kernel/bpf/inode.c

   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/fs_context.h>
  18 #include <linux/fs_parser.h>
  19 #include <linux/kdev_t.h>
  20 #include <linux/filter.h>
  21 #include <linux/bpf.h>
  22 #include <linux/bpf_trace.h>
  23
  24 enum bpf_type {
  25         BPF_TYPE_UNSPEC = 0,
  26         BPF_TYPE_PROG,
  27         BPF_TYPE_MAP,
  28         BPF_TYPE_LINK,
  29 };
  30
  31 static void *bpf_any_get(void *raw, enum bpf_type type)
  32 {
  33         switch (type) {
  34         case BPF_TYPE_PROG:
  35                 bpf_prog_inc(raw);
  36                 break;
  37         case BPF_TYPE_MAP:
  38                 bpf_map_inc_with_uref(raw);
  39                 break;
  40         case BPF_TYPE_LINK:
  41                 bpf_link_inc(raw);
  42                 break;
  43         default:
  44                 WARN_ON_ONCE(1);
  45                 break;
  46         }
  47
  48         return raw;
  49 }
  50
  51 static void bpf_any_put(void *raw, enum bpf_type type)
  52 {
  53         switch (type) {
  54         case BPF_TYPE_PROG:
  55                 bpf_prog_put(raw);
  56                 break;
  57         case BPF_TYPE_MAP:
  58                 bpf_map_put_with_uref(raw);
  59                 break;
  60         case BPF_TYPE_LINK:
  61                 bpf_link_put(raw);
  62                 break;
  63         default:
  64                 WARN_ON_ONCE(1);
  65                 break;
  66         }
  67 }
  68
  69 static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type)
  70 {
  71         void *raw;
  72
  73         raw = bpf_map_get_with_uref(ufd);
  74         if (!IS_ERR(raw)) {
  75                 *type = BPF_TYPE_MAP;
  76                 return raw;
  77         }
  78
  79         raw = bpf_prog_get(ufd);
  80         if (!IS_ERR(raw)) {
  81                 *type = BPF_TYPE_PROG;
  82                 return raw;
  83         }
  84
  85         raw = bpf_link_get_from_fd(ufd);
  86         if (!IS_ERR(raw)) {
  87                 *type = BPF_TYPE_LINK;
  88                 return raw;
  89         }
  90
  91         return ERR_PTR(-EINVAL);
  92 }
  93
  94 static const struct inode_operations bpf_dir_iops;
  95
  96 static const struct inode_operations bpf_prog_iops = { };
  97 static const struct inode_operations bpf_map_iops  = { };
  98 static const struct inode_operations bpf_link_iops  = { };
  99
 100 static struct inode *bpf_get_inode(struct super_block *sb,
 101                                    const struct inode *dir,
 102                                    umode_t mode)
 103 {
 104         struct inode *inode;
 105
 106         switch (mode & S_IFMT) {
 107         case S_IFDIR:
 108         case S_IFREG:
 109         case S_IFLNK:
 110                 break;
 111         default:
 112                 return ERR_PTR(-EINVAL);
 113         }
 114
 115         inode = new_inode(sb);
 116         if (!inode)
 117                 return ERR_PTR(-ENOSPC);
 118
 119         inode->i_ino = get_next_ino();
 120         inode->i_atime = current_time(inode);
 121         inode->i_mtime = inode->i_atime;
 122         inode->i_ctime = inode->i_atime;
 123
 124         inode_init_owner(inode, dir, mode);
 125
 126         return inode;
 127 }
 128
 129 static int bpf_inode_type(const struct inode *inode, enum bpf_type *type)
 130 {
 131         *type = BPF_TYPE_UNSPEC;
 132         if (inode->i_op == &bpf_prog_iops)
 133                 *type = BPF_TYPE_PROG;
 134         else if (inode->i_op == &bpf_map_iops)
 135                 *type = BPF_TYPE_MAP;
 136         else if (inode->i_op == &bpf_link_iops)
 137                 *type = BPF_TYPE_LINK;
 138         else
 139                 return -EACCES;
 140
 141         return 0;
 142 }
 143
 144 static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode,
 145                                 struct inode *dir)
 146 {
 147         d_instantiate(dentry, inode);
 148         dget(dentry);
 149
 150         dir->i_mtime = current_time(dir);
 151         dir->i_ctime = dir->i_mtime;
 152 }
 153
 154 static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 155 {
 156         struct inode *inode;
 157
 158         inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR);
 159         if (IS_ERR(inode))
 160                 return PTR_ERR(inode);
 161
 162         inode->i_op = &bpf_dir_iops;
 163         inode->i_fop = &simple_dir_operations;
 164
 165         inc_nlink(inode);
 166         inc_nlink(dir);
 167
 168         bpf_dentry_finalize(dentry, inode, dir);
 169         return 0;
 170 }
 171
 172 struct map_iter {
 173         void *key;
 174         bool done;
 175 };
 176
 177 static struct map_iter *map_iter(struct seq_file *m)
 178 {
 179         return m->private;
 180 }
 181
 182 static struct bpf_map *seq_file_to_map(struct seq_file *m)
 183 {
 184         return file_inode(m->file)->i_private;
 185 }
 186
 187 static void map_iter_free(struct map_iter *iter)
 188 {
 189         if (iter) {
 190                 kfree(iter->key);
 191                 kfree(iter);
 192         }
 193 }
 194
 195 static struct map_iter *map_iter_alloc(struct bpf_map *map)
 196 {
 197         struct map_iter *iter;
 198
 199         iter = kzalloc(sizeof(*iter), GFP_KERNEL | __GFP_NOWARN);
 200         if (!iter)
 201                 goto error;
 202
 203         iter->key = kzalloc(map->key_size, GFP_KERNEL | __GFP_NOWARN);
 204         if (!iter->key)
 205                 goto error;
 206
 207         return iter;
 208
 209 error:
 210         map_iter_free(iter);
 211         return NULL;
 212 }
 213
 214 static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos)
 215 {
 216         struct bpf_map *map = seq_file_to_map(m);
 217         void *key = map_iter(m)->key;
 218         void *prev_key;
 219
 220         (*pos)++;
 221         if (map_iter(m)->done)
 222                 return NULL;
 223
 224         if (unlikely(v == SEQ_START_TOKEN))
 225                 prev_key = NULL;
 226         else
 227                 prev_key = key;
 228
 229         if (map->ops->map_get_next_key(map, prev_key, key)) {
 230                 map_iter(m)->done = true;
 231                 return NULL;
 232         }
 233         return key;
 234 }
 235
 236 static void *map_seq_start(struct seq_file *m, loff_t *pos)
 237 {
 238         if (map_iter(m)->done)
 239                 return NULL;
 240
 241         return *pos ? map_iter(m)->key : SEQ_START_TOKEN;
 242 }
 243
 244 static void map_seq_stop(struct seq_file *m, void *v)
 245 {
 246 }
 247
 248 static int map_seq_show(struct seq_file *m, void *v)
 249 {
 250         struct bpf_map *map = seq_file_to_map(m);
 251         void *key = map_iter(m)->key;
 252
 253         if (unlikely(v == SEQ_START_TOKEN)) {
 254                 seq_puts(m, "# WARNING!! The output is for debug purpose only\n");
 255                 seq_puts(m, "# WARNING!! The output format will change\n");
 256         } else {
 257                 map->ops->map_seq_show_elem(map, key, m);
 258         }
 259
 260         return 0;
 261 }
 262
 263 static const struct seq_operations bpffs_map_seq_ops = {
 264         .start  = map_seq_start,
 265         .next   = map_seq_next,
 266         .show   = map_seq_show,
 267         .stop   = map_seq_stop,
 268 };
 269
 270 static int bpffs_map_open(struct inode *inode, struct file *file)
 271 {
 272         struct bpf_map *map = inode->i_private;
 273         struct map_iter *iter;
 274         struct seq_file *m;
 275         int err;
 276
 277         iter = map_iter_alloc(map);
 278         if (!iter)
 279                 return -ENOMEM;
 280
 281         err = seq_open(file, &bpffs_map_seq_ops);
 282         if (err) {
 283                 map_iter_free(iter);
 284                 return err;
 285         }
 286
 287         m = file->private_data;
 288         m->private = iter;
 289
 290         return 0;
 291 }
 292
 293 static int bpffs_map_release(struct inode *inode, struct file *file)
 294 {
 295         struct seq_file *m = file->private_data;
 296
 297         map_iter_free(map_iter(m));
 298
 299         return seq_release(inode, file);
 300 }
 301
 302 /* bpffs_map_fops should only implement the basic
 303  * read operation for a BPF map.  The purpose is to
 304  * provide a simple user intuitive way to do
 305  * "cat bpffs/pathto/a-pinned-map".
 306  *
 307  * Other operations (e.g. write, lookup...) should be realized by
 308  * the userspace tools (e.g. bpftool) through the
 309  * BPF_OBJ_GET_INFO_BY_FD and the map's lookup/update
 310  * interface.
 311  */
 312 static const struct file_operations bpffs_map_fops = {
 313         .open           = bpffs_map_open,
 314         .read           = seq_read,
 315         .release        = bpffs_map_release,
 316 };
 317
 318 static int bpffs_obj_open(struct inode *inode, struct file *file)
 319 {
 320         return -EIO;
 321 }
 322
 323 static const struct file_operations bpffs_obj_fops = {
 324         .open           = bpffs_obj_open,
 325 };
 326
 327 static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw,
 328                          const struct inode_operations *iops,
 329                          const struct file_operations *fops)
 330 {
 331         struct inode *dir = dentry->d_parent->d_inode;
 332         struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode);
 333         if (IS_ERR(inode))
 334                 return PTR_ERR(inode);
 335
 336         inode->i_op = iops;
 337         inode->i_fop = fops;
 338         inode->i_private = raw;
 339
 340         bpf_dentry_finalize(dentry, inode, dir);
 341         return 0;
 342 }
 343
 344 static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg)
 345 {
 346         return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops,
 347                              &bpffs_obj_fops);
 348 }
 349
 350 static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg)
 351 {
 352         struct bpf_map *map = arg;
 353
 354         return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops,
 355                              bpf_map_support_seq_show(map) ?
 356                              &bpffs_map_fops : &bpffs_obj_fops);
 357 }
 358
 359 static int bpf_mklink(struct dentry *dentry, umode_t mode, void *arg)
 360 {
 361         struct bpf_link *link = arg;
 362
 363         return bpf_mkobj_ops(dentry, mode, arg, &bpf_link_iops,
 364                              bpf_link_is_iter(link) ?
 365                              &bpf_iter_fops : &bpffs_obj_fops);
 366 }
 367
 368 static struct dentry *
 369 bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags)
 370 {
 371         /* Dots in names (e.g. "/sys/fs/bpf/foo.bar") are reserved for future
 372          * extensions.
 373          */
 374         if (strchr(dentry->d_name.name, '.'))
 375                 return ERR_PTR(-EPERM);
 376
 377         return simple_lookup(dir, dentry, flags);
 378 }
 379
 380 static int bpf_symlink(struct inode *dir, struct dentry *dentry,
 381                        const char *target)
 382 {
 383         char *link = kstrdup(target, GFP_USER | __GFP_NOWARN);
 384         struct inode *inode;
 385
 386         if (!link)
 387                 return -ENOMEM;
 388
 389         inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK);
 390         if (IS_ERR(inode)) {
 391                 kfree(link);
 392                 return PTR_ERR(inode);
 393         }
 394
 395         inode->i_op = &simple_symlink_inode_operations;
 396         inode->i_link = link;
 397
 398         bpf_dentry_finalize(dentry, inode, dir);
 399         return 0;
 400 }
 401
 402 static const struct inode_operations bpf_dir_iops = {
 403         .lookup         = bpf_lookup,
 404         .mkdir          = bpf_mkdir,
 405         .symlink        = bpf_symlink,
 406         .rmdir          = simple_rmdir,
 407         .rename         = simple_rename,
 408         .link           = simple_link,
 409         .unlink         = simple_unlink,
 410 };
 411
 412 static int bpf_obj_do_pin(const char __user *pathname, void *raw,
 413                           enum bpf_type type)
 414 {
 415         struct dentry *dentry;
 416         struct inode *dir;
 417         struct path path;
 418         umode_t mode;
 419         int ret;
 420
 421         dentry = user_path_create(AT_FDCWD, pathname, &path, 0);
 422         if (IS_ERR(dentry))
 423                 return PTR_ERR(dentry);
 424
 425         mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask());
 426
 427         ret = security_path_mknod(&path, dentry, mode, 0);
 428         if (ret)
 429                 goto out;
 430
 431         dir = d_inode(path.dentry);
 432         if (dir->i_op != &bpf_dir_iops) {
 433                 ret = -EPERM;
 434                 goto out;
 435         }
 436
 437         switch (type) {
 438         case BPF_TYPE_PROG:
 439                 ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw);
 440                 break;
 441         case BPF_TYPE_MAP:
 442                 ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw);
 443                 break;
 444         case BPF_TYPE_LINK:
 445                 ret = vfs_mkobj(dentry, mode, bpf_mklink, raw);
 446                 break;
 447         default:
 448                 ret = -EPERM;
 449         }
 450 out:
 451         done_path_create(&path, dentry);
 452         return ret;
 453 }
 454
 455 int bpf_obj_pin_user(u32 ufd, const char __user *pathname)
 456 {
 457         enum bpf_type type;
 458         void *raw;
 459         int ret;
 460
 461         raw = bpf_fd_probe_obj(ufd, &type);
 462         if (IS_ERR(raw))
 463                 return PTR_ERR(raw);
 464
 465         ret = bpf_obj_do_pin(pathname, raw, type);
 466         if (ret != 0)
 467                 bpf_any_put(raw, type);
 468
 469         return ret;
 470 }
 471
 472 static void *bpf_obj_do_get(const char __user *pathname,
 473                             enum bpf_type *type, int flags)
 474 {
 475         struct inode *inode;
 476         struct path path;
 477         void *raw;
 478         int ret;
 479
 480         ret = user_path_at(AT_FDCWD, pathname, LOOKUP_FOLLOW, &path);
 481         if (ret)
 482                 return ERR_PTR(ret);
 483
 484         inode = d_backing_inode(path.dentry);
 485         ret = inode_permission(inode, ACC_MODE(flags));
 486         if (ret)
 487                 goto out;
 488
 489         ret = bpf_inode_type(inode, type);
 490         if (ret)
 491                 goto out;
 492
 493         raw = bpf_any_get(inode->i_private, *type);
 494         if (!IS_ERR(raw))
 495                 touch_atime(&path);
 496
 497         path_put(&path);
 498         return raw;
 499 out:
 500         path_put(&path);
 501         return ERR_PTR(ret);
 502 }
 503
 504 int bpf_obj_get_user(const char __user *pathname, int flags)
 505 {
 506         enum bpf_type type = BPF_TYPE_UNSPEC;
 507         int f_flags;
 508         void *raw;
 509         int ret;
 510
 511         f_flags = bpf_get_file_flag(flags);
 512         if (f_flags < 0)
 513                 return f_flags;
 514
 515         raw = bpf_obj_do_get(pathname, &type, f_flags);
 516         if (IS_ERR(raw))
 517                 return PTR_ERR(raw);
 518
 519         if (type == BPF_TYPE_PROG)
 520                 ret = bpf_prog_new_fd(raw);
 521         else if (type == BPF_TYPE_MAP)
 522                 ret = bpf_map_new_fd(raw, f_flags);
 523         else if (type == BPF_TYPE_LINK)
 524                 ret = bpf_link_new_fd(raw);
 525         else
 526                 return -ENOENT;
 527
 528         if (ret < 0)
 529                 bpf_any_put(raw, type);
 530         return ret;
 531 }
 532
 533 static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type)
 534 {
 535         struct bpf_prog *prog;
 536         int ret = inode_permission(inode, MAY_READ);
 537         if (ret)
 538                 return ERR_PTR(ret);
 539
 540         if (inode->i_op == &bpf_map_iops)
 541                 return ERR_PTR(-EINVAL);
 542         if (inode->i_op == &bpf_link_iops)
 543                 return ERR_PTR(-EINVAL);
 544         if (inode->i_op != &bpf_prog_iops)
 545                 return ERR_PTR(-EACCES);
 546
 547         prog = inode->i_private;
 548
 549         ret = security_bpf_prog(prog);
 550         if (ret < 0)
 551                 return ERR_PTR(ret);
 552
 553         if (!bpf_prog_get_ok(prog, &type, false))
 554                 return ERR_PTR(-EINVAL);
 555
 556         bpf_prog_inc(prog);
 557         return prog;
 558 }
 559
 560 struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type)
 561 {
 562         struct bpf_prog *prog;
 563         struct path path;
 564         int ret = kern_path(name, LOOKUP_FOLLOW, &path);
 565         if (ret)
 566                 return ERR_PTR(ret);
 567         prog = __get_prog_inode(d_backing_inode(path.dentry), type);
 568         if (!IS_ERR(prog))
 569                 touch_atime(&path);
 570         path_put(&path);
 571         return prog;
 572 }
 573 EXPORT_SYMBOL(bpf_prog_get_type_path);
 574
 575 /*
 576  * Display the mount options in /proc/mounts.
 577  */
 578 static int bpf_show_options(struct seq_file *m, struct dentry *root)
 579 {
 580         umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX;
 581
 582         if (mode != S_IRWXUGO)
 583                 seq_printf(m, ",mode=%o", mode);
 584         return 0;
 585 }
 586
 587 static void bpf_free_inode(struct inode *inode)
 588 {
 589         enum bpf_type type;
 590
 591         if (S_ISLNK(inode->i_mode))
 592                 kfree(inode->i_link);
 593         if (!bpf_inode_type(inode, &type))
 594                 bpf_any_put(inode->i_private, type);
 595         free_inode_nonrcu(inode);
 596 }
 597
 598 static const struct super_operations bpf_super_ops = {
 599         .statfs         = simple_statfs,
 600         .drop_inode     = generic_delete_inode,
 601         .show_options   = bpf_show_options,
 602         .free_inode     = bpf_free_inode,
 603 };
 604
 605 enum {
 606         OPT_MODE,
 607 };
 608
 609 static const struct fs_parameter_spec bpf_fs_parameters[] = {
 610         fsparam_u32oct  ("mode",                        OPT_MODE),
 611         {}
 612 };
 613
 614 struct bpf_mount_opts {
 615         umode_t mode;
 616 };
 617
 618 static int bpf_parse_param(struct fs_context *fc, struct fs_parameter *param)
 619 {
 620         struct bpf_mount_opts *opts = fc->fs_private;
 621         struct fs_parse_result result;
 622         int opt;
 623
 624         opt = fs_parse(fc, bpf_fs_parameters, param, &result);
 625         if (opt < 0)
 626                 /* We might like to report bad mount options here, but
 627                  * traditionally we've ignored all mount options, so we'd
 628                  * better continue to ignore non-existing options for bpf.
 629                  */
 630                 return opt == -ENOPARAM ? 0 : opt;
 631
 632         switch (opt) {
 633         case OPT_MODE:
 634                 opts->mode = result.uint_32 & S_IALLUGO;
 635                 break;
 636         }
 637
 638         return 0;
 639 }
 640
 641 static int bpf_fill_super(struct super_block *sb, struct fs_context *fc)
 642 {
 643         static const struct tree_descr bpf_rfiles[] = { { "" } };
 644         struct bpf_mount_opts *opts = fc->fs_private;
 645         struct inode *inode;
 646         int ret;
 647
 648         ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles);
 649         if (ret)
 650                 return ret;
 651
 652         sb->s_op = &bpf_super_ops;
 653
 654         inode = sb->s_root->d_inode;
 655         inode->i_op = &bpf_dir_iops;
 656         inode->i_mode &= ~S_IALLUGO;
 657         inode->i_mode |= S_ISVTX | opts->mode;
 658
 659         return 0;
 660 }
 661
 662 static int bpf_get_tree(struct fs_context *fc)
 663 {
 664         return get_tree_nodev(fc, bpf_fill_super);
 665 }
 666
 667 static void bpf_free_fc(struct fs_context *fc)
 668 {
 669         kfree(fc->fs_private);
 670 }
 671
 672 static const struct fs_context_operations bpf_context_ops = {
 673         .free           = bpf_free_fc,
 674         .parse_param    = bpf_parse_param,
 675         .get_tree       = bpf_get_tree,
 676 };
 677
 678 /*
 679  * Set up the filesystem mount context.
 680  */
 681 static int bpf_init_fs_context(struct fs_context *fc)
 682 {
 683         struct bpf_mount_opts *opts;
 684
 685         opts = kzalloc(sizeof(struct bpf_mount_opts), GFP_KERNEL);
 686         if (!opts)
 687                 return -ENOMEM;
 688
 689         opts->mode = S_IRWXUGO;
 690
 691         fc->fs_private = opts;
 692         fc->ops = &bpf_context_ops;
 693         return 0;
 694 }
 695
 696 static struct file_system_type bpf_fs_type = {
 697         .owner          = THIS_MODULE,
 698         .name           = "bpf",
 699         .init_fs_context = bpf_init_fs_context,
 700         .parameters     = bpf_fs_parameters,
 701         .kill_sb        = kill_litter_super,
 702 };
 703
 704 static int __init bpf_init(void)
 705 {
 706         int ret;
 707
 708         ret = sysfs_create_mount_point(fs_kobj, "bpf");
 709         if (ret)
 710                 return ret;
 711
 712         ret = register_filesystem(&bpf_fs_type);
 713         if (ret)
 714                 sysfs_remove_mount_point(fs_kobj, "bpf");
 715
 716         return ret;
 717 }
 718 fs_initcall(bpf_init);