1 /* 2 * Minimal file system backend for holding eBPF maps and programs, 3 * used by bpf(2) object pinning. 4 * 5 * Authors: 6 * 7 * Daniel Borkmann <daniel@iogearbox.net> 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License 11 * version 2 as published by the Free Software Foundation. 12 */ 13 14 #include <linux/init.h> 15 #include <linux/magic.h> 16 #include <linux/major.h> 17 #include <linux/mount.h> 18 #include <linux/namei.h> 19 #include <linux/fs.h> 20 #include <linux/kdev_t.h> 21 #include <linux/parser.h> 22 #include <linux/filter.h> 23 #include <linux/bpf.h> 24 #include <linux/bpf_trace.h> 25 26 enum bpf_type { 27 BPF_TYPE_UNSPEC = 0, 28 BPF_TYPE_PROG, 29 BPF_TYPE_MAP, 30 }; 31 32 static void *bpf_any_get(void *raw, enum bpf_type type) 33 { 34 switch (type) { 35 case BPF_TYPE_PROG: 36 raw = bpf_prog_inc(raw); 37 break; 38 case BPF_TYPE_MAP: 39 raw = bpf_map_inc(raw, true); 40 break; 41 default: 42 WARN_ON_ONCE(1); 43 break; 44 } 45 46 return raw; 47 } 48 49 static void bpf_any_put(void *raw, enum bpf_type type) 50 { 51 switch (type) { 52 case BPF_TYPE_PROG: 53 bpf_prog_put(raw); 54 break; 55 case BPF_TYPE_MAP: 56 bpf_map_put_with_uref(raw); 57 break; 58 default: 59 WARN_ON_ONCE(1); 60 break; 61 } 62 } 63 64 static void *bpf_fd_probe_obj(u32 ufd, enum bpf_type *type) 65 { 66 void *raw; 67 68 *type = BPF_TYPE_MAP; 69 raw = bpf_map_get_with_uref(ufd); 70 if (IS_ERR(raw)) { 71 *type = BPF_TYPE_PROG; 72 raw = bpf_prog_get(ufd); 73 } 74 75 return raw; 76 } 77 78 static const struct inode_operations bpf_dir_iops; 79 80 static const struct inode_operations bpf_prog_iops = { }; 81 static const struct inode_operations bpf_map_iops = { }; 82 83 static struct inode *bpf_get_inode(struct super_block *sb, 84 const struct inode *dir, 85 umode_t mode) 86 { 87 struct inode *inode; 88 89 switch (mode & S_IFMT) { 90 case S_IFDIR: 91 case S_IFREG: 92 case S_IFLNK: 93 break; 94 default: 95 return ERR_PTR(-EINVAL); 96 } 97 98 inode = new_inode(sb); 99 if (!inode) 100 return ERR_PTR(-ENOSPC); 101 102 inode->i_ino = get_next_ino(); 103 inode->i_atime = current_time(inode); 104 inode->i_mtime = inode->i_atime; 105 inode->i_ctime = inode->i_atime; 106 107 inode_init_owner(inode, dir, mode); 108 109 return inode; 110 } 111 112 static int bpf_inode_type(const struct inode *inode, enum bpf_type *type) 113 { 114 *type = BPF_TYPE_UNSPEC; 115 if (inode->i_op == &bpf_prog_iops) 116 *type = BPF_TYPE_PROG; 117 else if (inode->i_op == &bpf_map_iops) 118 *type = BPF_TYPE_MAP; 119 else 120 return -EACCES; 121 122 return 0; 123 } 124 125 static void bpf_dentry_finalize(struct dentry *dentry, struct inode *inode, 126 struct inode *dir) 127 { 128 d_instantiate(dentry, inode); 129 dget(dentry); 130 131 dir->i_mtime = current_time(dir); 132 dir->i_ctime = dir->i_mtime; 133 } 134 135 static int bpf_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 136 { 137 struct inode *inode; 138 139 inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFDIR); 140 if (IS_ERR(inode)) 141 return PTR_ERR(inode); 142 143 inode->i_op = &bpf_dir_iops; 144 inode->i_fop = &simple_dir_operations; 145 146 inc_nlink(inode); 147 inc_nlink(dir); 148 149 bpf_dentry_finalize(dentry, inode, dir); 150 return 0; 151 } 152 153 static int bpf_mkobj_ops(struct dentry *dentry, umode_t mode, void *raw, 154 const struct inode_operations *iops) 155 { 156 struct inode *dir = dentry->d_parent->d_inode; 157 struct inode *inode = bpf_get_inode(dir->i_sb, dir, mode); 158 if (IS_ERR(inode)) 159 return PTR_ERR(inode); 160 161 inode->i_op = iops; 162 inode->i_private = raw; 163 164 bpf_dentry_finalize(dentry, inode, dir); 165 return 0; 166 } 167 168 static int bpf_mkprog(struct dentry *dentry, umode_t mode, void *arg) 169 { 170 return bpf_mkobj_ops(dentry, mode, arg, &bpf_prog_iops); 171 } 172 173 static int bpf_mkmap(struct dentry *dentry, umode_t mode, void *arg) 174 { 175 return bpf_mkobj_ops(dentry, mode, arg, &bpf_map_iops); 176 } 177 178 static struct dentry * 179 bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags) 180 { 181 if (strchr(dentry->d_name.name, '.')) 182 return ERR_PTR(-EPERM); 183 184 return simple_lookup(dir, dentry, flags); 185 } 186 187 static int bpf_symlink(struct inode *dir, struct dentry *dentry, 188 const char *target) 189 { 190 char *link = kstrdup(target, GFP_USER | __GFP_NOWARN); 191 struct inode *inode; 192 193 if (!link) 194 return -ENOMEM; 195 196 inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK); 197 if (IS_ERR(inode)) { 198 kfree(link); 199 return PTR_ERR(inode); 200 } 201 202 inode->i_op = &simple_symlink_inode_operations; 203 inode->i_link = link; 204 205 bpf_dentry_finalize(dentry, inode, dir); 206 return 0; 207 } 208 209 static const struct inode_operations bpf_dir_iops = { 210 .lookup = bpf_lookup, 211 .mkdir = bpf_mkdir, 212 .symlink = bpf_symlink, 213 .rmdir = simple_rmdir, 214 .rename = simple_rename, 215 .link = simple_link, 216 .unlink = simple_unlink, 217 }; 218 219 static int bpf_obj_do_pin(const struct filename *pathname, void *raw, 220 enum bpf_type type) 221 { 222 struct dentry *dentry; 223 struct inode *dir; 224 struct path path; 225 umode_t mode; 226 int ret; 227 228 dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0); 229 if (IS_ERR(dentry)) 230 return PTR_ERR(dentry); 231 232 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 233 234 ret = security_path_mknod(&path, dentry, mode, 0); 235 if (ret) 236 goto out; 237 238 dir = d_inode(path.dentry); 239 if (dir->i_op != &bpf_dir_iops) { 240 ret = -EPERM; 241 goto out; 242 } 243 244 switch (type) { 245 case BPF_TYPE_PROG: 246 ret = vfs_mkobj(dentry, mode, bpf_mkprog, raw); 247 break; 248 case BPF_TYPE_MAP: 249 ret = vfs_mkobj(dentry, mode, bpf_mkmap, raw); 250 break; 251 default: 252 ret = -EPERM; 253 } 254 out: 255 done_path_create(&path, dentry); 256 return ret; 257 } 258 259 int bpf_obj_pin_user(u32 ufd, const char __user *pathname) 260 { 261 struct filename *pname; 262 enum bpf_type type; 263 void *raw; 264 int ret; 265 266 pname = getname(pathname); 267 if (IS_ERR(pname)) 268 return PTR_ERR(pname); 269 270 raw = bpf_fd_probe_obj(ufd, &type); 271 if (IS_ERR(raw)) { 272 ret = PTR_ERR(raw); 273 goto out; 274 } 275 276 ret = bpf_obj_do_pin(pname, raw, type); 277 if (ret != 0) 278 bpf_any_put(raw, type); 279 if ((trace_bpf_obj_pin_prog_enabled() || 280 trace_bpf_obj_pin_map_enabled()) && !ret) { 281 if (type == BPF_TYPE_PROG) 282 trace_bpf_obj_pin_prog(raw, ufd, pname); 283 if (type == BPF_TYPE_MAP) 284 trace_bpf_obj_pin_map(raw, ufd, pname); 285 } 286 out: 287 putname(pname); 288 return ret; 289 } 290 291 static void *bpf_obj_do_get(const struct filename *pathname, 292 enum bpf_type *type, int flags) 293 { 294 struct inode *inode; 295 struct path path; 296 void *raw; 297 int ret; 298 299 ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path); 300 if (ret) 301 return ERR_PTR(ret); 302 303 inode = d_backing_inode(path.dentry); 304 ret = inode_permission(inode, ACC_MODE(flags)); 305 if (ret) 306 goto out; 307 308 ret = bpf_inode_type(inode, type); 309 if (ret) 310 goto out; 311 312 raw = bpf_any_get(inode->i_private, *type); 313 if (!IS_ERR(raw)) 314 touch_atime(&path); 315 316 path_put(&path); 317 return raw; 318 out: 319 path_put(&path); 320 return ERR_PTR(ret); 321 } 322 323 int bpf_obj_get_user(const char __user *pathname, int flags) 324 { 325 enum bpf_type type = BPF_TYPE_UNSPEC; 326 struct filename *pname; 327 int ret = -ENOENT; 328 int f_flags; 329 void *raw; 330 331 f_flags = bpf_get_file_flag(flags); 332 if (f_flags < 0) 333 return f_flags; 334 335 pname = getname(pathname); 336 if (IS_ERR(pname)) 337 return PTR_ERR(pname); 338 339 raw = bpf_obj_do_get(pname, &type, f_flags); 340 if (IS_ERR(raw)) { 341 ret = PTR_ERR(raw); 342 goto out; 343 } 344 345 if (type == BPF_TYPE_PROG) 346 ret = bpf_prog_new_fd(raw); 347 else if (type == BPF_TYPE_MAP) 348 ret = bpf_map_new_fd(raw, f_flags); 349 else 350 goto out; 351 352 if (ret < 0) { 353 bpf_any_put(raw, type); 354 } else if (trace_bpf_obj_get_prog_enabled() || 355 trace_bpf_obj_get_map_enabled()) { 356 if (type == BPF_TYPE_PROG) 357 trace_bpf_obj_get_prog(raw, ret, pname); 358 if (type == BPF_TYPE_MAP) 359 trace_bpf_obj_get_map(raw, ret, pname); 360 } 361 out: 362 putname(pname); 363 return ret; 364 } 365 366 static struct bpf_prog *__get_prog_inode(struct inode *inode, enum bpf_prog_type type) 367 { 368 struct bpf_prog *prog; 369 int ret = inode_permission(inode, MAY_READ | MAY_WRITE); 370 if (ret) 371 return ERR_PTR(ret); 372 373 if (inode->i_op == &bpf_map_iops) 374 return ERR_PTR(-EINVAL); 375 if (inode->i_op != &bpf_prog_iops) 376 return ERR_PTR(-EACCES); 377 378 prog = inode->i_private; 379 380 ret = security_bpf_prog(prog); 381 if (ret < 0) 382 return ERR_PTR(ret); 383 384 if (!bpf_prog_get_ok(prog, &type, false)) 385 return ERR_PTR(-EINVAL); 386 387 return bpf_prog_inc(prog); 388 } 389 390 struct bpf_prog *bpf_prog_get_type_path(const char *name, enum bpf_prog_type type) 391 { 392 struct bpf_prog *prog; 393 struct path path; 394 int ret = kern_path(name, LOOKUP_FOLLOW, &path); 395 if (ret) 396 return ERR_PTR(ret); 397 prog = __get_prog_inode(d_backing_inode(path.dentry), type); 398 if (!IS_ERR(prog)) 399 touch_atime(&path); 400 path_put(&path); 401 return prog; 402 } 403 EXPORT_SYMBOL(bpf_prog_get_type_path); 404 405 static void bpf_evict_inode(struct inode *inode) 406 { 407 enum bpf_type type; 408 409 truncate_inode_pages_final(&inode->i_data); 410 clear_inode(inode); 411 412 if (S_ISLNK(inode->i_mode)) 413 kfree(inode->i_link); 414 if (!bpf_inode_type(inode, &type)) 415 bpf_any_put(inode->i_private, type); 416 } 417 418 /* 419 * Display the mount options in /proc/mounts. 420 */ 421 static int bpf_show_options(struct seq_file *m, struct dentry *root) 422 { 423 umode_t mode = d_inode(root)->i_mode & S_IALLUGO & ~S_ISVTX; 424 425 if (mode != S_IRWXUGO) 426 seq_printf(m, ",mode=%o", mode); 427 return 0; 428 } 429 430 static const struct super_operations bpf_super_ops = { 431 .statfs = simple_statfs, 432 .drop_inode = generic_delete_inode, 433 .show_options = bpf_show_options, 434 .evict_inode = bpf_evict_inode, 435 }; 436 437 enum { 438 OPT_MODE, 439 OPT_ERR, 440 }; 441 442 static const match_table_t bpf_mount_tokens = { 443 { OPT_MODE, "mode=%o" }, 444 { OPT_ERR, NULL }, 445 }; 446 447 struct bpf_mount_opts { 448 umode_t mode; 449 }; 450 451 static int bpf_parse_options(char *data, struct bpf_mount_opts *opts) 452 { 453 substring_t args[MAX_OPT_ARGS]; 454 int option, token; 455 char *ptr; 456 457 opts->mode = S_IRWXUGO; 458 459 while ((ptr = strsep(&data, ",")) != NULL) { 460 if (!*ptr) 461 continue; 462 463 token = match_token(ptr, bpf_mount_tokens, args); 464 switch (token) { 465 case OPT_MODE: 466 if (match_octal(&args[0], &option)) 467 return -EINVAL; 468 opts->mode = option & S_IALLUGO; 469 break; 470 /* We might like to report bad mount options here, but 471 * traditionally we've ignored all mount options, so we'd 472 * better continue to ignore non-existing options for bpf. 473 */ 474 } 475 } 476 477 return 0; 478 } 479 480 static int bpf_fill_super(struct super_block *sb, void *data, int silent) 481 { 482 static const struct tree_descr bpf_rfiles[] = { { "" } }; 483 struct bpf_mount_opts opts; 484 struct inode *inode; 485 int ret; 486 487 ret = bpf_parse_options(data, &opts); 488 if (ret) 489 return ret; 490 491 ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles); 492 if (ret) 493 return ret; 494 495 sb->s_op = &bpf_super_ops; 496 497 inode = sb->s_root->d_inode; 498 inode->i_op = &bpf_dir_iops; 499 inode->i_mode &= ~S_IALLUGO; 500 inode->i_mode |= S_ISVTX | opts.mode; 501 502 return 0; 503 } 504 505 static struct dentry *bpf_mount(struct file_system_type *type, int flags, 506 const char *dev_name, void *data) 507 { 508 return mount_nodev(type, flags, data, bpf_fill_super); 509 } 510 511 static struct file_system_type bpf_fs_type = { 512 .owner = THIS_MODULE, 513 .name = "bpf", 514 .mount = bpf_mount, 515 .kill_sb = kill_litter_super, 516 }; 517 518 static int __init bpf_init(void) 519 { 520 int ret; 521 522 ret = sysfs_create_mount_point(fs_kobj, "bpf"); 523 if (ret) 524 return ret; 525 526 ret = register_filesystem(&bpf_fs_type); 527 if (ret) 528 sysfs_remove_mount_point(fs_kobj, "bpf"); 529 530 return ret; 531 } 532 fs_initcall(bpf_init); 533