, publishing an already
 285                  * deleted sdata to the cache will become a use-after-free
 286                  * problem in the next __sk_storage_lookup().
 287                  */
 288                 raw_spin_lock_bh(&sk_storage->lock);
 289                 if (selem_linked_to_sk(selem))
 290                         rcu_assign_pointer(sk_storage->cache[smap->cache_idx],
 291                                            sdata);
 292                 raw_spin_unlock_bh(&sk_storage->lock);
 293         }
 294 
 295         return sdata;
 296 }
 297 
 298 static struct bpf_sk_storage_data *
 299 sk_storage_lookup(struct sock *sk, struct bpf_map *map, bool cacheit_lockit)
 300 {
 301         struct bpf_sk_storage *sk_storage;
 302         struct bpf_sk_storage_map *smap;
 303 
 304         sk_storage = rcu_dereference(sk->sk_bpf_storage);
 305         if (!sk_storage)
 306                 return NULL;
 307 
 308         smap = (struct bpf_sk_storage_map *)map;
 309         return __sk_storage_lookup(sk_storage, smap, cacheit_lockit);
 310 }
 311 
 312 static int check_flags(const struct bpf_sk_storage_data *old_sdata,
 313                        u64 map_flags)
 314 {
 315         if (old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_NOEXIST)
 316                 /* elem already exists */
 317                 return -EEXIST;
 318 
 319         if (!old_sdata && (map_flags & ~BPF_F_LOCK) == BPF_EXIST)
 320                 /* elem doesn't exist, cannot update it */
 321                 return -ENOENT;
 322 
 323         return 0;
 324 }
 325 
 326 static int sk_storage_alloc(struct sock *sk,
 327                             struct bpf_sk_storage_map *smap,
 328                             struct bpf_sk_storage_elem *first_selem)
 329 {
 330         struct bpf_sk_storage *prev_sk_storage, *sk_storage;
 331         int err;
 332 
 333         err = omem_charge(sk, sizeof(*sk_storage));
 334         if (err)
 335                 return err;
 336 
 337         sk_storage = kzalloc(sizeof(*sk_storage), GFP_ATOMIC | __GFP_NOWARN);
 338         if (!sk_storage) {
 339                 err = -ENOMEM;
 340                 goto uncharge;
 341         }
 342         INIT_HLIST_HEAD(&sk_storage->list);
 343         raw_spin_lock_init(&sk_storage->lock);
 344         sk_storage->sk = sk;
 345 
 346         __selem_link_sk(sk_storage, first_selem);
 347         selem_link_map(smap, first_selem);
 348         /* Publish sk_storage to sk.  sk->sk_lock cannot be acquired.
 349          * Hence, atomic ops is used to set sk->sk_bpf_storage
 350          * from NULL to the newly allocated sk_storage ptr.
 351          *
 352          * From now on, the sk->sk_bpf_storage pointer is protected
 353          * by the sk_storage->lock.  Hence,  when freeing
 354          * the sk->sk_bpf_storage, the sk_storage->lock must
 355          * be held before setting sk->sk_bpf_storage to NULL.
 356          */
 357         prev_sk_storage = cmpxchg((struct bpf_sk_storage **)&sk->sk_bpf_storage,
 358                                   NULL, sk_storage);
 359         if (unlikely(prev_sk_storage)) {
 360                 selem_unlink_map(first_selem);
 361                 err = -EAGAIN;
 362                 goto uncharge;
 363 
 364                 /* Note that even first_selem was linked to smap's
 365                  * bucket->list, first_selem can be freed immediately
 366                  * (instead of kfree_rcu) because
 367                  * bpf_sk_storage_map_free() does a
 368                  * synchronize_rcu() before walking the bucket->list.
 369                  * Hence, no one is accessing selem from the
 370                  * bucket->list under rcu_read_lock().
 371                  */
 372         }
 373 
 374         return 0;
 375 
 376 uncharge:
 377         kfree(sk_storage);
 378         atomic_sub(sizeof(*sk_storage), &sk->sk_omem_alloc);
 379         return err;
 380 }
 381 
 382 /* sk cannot be going away because it is linking new elem
 383  * to sk->sk_bpf_storage. (i.e. sk->sk_refcnt cannot be 0).
 384  * Otherwise, it will become a leak (and other memory issues
 385  * during map destruction).
 386  */
 387 static struct bpf_sk_storage_data *sk_storage_update(struct sock *sk,
 388                                                      struct bpf_map *map,
 389                                                      void *value,
 390                                                      u64 map_flags)
 391 {
 392         struct bpf_sk_storage_data *old_sdata = NULL;
 393         struct bpf_sk_storage_elem *selem;
 394         struct bpf_sk_storage *sk_storage;
 395         struct bpf_sk_storage_map *smap;
 396         int err;
 397 
 398         /* BPF_EXIST and BPF_NOEXIST cannot be both set */
 399         if (unlikely((map_flags & ~BPF_F_LOCK) > BPF_EXIST) ||
 400             /* BPF_F_LOCK can only be used in a value with spin_lock */
 401             unlikely((map_flags & BPF_F_LOCK) && !map_value_has_spin_lock(map)))
 402                 return ERR_PTR(-EINVAL);
 403 
 404         smap = (struct bpf_sk_storage_map *)map;
 405         sk_storage = rcu_dereference(sk->sk_bpf_storage);
 406         if (!sk_storage || hlist_empty(&sk_storage->list)) {
 407                 /* Very first elem for this sk */
 408                 err = check_flags(NULL, map_flags);
 409                 if (err)
 410                         return ERR_PTR(err);
 411 
 412                 selem = selem_alloc(smap, sk, value, true);
 413                 if (!selem)
 414                         return ERR_PTR(-ENOMEM);
 415 
 416                 err = sk_storage_alloc(sk, smap, selem);
 417                 if (err) {
 418                         kfree(selem);
 419                         atomic_sub(smap->elem_size, &sk->sk_omem_alloc);
 420                         return ERR_PTR(err);
 421                 }
 422 
 423                 return SDATA(selem);
 424         }
 425 
 426         if ((map_flags & BPF_F_LOCK) && !(map_flags & BPF_NOEXIST)) {
 427                 /* Hoping to find an old_sdata to do inline update
 428                  * such that it can avoid taking the sk_storage->lock
 429                  * and changing the lists.
 430                  */
 431                 old_sdata = __sk_storage_lookup(sk_storage, smap, false);
 432                 err = check_flags(old_sdata, map_flags);
 433                 if (err)
 434                         return ERR_PTR(err);
 435                 if (old_sdata && selem_linked_to_sk(SELEM(old_sdata))) {
 436                         copy_map_value_locked(map, old_sdata->data,
 437                                               value, false);
 438                         return old_sdata;
 439                 }
 440         }
 441 
 442         raw_spin_lock_bh(&sk_storage->lock);
 443 
 444         /* Recheck sk_storage->list under sk_storage->lock */
 445         if (unlikely(hlist_empty(&sk_storage->list))) {
 446                 /* A parallel del is happening and sk_storage is going
 447                  * away.  It has just been checked before, so very
 448                  * unlikely.  Return instead of retry to keep things
 449                  * simple.
 450                  */
 451                 err = -EAGAIN;
 452                 goto unlock_err;
 453         }
 454 
 455         old_sdata = __sk_storage_lookup(sk_storage, smap, false);
 456         err = check_flags(old_sdata, map_flags);
 457         if (err)
 458                 goto unlock_err;
 459 
 460         if (old_sdata && (map_flags & BPF_F_LOCK)) {
 461                 copy_map_value_locked(map, old_sdata->data, value, false);
 462                 selem = SELEM(old_sdata);
 463                 goto unlock;
 464         }
 465 
 466         /* sk_storage->lock is held.  Hence, we are sure
 467          * we can unlink and uncharge the old_sdata successfully
 468          * later.  Hence, instead of charging the new selem now
 469          * and then uncharge the old selem later (which may cause
 470          * a potential but unnecessary charge failure),  avoid taking
 471          * a charge at all here (the "!old_sdata" check) and the
 472          * old_sdata will not be uncharged later during __selem_unlink_sk().
 473          */
 474         selem = selem_alloc(smap, sk, value, !old_sdata);
 475         if (!selem) {
 476                 err = -ENOMEM;
 477                 goto unlock_err;
 478         }
 479 
 480         /* First, link the new selem to the map */
 481         selem_link_map(smap, selem);
 482 
 483         /* Second, link (and publish) the new selem to sk_storage */
 484         __selem_link_sk(sk_storage, selem);
 485 
 486         /* Third, remove old selem, SELEM(old_sdata) */
 487         if (old_sdata) {
 488                 selem_unlink_map(SELEM(old_sdata));
 489                 __selem_unlink_sk(sk_storage, SELEM(old_sdata), false);
 490         }
 491 
 492 unlock:
 493         raw_spin_unlock_bh(&sk_storage->lock);
 494         return SDATA(selem);
 495 
 496 unlock_err:
 497         raw_spin_unlock_bh(&sk_storage->lock);
 498         return ERR_PTR(err);
 499 }
 500 
 501 static int sk_storage_delete(struct sock *sk, struct bpf_map *map)
 502 {
 503         struct bpf_sk_storage_data *sdata;
 504 
 505         sdata = sk_storage_lookup(sk, map, false);
 506         if (!sdata)
 507                 return -ENOENT;
 508 
 509         selem_unlink(SELEM(sdata));
 510 
 511         return 0;
 512 }
 513 
 514 /* Called by __sk_destruct() & bpf_sk_storage_clone() */
 515 void bpf_sk_storage_free(struct sock *sk)
 516 {
 517         struct bpf_sk_storage_elem *selem;
 518         struct bpf_sk_storage *sk_storage;
 519         bool free_sk_storage = false;
 520         struct hlist_node *n;
 521 
 522         rcu_read_lock();
 523         sk_storage = rcu_dereference(sk->sk_bpf_storage);
 524         if (!sk_storage) {
 525                 rcu_read_unlock();
 526                 return;
 527         }
 528 
 529         /* Netiher the bpf_prog nor the bpf-map's syscall
 530          * could be modifying the sk_storage->list now.
 531          * Thus, no elem can be added-to or deleted-from the
 532          * sk_storage->list by the bpf_prog or by the bpf-map's syscall.
 533          *
 534          * It is racing with bpf_sk_storage_map_free() alone
 535          * when unlinking elem from the sk_storage->list and
 536          * the map's bucket->list.
 537          */
 538         raw_spin_lock_bh(&sk_storage->lock);
 539         hlist_for_each_entry_safe(selem, n, &sk_storage->list, snode) {
 540                 /* Always unlink from map before unlinking from
 541                  * sk_storage.
 542                  */
 543                 selem_unlink_map(selem);
 544                 free_sk_storage = __selem_unlink_sk(sk_storage, selem, true);
 545         }
 546         raw_spin_unlock_bh(&sk_storage->lock);
 547         rcu_read_unlock();
 548 
 549         if (free_sk_storage)
 550                 kfree_rcu(sk_storage, rcu);
 551 }
 552 
 553 static void bpf_sk_storage_map_free(struct bpf_map *map)
 554 {
 555         struct bpf_sk_storage_elem *selem;
 556         struct bpf_sk_storage_map *smap;
 557         struct bucket *b;
 558         unsigned int i;
 559 
 560         smap = (struct bpf_sk_storage_map *)map;
 561 
 562         /* Note that this map might be concurrently cloned from
 563          * bpf_sk_storage_clone. Wait for any existing bpf_sk_storage_clone
 564          * RCU read section to finish before proceeding. New RCU
 565          * read sections should be prevented via bpf_map_inc_not_zero.
 566          */
 567         synchronize_rcu();
 568 
 569         /* bpf prog and the userspace can no longer access this map
 570          * now.  No new selem (of this map) can be added
 571          * to the sk->sk_bpf_storage or to the map bucket's list.
 572          *
 573          * The elem of this map can be cleaned up here
 574          * or
 575          * by bpf_sk_storage_free() during __sk_destruct().
 576          */
 577         for (i = 0; i < (1U << smap->bucket_log); i++) {
 578                 b = &smap->buckets[i];
 579 
 580                 rcu_read_lock();
 581                 /* No one is adding to b->list now */
 582                 while ((selem = hlist_entry_safe(rcu_dereference_raw(hlist_first_rcu(&b->list)),
 583                                                  struct bpf_sk_storage_elem,
 584                                                  map_node))) {
 585                         selem_unlink(selem);
 586                         cond_resched_rcu();
 587                 }
 588                 rcu_read_unlock();
 589         }
 590 
 591         /* bpf_sk_storage_free() may still need to access the map.
 592          * e.g. bpf_sk_storage_free() has unlinked selem from the map
 593          * which then made the above while((selem = ...)) loop
 594          * exited immediately.
 595          *
 596          * However, the bpf_sk_storage_free() still needs to access
 597          * the smap->elem_size to do the uncharging in
 598          * __selem_unlink_sk().
 599          *
 600          * Hence, wait another rcu grace period for the
 601          * bpf_sk_storage_free() to finish.
 602          */
 603         synchronize_rcu();
 604 
 605         kvfree(smap->buckets);
 606         kfree(map);
 607 }
 608 
 609 static int bpf_sk_storage_map_alloc_check(union bpf_attr *attr)
 610 {
 611         if (attr->map_flags & ~SK_STORAGE_CREATE_FLAG_MASK ||
 612             !(attr->map_flags & BPF_F_NO_PREALLOC) ||
 613             attr->max_entries ||
 614             attr->key_size != sizeof(int) || !attr->value_size ||
 615             /* Enforce BTF for userspace sk dumping */
 616             !attr->btf_key_type_id || !attr->btf_value_type_id)
 617                 return -EINVAL;
 618 
 619         if (!capable(CAP_SYS_ADMIN))
 620                 return -EPERM;
 621 
 622         if (attr->value_size >= KMALLOC_MAX_SIZE -
 623             MAX_BPF_STACK - sizeof(struct bpf_sk_storage_elem) ||
 624             /* U16_MAX is much more than enough for sk local storage
 625              * considering a tcp_sock is ~2k.
 626              */
 627             attr->value_size > U16_MAX - sizeof(struct bpf_sk_storage_elem))
 628                 return -E2BIG;
 629 
 630         return 0;
 631 }
 632 
 633 static struct bpf_map *bpf_sk_storage_map_alloc(union bpf_attr *attr)
 634 {
 635         struct bpf_sk_storage_map *smap;
 636         unsigned int i;
 637         u32 nbuckets;
 638         u64 cost;
 639         int ret;
 640 
 641         smap = kzalloc(sizeof(*smap), GFP_USER | __GFP_NOWARN);
 642         if (!smap)
 643                 return ERR_PTR(-ENOMEM);
 644         bpf_map_init_from_attr(&smap->map, attr);
 645 
 646         nbuckets = roundup_pow_of_two(num_possible_cpus());
 647         /* Use at least 2 buckets, select_bucket() is undefined behavior with 1 bucket */
 648         nbuckets = max_t(u32, 2, nbuckets);
 649         smap->bucket_log = ilog2(nbuckets);
 650         cost = sizeof(*smap->buckets) * nbuckets + sizeof(*smap);
 651 
 652         ret = bpf_map_charge_init(&smap->map.memory, cost);
 653         if (ret < 0) {
 654                 kfree(smap);
 655                 return ERR_PTR(ret);
 656         }
 657 
 658         smap->buckets = kvcalloc(sizeof(*smap->buckets), nbuckets,
 659                                  GFP_USER | __GFP_NOWARN);
 660         if (!smap->buckets) {
 661                 bpf_map_charge_finish(&smap->map.memory);
 662                 kfree(smap);
 663                 return ERR_PTR(-ENOMEM);
 664         }
 665 
 666         for (i = 0; i < nbuckets; i++) {
 667                 INIT_HLIST_HEAD(&smap->buckets[i].list);
 668                 raw_spin_lock_init(&smap->buckets[i].lock);
 669         }
 670 
 671         smap->elem_size = sizeof(struct bpf_sk_storage_elem) + attr->value_size;
 672         smap->cache_idx = (unsigned int)atomic_inc_return(&cache_idx) %
 673                 BPF_SK_STORAGE_CACHE_SIZE;
 674 
 675         return &smap->map;
 676 }
 677 
 678 static int notsupp_get_next_key(struct bpf_map *map, void *key,
 679                                 void *next_key)
 680 {
 681         return -ENOTSUPP;
 682 }
 683 
 684 static int bpf_sk_storage_map_check_btf(const struct bpf_map *map,
 685                                         const struct btf *btf,
 686                                         const struct btf_type *key_type,
 687                                         const struct btf_type *value_type)
 688 {
 689         u32 int_data;
 690 
 691         if (BTF_INFO_KIND(key_type->info) != BTF_KIND_INT)
 692                 return -EINVAL;
 693 
 694         int_data = *(u32 *)(key_type + 1);
 695         if (BTF_INT_BITS(int_data) != 32 || BTF_INT_OFFSET(int_data))
 696                 return -EINVAL;
 697 
 698         return 0;
 699 }
 700 
 701 static void *bpf_fd_sk_storage_lookup_elem(struct bpf_map *map, void *key)
 702 {
 703         struct bpf_sk_storage_data *sdata;
 704         struct socket *sock;
 705         int fd, err;
 706 
 707         fd = *(int *)key;
 708         sock = sockfd_lookup(fd, &err);
 709         if (sock) {
 710                 sdata = sk_storage_lookup(sock->sk, map, true);
 711                 sockfd_put(sock);
 712                 return sdata ? sdata->data : NULL;
 713         }
 714 
 715         return ERR_PTR(err);
 716 }
 717 
 718 static int bpf_fd_sk_storage_update_elem(struct bpf_map *map, void *key,
 719                                          void *value, u64 map_flags)
 720 {
 721         struct bpf_sk_storage_data *sdata;
 722         struct socket *sock;
 723         int fd, err;
 724 
 725         fd = *(int *)key;
 726         sock = sockfd_lookup(fd, &err);
 727         if (sock) {
 728                 sdata = sk_storage_update(sock->sk, map, value, map_flags);
 729                 sockfd_put(sock);
 730                 return PTR_ERR_OR_ZERO(sdata);
 731         }
 732 
 733         return err;
 734 }
 735 
 736 static int bpf_fd_sk_storage_delete_elem(struct bpf_map *map, void *key)
 737 {
 738         struct socket *sock;
 739         int fd, err;
 740 
 741         fd = *(int *)key;
 742         sock = sockfd_lookup(fd, &err);
 743         if (sock) {
 744                 err = sk_storage_delete(sock->sk, map);
 745                 sockfd_put(sock);
 746                 return err;
 747         }
 748 
 749         return err;
 750 }
 751 
 752 static struct bpf_sk_storage_elem *
 753 bpf_sk_storage_clone_elem(struct sock *newsk,
 754                           struct bpf_sk_storage_map *smap,
 755                           struct bpf_sk_storage_elem *selem)
 756 {
 757         struct bpf_sk_storage_elem *copy_selem;
 758 
 759         copy_selem = selem_alloc(smap, newsk, NULL, true);
 760         if (!copy_selem)
 761                 return NULL;
 762 
 763         if (map_value_has_spin_lock(&smap->map))
 764                 copy_map_value_locked(&smap->map, SDATA(copy_selem)->data,
 765                                       SDATA(selem)->data, true);
 766         else
 767                 copy_map_value(&smap->map, SDATA(copy_selem)->data,
 768                                SDATA(selem)->data);
 769 
 770         return copy_selem;
 771 }
 772 
 773 int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk)
 774 {
 775         struct bpf_sk_storage *new_sk_storage = NULL;
 776         struct bpf_sk_storage *sk_storage;
 777         struct bpf_sk_storage_elem *selem;
 778         int ret = 0;
 779 
 780         RCU_INIT_POINTER(newsk->sk_bpf_storage, NULL);
 781 
 782         rcu_read_lock();
 783         sk_storage = rcu_dereference(sk->sk_bpf_storage);
 784 
 785         if (!sk_storage || hlist_empty(&sk_storage->list))
 786                 goto out;
 787 
 788         hlist_for_each_entry_rcu(selem, &sk_storage->list, snode) {
 789                 struct bpf_sk_storage_elem *copy_selem;
 790                 struct bpf_sk_storage_map *smap;
 791                 struct bpf_map *map;
 792 
 793                 smap = rcu_dereference(SDATA(selem)->smap);
 794                 if (!(smap->map.map_flags & BPF_F_CLONE))
 795                         continue;
 796 
 797                 /* Note that for lockless listeners adding new element
 798                  * here can race with cleanup in bpf_sk_storage_map_free.
 799                  * Try to grab map refcnt to make sure that it's still
 800                  * alive and prevent concurrent removal.
 801                  */
 802                 map = bpf_map_inc_not_zero(&smap->map, false);
 803                 if (IS_ERR(map))
 804                         continue;
 805 
 806                 copy_selem = bpf_sk_storage_clone_elem(newsk, smap, selem);
 807                 if (!copy_selem) {
 808                         ret = -ENOMEM;
 809                         bpf_map_put(map);
 810                         goto out;
 811                 }
 812 
 813                 if (new_sk_storage) {
 814                         selem_link_map(smap, copy_selem);
 815                         __selem_link_sk(new_sk_storage, copy_selem);
 816                 } else {
 817                         ret = sk_storage_alloc(newsk, smap, copy_selem);
 818                         if (ret) {
 819                                 kfree(copy_selem);
 820                                 atomic_sub(smap->elem_size,
 821                                            &newsk->sk_omem_alloc);
 822                                 bpf_map_put(map);
 823                                 goto out;
 824                         }
 825 
 826                         new_sk_storage = rcu_dereference(copy_selem->sk_storage);
 827                 }
 828                 bpf_map_put(map);
 829         }
 830 
 831 out:
 832         rcu_read_unlock();
 833 
 834         /* In case of an error, don't free anything explicitly here, the
 835          * caller is responsible to call bpf_sk_storage_free.
 836          */
 837 
 838         return ret;
 839 }
 840 
 841 BPF_CALL_4(bpf_sk_storage_get, struct bpf_map *, map, struct sock *, sk,
 842            void *, value, u64, flags)
 843 {
 844         struct bpf_sk_storage_data *sdata;
 845 
 846         if (flags > BPF_SK_STORAGE_GET_F_CREATE)
 847                 return (unsigned long)NULL;
 848 
 849         sdata = sk_storage_lookup(sk, map, true);
 850         if (sdata)
 851                 return (unsigned long)sdata->data;
 852 
 853         if (flags == BPF_SK_STORAGE_GET_F_CREATE &&
 854             /* Cannot add new elem to a going away sk.
 855              * Otherwise, the new elem may become a leak
 856              * (and also other memory issues during map
 857              *  destruction).
 858              */
 859             refcount_inc_not_zero(&sk->sk_refcnt)) {
 860                 sdata = sk_storage_update(sk, map, value, BPF_NOEXIST);
 861                 /* sk must be a fullsock (guaranteed by verifier),
 862                  * so sock_gen_put() is unnecessary.
 863                  */
 864                 sock_put(sk);
 865                 return IS_ERR(sdata) ?
 866                         (unsigned long)NULL : (unsigned long)sdata->data;
 867         }
 868 
 869         return (unsigned long)NULL;
 870 }
 871 
 872 BPF_CALL_2(bpf_sk_storage_delete, struct bpf_map *, map, struct sock *, sk)
 873 {
 874         if (refcount_inc_not_zero(&sk->sk_refcnt)) {
 875                 int err;
 876 
 877                 err = sk_storage_delete(sk, map);
 878                 sock_put(sk);
 879                 return err;
 880         }
 881 
 882         return -ENOENT;
 883 }
 884 
 885 const struct bpf_map_ops sk_storage_map_ops = {
 886         .map_alloc_check = bpf_sk_storage_map_alloc_check,
 887         .map_alloc = bpf_sk_storage_map_alloc,
 888         .map_free = bpf_sk_storage_map_free,
 889         .map_get_next_key = notsupp_get_next_key,
 890         .map_lookup_elem = bpf_fd_sk_storage_lookup_elem,
 891         .map_update_elem = bpf_fd_sk_storage_update_elem,
 892         .map_delete_elem = bpf_fd_sk_storage_delete_elem,
 893         .map_check_btf = bpf_sk_storage_map_check_btf,
 894 };
 895 
 896 const struct bpf_func_proto bpf_sk_storage_get_proto = {
 897         .func           = bpf_sk_storage_get,
 898         .gpl_only       = false,
 899         .ret_type       = RET_PTR_TO_MAP_VALUE_OR_NULL,
 900         .arg1_type      = ARG_CONST_MAP_PTR,
 901         .arg2_type      = ARG_PTR_TO_SOCKET,
 902         .arg3_type      = ARG_PTR_TO_MAP_VALUE_OR_NULL,
 903         .arg4_type      = ARG_ANYTHING,
 904 };
 905 
 906 const struct bpf_func_proto bpf_sk_storage_delete_proto = {
 907         .func           = bpf_sk_storage_delete,
 908         .gpl_only       = false,
 909         .ret_type       = RET_INTEGER,
 910         .arg1_type      = ARG_CONST_MAP_PTR,
 911         .arg2_type      = ARG_PTR_TO_SOCKET,
 912 };
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root/net/core/bpf_sk_storage.c

DEFINITIONS
