1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Minimal file system backend for holding eBPF maps and programs, 4 * used by bpf(2) object pinning. 5 * 6 * Authors: 7 * 8 * Daniel Borkmann <daniel@iogearbox.net> 9 */ 10 11 #include <linux/init.h> 12 #include <linux/magic.h> 13 #include <linux/major.h> 14 #include <linux/mount.h> 15 #include <linux/namei.h> 16 #include <linux/fs.h> 17 #include <linux/kdev_t.h> 18 #include <linux/parser.h> 19 #include <linux/filter.h> 20 #include <linux/bpf.h> 21 #include <linux/bpf_trace.h> 22 23 enum bpf_type { 24 BPF_TYPE_UNSPEC = 0, 25 BPF_TYPE_PROG, 26 BPF_TYPE_MAP, 27 }; 28 29 static void *bpf_any_get(void *raw, enum bpf_type type) 30 { 31 switch (type) { 32 case BPF_TYPE_PROG: 33 raw = bpf_prog_inc(raw); 34 break; 35 case BPF_TYPE_MAP: 36 raw = bpf_map_inc(raw, true); 37 break; 38 default: 39 WARN_ON_ONCE(1); 40 break; 41 } 42 43 return raw; 44 } 45 46 static void bpf_any_put(void *raw, enum bpf_type type) 47 { 48 switch (type) { 49 case BPF_TYPE_PROG: 50 bpf_prog_put(raw); 51 break; 52 case BPF_TYPE_MAP: 53 bpf_map_put_with_uref(raw); 54 break; 55 default: 56 WARN_ON_ONCE(1); 57 break; 58 } 59 } 60 61 static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type) 62 { 63 void *raw; 64 65 *type = BPF_TYPE_MAP; 66 raw = bpf_map_get_with_uref(ufd); 67 if (IS_ERR(raw)) { 68 *type = BPF_TYPE_PROG; 69 raw = bpf_prog_get(ufd); 70 } 71 72 return raw; 73 } 74 75 static const struct inode_operations bpf_dir_iops; 76 77 static const struct inode_operations bpf_prog_iops = { }; 78 static const struct inode_operations bpf_map_iops = { }; 79 80 static struct inode *bpf_get_inode(struct super_block *sb, 81 const struct inode *dir, 82 umode_t mode) 83 { 84 struct inode *inode; 85 86 switch (mode & S_IFMT) { 87 case S_IFDIR: 88 case S_IFREG: 89 case S_IFLNK: 90 break; 91 default: 92 return ERR_PTR(-EINVAL); 93 } 94 95 inode = new_inode(sb); 96 if (!inode) 97 return ERR_PTR(-ENOSPC); 98 99 inode->i_ino = get_next_ino(); 100 inode->i_atime = current_time(inode); 101 inode->i_mtime = inode->i_atime; 102 inode->i_ctime = inode->i_atime; 103 104 inode_init_owner(inode, dir, mode); 105 106 return inode; 107 } 108 109 static int bpf_inode_type(const struct inode *inode, enum bpf_type *type) 110 { 111 *type = BPF_TYPE_UNSPEC; 112 if (inode->i_op == &bpf_prog_iops) 113 *type = BPF_TYPE_PROG; 114 else if (inode->i_op == &bpf_map_iops) 115 *type = BPF_TYPE_MAP; 116 else 117 return -EACCES; 118 119 return 0; 120 } 121 122 static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode, 123 struct inode *dir) 124 { 125 d_instantiate(dentry, inode); 126 dget(dentry); 127 128 dir->i_mtime = current_time(dir); 129 dir->i_ctime = dir->i_mtime; 130 } 131 132 static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 133 { 134 struct inode *inode; 135 136 inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR); 137 if (IS_ERR(inode)) 138 return PTR_ERR(inode); 139 140 inode->i_op = &bpf_dir_iops; 141 inode->i_fop = &simple_dir_operations; 142 143 inc_nlink(inode); 144 inc_nlink(dir); 145 146 bpf_dentry_finalize(dentry, inode, dir); 147 return 0; 148 } 149 150 struct map_iter { 151 void *key; 152 bool done; 153 }; 154 155 static struct map_iter *map_iter(struct seq_file *m) 156 { 157 return m->private; 158 } 159 160 static struct bpf_map *seq_file_to_map(struct seq_file *m) 161 { 162 return file_inode(m->file)->i_private; 163 } 164 165 static void map_iter_free(struct map_iter *iter) 166 { 167 if (iter) { 168 kfree(iter->key); 169 kfree(iter); 170 } 171 } 172 173 static struct map_iter *map_iter_alloc(struct bpf_map *map) 174 { 175 struct map_iter *iter; 176 177 iter = kzalloc(sizeof(*iter), GFP_KERNEL | __GFP_NOWARN); 178 if (!iter) 179 goto error; 180 181 iter->key = kzalloc(map->key_size, GFP_KERNEL | __GFP_NOWARN); 182 if (!iter->key) 183 goto error; 184 185 return iter; 186 187 error: 188 map_iter_free(iter); 189 return NULL; 190 } 191 192 static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos) 193 { 194 struct bpf_map *map = seq_file_to_map(m); 195 void *key = map_iter(m)->key; 196 void *prev_key; 197 198 if (map_iter(m)->done) 199 return NULL; 200 201 if (unlikely(v == SEQ_START_TOKEN)) 202 prev_key = NULL; 203 else 204 prev_key = key; 205 206 if (map->ops->map_get_next_key(map, prev_key, key)) { 207 map_iter(m)->done = true; 208 return NULL; 209 } 210 211 ++(*pos); 212 return key; 213 } 214 215 static void *map_seq_start(struct seq_file *m, loff_t *pos) 216 { 217 if (map_iter(m)->done) 218 return NULL; 219 220 return *pos ? map_iter(m)->key : SEQ_START_TOKEN; 221 } 222 223 static void map_seq_stop(struct seq_file *m, void *v) 224 { 225 } 226 227 static int map_seq_show(struct seq_file *m, void *v) 228 { 229 struct bpf_map *map = seq_file_to_map(m); 230 void *key = map_iter(m)->key; 231 232 if (unlikely(v == SEQ_START_TOKEN)) { 233 seq_puts(m, "# WARNING!! The output is for debug purpose only\n"); 234 seq_puts(m, "# WARNING!! The output format will change\n"); 235 } else { 236 map->ops->map_seq_show_elem(map, key, m); 237 } 238 239 return 0; 240 } 241 242 static const struct seq_operations bpffs_map_seq_ops = { 243 .start = map_seq_start, 244 .next = map_seq_next, 245 .show = map_seq_show, 246 .stop = map_seq_stop, 247 }; 248 249 static int bpffs_map_open(struct inode *inode, struct file *file) 250 { 251 struct bpf_map *map = inode->i_private; 252 struct map_iter *iter; 253 struct seq_file *m; 254 int err; 255 256 iter = map_iter_alloc(map); 257 if (!iter) 258 return -ENOMEM; 259 260 err = seq_open(file, &bpffs_map_seq_ops); 261 if (err) { 262 map_iter_free(iter); 263 return err; 264 } 265 266 m = file->private_data; 267 m->private = iter; 268 269 return 0; 270 } 271 272 static int bpffs_map_release(struct inode *inode, struct file *file) 273 { 274 struct seq_file *m = file->private_data; 275 276 map_iter_free(map_iter(m)); 277 278 return seq_release(inode, file); 279 } 280 281 /* bpffs_map_fops should only implement the basic 282 * read operation for a BPF map. The purpose is to 283 * provide a simple user intuitive way to do 284 * "cat bpffs/pathto/a-pinned-map". 285 * 286 * Other operations (e.g. write, lookup...) should be realized by 287 * the userspace tools (e.g. bpftool) through the 288 * BPF_OBJ_GET_INFO_BY_FD and the map's lookup/update 289 * interface. 290 */ 291 static const struct file_operations bpffs_map_fops = { 292 .open = bpffs_map_open, 293 .read = seq_read, 294 .release = bpffs_map_release, 295 }; 296 297 static int bpffs_obj_open(struct inode *inode, struct file *file) 298 { 299 return -EIO; 300 } 301 302 static const struct file_operations bpffs_obj_fops = { 303 .open = bpffs_obj_open, 304 }; 305 306 static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw, 307 const struct inode_operations *iops, 308 const struct file_operations *fops) 309 { 310 struct inode *dir = dentry->d_parent->d_inode; 311 struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode); 312 if (IS_ERR(inode)) 313 return PTR_ERR(inode); 314 315 inode->i_op = iops; 316 inode->i_fop = fops; 317 inode->i_private = raw; 318 319 bpf_dentry_finalize(dentry, inode, dir); 320 return 0; 321 } 322 323 static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg) 324 { 325 return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops, 326 &bpffs_obj_fops); 327 } 328 329 static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg) 330 { 331 struct bpf_map *map = arg; 332 333 return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops, 334 bpf_map_support_seq_show(map) ? 335 &bpffs_map_fops : &bpffs_obj_fops); 336 } 337 338 static struct dentry * 339 bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags) 340 { 341 /* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future 342 * extensions. 343 */ 344 if (strchr(dentry->d_name.name, '.')) 345 return ERR_PTR(-EPERM); 346 347 return simple_lookup(dir, dentry, flags); 348 } 349 350 static int bpf_symlink(struct inode *dir, struct dentry *dentry, 351 const char *target) 352 { 353 char *link = kstrdup(target, GFP_USER | __GFP_NOWARN); 354 struct inode *inode; 355 356 if (!link) 357 return -ENOMEM; 358 359 inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK); 360 if (IS_ERR(inode)) { 361 kfree(link); 362 return PTR_ERR(inode); 363 } 364 365 inode->i_op = &simple_symlink_inode_operations; 366 inode->i_link = link; 367 368 bpf_dentry_finalize(dentry, inode, dir); 369 return 0; 370 } 371 372 static const struct inode_operations bpf_dir_iops = { 373 .lookup = bpf_lookup, 374 .mkdir = bpf_mkdir, 375 .symlink = bpf_symlink, 376 .rmdir = simple_rmdir, 377 .rename = simple_rename, 378 .link = simple_link, 379 .unlink = simple_unlink, 380 }; 381 382 static int bpf_obj_do_pin(const struct filename *pathname, void *raw, 383 enum bpf_type type) 384 { 385 struct dentry *dentry; 386 struct inode *dir; 387 struct path path; 388 umode_t mode; 389 int ret; 390 391 dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0); 392 if (IS_ERR(dentry)) 393 return PTR_ERR(dentry); 394 395 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 396 397 ret = security_path_mknod(&path, dentry, mode, 0); 398 if (ret) 399 goto out; 400 401 dir = d_inode(path.dentry); 402 if (dir->i_op != &bpf_dir_iops) { 403 ret = -EPERM; 404 goto out; 405 } 406 407 switch (type) { 408 case BPF_TYPE_PROG: 409 ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw); 410 break; 411 case BPF_TYPE_MAP: 412 ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw); 413 break; 414 default: 415 ret = -EPERM; 416 } 417 out: 418 done_path_create(&path, dentry); 419 return ret; 420 } 421 422 int bpf_obj_pin_user(u32 ufd, const char __user *pathname) 423 { 424 struct filename *pname; 425 enum bpf_type type; 426 void *raw; 427 int ret; 428 429 pname = getname(pathname); 430 if (IS_ERR(pname)) 431 return PTR_ERR(pname); 432 433 raw = bpf_fd_probe_obj(ufd, &type); 434 if (IS_ERR(raw)) { 435 ret = PTR_ERR(raw); 436 goto out; 437 } 438 439 ret = bpf_obj_do_pin(pname, raw, type); 440 if (ret != 0) 441 bpf_any_put(raw, type); 442 out: 443 putname(pname); 444 return ret; 445 } 446 447 static void *bpf_obj_do_get(const struct filename *pathname, 448 enum bpf_type *type, int flags) 449 { 450 struct inode *inode; 451 struct path path; 452 void *raw; 453 int ret; 454 455 ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path); 456 if (ret) 457 return ERR_PTR(ret); 458 459 inode = d_backing_inode(path.dentry); 460 ret = inode_permission(inode, ACC_MODE(flags)); 461 if (ret) 462 goto out; 463 464 ret = bpf_inode_type(inode, type); 465 if (ret) 466 goto out; 467 468 raw = bpf_any_get(inode->i_private, *type); 469 if (!IS_ERR(raw)) 470 touch_atime(&path); 471 472 path_put(&path); 473 return raw; 474 out: 475 path_put(&path); 476 return ERR_PTR(ret); 477 } 478 479 int bpf_obj_get_user(const char __user *pathname, int flags) 480 { 481 enum bpf_type type = BPF_TYPE_UNSPEC; 482 struct filename *pname; 483 int ret = -ENOENT; 484 int f_flags; 485 void *raw; 486 487 f_flags = bpf_get_file_flag(flags); 488 if (f_flags < 0) 489 return f_flags; 490 491 pname = getname(pathname); 492 if (IS_ERR(pname)) 493 return PTR_ERR(pname); 494 495 raw = bpf_obj_do_get(pname, &type, f_flags); 496 if (IS_ERR(raw)) { 497 ret = PTR_ERR(raw); 498 goto out; 499 } 500 501 if (type == BPF_TYPE_PROG) 502 ret = bpf_prog_new_fd(raw); 503 else if (type == BPF_TYPE_MAP) 504 ret = bpf_map_new_fd(raw, f_flags); 505 else 506 goto out; 507 508 if (ret < 0) 509 bpf_any_put(raw, type); 510 out: 511 putname(pname); 512 return ret; 513 } 514 515 static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type) 516 { 517 struct bpf_prog *prog; 518 int ret = inode_permission(inode, MAY_READ); 519 if (ret) 520 return ERR_PTR(ret); 521 522 if (inode->i_op == &bpf_map_iops) 523 return ERR_PTR(-EINVAL); 524 if (inode->i_op != &bpf_prog_iops) 525 return ERR_PTR(-EACCES); 526 527 prog = inode->i_private; 528 529 ret = security_bpf_prog(prog); 530 if (ret < 0) 531 return ERR_PTR(ret); 532 533 if (!bpf_prog_get_ok(prog, &type, false)) 534 return ERR_PTR(-EINVAL); 535 536 return bpf_prog_inc(prog); 537 } 538 539 struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type) 540 { 541 struct bpf_prog *prog; 542 struct path path; 543 int ret = kern_path(name, LOOKUP_FOLLOW, &path); 544 if (ret) 545 return ERR_PTR(ret); 546 prog = __get_prog_inode(d_backing_inode(path.dentry), type); 547 if (!IS_ERR(prog)) 548 touch_atime(&path); 549 path_put(&path); 550 return prog; 551 } 552 EXPORT_SYMBOL(bpf_prog_get_type_path); 553 554 /* 555 * Display the mount options in /proc/mounts. 556 */ 557 static int bpf_show_options(struct seq_file *m, struct dentry *root) 558 { 559 umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX; 560 561 if (mode != S_IRWXUGO) 562 seq_printf(m, ",mode=%o", mode); 563 return 0; 564 } 565 566 static void bpf_free_inode(struct inode *inode) 567 { 568 enum bpf_type type; 569 570 if (S_ISLNK(inode->i_mode)) 571 kfree(inode->i_link); 572 if (!bpf_inode_type(inode, &type)) 573 bpf_any_put(inode->i_private, type); 574 free_inode_nonrcu(inode); 575 } 576 577 static const struct super_operations bpf_super_ops = { 578 .statfs = simple_statfs, 579 .drop_inode = generic_delete_inode, 580 .show_options = bpf_show_options, 581 .free_inode = bpf_free_inode, 582 }; 583 584 enum { 585 OPT_MODE, 586 OPT_ERR, 587 }; 588 589 static const match_table_t bpf_mount_tokens = { 590 { OPT_MODE, "mode=%o" }, 591 { OPT_ERR, NULL }, 592 }; 593 594 struct bpf_mount_opts { 595 umode_t mode; 596 }; 597 598 static int bpf_parse_options(char *data, struct bpf_mount_opts *opts) 599 { 600 substring_t args[MAX_OPT_ARGS]; 601 int option, token; 602 char *ptr; 603 604 opts->mode = S_IRWXUGO; 605 606 while ((ptr = strsep(&data, ",")) != NULL) { 607 if (!*ptr) 608 continue; 609 610 token = match_token(ptr, bpf_mount_tokens, args); 611 switch (token) { 612 case OPT_MODE: 613 if (match_octal(&args[0], &option)) 614 return -EINVAL; 615 opts->mode = option & S_IALLUGO; 616 break; 617 /* We might like to report bad mount options here, but 618 * traditionally we've ignored all mount options, so we'd 619 * better continue to ignore non-existing options for bpf. 620 */ 621 } 622 } 623 624 return 0; 625 } 626 627 static int bpf_fill_super(struct super_block *sb, void *data, int silent) 628 { 629 static const struct tree_descr bpf_rfiles[] = { { "" } }; 630 struct bpf_mount_opts opts; 631 struct inode *inode; 632 int ret; 633 634 ret = bpf_parse_options(data, &opts); 635 if (ret) 636 return ret; 637 638 ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles); 639 if (ret) 640 return ret; 641 642 sb->s_op = &bpf_super_ops; 643 644 inode = sb->s_root->d_inode; 645 inode->i_op = &bpf_dir_iops; 646 inode->i_mode &= ~S_IALLUGO; 647 inode->i_mode |= S_ISVTX | opts.mode; 648 649 return 0; 650 } 651 652 static struct dentry *bpf_mount(struct file_system_type *type, int flags, 653 const char *dev_name, void *data) 654 { 655 return mount_nodev(type, flags, data, bpf_fill_super); 656 } 657 658 static struct file_system_type bpf_fs_type = { 659 .owner = THIS_MODULE, 660 .name = "bpf", 661 .mount = bpf_mount, 662 .kill_sb = kill_litter_super, 663 }; 664 665 static int __init bpf_init(void) 666 { 667 int ret; 668 669 ret = sysfs_create_mount_point(fs_kobj, "bpf"); 670 if (ret) 671 return ret; 672 673 ret = register_filesystem(&bpf_fs_type); 674 if (ret) 675 sysfs_remove_mount_point(fs_kobj, "bpf"); 676 677 return ret; 678 } 679 fs_initcall(bpf_init); 680