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 inode *dir, struct dentry *dentry, 154 umode_t mode, const struct inode_operations *iops) 155 { 156 struct inode *inode; 157 158 inode = bpf_get_inode(dir->i_sb, dir, mode | S_IFREG); 159 if (IS_ERR(inode)) 160 return PTR_ERR(inode); 161 162 inode->i_op = iops; 163 inode->i_private = dentry->d_fsdata; 164 165 bpf_dentry_finalize(dentry, inode, dir); 166 return 0; 167 } 168 169 static int bpf_mkobj(struct inode *dir, struct dentry *dentry, umode_t mode, 170 dev_t devt) 171 { 172 enum bpf_type type = MINOR(devt); 173 174 if (MAJOR(devt) != UNNAMED_MAJOR || !S_ISREG(mode) || 175 dentry->d_fsdata == NULL) 176 return -EPERM; 177 178 switch (type) { 179 case BPF_TYPE_PROG: 180 return bpf_mkobj_ops(dir, dentry, mode, &bpf_prog_iops); 181 case BPF_TYPE_MAP: 182 return bpf_mkobj_ops(dir, dentry, mode, &bpf_map_iops); 183 default: 184 return -EPERM; 185 } 186 } 187 188 static struct dentry * 189 bpf_lookup(struct inode *dir, struct dentry *dentry, unsigned flags) 190 { 191 if (strchr(dentry->d_name.name, '.')) 192 return ERR_PTR(-EPERM); 193 194 return simple_lookup(dir, dentry, flags); 195 } 196 197 static int bpf_symlink(struct inode *dir, struct dentry *dentry, 198 const char *target) 199 { 200 char *link = kstrdup(target, GFP_USER | __GFP_NOWARN); 201 struct inode *inode; 202 203 if (!link) 204 return -ENOMEM; 205 206 inode = bpf_get_inode(dir->i_sb, dir, S_IRWXUGO | S_IFLNK); 207 if (IS_ERR(inode)) { 208 kfree(link); 209 return PTR_ERR(inode); 210 } 211 212 inode->i_op = &simple_symlink_inode_operations; 213 inode->i_link = link; 214 215 bpf_dentry_finalize(dentry, inode, dir); 216 return 0; 217 } 218 219 static const struct inode_operations bpf_dir_iops = { 220 .lookup = bpf_lookup, 221 .mknod = bpf_mkobj, 222 .mkdir = bpf_mkdir, 223 .symlink = bpf_symlink, 224 .rmdir = simple_rmdir, 225 .rename = simple_rename, 226 .link = simple_link, 227 .unlink = simple_unlink, 228 }; 229 230 static int bpf_obj_do_pin(const struct filename *pathname, void *raw, 231 enum bpf_type type) 232 { 233 struct dentry *dentry; 234 struct inode *dir; 235 struct path path; 236 umode_t mode; 237 dev_t devt; 238 int ret; 239 240 dentry = kern_path_create(AT_FDCWD, pathname->name, &path, 0); 241 if (IS_ERR(dentry)) 242 return PTR_ERR(dentry); 243 244 mode = S_IFREG | ((S_IRUSR | S_IWUSR) & ~current_umask()); 245 devt = MKDEV(UNNAMED_MAJOR, type); 246 247 ret = security_path_mknod(&path, dentry, mode, devt); 248 if (ret) 249 goto out; 250 251 dir = d_inode(path.dentry); 252 if (dir->i_op != &bpf_dir_iops) { 253 ret = -EPERM; 254 goto out; 255 } 256 257 dentry->d_fsdata = raw; 258 ret = vfs_mknod(dir, dentry, mode, devt); 259 dentry->d_fsdata = NULL; 260 out: 261 done_path_create(&path, dentry); 262 return ret; 263 } 264 265 int bpf_obj_pin_user(u32 ufd, const char __user *pathname) 266 { 267 struct filename *pname; 268 enum bpf_type type; 269 void *raw; 270 int ret; 271 272 pname = getname(pathname); 273 if (IS_ERR(pname)) 274 return PTR_ERR(pname); 275 276 raw = bpf_fd_probe_obj(ufd, &type); 277 if (IS_ERR(raw)) { 278 ret = PTR_ERR(raw); 279 goto out; 280 } 281 282 ret = bpf_obj_do_pin(pname, raw, type); 283 if (ret != 0) 284 bpf_any_put(raw, type); 285 if ((trace_bpf_obj_pin_prog_enabled() || 286 trace_bpf_obj_pin_map_enabled()) && !ret) { 287 if (type == BPF_TYPE_PROG) 288 trace_bpf_obj_pin_prog(raw, ufd, pname); 289 if (type == BPF_TYPE_MAP) 290 trace_bpf_obj_pin_map(raw, ufd, pname); 291 } 292 out: 293 putname(pname); 294 return ret; 295 } 296 297 static void *bpf_obj_do_get(const struct filename *pathname, 298 enum bpf_type *type) 299 { 300 struct inode *inode; 301 struct path path; 302 void *raw; 303 int ret; 304 305 ret = kern_path(pathname->name, LOOKUP_FOLLOW, &path); 306 if (ret) 307 return ERR_PTR(ret); 308 309 inode = d_backing_inode(path.dentry); 310 ret = inode_permission(inode, MAY_WRITE); 311 if (ret) 312 goto out; 313 314 ret = bpf_inode_type(inode, type); 315 if (ret) 316 goto out; 317 318 raw = bpf_any_get(inode->i_private, *type); 319 if (!IS_ERR(raw)) 320 touch_atime(&path); 321 322 path_put(&path); 323 return raw; 324 out: 325 path_put(&path); 326 return ERR_PTR(ret); 327 } 328 329 int bpf_obj_get_user(const char __user *pathname) 330 { 331 enum bpf_type type = BPF_TYPE_UNSPEC; 332 struct filename *pname; 333 int ret = -ENOENT; 334 void *raw; 335 336 pname = getname(pathname); 337 if (IS_ERR(pname)) 338 return PTR_ERR(pname); 339 340 raw = bpf_obj_do_get(pname, &type); 341 if (IS_ERR(raw)) { 342 ret = PTR_ERR(raw); 343 goto out; 344 } 345 346 if (type == BPF_TYPE_PROG) 347 ret = bpf_prog_new_fd(raw); 348 else if (type == BPF_TYPE_MAP) 349 ret = bpf_map_new_fd(raw); 350 else 351 goto out; 352 353 if (ret < 0) { 354 bpf_any_put(raw, type); 355 } else if (trace_bpf_obj_get_prog_enabled() || 356 trace_bpf_obj_get_map_enabled()) { 357 if (type == BPF_TYPE_PROG) 358 trace_bpf_obj_get_prog(raw, ret, pname); 359 if (type == BPF_TYPE_MAP) 360 trace_bpf_obj_get_map(raw, ret, pname); 361 } 362 out: 363 putname(pname); 364 return ret; 365 } 366 367 static void bpf_evict_inode(struct inode *inode) 368 { 369 enum bpf_type type; 370 371 truncate_inode_pages_final(&inode->i_data); 372 clear_inode(inode); 373 374 if (S_ISLNK(inode->i_mode)) 375 kfree(inode->i_link); 376 if (!bpf_inode_type(inode, &type)) 377 bpf_any_put(inode->i_private, type); 378 } 379 380 static const struct super_operations bpf_super_ops = { 381 .statfs = simple_statfs, 382 .drop_inode = generic_delete_inode, 383 .show_options = generic_show_options, 384 .evict_inode = bpf_evict_inode, 385 }; 386 387 enum { 388 OPT_MODE, 389 OPT_ERR, 390 }; 391 392 static const match_table_t bpf_mount_tokens = { 393 { OPT_MODE, "mode=%o" }, 394 { OPT_ERR, NULL }, 395 }; 396 397 struct bpf_mount_opts { 398 umode_t mode; 399 }; 400 401 static int bpf_parse_options(char *data, struct bpf_mount_opts *opts) 402 { 403 substring_t args[MAX_OPT_ARGS]; 404 int option, token; 405 char *ptr; 406 407 opts->mode = S_IRWXUGO; 408 409 while ((ptr = strsep(&data, ",")) != NULL) { 410 if (!*ptr) 411 continue; 412 413 token = match_token(ptr, bpf_mount_tokens, args); 414 switch (token) { 415 case OPT_MODE: 416 if (match_octal(&args[0], &option)) 417 return -EINVAL; 418 opts->mode = option & S_IALLUGO; 419 break; 420 /* We might like to report bad mount options here, but 421 * traditionally we've ignored all mount options, so we'd 422 * better continue to ignore non-existing options for bpf. 423 */ 424 } 425 } 426 427 return 0; 428 } 429 430 static int bpf_fill_super(struct super_block *sb, void *data, int silent) 431 { 432 static const struct tree_descr bpf_rfiles[] = { { "" } }; 433 struct bpf_mount_opts opts; 434 struct inode *inode; 435 int ret; 436 437 save_mount_options(sb, data); 438 439 ret = bpf_parse_options(data, &opts); 440 if (ret) 441 return ret; 442 443 ret = simple_fill_super(sb, BPF_FS_MAGIC, bpf_rfiles); 444 if (ret) 445 return ret; 446 447 sb->s_op = &bpf_super_ops; 448 449 inode = sb->s_root->d_inode; 450 inode->i_op = &bpf_dir_iops; 451 inode->i_mode &= ~S_IALLUGO; 452 inode->i_mode |= S_ISVTX | opts.mode; 453 454 return 0; 455 } 456 457 static struct dentry *bpf_mount(struct file_system_type *type, int flags, 458 const char *dev_name, void *data) 459 { 460 return mount_nodev(type, flags, data, bpf_fill_super); 461 } 462 463 static struct file_system_type bpf_fs_type = { 464 .owner = THIS_MODULE, 465 .name = "bpf", 466 .mount = bpf_mount, 467 .kill_sb = kill_litter_super, 468 }; 469 470 static int __init bpf_init(void) 471 { 472 int ret; 473 474 ret = sysfs_create_mount_point(fs_kobj, "bpf"); 475 if (ret) 476 return ret; 477 478 ret = register_filesystem(&bpf_fs_type); 479 if (ret) 480 sysfs_remove_mount_point(fs_kobj, "bpf"); 481 482 return ret; 483 } 484 fs_initcall(bpf_init); 485