kernel/bpf/syscall.c

   1 /* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  *
   7  * This program is distributed in the hope that it will be useful, but
   8  * WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10  * General Public License for more details.
  11  */
  12 #include <linux/bpf.h>
  13 #include <linux/syscalls.h>
  14 #include <linux/slab.h>
  15 #include <linux/anon_inodes.h>
  16 #include <linux/file.h>
  17 #include <linux/license.h>
  18 #include <linux/filter.h>
  19 #include <linux/version.h>
  20
  21 int sysctl_unprivileged_bpf_disabled __read_mostly;
  22
  23 static LIST_HEAD(bpf_map_types);
  24
  25 static struct bpf_map *find_and_alloc_map(union bpf_attr *attr)
  26 {
  27         struct bpf_map_type_list *tl;
  28         struct bpf_map *map;
  29
  30         list_for_each_entry(tl, &bpf_map_types, list_node) {
  31                 if (tl->type == attr->map_type) {
  32                         map = tl->ops->map_alloc(attr);
  33                         if (IS_ERR(map))
  34                                 return map;
  35                         map->ops = tl->ops;
  36                         map->map_type = attr->map_type;
  37                         return map;
  38                 }
  39         }
  40         return ERR_PTR(-EINVAL);
  41 }
  42
  43 /* boot time registration of different map implementations */
  44 void bpf_register_map_type(struct bpf_map_type_list *tl)
  45 {
  46         list_add(&tl->list_node, &bpf_map_types);
  47 }
  48
  49 static int bpf_map_charge_memlock(struct bpf_map *map)
  50 {
  51         struct user_struct *user = get_current_user();
  52         unsigned long memlock_limit;
  53
  54         memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
  55
  56         atomic_long_add(map->pages, &user->locked_vm);
  57
  58         if (atomic_long_read(&user->locked_vm) > memlock_limit) {
  59                 atomic_long_sub(map->pages, &user->locked_vm);
  60                 free_uid(user);
  61                 return -EPERM;
  62         }
  63         map->user = user;
  64         return 0;
  65 }
  66
  67 static void bpf_map_uncharge_memlock(struct bpf_map *map)
  68 {
  69         struct user_struct *user = map->user;
  70
  71         atomic_long_sub(map->pages, &user->locked_vm);
  72         free_uid(user);
  73 }
  74
  75 /* called from workqueue */
  76 static void bpf_map_free_deferred(struct work_struct *work)
  77 {
  78         struct bpf_map *map = container_of(work, struct bpf_map, work);
  79
  80         bpf_map_uncharge_memlock(map);
  81         /* implementation dependent freeing */
  82         map->ops->map_free(map);
  83 }
  84
  85 static void bpf_map_put_uref(struct bpf_map *map)
  86 {
  87         if (atomic_dec_and_test(&map->usercnt)) {
  88                 if (map->map_type == BPF_MAP_TYPE_PROG_ARRAY)
  89                         bpf_fd_array_map_clear(map);
  90         }
  91 }
  92
  93 /* decrement map refcnt and schedule it for freeing via workqueue
  94  * (unrelying map implementation ops->map_free() might sleep)
  95  */
  96 void bpf_map_put(struct bpf_map *map)
  97 {
  98         if (atomic_dec_and_test(&map->refcnt)) {
  99                 INIT_WORK(&map->work, bpf_map_free_deferred);
 100                 schedule_work(&map->work);
 101         }
 102 }
 103
 104 void bpf_map_put_with_uref(struct bpf_map *map)
 105 {
 106         bpf_map_put_uref(map);
 107         bpf_map_put(map);
 108 }
 109
 110 static int bpf_map_release(struct inode *inode, struct file *filp)
 111 {
 112         bpf_map_put_with_uref(filp->private_data);
 113         return 0;
 114 }
 115
 116 static const struct file_operations bpf_map_fops = {
 117         .release = bpf_map_release,
 118 };
 119
 120 int bpf_map_new_fd(struct bpf_map *map)
 121 {
 122         return anon_inode_getfd("bpf-map", &bpf_map_fops, map,
 123                                 O_RDWR | O_CLOEXEC);
 124 }
 125
 126 /* helper macro to check that unused fields 'union bpf_attr' are zero */
 127 #define CHECK_ATTR(CMD) \
 128         memchr_inv((void *) &attr->CMD##_LAST_FIELD + \
 129                    sizeof(attr->CMD##_LAST_FIELD), 0, \
 130                    sizeof(*attr) - \
 131                    offsetof(union bpf_attr, CMD##_LAST_FIELD) - \
 132                    sizeof(attr->CMD##_LAST_FIELD)) != NULL
 133
 134 #define BPF_MAP_CREATE_LAST_FIELD max_entries
 135 /* called via syscall */
 136 static int map_create(union bpf_attr *attr)
 137 {
 138         struct bpf_map *map;
 139         int err;
 140
 141         err = CHECK_ATTR(BPF_MAP_CREATE);
 142         if (err)
 143                 return -EINVAL;
 144
 145         /* find map type and init map: hashtable vs rbtree vs bloom vs ... */
 146         map = find_and_alloc_map(attr);
 147         if (IS_ERR(map))
 148                 return PTR_ERR(map);
 149
 150         atomic_set(&map->refcnt, 1);
 151         atomic_set(&map->usercnt, 1);
 152
 153         err = bpf_map_charge_memlock(map);
 154         if (err)
 155                 goto free_map;
 156
 157         err = bpf_map_new_fd(map);
 158         if (err < 0)
 159                 /* failed to allocate fd */
 160                 goto free_map;
 161
 162         return err;
 163
 164 free_map:
 165         map->ops->map_free(map);
 166         return err;
 167 }
 168
 169 /* if error is returned, fd is released.
 170  * On success caller should complete fd access with matching fdput()
 171  */
 172 struct bpf_map *__bpf_map_get(struct fd f)
 173 {
 174         if (!f.file)
 175                 return ERR_PTR(-EBADF);
 176         if (f.file->f_op != &bpf_map_fops) {
 177                 fdput(f);
 178                 return ERR_PTR(-EINVAL);
 179         }
 180
 181         return f.file->private_data;
 182 }
 183
 184 void bpf_map_inc(struct bpf_map *map, bool uref)
 185 {
 186         atomic_inc(&map->refcnt);
 187         if (uref)
 188                 atomic_inc(&map->usercnt);
 189 }
 190
 191 struct bpf_map *bpf_map_get_with_uref(u32 ufd)
 192 {
 193         struct fd f = fdget(ufd);
 194         struct bpf_map *map;
 195
 196         map = __bpf_map_get(f);
 197         if (IS_ERR(map))
 198                 return map;
 199
 200         bpf_map_inc(map, true);
 201         fdput(f);
 202
 203         return map;
 204 }
 205
 206 /* helper to convert user pointers passed inside __aligned_u64 fields */
 207 static void __user *u64_to_ptr(__u64 val)
 208 {
 209         return (void __user *) (unsigned long) val;
 210 }
 211
 212 /* last field in 'union bpf_attr' used by this command */
 213 #define BPF_MAP_LOOKUP_ELEM_LAST_FIELD value
 214
 215 static int map_lookup_elem(union bpf_attr *attr)
 216 {
 217         void __user *ukey = u64_to_ptr(attr->key);
 218         void __user *uvalue = u64_to_ptr(attr->value);
 219         int ufd = attr->map_fd;
 220         struct bpf_map *map;
 221         void *key, *value, *ptr;
 222         struct fd f;
 223         int err;
 224
 225         if (CHECK_ATTR(BPF_MAP_LOOKUP_ELEM))
 226                 return -EINVAL;
 227
 228         f = fdget(ufd);
 229         map = __bpf_map_get(f);
 230         if (IS_ERR(map))
 231                 return PTR_ERR(map);
 232
 233         err = -ENOMEM;
 234         key = kmalloc(map->key_size, GFP_USER);
 235         if (!key)
 236                 goto err_put;
 237
 238         err = -EFAULT;
 239         if (copy_from_user(key, ukey, map->key_size) != 0)
 240                 goto free_key;
 241
 242         err = -ENOMEM;
 243         value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN);
 244         if (!value)
 245                 goto free_key;
 246
 247         rcu_read_lock();
 248         ptr = map->ops->map_lookup_elem(map, key);
 249         if (ptr)
 250                 memcpy(value, ptr, map->value_size);
 251         rcu_read_unlock();
 252
 253         err = -ENOENT;
 254         if (!ptr)
 255                 goto free_value;
 256
 257         err = -EFAULT;
 258         if (copy_to_user(uvalue, value, map->value_size) != 0)
 259                 goto free_value;
 260
 261         err = 0;
 262
 263 free_value:
 264         kfree(value);
 265 free_key:
 266         kfree(key);
 267 err_put:
 268         fdput(f);
 269         return err;
 270 }
 271
 272 #define BPF_MAP_UPDATE_ELEM_LAST_FIELD flags
 273
 274 static int map_update_elem(union bpf_attr *attr)
 275 {
 276         void __user *ukey = u64_to_ptr(attr->key);
 277         void __user *uvalue = u64_to_ptr(attr->value);
 278         int ufd = attr->map_fd;
 279         struct bpf_map *map;
 280         void *key, *value;
 281         struct fd f;
 282         int err;
 283
 284         if (CHECK_ATTR(BPF_MAP_UPDATE_ELEM))
 285                 return -EINVAL;
 286
 287         f = fdget(ufd);
 288         map = __bpf_map_get(f);
 289         if (IS_ERR(map))
 290                 return PTR_ERR(map);
 291
 292         err = -ENOMEM;
 293         key = kmalloc(map->key_size, GFP_USER);
 294         if (!key)
 295                 goto err_put;
 296
 297         err = -EFAULT;
 298         if (copy_from_user(key, ukey, map->key_size) != 0)
 299                 goto free_key;
 300
 301         err = -ENOMEM;
 302         value = kmalloc(map->value_size, GFP_USER | __GFP_NOWARN);
 303         if (!value)
 304                 goto free_key;
 305
 306         err = -EFAULT;
 307         if (copy_from_user(value, uvalue, map->value_size) != 0)
 308                 goto free_value;
 309
 310         /* eBPF program that use maps are running under rcu_read_lock(),
 311          * therefore all map accessors rely on this fact, so do the same here
 312          */
 313         rcu_read_lock();
 314         err = map->ops->map_update_elem(map, key, value, attr->flags);
 315         rcu_read_unlock();
 316
 317 free_value:
 318         kfree(value);
 319 free_key:
 320         kfree(key);
 321 err_put:
 322         fdput(f);
 323         return err;
 324 }
 325
 326 #define BPF_MAP_DELETE_ELEM_LAST_FIELD key
 327
 328 static int map_delete_elem(union bpf_attr *attr)
 329 {
 330         void __user *ukey = u64_to_ptr(attr->key);
 331         int ufd = attr->map_fd;
 332         struct bpf_map *map;
 333         struct fd f;
 334         void *key;
 335         int err;
 336
 337         if (CHECK_ATTR(BPF_MAP_DELETE_ELEM))
 338                 return -EINVAL;
 339
 340         f = fdget(ufd);
 341         map = __bpf_map_get(f);
 342         if (IS_ERR(map))
 343                 return PTR_ERR(map);
 344
 345         err = -ENOMEM;
 346         key = kmalloc(map->key_size, GFP_USER);
 347         if (!key)
 348                 goto err_put;
 349
 350         err = -EFAULT;
 351         if (copy_from_user(key, ukey, map->key_size) != 0)
 352                 goto free_key;
 353
 354         rcu_read_lock();
 355         err = map->ops->map_delete_elem(map, key);
 356         rcu_read_unlock();
 357
 358 free_key:
 359         kfree(key);
 360 err_put:
 361         fdput(f);
 362         return err;
 363 }
 364
 365 /* last field in 'union bpf_attr' used by this command */
 366 #define BPF_MAP_GET_NEXT_KEY_LAST_FIELD next_key
 367
 368 static int map_get_next_key(union bpf_attr *attr)
 369 {
 370         void __user *ukey = u64_to_ptr(attr->key);
 371         void __user *unext_key = u64_to_ptr(attr->next_key);
 372         int ufd = attr->map_fd;
 373         struct bpf_map *map;
 374         void *key, *next_key;
 375         struct fd f;
 376         int err;
 377
 378         if (CHECK_ATTR(BPF_MAP_GET_NEXT_KEY))
 379                 return -EINVAL;
 380
 381         f = fdget(ufd);
 382         map = __bpf_map_get(f);
 383         if (IS_ERR(map))
 384                 return PTR_ERR(map);
 385
 386         err = -ENOMEM;
 387         key = kmalloc(map->key_size, GFP_USER);
 388         if (!key)
 389                 goto err_put;
 390
 391         err = -EFAULT;
 392         if (copy_from_user(key, ukey, map->key_size) != 0)
 393                 goto free_key;
 394
 395         err = -ENOMEM;
 396         next_key = kmalloc(map->key_size, GFP_USER);
 397         if (!next_key)
 398                 goto free_key;
 399
 400         rcu_read_lock();
 401         err = map->ops->map_get_next_key(map, key, next_key);
 402         rcu_read_unlock();
 403         if (err)
 404                 goto free_next_key;
 405
 406         err = -EFAULT;
 407         if (copy_to_user(unext_key, next_key, map->key_size) != 0)
 408                 goto free_next_key;
 409
 410         err = 0;
 411
 412 free_next_key:
 413         kfree(next_key);
 414 free_key:
 415         kfree(key);
 416 err_put:
 417         fdput(f);
 418         return err;
 419 }
 420
 421 static LIST_HEAD(bpf_prog_types);
 422
 423 static int find_prog_type(enum bpf_prog_type type, struct bpf_prog *prog)
 424 {
 425         struct bpf_prog_type_list *tl;
 426
 427         list_for_each_entry(tl, &bpf_prog_types, list_node) {
 428                 if (tl->type == type) {
 429                         prog->aux->ops = tl->ops;
 430                         prog->type = type;
 431                         return 0;
 432                 }
 433         }
 434
 435         return -EINVAL;
 436 }
 437
 438 void bpf_register_prog_type(struct bpf_prog_type_list *tl)
 439 {
 440         list_add(&tl->list_node, &bpf_prog_types);
 441 }
 442
 443 /* fixup insn->imm field of bpf_call instructions:
 444  * if (insn->imm == BPF_FUNC_map_lookup_elem)
 445  *      insn->imm = bpf_map_lookup_elem - __bpf_call_base;
 446  * else if (insn->imm == BPF_FUNC_map_update_elem)
 447  *      insn->imm = bpf_map_update_elem - __bpf_call_base;
 448  * else ...
 449  *
 450  * this function is called after eBPF program passed verification
 451  */
 452 static void fixup_bpf_calls(struct bpf_prog *prog)
 453 {
 454         const struct bpf_func_proto *fn;
 455         int i;
 456
 457         for (i = 0; i < prog->len; i++) {
 458                 struct bpf_insn *insn = &prog->insnsi[i];
 459
 460                 if (insn->code == (BPF_JMP | BPF_CALL)) {
 461                         /* we reach here when program has bpf_call instructions
 462                          * and it passed bpf_check(), means that
 463                          * ops->get_func_proto must have been supplied, check it
 464                          */
 465                         BUG_ON(!prog->aux->ops->get_func_proto);
 466
 467                         if (insn->imm == BPF_FUNC_get_route_realm)
 468                                 prog->dst_needed = 1;
 469                         if (insn->imm == BPF_FUNC_get_prandom_u32)
 470                                 bpf_user_rnd_init_once();
 471                         if (insn->imm == BPF_FUNC_tail_call) {
 472                                 /* mark bpf_tail_call as different opcode
 473                                  * to avoid conditional branch in
 474                                  * interpeter for every normal call
 475                                  * and to prevent accidental JITing by
 476                                  * JIT compiler that doesn't support
 477                                  * bpf_tail_call yet
 478                                  */
 479                                 insn->imm = 0;
 480                                 insn->code |= BPF_X;
 481                                 continue;
 482                         }
 483
 484                         fn = prog->aux->ops->get_func_proto(insn->imm);
 485                         /* all functions that have prototype and verifier allowed
 486                          * programs to call them, must be real in-kernel functions
 487                          */
 488                         BUG_ON(!fn->func);
 489                         insn->imm = fn->func - __bpf_call_base;
 490                 }
 491         }
 492 }
 493
 494 /* drop refcnt on maps used by eBPF program and free auxilary data */
 495 static void free_used_maps(struct bpf_prog_aux *aux)
 496 {
 497         int i;
 498
 499         for (i = 0; i < aux->used_map_cnt; i++)
 500                 bpf_map_put(aux->used_maps[i]);
 501
 502         kfree(aux->used_maps);
 503 }
 504
 505 static int bpf_prog_charge_memlock(struct bpf_prog *prog)
 506 {
 507         struct user_struct *user = get_current_user();
 508         unsigned long memlock_limit;
 509
 510         memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
 511
 512         atomic_long_add(prog->pages, &user->locked_vm);
 513         if (atomic_long_read(&user->locked_vm) > memlock_limit) {
 514                 atomic_long_sub(prog->pages, &user->locked_vm);
 515                 free_uid(user);
 516                 return -EPERM;
 517         }
 518         prog->aux->user = user;
 519         return 0;
 520 }
 521
 522 static void bpf_prog_uncharge_memlock(struct bpf_prog *prog)
 523 {
 524         struct user_struct *user = prog->aux->user;
 525
 526         atomic_long_sub(prog->pages, &user->locked_vm);
 527         free_uid(user);
 528 }
 529
 530 static void __prog_put_common(struct rcu_head *rcu)
 531 {
 532         struct bpf_prog_aux *aux = container_of(rcu, struct bpf_prog_aux, rcu);
 533
 534         free_used_maps(aux);
 535         bpf_prog_uncharge_memlock(aux->prog);
 536         bpf_prog_free(aux->prog);
 537 }
 538
 539 /* version of bpf_prog_put() that is called after a grace period */
 540 void bpf_prog_put_rcu(struct bpf_prog *prog)
 541 {
 542         if (atomic_dec_and_test(&prog->aux->refcnt))
 543                 call_rcu(&prog->aux->rcu, __prog_put_common);
 544 }
 545
 546 void bpf_prog_put(struct bpf_prog *prog)
 547 {
 548         if (atomic_dec_and_test(&prog->aux->refcnt))
 549                 __prog_put_common(&prog->aux->rcu);
 550 }
 551 EXPORT_SYMBOL_GPL(bpf_prog_put);
 552
 553 static int bpf_prog_release(struct inode *inode, struct file *filp)
 554 {
 555         struct bpf_prog *prog = filp->private_data;
 556
 557         bpf_prog_put_rcu(prog);
 558         return 0;
 559 }
 560
 561 static const struct file_operations bpf_prog_fops = {
 562         .release = bpf_prog_release,
 563 };
 564
 565 int bpf_prog_new_fd(struct bpf_prog *prog)
 566 {
 567         return anon_inode_getfd("bpf-prog", &bpf_prog_fops, prog,
 568                                 O_RDWR | O_CLOEXEC);
 569 }
 570
 571 static struct bpf_prog *__bpf_prog_get(struct fd f)
 572 {
 573         if (!f.file)
 574                 return ERR_PTR(-EBADF);
 575         if (f.file->f_op != &bpf_prog_fops) {
 576                 fdput(f);
 577                 return ERR_PTR(-EINVAL);
 578         }
 579
 580         return f.file->private_data;
 581 }
 582
 583 /* called by sockets/tracing/seccomp before attaching program to an event
 584  * pairs with bpf_prog_put()
 585  */
 586 struct bpf_prog *bpf_prog_get(u32 ufd)
 587 {
 588         struct fd f = fdget(ufd);
 589         struct bpf_prog *prog;
 590
 591         prog = __bpf_prog_get(f);
 592         if (IS_ERR(prog))
 593                 return prog;
 594
 595         atomic_inc(&prog->aux->refcnt);
 596         fdput(f);
 597
 598         return prog;
 599 }
 600 EXPORT_SYMBOL_GPL(bpf_prog_get);
 601
 602 /* last field in 'union bpf_attr' used by this command */
 603 #define BPF_PROG_LOAD_LAST_FIELD kern_version
 604
 605 static int bpf_prog_load(union bpf_attr *attr)
 606 {
 607         enum bpf_prog_type type = attr->prog_type;
 608         struct bpf_prog *prog;
 609         int err;
 610         char license[128];
 611         bool is_gpl;
 612
 613         if (CHECK_ATTR(BPF_PROG_LOAD))
 614                 return -EINVAL;
 615
 616         /* copy eBPF program license from user space */
 617         if (strncpy_from_user(license, u64_to_ptr(attr->license),
 618                               sizeof(license) - 1) < 0)
 619                 return -EFAULT;
 620         license[sizeof(license) - 1] = 0;
 621
 622         /* eBPF programs must be GPL compatible to use GPL-ed functions */
 623         is_gpl = license_is_gpl_compatible(license);
 624
 625         if (attr->insn_cnt >= BPF_MAXINSNS)
 626                 return -EINVAL;
 627
 628         if (type == BPF_PROG_TYPE_KPROBE &&
 629             attr->kern_version != LINUX_VERSION_CODE)
 630                 return -EINVAL;
 631
 632         if (type != BPF_PROG_TYPE_SOCKET_FILTER && !capable(CAP_SYS_ADMIN))
 633                 return -EPERM;
 634
 635         /* plain bpf_prog allocation */
 636         prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
 637         if (!prog)
 638                 return -ENOMEM;
 639
 640         err = bpf_prog_charge_memlock(prog);
 641         if (err)
 642                 goto free_prog_nouncharge;
 643
 644         prog->len = attr->insn_cnt;
 645
 646         err = -EFAULT;
 647         if (copy_from_user(prog->insns, u64_to_ptr(attr->insns),
 648                            prog->len * sizeof(struct bpf_insn)) != 0)
 649                 goto free_prog;
 650
 651         prog->orig_prog = NULL;
 652         prog->jited = 0;
 653
 654         atomic_set(&prog->aux->refcnt, 1);
 655         prog->gpl_compatible = is_gpl ? 1 : 0;
 656
 657         /* find program type: socket_filter vs tracing_filter */
 658         err = find_prog_type(type, prog);
 659         if (err < 0)
 660                 goto free_prog;
 661
 662         /* run eBPF verifier */
 663         err = bpf_check(&prog, attr);
 664         if (err < 0)
 665                 goto free_used_maps;
 666
 667         /* fixup BPF_CALL->imm field */
 668         fixup_bpf_calls(prog);
 669
 670         /* eBPF program is ready to be JITed */
 671         err = bpf_prog_select_runtime(prog);
 672         if (err < 0)
 673                 goto free_used_maps;
 674
 675         err = bpf_prog_new_fd(prog);
 676         if (err < 0)
 677                 /* failed to allocate fd */
 678                 goto free_used_maps;
 679
 680         return err;
 681
 682 free_used_maps:
 683         free_used_maps(prog->aux);
 684 free_prog:
 685         bpf_prog_uncharge_memlock(prog);
 686 free_prog_nouncharge:
 687         bpf_prog_free(prog);
 688         return err;
 689 }
 690
 691 #define BPF_OBJ_LAST_FIELD bpf_fd
 692
 693 static int bpf_obj_pin(const union bpf_attr *attr)
 694 {
 695         if (CHECK_ATTR(BPF_OBJ))
 696                 return -EINVAL;
 697
 698         return bpf_obj_pin_user(attr->bpf_fd, u64_to_ptr(attr->pathname));
 699 }
 700
 701 static int bpf_obj_get(const union bpf_attr *attr)
 702 {
 703         if (CHECK_ATTR(BPF_OBJ) || attr->bpf_fd != 0)
 704                 return -EINVAL;
 705
 706         return bpf_obj_get_user(u64_to_ptr(attr->pathname));
 707 }
 708
 709 SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
 710 {
 711         union bpf_attr attr = {};
 712         int err;
 713
 714         if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled)
 715                 return -EPERM;
 716
 717         if (!access_ok(VERIFY_READ, uattr, 1))
 718                 return -EFAULT;
 719
 720         if (size > PAGE_SIZE)   /* silly large */
 721                 return -E2BIG;
 722
 723         /* If we're handed a bigger struct than we know of,
 724          * ensure all the unknown bits are 0 - i.e. new
 725          * user-space does not rely on any kernel feature
 726          * extensions we dont know about yet.
 727          */
 728         if (size > sizeof(attr)) {
 729                 unsigned char __user *addr;
 730                 unsigned char __user *end;
 731                 unsigned char val;
 732
 733                 addr = (void __user *)uattr + sizeof(attr);
 734                 end  = (void __user *)uattr + size;
 735
 736                 for (; addr < end; addr++) {
 737                         err = get_user(val, addr);
 738                         if (err)
 739                                 return err;
 740                         if (val)
 741                                 return -E2BIG;
 742                 }
 743                 size = sizeof(attr);
 744         }
 745
 746         /* copy attributes from user space, may be less than sizeof(bpf_attr) */
 747         if (copy_from_user(&attr, uattr, size) != 0)
 748                 return -EFAULT;
 749
 750         switch (cmd) {
 751         case BPF_MAP_CREATE:
 752                 err = map_create(&attr);
 753                 break;
 754         case BPF_MAP_LOOKUP_ELEM:
 755                 err = map_lookup_elem(&attr);
 756                 break;
 757         case BPF_MAP_UPDATE_ELEM:
 758                 err = map_update_elem(&attr);
 759                 break;
 760         case BPF_MAP_DELETE_ELEM:
 761                 err = map_delete_elem(&attr);
 762                 break;
 763         case BPF_MAP_GET_NEXT_KEY:
 764                 err = map_get_next_key(&attr);
 765                 break;
 766         case BPF_PROG_LOAD:
 767                 err = bpf_prog_load(&attr);
 768                 break;
 769         case BPF_OBJ_PIN:
 770                 err = bpf_obj_pin(&attr);
 771                 break;
 772         case BPF_OBJ_GET:
 773                 err = bpf_obj_get(&attr);
 774                 break;
 775         default:
 776                 err = -EINVAL;
 777                 break;
 778         }
 779
 780         return err;
 781 }