1 /* 2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 3 * Licensed under the GPL 4 * 5 * Ported the filesystem routines to 2.5. 6 * 2003-02-10 Petr Baudis <pasky@ucw.cz> 7 */ 8 9 #include <linux/fs.h> 10 #include <linux/magic.h> 11 #include <linux/module.h> 12 #include <linux/mm.h> 13 #include <linux/pagemap.h> 14 #include <linux/statfs.h> 15 #include <linux/slab.h> 16 #include <linux/seq_file.h> 17 #include <linux/writeback.h> 18 #include <linux/mount.h> 19 #include <linux/fs_context.h> 20 #include <linux/fs_parser.h> 21 #include <linux/namei.h> 22 #include "hostfs.h" 23 #include <init.h> 24 #include <kern.h> 25 26 struct hostfs_fs_info { 27 char *host_root_path; 28 }; 29 30 struct hostfs_inode_info { 31 int fd; 32 fmode_t mode; 33 struct inode vfs_inode; 34 struct mutex open_mutex; 35 dev_t dev; 36 }; 37 38 static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode) 39 { 40 return list_entry(inode, struct hostfs_inode_info, vfs_inode); 41 } 42 43 #define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file)) 44 45 static struct kmem_cache *hostfs_inode_cache; 46 47 /* Changed in hostfs_args before the kernel starts running */ 48 static char *root_ino = ""; 49 static int append = 0; 50 51 static const struct inode_operations hostfs_iops; 52 static const struct inode_operations hostfs_dir_iops; 53 static const struct inode_operations hostfs_link_iops; 54 55 #ifndef MODULE 56 static int __init hostfs_args(char *options, int *add) 57 { 58 char *ptr; 59 60 *add = 0; 61 ptr = strchr(options, ','); 62 if (ptr != NULL) 63 *ptr++ = '\0'; 64 if (*options != '\0') 65 root_ino = options; 66 67 options = ptr; 68 while (options) { 69 ptr = strchr(options, ','); 70 if (ptr != NULL) 71 *ptr++ = '\0'; 72 if (*options != '\0') { 73 if (!strcmp(options, "append")) 74 append = 1; 75 else printf("hostfs_args - unsupported option - %s\n", 76 options); 77 } 78 options = ptr; 79 } 80 return 0; 81 } 82 83 __uml_setup("hostfs=", hostfs_args, 84 "hostfs=<root dir>,<flags>,...\n" 85 " This is used to set hostfs parameters. The root directory argument\n" 86 " is used to confine all hostfs mounts to within the specified directory\n" 87 " tree on the host. If this isn't specified, then a user inside UML can\n" 88 " mount anything on the host that's accessible to the user that's running\n" 89 " it.\n" 90 " The only flag currently supported is 'append', which specifies that all\n" 91 " files opened by hostfs will be opened in append mode.\n\n" 92 ); 93 #endif 94 95 static char *__dentry_name(struct dentry *dentry, char *name) 96 { 97 char *p = dentry_path_raw(dentry, name, PATH_MAX); 98 char *root; 99 size_t len; 100 struct hostfs_fs_info *fsi; 101 102 fsi = dentry->d_sb->s_fs_info; 103 root = fsi->host_root_path; 104 len = strlen(root); 105 if (IS_ERR(p)) { 106 __putname(name); 107 return NULL; 108 } 109 110 /* 111 * This function relies on the fact that dentry_path_raw() will place 112 * the path name at the end of the provided buffer. 113 */ 114 BUG_ON(p + strlen(p) + 1 != name + PATH_MAX); 115 116 strscpy(name, root, PATH_MAX); 117 if (len > p - name) { 118 __putname(name); 119 return NULL; 120 } 121 122 if (p > name + len) 123 strcpy(name + len, p); 124 125 return name; 126 } 127 128 static char *dentry_name(struct dentry *dentry) 129 { 130 char *name = __getname(); 131 if (!name) 132 return NULL; 133 134 return __dentry_name(dentry, name); 135 } 136 137 static char *inode_name(struct inode *ino) 138 { 139 struct dentry *dentry; 140 char *name; 141 142 dentry = d_find_alias(ino); 143 if (!dentry) 144 return NULL; 145 146 name = dentry_name(dentry); 147 148 dput(dentry); 149 150 return name; 151 } 152 153 static char *follow_link(char *link) 154 { 155 char *name, *resolved, *end; 156 int n; 157 158 name = kmalloc(PATH_MAX, GFP_KERNEL); 159 if (!name) { 160 n = -ENOMEM; 161 goto out_free; 162 } 163 164 n = hostfs_do_readlink(link, name, PATH_MAX); 165 if (n < 0) 166 goto out_free; 167 else if (n == PATH_MAX) { 168 n = -E2BIG; 169 goto out_free; 170 } 171 172 if (*name == '/') 173 return name; 174 175 end = strrchr(link, '/'); 176 if (end == NULL) 177 return name; 178 179 *(end + 1) = '\0'; 180 181 resolved = kasprintf(GFP_KERNEL, "%s%s", link, name); 182 if (resolved == NULL) { 183 n = -ENOMEM; 184 goto out_free; 185 } 186 187 kfree(name); 188 return resolved; 189 190 out_free: 191 kfree(name); 192 return ERR_PTR(n); 193 } 194 195 static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf) 196 { 197 /* 198 * do_statfs uses struct statfs64 internally, but the linux kernel 199 * struct statfs still has 32-bit versions for most of these fields, 200 * so we convert them here 201 */ 202 int err; 203 long long f_blocks; 204 long long f_bfree; 205 long long f_bavail; 206 long long f_files; 207 long long f_ffree; 208 struct hostfs_fs_info *fsi; 209 210 fsi = dentry->d_sb->s_fs_info; 211 err = do_statfs(fsi->host_root_path, 212 &sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files, 213 &f_ffree, &sf->f_fsid, sizeof(sf->f_fsid), 214 &sf->f_namelen); 215 if (err) 216 return err; 217 sf->f_blocks = f_blocks; 218 sf->f_bfree = f_bfree; 219 sf->f_bavail = f_bavail; 220 sf->f_files = f_files; 221 sf->f_ffree = f_ffree; 222 sf->f_type = HOSTFS_SUPER_MAGIC; 223 return 0; 224 } 225 226 static struct inode *hostfs_alloc_inode(struct super_block *sb) 227 { 228 struct hostfs_inode_info *hi; 229 230 hi = alloc_inode_sb(sb, hostfs_inode_cache, GFP_KERNEL_ACCOUNT); 231 if (hi == NULL) 232 return NULL; 233 hi->fd = -1; 234 hi->mode = 0; 235 hi->dev = 0; 236 inode_init_once(&hi->vfs_inode); 237 mutex_init(&hi->open_mutex); 238 return &hi->vfs_inode; 239 } 240 241 static void hostfs_evict_inode(struct inode *inode) 242 { 243 truncate_inode_pages_final(&inode->i_data); 244 clear_inode(inode); 245 if (HOSTFS_I(inode)->fd != -1) { 246 close_file(&HOSTFS_I(inode)->fd); 247 HOSTFS_I(inode)->fd = -1; 248 HOSTFS_I(inode)->dev = 0; 249 } 250 } 251 252 static void hostfs_free_inode(struct inode *inode) 253 { 254 kmem_cache_free(hostfs_inode_cache, HOSTFS_I(inode)); 255 } 256 257 static int hostfs_show_options(struct seq_file *seq, struct dentry *root) 258 { 259 struct hostfs_fs_info *fsi; 260 const char *root_path; 261 262 fsi = root->d_sb->s_fs_info; 263 root_path = fsi->host_root_path; 264 size_t offset = strlen(root_ino) + 1; 265 266 if (strlen(root_path) > offset) 267 seq_show_option(seq, root_path + offset, NULL); 268 269 if (append) 270 seq_puts(seq, ",append"); 271 272 return 0; 273 } 274 275 static const struct super_operations hostfs_sbops = { 276 .alloc_inode = hostfs_alloc_inode, 277 .free_inode = hostfs_free_inode, 278 .drop_inode = generic_delete_inode, 279 .evict_inode = hostfs_evict_inode, 280 .statfs = hostfs_statfs, 281 .show_options = hostfs_show_options, 282 }; 283 284 static int hostfs_readdir(struct file *file, struct dir_context *ctx) 285 { 286 void *dir; 287 char *name; 288 unsigned long long next, ino; 289 int error, len; 290 unsigned int type; 291 292 name = dentry_name(file->f_path.dentry); 293 if (name == NULL) 294 return -ENOMEM; 295 dir = open_dir(name, &error); 296 __putname(name); 297 if (dir == NULL) 298 return -error; 299 next = ctx->pos; 300 seek_dir(dir, next); 301 while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) { 302 if (!dir_emit(ctx, name, len, ino, type)) 303 break; 304 ctx->pos = next; 305 } 306 close_dir(dir); 307 return 0; 308 } 309 310 static int hostfs_open(struct inode *ino, struct file *file) 311 { 312 char *name; 313 fmode_t mode; 314 int err; 315 int r, w, fd; 316 317 mode = file->f_mode & (FMODE_READ | FMODE_WRITE); 318 if ((mode & HOSTFS_I(ino)->mode) == mode) 319 return 0; 320 321 mode |= HOSTFS_I(ino)->mode; 322 323 retry: 324 r = w = 0; 325 326 if (mode & FMODE_READ) 327 r = 1; 328 if (mode & FMODE_WRITE) 329 r = w = 1; 330 331 name = dentry_name(file_dentry(file)); 332 if (name == NULL) 333 return -ENOMEM; 334 335 fd = open_file(name, r, w, append); 336 __putname(name); 337 if (fd < 0) 338 return fd; 339 340 mutex_lock(&HOSTFS_I(ino)->open_mutex); 341 /* somebody else had handled it first? */ 342 if ((mode & HOSTFS_I(ino)->mode) == mode) { 343 mutex_unlock(&HOSTFS_I(ino)->open_mutex); 344 close_file(&fd); 345 return 0; 346 } 347 if ((mode | HOSTFS_I(ino)->mode) != mode) { 348 mode |= HOSTFS_I(ino)->mode; 349 mutex_unlock(&HOSTFS_I(ino)->open_mutex); 350 close_file(&fd); 351 goto retry; 352 } 353 if (HOSTFS_I(ino)->fd == -1) { 354 HOSTFS_I(ino)->fd = fd; 355 } else { 356 err = replace_file(fd, HOSTFS_I(ino)->fd); 357 close_file(&fd); 358 if (err < 0) { 359 mutex_unlock(&HOSTFS_I(ino)->open_mutex); 360 return err; 361 } 362 } 363 HOSTFS_I(ino)->mode = mode; 364 mutex_unlock(&HOSTFS_I(ino)->open_mutex); 365 366 return 0; 367 } 368 369 static int hostfs_file_release(struct inode *inode, struct file *file) 370 { 371 filemap_write_and_wait(inode->i_mapping); 372 373 return 0; 374 } 375 376 static int hostfs_fsync(struct file *file, loff_t start, loff_t end, 377 int datasync) 378 { 379 struct inode *inode = file->f_mapping->host; 380 int ret; 381 382 ret = file_write_and_wait_range(file, start, end); 383 if (ret) 384 return ret; 385 386 inode_lock(inode); 387 ret = fsync_file(HOSTFS_I(inode)->fd, datasync); 388 inode_unlock(inode); 389 390 return ret; 391 } 392 393 static const struct file_operations hostfs_file_fops = { 394 .llseek = generic_file_llseek, 395 .splice_read = filemap_splice_read, 396 .splice_write = iter_file_splice_write, 397 .read_iter = generic_file_read_iter, 398 .write_iter = generic_file_write_iter, 399 .mmap = generic_file_mmap, 400 .open = hostfs_open, 401 .release = hostfs_file_release, 402 .fsync = hostfs_fsync, 403 }; 404 405 static const struct file_operations hostfs_dir_fops = { 406 .llseek = generic_file_llseek, 407 .iterate_shared = hostfs_readdir, 408 .read = generic_read_dir, 409 .open = hostfs_open, 410 .fsync = hostfs_fsync, 411 }; 412 413 static int hostfs_writepage(struct page *page, struct writeback_control *wbc) 414 { 415 struct address_space *mapping = page->mapping; 416 struct inode *inode = mapping->host; 417 char *buffer; 418 loff_t base = page_offset(page); 419 int count = PAGE_SIZE; 420 int end_index = inode->i_size >> PAGE_SHIFT; 421 int err; 422 423 if (page->index >= end_index) 424 count = inode->i_size & (PAGE_SIZE-1); 425 426 buffer = kmap_local_page(page); 427 428 err = write_file(HOSTFS_I(inode)->fd, &base, buffer, count); 429 if (err != count) { 430 if (err >= 0) 431 err = -EIO; 432 mapping_set_error(mapping, err); 433 goto out; 434 } 435 436 if (base > inode->i_size) 437 inode->i_size = base; 438 439 err = 0; 440 441 out: 442 kunmap_local(buffer); 443 unlock_page(page); 444 445 return err; 446 } 447 448 static int hostfs_read_folio(struct file *file, struct folio *folio) 449 { 450 char *buffer; 451 loff_t start = folio_pos(folio); 452 int bytes_read, ret = 0; 453 454 buffer = kmap_local_folio(folio, 0); 455 bytes_read = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer, 456 PAGE_SIZE); 457 if (bytes_read < 0) 458 ret = bytes_read; 459 else 460 buffer = folio_zero_tail(folio, bytes_read, buffer + bytes_read); 461 kunmap_local(buffer); 462 463 folio_end_read(folio, ret == 0); 464 return ret; 465 } 466 467 static int hostfs_write_begin(struct file *file, struct address_space *mapping, 468 loff_t pos, unsigned len, 469 struct folio **foliop, void **fsdata) 470 { 471 pgoff_t index = pos >> PAGE_SHIFT; 472 473 *foliop = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN, 474 mapping_gfp_mask(mapping)); 475 if (IS_ERR(*foliop)) 476 return PTR_ERR(*foliop); 477 return 0; 478 } 479 480 static int hostfs_write_end(struct file *file, struct address_space *mapping, 481 loff_t pos, unsigned len, unsigned copied, 482 struct folio *folio, void *fsdata) 483 { 484 struct inode *inode = mapping->host; 485 void *buffer; 486 size_t from = offset_in_folio(folio, pos); 487 int err; 488 489 buffer = kmap_local_folio(folio, from); 490 err = write_file(FILE_HOSTFS_I(file)->fd, &pos, buffer, copied); 491 kunmap_local(buffer); 492 493 if (!folio_test_uptodate(folio) && err == folio_size(folio)) 494 folio_mark_uptodate(folio); 495 496 /* 497 * If err > 0, write_file has added err to pos, so we are comparing 498 * i_size against the last byte written. 499 */ 500 if (err > 0 && (pos > inode->i_size)) 501 inode->i_size = pos; 502 folio_unlock(folio); 503 folio_put(folio); 504 505 return err; 506 } 507 508 static const struct address_space_operations hostfs_aops = { 509 .writepage = hostfs_writepage, 510 .read_folio = hostfs_read_folio, 511 .dirty_folio = filemap_dirty_folio, 512 .write_begin = hostfs_write_begin, 513 .write_end = hostfs_write_end, 514 }; 515 516 static int hostfs_inode_update(struct inode *ino, const struct hostfs_stat *st) 517 { 518 set_nlink(ino, st->nlink); 519 i_uid_write(ino, st->uid); 520 i_gid_write(ino, st->gid); 521 inode_set_atime_to_ts(ino, (struct timespec64){ 522 st->atime.tv_sec, 523 st->atime.tv_nsec, 524 }); 525 inode_set_mtime_to_ts(ino, (struct timespec64){ 526 st->mtime.tv_sec, 527 st->mtime.tv_nsec, 528 }); 529 inode_set_ctime(ino, st->ctime.tv_sec, st->ctime.tv_nsec); 530 ino->i_size = st->size; 531 ino->i_blocks = st->blocks; 532 return 0; 533 } 534 535 static int hostfs_inode_set(struct inode *ino, void *data) 536 { 537 struct hostfs_stat *st = data; 538 dev_t dev, rdev; 539 540 /* Reencode maj and min with the kernel encoding.*/ 541 rdev = MKDEV(st->rdev.maj, st->rdev.min); 542 dev = MKDEV(st->dev.maj, st->dev.min); 543 544 switch (st->mode & S_IFMT) { 545 case S_IFLNK: 546 ino->i_op = &hostfs_link_iops; 547 break; 548 case S_IFDIR: 549 ino->i_op = &hostfs_dir_iops; 550 ino->i_fop = &hostfs_dir_fops; 551 break; 552 case S_IFCHR: 553 case S_IFBLK: 554 case S_IFIFO: 555 case S_IFSOCK: 556 init_special_inode(ino, st->mode & S_IFMT, rdev); 557 ino->i_op = &hostfs_iops; 558 break; 559 case S_IFREG: 560 ino->i_op = &hostfs_iops; 561 ino->i_fop = &hostfs_file_fops; 562 ino->i_mapping->a_ops = &hostfs_aops; 563 break; 564 default: 565 return -EIO; 566 } 567 568 HOSTFS_I(ino)->dev = dev; 569 ino->i_ino = st->ino; 570 ino->i_mode = st->mode; 571 return hostfs_inode_update(ino, st); 572 } 573 574 static int hostfs_inode_test(struct inode *inode, void *data) 575 { 576 const struct hostfs_stat *st = data; 577 dev_t dev = MKDEV(st->dev.maj, st->dev.min); 578 579 return inode->i_ino == st->ino && HOSTFS_I(inode)->dev == dev; 580 } 581 582 static struct inode *hostfs_iget(struct super_block *sb, char *name) 583 { 584 struct inode *inode; 585 struct hostfs_stat st; 586 int err = stat_file(name, &st, -1); 587 588 if (err) 589 return ERR_PTR(err); 590 591 inode = iget5_locked(sb, st.ino, hostfs_inode_test, hostfs_inode_set, 592 &st); 593 if (!inode) 594 return ERR_PTR(-ENOMEM); 595 596 if (inode->i_state & I_NEW) { 597 unlock_new_inode(inode); 598 } else { 599 spin_lock(&inode->i_lock); 600 hostfs_inode_update(inode, &st); 601 spin_unlock(&inode->i_lock); 602 } 603 604 return inode; 605 } 606 607 static int hostfs_create(struct mnt_idmap *idmap, struct inode *dir, 608 struct dentry *dentry, umode_t mode, bool excl) 609 { 610 struct inode *inode; 611 char *name; 612 int fd; 613 614 name = dentry_name(dentry); 615 if (name == NULL) 616 return -ENOMEM; 617 618 fd = file_create(name, mode & 0777); 619 if (fd < 0) { 620 __putname(name); 621 return fd; 622 } 623 624 inode = hostfs_iget(dir->i_sb, name); 625 __putname(name); 626 if (IS_ERR(inode)) 627 return PTR_ERR(inode); 628 629 HOSTFS_I(inode)->fd = fd; 630 HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE; 631 d_instantiate(dentry, inode); 632 return 0; 633 } 634 635 static struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry, 636 unsigned int flags) 637 { 638 struct inode *inode = NULL; 639 char *name; 640 641 name = dentry_name(dentry); 642 if (name == NULL) 643 return ERR_PTR(-ENOMEM); 644 645 inode = hostfs_iget(ino->i_sb, name); 646 __putname(name); 647 if (inode == ERR_PTR(-ENOENT)) 648 inode = NULL; 649 650 return d_splice_alias(inode, dentry); 651 } 652 653 static int hostfs_link(struct dentry *to, struct inode *ino, 654 struct dentry *from) 655 { 656 char *from_name, *to_name; 657 int err; 658 659 if ((from_name = dentry_name(from)) == NULL) 660 return -ENOMEM; 661 to_name = dentry_name(to); 662 if (to_name == NULL) { 663 __putname(from_name); 664 return -ENOMEM; 665 } 666 err = link_file(to_name, from_name); 667 __putname(from_name); 668 __putname(to_name); 669 return err; 670 } 671 672 static int hostfs_unlink(struct inode *ino, struct dentry *dentry) 673 { 674 char *file; 675 int err; 676 677 if (append) 678 return -EPERM; 679 680 if ((file = dentry_name(dentry)) == NULL) 681 return -ENOMEM; 682 683 err = unlink_file(file); 684 __putname(file); 685 return err; 686 } 687 688 static int hostfs_symlink(struct mnt_idmap *idmap, struct inode *ino, 689 struct dentry *dentry, const char *to) 690 { 691 char *file; 692 int err; 693 694 if ((file = dentry_name(dentry)) == NULL) 695 return -ENOMEM; 696 err = make_symlink(file, to); 697 __putname(file); 698 return err; 699 } 700 701 static int hostfs_mkdir(struct mnt_idmap *idmap, struct inode *ino, 702 struct dentry *dentry, umode_t mode) 703 { 704 char *file; 705 int err; 706 707 if ((file = dentry_name(dentry)) == NULL) 708 return -ENOMEM; 709 err = do_mkdir(file, mode); 710 __putname(file); 711 return err; 712 } 713 714 static int hostfs_rmdir(struct inode *ino, struct dentry *dentry) 715 { 716 char *file; 717 int err; 718 719 if ((file = dentry_name(dentry)) == NULL) 720 return -ENOMEM; 721 err = hostfs_do_rmdir(file); 722 __putname(file); 723 return err; 724 } 725 726 static int hostfs_mknod(struct mnt_idmap *idmap, struct inode *dir, 727 struct dentry *dentry, umode_t mode, dev_t dev) 728 { 729 struct inode *inode; 730 char *name; 731 int err; 732 733 name = dentry_name(dentry); 734 if (name == NULL) 735 return -ENOMEM; 736 737 err = do_mknod(name, mode, MAJOR(dev), MINOR(dev)); 738 if (err) { 739 __putname(name); 740 return err; 741 } 742 743 inode = hostfs_iget(dir->i_sb, name); 744 __putname(name); 745 if (IS_ERR(inode)) 746 return PTR_ERR(inode); 747 748 d_instantiate(dentry, inode); 749 return 0; 750 } 751 752 static int hostfs_rename2(struct mnt_idmap *idmap, 753 struct inode *old_dir, struct dentry *old_dentry, 754 struct inode *new_dir, struct dentry *new_dentry, 755 unsigned int flags) 756 { 757 char *old_name, *new_name; 758 int err; 759 760 if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE)) 761 return -EINVAL; 762 763 old_name = dentry_name(old_dentry); 764 if (old_name == NULL) 765 return -ENOMEM; 766 new_name = dentry_name(new_dentry); 767 if (new_name == NULL) { 768 __putname(old_name); 769 return -ENOMEM; 770 } 771 if (!flags) 772 err = rename_file(old_name, new_name); 773 else 774 err = rename2_file(old_name, new_name, flags); 775 776 __putname(old_name); 777 __putname(new_name); 778 return err; 779 } 780 781 static int hostfs_permission(struct mnt_idmap *idmap, 782 struct inode *ino, int desired) 783 { 784 char *name; 785 int r = 0, w = 0, x = 0, err; 786 787 if (desired & MAY_NOT_BLOCK) 788 return -ECHILD; 789 790 if (desired & MAY_READ) r = 1; 791 if (desired & MAY_WRITE) w = 1; 792 if (desired & MAY_EXEC) x = 1; 793 name = inode_name(ino); 794 if (name == NULL) 795 return -ENOMEM; 796 797 if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) || 798 S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode)) 799 err = 0; 800 else 801 err = access_file(name, r, w, x); 802 __putname(name); 803 if (!err) 804 err = generic_permission(&nop_mnt_idmap, ino, desired); 805 return err; 806 } 807 808 static int hostfs_setattr(struct mnt_idmap *idmap, 809 struct dentry *dentry, struct iattr *attr) 810 { 811 struct inode *inode = d_inode(dentry); 812 struct hostfs_iattr attrs; 813 char *name; 814 int err; 815 816 int fd = HOSTFS_I(inode)->fd; 817 818 err = setattr_prepare(&nop_mnt_idmap, dentry, attr); 819 if (err) 820 return err; 821 822 if (append) 823 attr->ia_valid &= ~ATTR_SIZE; 824 825 attrs.ia_valid = 0; 826 if (attr->ia_valid & ATTR_MODE) { 827 attrs.ia_valid |= HOSTFS_ATTR_MODE; 828 attrs.ia_mode = attr->ia_mode; 829 } 830 if (attr->ia_valid & ATTR_UID) { 831 attrs.ia_valid |= HOSTFS_ATTR_UID; 832 attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid); 833 } 834 if (attr->ia_valid & ATTR_GID) { 835 attrs.ia_valid |= HOSTFS_ATTR_GID; 836 attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid); 837 } 838 if (attr->ia_valid & ATTR_SIZE) { 839 attrs.ia_valid |= HOSTFS_ATTR_SIZE; 840 attrs.ia_size = attr->ia_size; 841 } 842 if (attr->ia_valid & ATTR_ATIME) { 843 attrs.ia_valid |= HOSTFS_ATTR_ATIME; 844 attrs.ia_atime = (struct hostfs_timespec) 845 { attr->ia_atime.tv_sec, attr->ia_atime.tv_nsec }; 846 } 847 if (attr->ia_valid & ATTR_MTIME) { 848 attrs.ia_valid |= HOSTFS_ATTR_MTIME; 849 attrs.ia_mtime = (struct hostfs_timespec) 850 { attr->ia_mtime.tv_sec, attr->ia_mtime.tv_nsec }; 851 } 852 if (attr->ia_valid & ATTR_CTIME) { 853 attrs.ia_valid |= HOSTFS_ATTR_CTIME; 854 attrs.ia_ctime = (struct hostfs_timespec) 855 { attr->ia_ctime.tv_sec, attr->ia_ctime.tv_nsec }; 856 } 857 if (attr->ia_valid & ATTR_ATIME_SET) { 858 attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET; 859 } 860 if (attr->ia_valid & ATTR_MTIME_SET) { 861 attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET; 862 } 863 name = dentry_name(dentry); 864 if (name == NULL) 865 return -ENOMEM; 866 err = set_attr(name, &attrs, fd); 867 __putname(name); 868 if (err) 869 return err; 870 871 if ((attr->ia_valid & ATTR_SIZE) && 872 attr->ia_size != i_size_read(inode)) 873 truncate_setsize(inode, attr->ia_size); 874 875 setattr_copy(&nop_mnt_idmap, inode, attr); 876 mark_inode_dirty(inode); 877 return 0; 878 } 879 880 static const struct inode_operations hostfs_iops = { 881 .permission = hostfs_permission, 882 .setattr = hostfs_setattr, 883 }; 884 885 static const struct inode_operations hostfs_dir_iops = { 886 .create = hostfs_create, 887 .lookup = hostfs_lookup, 888 .link = hostfs_link, 889 .unlink = hostfs_unlink, 890 .symlink = hostfs_symlink, 891 .mkdir = hostfs_mkdir, 892 .rmdir = hostfs_rmdir, 893 .mknod = hostfs_mknod, 894 .rename = hostfs_rename2, 895 .permission = hostfs_permission, 896 .setattr = hostfs_setattr, 897 }; 898 899 static const char *hostfs_get_link(struct dentry *dentry, 900 struct inode *inode, 901 struct delayed_call *done) 902 { 903 char *link; 904 if (!dentry) 905 return ERR_PTR(-ECHILD); 906 link = kmalloc(PATH_MAX, GFP_KERNEL); 907 if (link) { 908 char *path = dentry_name(dentry); 909 int err = -ENOMEM; 910 if (path) { 911 err = hostfs_do_readlink(path, link, PATH_MAX); 912 if (err == PATH_MAX) 913 err = -E2BIG; 914 __putname(path); 915 } 916 if (err < 0) { 917 kfree(link); 918 return ERR_PTR(err); 919 } 920 } else { 921 return ERR_PTR(-ENOMEM); 922 } 923 924 set_delayed_call(done, kfree_link, link); 925 return link; 926 } 927 928 static const struct inode_operations hostfs_link_iops = { 929 .get_link = hostfs_get_link, 930 }; 931 932 static int hostfs_fill_super(struct super_block *sb, struct fs_context *fc) 933 { 934 struct hostfs_fs_info *fsi = sb->s_fs_info; 935 struct inode *root_inode; 936 int err; 937 938 sb->s_blocksize = 1024; 939 sb->s_blocksize_bits = 10; 940 sb->s_magic = HOSTFS_SUPER_MAGIC; 941 sb->s_op = &hostfs_sbops; 942 sb->s_d_op = &simple_dentry_operations; 943 sb->s_maxbytes = MAX_LFS_FILESIZE; 944 err = super_setup_bdi(sb); 945 if (err) 946 return err; 947 948 root_inode = hostfs_iget(sb, fsi->host_root_path); 949 if (IS_ERR(root_inode)) 950 return PTR_ERR(root_inode); 951 952 if (S_ISLNK(root_inode->i_mode)) { 953 char *name; 954 955 iput(root_inode); 956 name = follow_link(fsi->host_root_path); 957 if (IS_ERR(name)) 958 return PTR_ERR(name); 959 960 root_inode = hostfs_iget(sb, name); 961 kfree(name); 962 if (IS_ERR(root_inode)) 963 return PTR_ERR(root_inode); 964 } 965 966 sb->s_root = d_make_root(root_inode); 967 if (sb->s_root == NULL) 968 return -ENOMEM; 969 970 return 0; 971 } 972 973 enum hostfs_parma { 974 Opt_hostfs, 975 }; 976 977 static const struct fs_parameter_spec hostfs_param_specs[] = { 978 fsparam_string_empty("hostfs", Opt_hostfs), 979 {} 980 }; 981 982 static int hostfs_parse_param(struct fs_context *fc, struct fs_parameter *param) 983 { 984 struct hostfs_fs_info *fsi = fc->s_fs_info; 985 struct fs_parse_result result; 986 char *host_root; 987 int opt; 988 989 opt = fs_parse(fc, hostfs_param_specs, param, &result); 990 if (opt < 0) 991 return opt; 992 993 switch (opt) { 994 case Opt_hostfs: 995 host_root = param->string; 996 if (!*host_root) 997 host_root = ""; 998 fsi->host_root_path = 999 kasprintf(GFP_KERNEL, "%s/%s", root_ino, host_root); 1000 if (fsi->host_root_path == NULL) 1001 return -ENOMEM; 1002 break; 1003 } 1004 1005 return 0; 1006 } 1007 1008 static int hostfs_parse_monolithic(struct fs_context *fc, void *data) 1009 { 1010 struct hostfs_fs_info *fsi = fc->s_fs_info; 1011 char *host_root = (char *)data; 1012 1013 /* NULL is printed as '(null)' by printf(): avoid that. */ 1014 if (host_root == NULL) 1015 host_root = ""; 1016 1017 fsi->host_root_path = 1018 kasprintf(GFP_KERNEL, "%s/%s", root_ino, host_root); 1019 if (fsi->host_root_path == NULL) 1020 return -ENOMEM; 1021 1022 return 0; 1023 } 1024 1025 static int hostfs_fc_get_tree(struct fs_context *fc) 1026 { 1027 return get_tree_nodev(fc, hostfs_fill_super); 1028 } 1029 1030 static void hostfs_fc_free(struct fs_context *fc) 1031 { 1032 struct hostfs_fs_info *fsi = fc->s_fs_info; 1033 1034 if (!fsi) 1035 return; 1036 1037 kfree(fsi->host_root_path); 1038 kfree(fsi); 1039 } 1040 1041 static const struct fs_context_operations hostfs_context_ops = { 1042 .parse_monolithic = hostfs_parse_monolithic, 1043 .parse_param = hostfs_parse_param, 1044 .get_tree = hostfs_fc_get_tree, 1045 .free = hostfs_fc_free, 1046 }; 1047 1048 static int hostfs_init_fs_context(struct fs_context *fc) 1049 { 1050 struct hostfs_fs_info *fsi; 1051 1052 fsi = kzalloc(sizeof(*fsi), GFP_KERNEL); 1053 if (!fsi) 1054 return -ENOMEM; 1055 1056 fc->s_fs_info = fsi; 1057 fc->ops = &hostfs_context_ops; 1058 return 0; 1059 } 1060 1061 static void hostfs_kill_sb(struct super_block *s) 1062 { 1063 kill_anon_super(s); 1064 kfree(s->s_fs_info); 1065 } 1066 1067 static struct file_system_type hostfs_type = { 1068 .owner = THIS_MODULE, 1069 .name = "hostfs", 1070 .init_fs_context = hostfs_init_fs_context, 1071 .kill_sb = hostfs_kill_sb, 1072 .fs_flags = 0, 1073 }; 1074 MODULE_ALIAS_FS("hostfs"); 1075 1076 static int __init init_hostfs(void) 1077 { 1078 hostfs_inode_cache = KMEM_CACHE(hostfs_inode_info, 0); 1079 if (!hostfs_inode_cache) 1080 return -ENOMEM; 1081 return register_filesystem(&hostfs_type); 1082 } 1083 1084 static void __exit exit_hostfs(void) 1085 { 1086 unregister_filesystem(&hostfs_type); 1087 kmem_cache_destroy(hostfs_inode_cache); 1088 } 1089 1090 module_init(init_hostfs) 1091 module_exit(exit_hostfs) 1092 MODULE_DESCRIPTION("User-Mode Linux Host filesystem"); 1093 MODULE_LICENSE("GPL"); 1094