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_NOEXIST)
 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, __GFP_ZERO | GFP_USER,
 143                            map->numa_node);
 144         if (!new)
 145                 return -ENOMEM;
 146
 147         memcpy(&new->data[0], value, map->value_size);
 148
 149         new = xchg(&storage->buf, new);
 150         kfree_rcu(new, rcu);
 151
 152         return 0;
 153 }
 154
 155 int bpf_percpu_cgroup_storage_copy(struct bpf_map *_map, void *_key,
 156                                    void *value)
 157 {
 158         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 159         struct bpf_cgroup_storage_key *key = _key;
 160         struct bpf_cgroup_storage *storage;
 161         int cpu, off = 0;
 162         u32 size;
 163
 164         rcu_read_lock();
 165         storage = cgroup_storage_lookup(map, key, false);
 166         if (!storage) {
 167                 rcu_read_unlock();
 168                 return -ENOENT;
 169         }
 170
 171         /* per_cpu areas are zero-filled and bpf programs can only
 172          * access 'value_size' of them, so copying rounded areas
 173          * will not leak any kernel data
 174          */
 175         size = round_up(_map->value_size, 8);
 176         for_each_possible_cpu(cpu) {
 177                 bpf_long_memcpy(value + off,
 178                                 per_cpu_ptr(storage->percpu_buf, cpu), size);
 179                 off += size;
 180         }
 181         rcu_read_unlock();
 182         return 0;
 183 }
 184
 185 int bpf_percpu_cgroup_storage_update(struct bpf_map *_map, void *_key,
 186                                      void *value, u64 map_flags)
 187 {
 188         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 189         struct bpf_cgroup_storage_key *key = _key;
 190         struct bpf_cgroup_storage *storage;
 191         int cpu, off = 0;
 192         u32 size;
 193
 194         if (map_flags != BPF_ANY && map_flags != BPF_EXIST)
 195                 return -EINVAL;
 196
 197         rcu_read_lock();
 198         storage = cgroup_storage_lookup(map, key, false);
 199         if (!storage) {
 200                 rcu_read_unlock();
 201                 return -ENOENT;
 202         }
 203
 204         /* the user space will provide round_up(value_size, 8) bytes that
 205          * will be copied into per-cpu area. bpf programs can only access
 206          * value_size of it. During lookup the same extra bytes will be
 207          * returned or zeros which were zero-filled by percpu_alloc,
 208          * so no kernel data leaks possible
 209          */
 210         size = round_up(_map->value_size, 8);
 211         for_each_possible_cpu(cpu) {
 212                 bpf_long_memcpy(per_cpu_ptr(storage->percpu_buf, cpu),
 213                                 value + off, size);
 214                 off += size;
 215         }
 216         rcu_read_unlock();
 217         return 0;
 218 }
 219
 220 static int cgroup_storage_get_next_key(struct bpf_map *_map, void *_key,
 221                                        void *_next_key)
 222 {
 223         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 224         struct bpf_cgroup_storage_key *key = _key;
 225         struct bpf_cgroup_storage_key *next = _next_key;
 226         struct bpf_cgroup_storage *storage;
 227
 228         spin_lock_bh(&map->lock);
 229
 230         if (list_empty(&map->list))
 231                 goto enoent;
 232
 233         if (key) {
 234                 storage = cgroup_storage_lookup(map, key, true);
 235                 if (!storage)
 236                         goto enoent;
 237
 238                 storage = list_next_entry(storage, list);
 239                 if (!storage)
 240                         goto enoent;
 241         } else {
 242                 storage = list_first_entry(&map->list,
 243                                          struct bpf_cgroup_storage, list);
 244         }
 245
 246         spin_unlock_bh(&map->lock);
 247         next->attach_type = storage->key.attach_type;
 248         next->cgroup_inode_id = storage->key.cgroup_inode_id;
 249         return 0;
 250
 251 enoent:
 252         spin_unlock_bh(&map->lock);
 253         return -ENOENT;
 254 }
 255
 256 static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
 257 {
 258         int numa_node = bpf_map_attr_numa_node(attr);
 259         struct bpf_cgroup_storage_map *map;
 260
 261         if (attr->key_size != sizeof(struct bpf_cgroup_storage_key))
 262                 return ERR_PTR(-EINVAL);
 263
 264         if (attr->value_size > PAGE_SIZE)
 265                 return ERR_PTR(-E2BIG);
 266
 267         if (attr->map_flags & ~LOCAL_STORAGE_CREATE_FLAG_MASK)
 268                 /* reserved bits should not be used */
 269                 return ERR_PTR(-EINVAL);
 270
 271         if (attr->max_entries)
 272                 /* max_entries is not used and enforced to be 0 */
 273                 return ERR_PTR(-EINVAL);
 274
 275         map = kmalloc_node(sizeof(struct bpf_cgroup_storage_map),
 276                            __GFP_ZERO | GFP_USER, numa_node);
 277         if (!map)
 278                 return ERR_PTR(-ENOMEM);
 279
 280         map->map.pages = round_up(sizeof(struct bpf_cgroup_storage_map),
 281                                   PAGE_SIZE) >> PAGE_SHIFT;
 282
 283         /* copy mandatory map attributes */
 284         bpf_map_init_from_attr(&map->map, attr);
 285
 286         spin_lock_init(&map->lock);
 287         map->root = RB_ROOT;
 288         INIT_LIST_HEAD(&map->list);
 289
 290         return &map->map;
 291 }
 292
 293 static void cgroup_storage_map_free(struct bpf_map *_map)
 294 {
 295         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 296
 297         WARN_ON(!RB_EMPTY_ROOT(&map->root));
 298         WARN_ON(!list_empty(&map->list));
 299
 300         kfree(map);
 301 }
 302
 303 static int cgroup_storage_delete_elem(struct bpf_map *map, void *key)
 304 {
 305         return -EINVAL;
 306 }
 307
 308 const struct bpf_map_ops cgroup_storage_map_ops = {
 309         .map_alloc = cgroup_storage_map_alloc,
 310         .map_free = cgroup_storage_map_free,
 311         .map_get_next_key = cgroup_storage_get_next_key,
 312         .map_lookup_elem = cgroup_storage_lookup_elem,
 313         .map_update_elem = cgroup_storage_update_elem,
 314         .map_delete_elem = cgroup_storage_delete_elem,
 315         .map_check_btf = map_check_no_btf,
 316 };
 317
 318 int bpf_cgroup_storage_assign(struct bpf_prog *prog, struct bpf_map *_map)
 319 {
 320         enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);
 321         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 322         int ret = -EBUSY;
 323
 324         spin_lock_bh(&map->lock);
 325
 326         if (map->prog && map->prog != prog)
 327                 goto unlock;
 328         if (prog->aux->cgroup_storage[stype] &&
 329             prog->aux->cgroup_storage[stype] != _map)
 330                 goto unlock;
 331
 332         map->prog = prog;
 333         prog->aux->cgroup_storage[stype] = _map;
 334         ret = 0;
 335 unlock:
 336         spin_unlock_bh(&map->lock);
 337
 338         return ret;
 339 }
 340
 341 void bpf_cgroup_storage_release(struct bpf_prog *prog, struct bpf_map *_map)
 342 {
 343         enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);
 344         struct bpf_cgroup_storage_map *map = map_to_storage(_map);
 345
 346         spin_lock_bh(&map->lock);
 347         if (map->prog == prog) {
 348                 WARN_ON(prog->aux->cgroup_storage[stype] != _map);
 349                 map->prog = NULL;
 350                 prog->aux->cgroup_storage[stype] = NULL;
 351         }
 352         spin_unlock_bh(&map->lock);
 353 }
 354
 355 static size_t bpf_cgroup_storage_calculate_size(struct bpf_map *map, u32 *pages)
 356 {
 357         size_t size;
 358
 359         if (cgroup_storage_type(map) == BPF_CGROUP_STORAGE_SHARED) {
 360                 size = sizeof(struct bpf_storage_buffer) + map->value_size;
 361                 *pages = round_up(sizeof(struct bpf_cgroup_storage) + size,
 362                                   PAGE_SIZE) >> PAGE_SHIFT;
 363         } else {
 364                 size = map->value_size;
 365                 *pages = round_up(round_up(size, 8) * num_possible_cpus(),
 366                                   PAGE_SIZE) >> PAGE_SHIFT;
 367         }
 368
 369         return size;
 370 }
 371
 372 struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog,
 373                                         enum bpf_cgroup_storage_type stype)
 374 {
 375         struct bpf_cgroup_storage *storage;
 376         struct bpf_map *map;
 377         gfp_t flags;
 378         size_t size;
 379         u32 pages;
 380
 381         map = prog->aux->cgroup_storage[stype];
 382         if (!map)
 383                 return NULL;
 384
 385         size = bpf_cgroup_storage_calculate_size(map, &pages);
 386
 387         if (bpf_map_charge_memlock(map, pages))
 388                 return ERR_PTR(-EPERM);
 389
 390         storage = kmalloc_node(sizeof(struct bpf_cgroup_storage),
 391                                __GFP_ZERO | GFP_USER, map->numa_node);
 392         if (!storage)
 393                 goto enomem;
 394
 395         flags = __GFP_ZERO | GFP_USER;
 396
 397         if (stype == BPF_CGROUP_STORAGE_SHARED) {
 398                 storage->buf = kmalloc_node(size, flags, map->numa_node);
 399                 if (!storage->buf)
 400                         goto enomem;
 401         } else {
 402                 storage->percpu_buf = __alloc_percpu_gfp(size, 8, flags);
 403                 if (!storage->percpu_buf)
 404                         goto enomem;
 405         }
 406
 407         storage->map = (struct bpf_cgroup_storage_map *)map;
 408
 409         return storage;
 410
 411 enomem:
 412         bpf_map_uncharge_memlock(map, pages);
 413         kfree(storage);
 414         return ERR_PTR(-ENOMEM);
 415 }
 416
 417 static void free_shared_cgroup_storage_rcu(struct rcu_head *rcu)
 418 {
 419         struct bpf_cgroup_storage *storage =
 420                 container_of(rcu, struct bpf_cgroup_storage, rcu);
 421
 422         kfree(storage->buf);
 423         kfree(storage);
 424 }
 425
 426 static void free_percpu_cgroup_storage_rcu(struct rcu_head *rcu)
 427 {
 428         struct bpf_cgroup_storage *storage =
 429                 container_of(rcu, struct bpf_cgroup_storage, rcu);
 430
 431         free_percpu(storage->percpu_buf);
 432         kfree(storage);
 433 }
 434
 435 void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage)
 436 {
 437         enum bpf_cgroup_storage_type stype;
 438         struct bpf_map *map;
 439         u32 pages;
 440
 441         if (!storage)
 442                 return;
 443
 444         map = &storage->map->map;
 445
 446         bpf_cgroup_storage_calculate_size(map, &pages);
 447         bpf_map_uncharge_memlock(map, pages);
 448
 449         stype = cgroup_storage_type(map);
 450         if (stype == BPF_CGROUP_STORAGE_SHARED)
 451                 call_rcu(&storage->rcu, free_shared_cgroup_storage_rcu);
 452         else
 453                 call_rcu(&storage->rcu, free_percpu_cgroup_storage_rcu);
 454 }
 455
 456 void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
 457                              struct cgroup *cgroup,
 458                              enum bpf_attach_type type)
 459 {
 460         struct bpf_cgroup_storage_map *map;
 461
 462         if (!storage)
 463                 return;
 464
 465         storage->key.attach_type = type;
 466         storage->key.cgroup_inode_id = cgroup->kn->id.id;
 467
 468         map = storage->map;
 469
 470         spin_lock_bh(&map->lock);
 471         WARN_ON(cgroup_storage_insert(map, storage));
 472         list_add(&storage->list, &map->list);
 473         spin_unlock_bh(&map->lock);
 474 }
 475
 476 void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage)
 477 {
 478         struct bpf_cgroup_storage_map *map;
 479         struct rb_root *root;
 480
 481         if (!storage)
 482                 return;
 483
 484         map = storage->map;
 485
 486         spin_lock_bh(&map->lock);
 487         root = &map->root;
 488         rb_erase(&storage->node, root);
 489
 490         list_del(&storage->list);
 491         spin_unlock_bh(&map->lock);
 492 }
 493
 494 #endif