kernel/bpf/local_storage.c

   1 //SPDX-License-Identifier: GPL-2.0
   2 #include <linux/bpf-cgroup.h>
   3 #include <linux/bpf.h>
   4 #include <linux/bug.h>
   5 #include <linux/filter.h>
   6 #include <linux/mm.h>
   7 #include <linux/rbtree.h>
   8 #include <linux/slab.h>
   9
  10 DEFINE_PER_CPU(struct bpf_cgroup_storage*,
  11                bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
  12
  13 #ifdef CONFIG_CGROUP_BPF
  14
  15 #define LOCAL_STORAGE_CREATE_FLAG_MASK                                  \
  16         (BPF_F_NUMA_NODE | BPF_F_RDONLY | BPF_F_WRONLY)
  17
  18 struct bpf_cgroup_storage_map {
  19         struct bpf_map map;
  20
  21         spinlock_t lock;
  22         struct bpf_prog *prog;
  23         struct rb_root root;
  24         struct list_head list;
  25 };
  26
  27 static struct bpf_cgroup_storage_map *map_to_storage(struct bpf_map *map)
  28 {
  29         return container_of(map, struct bpf_cgroup_storage_map, map);
  30 }
  31
  32 static int bpf_cgroup_storage_key_cmp(
  33         const struct bpf_cgroup_storage_key *key1,
  34         const struct bpf_cgroup_storage_key *key2)
  35 {
  36         if (key1->cgroup_inode_id < key2->cgroup_inode_id)
  37                 return -1;
  38         else if (key1->cgroup_inode_id > key2->cgroup_inode_id)
  39                 return 1;
  40         else if (key1->attach_type < key2->attach_type)
  41                 return -1;
  42         else if (key1->attach_type > key2->attach_type)
  43                 return 1;
  44         return 0;
  45 }
  46
  47 static struct bpf_cgroup_storage *cgroup_storage_lookup(
  48         struct bpf_cgroup_storage_map *map, struct bpf_cgroup_storage_key *key,
  49         bool locked)
  50 {
  51         struct rb_root *root = &map->root;
  52         struct rb_node *node;
  53
  54         if (!locked)
  55                 spin_lock_bh(&map->lock);
  56
  57         node = root->rb_node;
  58         while (node) {
  59                 struct bpf_cgroup_storage *storage;
  60
  61                 storage = container_of(node, struct bpf_cgroup_storage, node);
  62
  63                 switch (bpf_cgroup_storage_key_cmp(key, &storage->key)) {
  64                 case -1:
  65                         node = node->rb_left;
  66                         break;
  67                 case 1:
  68                         node = node->rb_right;
  69                         break;
  70                 default:
  71                         if (!locked)
  72                                 spin_unlock_bh(&map->lock);
  73                         return storage;
  74                 }
  75         }
  76
  77         if (!locked)
  78                 spin_unlock_bh(&map->lock);
  79
  80         return NULL;
  81 }
  82
  83 static int cgroup_storage_insert(struct bpf_cgroup_storage_map *map,
  84                                  struct bpf_cgroup_storage *storage)
  85 {
  86         struct rb_root *root = &map->root;
  87         struct rb_node **new = &(root->rb_node), *parent = NULL;
  88
  89         while (*new) {
  90                 struct bpf_cgroup_storage *this;
  91
  92                 this = container_of(*new, struct bpf_cgroup_storage, node);
  93
  94                 parent = *new;
  95                 switch (bpf_cgroup_storage_key_cmp(&storage->key, &this->key)) {
  96                 case -1:
  97                         new = &((*new)->rb_left);
  98                         break;
  99                 case 1:
 100                         new = &((*new)->rb_right);
 101                         break;
 102                 default:
 103                         return -EEXIST;
 104                 }
 105         }
 106
 107         rb_link_node(&storage->node, parent, new);
 108         rb_insert_color(&storage->node, root);
 109
 110         return 0;
 111 }
 112
 113 static void *cgroup_storage_lookup_elem(struct bpf_map *_map, void *_key)
 114 {
 115         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 116         struct bpf_cgroup_storage_key *key = _key;
 117         struct bpf_cgroup_storage *storage;
 118
 119         storage = cgroup_storage_lookup(map, key, false);
 120         if (!storage)
 121                 return NULL;
 122
 123         return &READ_ONCE(storage->buf)->data[0];
 124 }
 125
 126 static int cgroup_storage_update_elem(struct bpf_map *map, void *_key,
 127                                       void *value, u64 flags)
 128 {
 129         struct bpf_cgroup_storage_key *key = _key;
 130         struct bpf_cgroup_storage *storage;
 131         struct bpf_storage_buffer *new;
 132
 133         if (flags != BPF_ANY && flags != BPF_EXIST)
 134                 return -EINVAL;
 135
 136         storage = cgroup_storage_lookup((struct bpf_cgroup_storage_map *)map,
 137                                         key, false);
 138         if (!storage)
 139                 return -ENOENT;
 140
 141         new = kmalloc_node(sizeof(struct bpf_storage_buffer) +
 142                            map->value_size,
 143                            __GFP_ZERO | GFP_ATOMIC | __GFP_NOWARN,
 144                            map->numa_node);
 145         if (!new)
 146                 return -ENOMEM;
 147
 148         memcpy(&new->data[0], value, map->value_size);
 149
 150         new = xchg(&storage->buf, new);
 151         kfree_rcu(new, rcu);
 152
 153         return 0;
 154 }
 155
 156 int bpf_percpu_cgroup_storage_copy(struct bpf_map *_map, void *_key,
 157                                    void *value)
 158 {
 159         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 160         struct bpf_cgroup_storage_key *key = _key;
 161         struct bpf_cgroup_storage *storage;
 162         int cpu, off = 0;
 163         u32 size;
 164
 165         rcu_read_lock();
 166         storage = cgroup_storage_lookup(map, key, false);
 167         if (!storage) {
 168                 rcu_read_unlock();
 169                 return -ENOENT;
 170         }
 171
 172         /* per_cpu areas are zero-filled and bpf programs can only
 173          * access 'value_size' of them, so copying rounded areas
 174          * will not leak any kernel data
 175          */
 176         size = round_up(_map->value_size, 8);
 177         for_each_possible_cpu(cpu) {
 178                 bpf_long_memcpy(value + off,
 179                                 per_cpu_ptr(storage->percpu_buf, cpu), size);
 180                 off += size;
 181         }
 182         rcu_read_unlock();
 183         return 0;
 184 }
 185
 186 int bpf_percpu_cgroup_storage_update(struct bpf_map *_map, void *_key,
 187                                      void *value, u64 map_flags)
 188 {
 189         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 190         struct bpf_cgroup_storage_key *key = _key;
 191         struct bpf_cgroup_storage *storage;
 192         int cpu, off = 0;
 193         u32 size;
 194
 195         if (map_flags != BPF_ANY && map_flags != BPF_EXIST)
 196                 return -EINVAL;
 197
 198         rcu_read_lock();
 199         storage = cgroup_storage_lookup(map, key, false);
 200         if (!storage) {
 201                 rcu_read_unlock();
 202                 return -ENOENT;
 203         }
 204
 205         /* the user space will provide round_up(value_size, 8) bytes that
 206          * will be copied into per-cpu area. bpf programs can only access
 207          * value_size of it. During lookup the same extra bytes will be
 208          * returned or zeros which were zero-filled by percpu_alloc,
 209          * so no kernel data leaks possible
 210          */
 211         size = round_up(_map->value_size, 8);
 212         for_each_possible_cpu(cpu) {
 213                 bpf_long_memcpy(per_cpu_ptr(storage->percpu_buf, cpu),
 214                                 value + off, size);
 215                 off += size;
 216         }
 217         rcu_read_unlock();
 218         return 0;
 219 }
 220
 221 static int cgroup_storage_get_next_key(struct bpf_map *_map, void *_key,
 222                                        void *_next_key)
 223 {
 224         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 225         struct bpf_cgroup_storage_key *key = _key;
 226         struct bpf_cgroup_storage_key *next = _next_key;
 227         struct bpf_cgroup_storage *storage;
 228
 229         spin_lock_bh(&map->lock);
 230
 231         if (list_empty(&map->list))
 232                 goto enoent;
 233
 234         if (key) {
 235                 storage = cgroup_storage_lookup(map, key, true);
 236                 if (!storage)
 237                         goto enoent;
 238
 239                 storage = list_next_entry(storage, list);
 240                 if (!storage)
 241                         goto enoent;
 242         } else {
 243                 storage = list_first_entry(&map->list,
 244                                          struct bpf_cgroup_storage, list);
 245         }
 246
 247         spin_unlock_bh(&map->lock);
 248         next->attach_type = storage->key.attach_type;
 249         next->cgroup_inode_id = storage->key.cgroup_inode_id;
 250         return 0;
 251
 252 enoent:
 253         spin_unlock_bh(&map->lock);
 254         return -ENOENT;
 255 }
 256
 257 static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
 258 {
 259         int numa_node = bpf_map_attr_numa_node(attr);
 260         struct bpf_cgroup_storage_map *map;
 261
 262         if (attr->key_size != sizeof(struct bpf_cgroup_storage_key))
 263                 return ERR_PTR(-EINVAL);
 264
 265         if (attr->value_size == 0)
 266                 return ERR_PTR(-EINVAL);
 267
 268         if (attr->value_size > PAGE_SIZE)
 269                 return ERR_PTR(-E2BIG);
 270
 271         if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK)
 272                 /* reserved bits should not be used */
 273                 return ERR_PTR(-EINVAL);
 274
 275         if (attr->max_entries)
 276                 /* max_entries is not used and enforced to be 0 */
 277                 return ERR_PTR(-EINVAL);
 278
 279         map = kmalloc_node(sizeof(struct bpf_cgroup_storage_map),
 280                            __GFP_ZERO | GFP_USER, numa_node);
 281         if (!map)
 282                 return ERR_PTR(-ENOMEM);
 283
 284         map->map.pages = round_up(sizeof(struct bpf_cgroup_storage_map),
 285                                   PAGE_SIZE) >> PAGE_SHIFT;
 286
 287         /* copy mandatory map attributes */
 288         bpf_map_init_from_attr(&map->map, attr);
 289
 290         spin_lock_init(&map->lock);
 291         map->root = RB_ROOT;
 292         INIT_LIST_HEAD(&map->list);
 293
 294         return &map->map;
 295 }
 296
 297 static void cgroup_storage_map_free(struct bpf_map *_map)
 298 {
 299         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 300
 301         WARN_ON(!RB_EMPTY_ROOT(&map->root));
 302         WARN_ON(!list_empty(&map->list));
 303
 304         kfree(map);
 305 }
 306
 307 static int cgroup_storage_delete_elem(struct bpf_map *map, void *key)
 308 {
 309         return -EINVAL;
 310 }
 311
 312 const struct bpf_map_ops cgroup_storage_map_ops = {
 313         .map_alloc = cgroup_storage_map_alloc,
 314         .map_free = cgroup_storage_map_free,
 315         .map_get_next_key = cgroup_storage_get_next_key,
 316         .map_lookup_elem = cgroup_storage_lookup_elem,
 317         .map_update_elem = cgroup_storage_update_elem,
 318         .map_delete_elem = cgroup_storage_delete_elem,
 319         .map_check_btf = map_check_no_btf,
 320 };
 321
 322 int bpf_cgroup_storage_assign(struct bpf_prog *prog, struct bpf_map *_map)
 323 {
 324         enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);
 325         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 326         int ret = -EBUSY;
 327
 328         spin_lock_bh(&map->lock);
 329
 330         if (map->prog && map->prog != prog)
 331                 goto unlock;
 332         if (prog->aux->cgroup_storage[stype] &&
 333             prog->aux->cgroup_storage[stype] != _map)
 334                 goto unlock;
 335
 336         map->prog = prog;
 337         prog->aux->cgroup_storage[stype] = _map;
 338         ret = 0;
 339 unlock:
 340         spin_unlock_bh(&map->lock);
 341
 342         return ret;
 343 }
 344
 345 void bpf_cgroup_storage_release(struct bpf_prog *prog, struct bpf_map *_map)
 346 {
 347         enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);
 348         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 349
 350         spin_lock_bh(&map->lock);
 351         if (map->prog == prog) {
 352                 WARN_ON(prog->aux->cgroup_storage[stype] != _map);
 353                 map->prog = NULL;
 354                 prog->aux->cgroup_storage[stype] = NULL;
 355         }
 356         spin_unlock_bh(&map->lock);
 357 }
 358
 359 static size_t bpf_cgroup_storage_calculate_size(struct bpf_map *map, u32 *pages)
 360 {
 361         size_t size;
 362
 363         if (cgroup_storage_type(map) == BPF_CGROUP_STORAGE_SHARED) {
 364                 size = sizeof(struct bpf_storage_buffer) + map->value_size;
 365                 *pages = round_up(sizeof(struct bpf_cgroup_storage) + size,
 366                                   PAGE_SIZE) >> PAGE_SHIFT;
 367         } else {
 368                 size = map->value_size;
 369                 *pages = round_up(round_up(size, 8) * num_possible_cpus(),
 370                                   PAGE_SIZE) >> PAGE_SHIFT;
 371         }
 372
 373         return size;
 374 }
 375
 376 struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog,
 377                                         enum bpf_cgroup_storage_type stype)
 378 {
 379         struct bpf_cgroup_storage *storage;
 380         struct bpf_map *map;
 381         gfp_t flags;
 382         size_t size;
 383         u32 pages;
 384
 385         map = prog->aux->cgroup_storage[stype];
 386         if (!map)
 387                 return NULL;
 388
 389         size = bpf_cgroup_storage_calculate_size(map, &pages);
 390
 391         if (bpf_map_charge_memlock(map, pages))
 392                 return ERR_PTR(-EPERM);
 393
 394         storage = kmalloc_node(sizeof(struct bpf_cgroup_storage),
 395                                __GFP_ZERO | GFP_USER, map->numa_node);
 396         if (!storage)
 397                 goto enomem;
 398
 399         flags = __GFP_ZERO | GFP_USER;
 400
 401         if (stype == BPF_CGROUP_STORAGE_SHARED) {
 402                 storage->buf = kmalloc_node(size, flags, map->numa_node);
 403                 if (!storage->buf)
 404                         goto enomem;
 405         } else {
 406                 storage->percpu_buf = __alloc_percpu_gfp(size, 8, flags);
 407                 if (!storage->percpu_buf)
 408                         goto enomem;
 409         }
 410
 411         storage->map = (struct bpf_cgroup_storage_map *)map;
 412
 413         return storage;
 414
 415 enomem:
 416         bpf_map_uncharge_memlock(map, pages);
 417         kfree(storage);
 418         return ERR_PTR(-ENOMEM);
 419 }
 420
 421 static void free_shared_cgroup_storage_rcu(struct rcu_head *rcu)
 422 {
 423         struct bpf_cgroup_storage *storage =
 424                 container_of(rcu, struct bpf_cgroup_storage, rcu);
 425
 426         kfree(storage->buf);
 427         kfree(storage);
 428 }
 429
 430 static void free_percpu_cgroup_storage_rcu(struct rcu_head *rcu)
 431 {
 432         struct bpf_cgroup_storage *storage =
 433                 container_of(rcu, struct bpf_cgroup_storage, rcu);
 434
 435         free_percpu(storage->percpu_buf);
 436         kfree(storage);
 437 }
 438
 439 void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage)
 440 {
 441         enum bpf_cgroup_storage_type stype;
 442         struct bpf_map *map;
 443         u32 pages;
 444
 445         if (!storage)
 446                 return;
 447
 448         map = &storage->map->map;
 449
 450         bpf_cgroup_storage_calculate_size(map, &pages);
 451         bpf_map_uncharge_memlock(map, pages);
 452
 453         stype = cgroup_storage_type(map);
 454         if (stype == BPF_CGROUP_STORAGE_SHARED)
 455                 call_rcu(&storage->rcu, free_shared_cgroup_storage_rcu);
 456         else
 457                 call_rcu(&storage->rcu, free_percpu_cgroup_storage_rcu);
 458 }
 459
 460 void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
 461                              struct cgroup *cgroup,
 462                              enum bpf_attach_type type)
 463 {
 464         struct bpf_cgroup_storage_map *map;
 465
 466         if (!storage)
 467                 return;
 468
 469         storage->key.attach_type = type;
 470         storage->key.cgroup_inode_id = cgroup->kn->id.id;
 471
 472         map = storage->map;
 473
 474         spin_lock_bh(&map->lock);
 475         WARN_ON(cgroup_storage_insert(map, storage));
 476         list_add(&storage->list, &map->list);
 477         spin_unlock_bh(&map->lock);
 478 }
 479
 480 void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage)
 481 {
 482         struct bpf_cgroup_storage_map *map;
 483         struct rb_root *root;
 484
 485         if (!storage)
 486                 return;
 487
 488         map = storage->map;
 489
 490         spin_lock_bh(&map->lock);
 491         root = &map->root;
 492         rb_erase(&storage->node, root);
 493
 494         list_del(&storage->list);
 495         spin_unlock_bh(&map->lock);
 496 }
 497
 498 #endif