1 /* 2 * linux/fs/open.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 #include <linux/string.h> 8 #include <linux/mm.h> 9 #include <linux/file.h> 10 #include <linux/quotaops.h> 11 #include <linux/fsnotify.h> 12 #include <linux/module.h> 13 #include <linux/slab.h> 14 #include <linux/tty.h> 15 #include <linux/namei.h> 16 #include <linux/backing-dev.h> 17 #include <linux/capability.h> 18 #include <linux/security.h> 19 #include <linux/mount.h> 20 #include <linux/vfs.h> 21 #include <linux/fcntl.h> 22 #include <asm/uaccess.h> 23 #include <linux/fs.h> 24 #include <linux/personality.h> 25 #include <linux/pagemap.h> 26 #include <linux/syscalls.h> 27 #include <linux/rcupdate.h> 28 #include <linux/audit.h> 29 #include <linux/falloc.h> 30 31 int vfs_statfs(struct dentry *dentry, struct kstatfs *buf) 32 { 33 int retval = -ENODEV; 34 35 if (dentry) { 36 retval = -ENOSYS; 37 if (dentry->d_sb->s_op->statfs) { 38 memset(buf, 0, sizeof(*buf)); 39 retval = security_sb_statfs(dentry); 40 if (retval) 41 return retval; 42 retval = dentry->d_sb->s_op->statfs(dentry, buf); 43 if (retval == 0 && buf->f_frsize == 0) 44 buf->f_frsize = buf->f_bsize; 45 } 46 } 47 return retval; 48 } 49 50 EXPORT_SYMBOL(vfs_statfs); 51 52 static int vfs_statfs_native(struct dentry *dentry, struct statfs *buf) 53 { 54 struct kstatfs st; 55 int retval; 56 57 retval = vfs_statfs(dentry, &st); 58 if (retval) 59 return retval; 60 61 if (sizeof(*buf) == sizeof(st)) 62 memcpy(buf, &st, sizeof(st)); 63 else { 64 if (sizeof buf->f_blocks == 4) { 65 if ((st.f_blocks | st.f_bfree | st.f_bavail) & 66 0xffffffff00000000ULL) 67 return -EOVERFLOW; 68 /* 69 * f_files and f_ffree may be -1; it's okay to stuff 70 * that into 32 bits 71 */ 72 if (st.f_files != -1 && 73 (st.f_files & 0xffffffff00000000ULL)) 74 return -EOVERFLOW; 75 if (st.f_ffree != -1 && 76 (st.f_ffree & 0xffffffff00000000ULL)) 77 return -EOVERFLOW; 78 } 79 80 buf->f_type = st.f_type; 81 buf->f_bsize = st.f_bsize; 82 buf->f_blocks = st.f_blocks; 83 buf->f_bfree = st.f_bfree; 84 buf->f_bavail = st.f_bavail; 85 buf->f_files = st.f_files; 86 buf->f_ffree = st.f_ffree; 87 buf->f_fsid = st.f_fsid; 88 buf->f_namelen = st.f_namelen; 89 buf->f_frsize = st.f_frsize; 90 memset(buf->f_spare, 0, sizeof(buf->f_spare)); 91 } 92 return 0; 93 } 94 95 static int vfs_statfs64(struct dentry *dentry, struct statfs64 *buf) 96 { 97 struct kstatfs st; 98 int retval; 99 100 retval = vfs_statfs(dentry, &st); 101 if (retval) 102 return retval; 103 104 if (sizeof(*buf) == sizeof(st)) 105 memcpy(buf, &st, sizeof(st)); 106 else { 107 buf->f_type = st.f_type; 108 buf->f_bsize = st.f_bsize; 109 buf->f_blocks = st.f_blocks; 110 buf->f_bfree = st.f_bfree; 111 buf->f_bavail = st.f_bavail; 112 buf->f_files = st.f_files; 113 buf->f_ffree = st.f_ffree; 114 buf->f_fsid = st.f_fsid; 115 buf->f_namelen = st.f_namelen; 116 buf->f_frsize = st.f_frsize; 117 memset(buf->f_spare, 0, sizeof(buf->f_spare)); 118 } 119 return 0; 120 } 121 122 asmlinkage long sys_statfs(const char __user * path, struct statfs __user * buf) 123 { 124 struct nameidata nd; 125 int error; 126 127 error = user_path_walk(path, &nd); 128 if (!error) { 129 struct statfs tmp; 130 error = vfs_statfs_native(nd.dentry, &tmp); 131 if (!error && copy_to_user(buf, &tmp, sizeof(tmp))) 132 error = -EFAULT; 133 path_release(&nd); 134 } 135 return error; 136 } 137 138 139 asmlinkage long sys_statfs64(const char __user *path, size_t sz, struct statfs64 __user *buf) 140 { 141 struct nameidata nd; 142 long error; 143 144 if (sz != sizeof(*buf)) 145 return -EINVAL; 146 error = user_path_walk(path, &nd); 147 if (!error) { 148 struct statfs64 tmp; 149 error = vfs_statfs64(nd.dentry, &tmp); 150 if (!error && copy_to_user(buf, &tmp, sizeof(tmp))) 151 error = -EFAULT; 152 path_release(&nd); 153 } 154 return error; 155 } 156 157 158 asmlinkage long sys_fstatfs(unsigned int fd, struct statfs __user * buf) 159 { 160 struct file * file; 161 struct statfs tmp; 162 int error; 163 164 error = -EBADF; 165 file = fget(fd); 166 if (!file) 167 goto out; 168 error = vfs_statfs_native(file->f_path.dentry, &tmp); 169 if (!error && copy_to_user(buf, &tmp, sizeof(tmp))) 170 error = -EFAULT; 171 fput(file); 172 out: 173 return error; 174 } 175 176 asmlinkage long sys_fstatfs64(unsigned int fd, size_t sz, struct statfs64 __user *buf) 177 { 178 struct file * file; 179 struct statfs64 tmp; 180 int error; 181 182 if (sz != sizeof(*buf)) 183 return -EINVAL; 184 185 error = -EBADF; 186 file = fget(fd); 187 if (!file) 188 goto out; 189 error = vfs_statfs64(file->f_path.dentry, &tmp); 190 if (!error && copy_to_user(buf, &tmp, sizeof(tmp))) 191 error = -EFAULT; 192 fput(file); 193 out: 194 return error; 195 } 196 197 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs, 198 struct file *filp) 199 { 200 int err; 201 struct iattr newattrs; 202 203 /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */ 204 if (length < 0) 205 return -EINVAL; 206 207 newattrs.ia_size = length; 208 newattrs.ia_valid = ATTR_SIZE | time_attrs; 209 if (filp) { 210 newattrs.ia_file = filp; 211 newattrs.ia_valid |= ATTR_FILE; 212 } 213 214 /* Remove suid/sgid on truncate too */ 215 newattrs.ia_valid |= should_remove_suid(dentry); 216 217 mutex_lock(&dentry->d_inode->i_mutex); 218 err = notify_change(dentry, &newattrs); 219 mutex_unlock(&dentry->d_inode->i_mutex); 220 return err; 221 } 222 223 static long do_sys_truncate(const char __user * path, loff_t length) 224 { 225 struct nameidata nd; 226 struct inode * inode; 227 int error; 228 229 error = -EINVAL; 230 if (length < 0) /* sorry, but loff_t says... */ 231 goto out; 232 233 error = user_path_walk(path, &nd); 234 if (error) 235 goto out; 236 inode = nd.dentry->d_inode; 237 238 /* For directories it's -EISDIR, for other non-regulars - -EINVAL */ 239 error = -EISDIR; 240 if (S_ISDIR(inode->i_mode)) 241 goto dput_and_out; 242 243 error = -EINVAL; 244 if (!S_ISREG(inode->i_mode)) 245 goto dput_and_out; 246 247 error = vfs_permission(&nd, MAY_WRITE); 248 if (error) 249 goto dput_and_out; 250 251 error = -EROFS; 252 if (IS_RDONLY(inode)) 253 goto dput_and_out; 254 255 error = -EPERM; 256 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 257 goto dput_and_out; 258 259 error = get_write_access(inode); 260 if (error) 261 goto dput_and_out; 262 263 /* 264 * Make sure that there are no leases. get_write_access() protects 265 * against the truncate racing with a lease-granting setlease(). 266 */ 267 error = break_lease(inode, FMODE_WRITE); 268 if (error) 269 goto put_write_and_out; 270 271 error = locks_verify_truncate(inode, NULL, length); 272 if (!error) { 273 DQUOT_INIT(inode); 274 error = do_truncate(nd.dentry, length, 0, NULL); 275 } 276 277 put_write_and_out: 278 put_write_access(inode); 279 dput_and_out: 280 path_release(&nd); 281 out: 282 return error; 283 } 284 285 asmlinkage long sys_truncate(const char __user * path, unsigned long length) 286 { 287 /* on 32-bit boxen it will cut the range 2^31--2^32-1 off */ 288 return do_sys_truncate(path, (long)length); 289 } 290 291 static long do_sys_ftruncate(unsigned int fd, loff_t length, int small) 292 { 293 struct inode * inode; 294 struct dentry *dentry; 295 struct file * file; 296 int error; 297 298 error = -EINVAL; 299 if (length < 0) 300 goto out; 301 error = -EBADF; 302 file = fget(fd); 303 if (!file) 304 goto out; 305 306 /* explicitly opened as large or we are on 64-bit box */ 307 if (file->f_flags & O_LARGEFILE) 308 small = 0; 309 310 dentry = file->f_path.dentry; 311 inode = dentry->d_inode; 312 error = -EINVAL; 313 if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE)) 314 goto out_putf; 315 316 error = -EINVAL; 317 /* Cannot ftruncate over 2^31 bytes without large file support */ 318 if (small && length > MAX_NON_LFS) 319 goto out_putf; 320 321 error = -EPERM; 322 if (IS_APPEND(inode)) 323 goto out_putf; 324 325 error = locks_verify_truncate(inode, file, length); 326 if (!error) 327 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file); 328 out_putf: 329 fput(file); 330 out: 331 return error; 332 } 333 334 asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length) 335 { 336 long ret = do_sys_ftruncate(fd, length, 1); 337 /* avoid REGPARM breakage on x86: */ 338 prevent_tail_call(ret); 339 return ret; 340 } 341 342 /* LFS versions of truncate are only needed on 32 bit machines */ 343 #if BITS_PER_LONG == 32 344 asmlinkage long sys_truncate64(const char __user * path, loff_t length) 345 { 346 return do_sys_truncate(path, length); 347 } 348 349 asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length) 350 { 351 long ret = do_sys_ftruncate(fd, length, 0); 352 /* avoid REGPARM breakage on x86: */ 353 prevent_tail_call(ret); 354 return ret; 355 } 356 #endif 357 358 asmlinkage long sys_fallocate(int fd, int mode, loff_t offset, loff_t len) 359 { 360 struct file *file; 361 struct inode *inode; 362 long ret = -EINVAL; 363 364 if (offset < 0 || len <= 0) 365 goto out; 366 367 /* Return error if mode is not supported */ 368 ret = -EOPNOTSUPP; 369 if (mode && !(mode & FALLOC_FL_KEEP_SIZE)) 370 goto out; 371 372 ret = -EBADF; 373 file = fget(fd); 374 if (!file) 375 goto out; 376 if (!(file->f_mode & FMODE_WRITE)) 377 goto out_fput; 378 /* 379 * Revalidate the write permissions, in case security policy has 380 * changed since the files were opened. 381 */ 382 ret = security_file_permission(file, MAY_WRITE); 383 if (ret) 384 goto out_fput; 385 386 inode = file->f_path.dentry->d_inode; 387 388 ret = -ESPIPE; 389 if (S_ISFIFO(inode->i_mode)) 390 goto out_fput; 391 392 ret = -ENODEV; 393 /* 394 * Let individual file system decide if it supports preallocation 395 * for directories or not. 396 */ 397 if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode)) 398 goto out_fput; 399 400 ret = -EFBIG; 401 /* Check for wrap through zero too */ 402 if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0)) 403 goto out_fput; 404 405 if (inode->i_op && inode->i_op->fallocate) 406 ret = inode->i_op->fallocate(inode, mode, offset, len); 407 else 408 ret = -EOPNOTSUPP; 409 410 out_fput: 411 fput(file); 412 out: 413 return ret; 414 } 415 416 /* 417 * access() needs to use the real uid/gid, not the effective uid/gid. 418 * We do this by temporarily clearing all FS-related capabilities and 419 * switching the fsuid/fsgid around to the real ones. 420 */ 421 asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode) 422 { 423 struct nameidata nd; 424 int old_fsuid, old_fsgid; 425 kernel_cap_t old_cap; 426 int res; 427 428 if (mode & ~S_IRWXO) /* where's F_OK, X_OK, W_OK, R_OK? */ 429 return -EINVAL; 430 431 old_fsuid = current->fsuid; 432 old_fsgid = current->fsgid; 433 old_cap = current->cap_effective; 434 435 current->fsuid = current->uid; 436 current->fsgid = current->gid; 437 438 /* 439 * Clear the capabilities if we switch to a non-root user 440 * 441 * FIXME: There is a race here against sys_capset. The 442 * capabilities can change yet we will restore the old 443 * value below. We should hold task_capabilities_lock, 444 * but we cannot because user_path_walk can sleep. 445 */ 446 if (current->uid) 447 cap_clear(current->cap_effective); 448 else 449 current->cap_effective = current->cap_permitted; 450 451 res = __user_walk_fd(dfd, filename, LOOKUP_FOLLOW|LOOKUP_ACCESS, &nd); 452 if (res) 453 goto out; 454 455 res = vfs_permission(&nd, mode); 456 /* SuS v2 requires we report a read only fs too */ 457 if(res || !(mode & S_IWOTH) || 458 special_file(nd.dentry->d_inode->i_mode)) 459 goto out_path_release; 460 461 if(IS_RDONLY(nd.dentry->d_inode)) 462 res = -EROFS; 463 464 out_path_release: 465 path_release(&nd); 466 out: 467 current->fsuid = old_fsuid; 468 current->fsgid = old_fsgid; 469 current->cap_effective = old_cap; 470 471 return res; 472 } 473 474 asmlinkage long sys_access(const char __user *filename, int mode) 475 { 476 return sys_faccessat(AT_FDCWD, filename, mode); 477 } 478 479 asmlinkage long sys_chdir(const char __user * filename) 480 { 481 struct nameidata nd; 482 int error; 483 484 error = __user_walk(filename, 485 LOOKUP_FOLLOW|LOOKUP_DIRECTORY|LOOKUP_CHDIR, &nd); 486 if (error) 487 goto out; 488 489 error = vfs_permission(&nd, MAY_EXEC); 490 if (error) 491 goto dput_and_out; 492 493 set_fs_pwd(current->fs, nd.mnt, nd.dentry); 494 495 dput_and_out: 496 path_release(&nd); 497 out: 498 return error; 499 } 500 501 asmlinkage long sys_fchdir(unsigned int fd) 502 { 503 struct file *file; 504 struct dentry *dentry; 505 struct inode *inode; 506 struct vfsmount *mnt; 507 int error; 508 509 error = -EBADF; 510 file = fget(fd); 511 if (!file) 512 goto out; 513 514 dentry = file->f_path.dentry; 515 mnt = file->f_path.mnt; 516 inode = dentry->d_inode; 517 518 error = -ENOTDIR; 519 if (!S_ISDIR(inode->i_mode)) 520 goto out_putf; 521 522 error = file_permission(file, MAY_EXEC); 523 if (!error) 524 set_fs_pwd(current->fs, mnt, dentry); 525 out_putf: 526 fput(file); 527 out: 528 return error; 529 } 530 531 asmlinkage long sys_chroot(const char __user * filename) 532 { 533 struct nameidata nd; 534 int error; 535 536 error = __user_walk(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd); 537 if (error) 538 goto out; 539 540 error = vfs_permission(&nd, MAY_EXEC); 541 if (error) 542 goto dput_and_out; 543 544 error = -EPERM; 545 if (!capable(CAP_SYS_CHROOT)) 546 goto dput_and_out; 547 548 set_fs_root(current->fs, nd.mnt, nd.dentry); 549 set_fs_altroot(); 550 error = 0; 551 dput_and_out: 552 path_release(&nd); 553 out: 554 return error; 555 } 556 557 asmlinkage long sys_fchmod(unsigned int fd, mode_t mode) 558 { 559 struct inode * inode; 560 struct dentry * dentry; 561 struct file * file; 562 int err = -EBADF; 563 struct iattr newattrs; 564 565 file = fget(fd); 566 if (!file) 567 goto out; 568 569 dentry = file->f_path.dentry; 570 inode = dentry->d_inode; 571 572 audit_inode(NULL, inode); 573 574 err = -EROFS; 575 if (IS_RDONLY(inode)) 576 goto out_putf; 577 err = -EPERM; 578 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 579 goto out_putf; 580 mutex_lock(&inode->i_mutex); 581 if (mode == (mode_t) -1) 582 mode = inode->i_mode; 583 newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO); 584 newattrs.ia_valid = ATTR_MODE | ATTR_CTIME; 585 err = notify_change(dentry, &newattrs); 586 mutex_unlock(&inode->i_mutex); 587 588 out_putf: 589 fput(file); 590 out: 591 return err; 592 } 593 594 asmlinkage long sys_fchmodat(int dfd, const char __user *filename, 595 mode_t mode) 596 { 597 struct nameidata nd; 598 struct inode * inode; 599 int error; 600 struct iattr newattrs; 601 602 error = __user_walk_fd(dfd, filename, LOOKUP_FOLLOW, &nd); 603 if (error) 604 goto out; 605 inode = nd.dentry->d_inode; 606 607 error = -EROFS; 608 if (IS_RDONLY(inode)) 609 goto dput_and_out; 610 611 error = -EPERM; 612 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 613 goto dput_and_out; 614 615 mutex_lock(&inode->i_mutex); 616 if (mode == (mode_t) -1) 617 mode = inode->i_mode; 618 newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO); 619 newattrs.ia_valid = ATTR_MODE | ATTR_CTIME; 620 error = notify_change(nd.dentry, &newattrs); 621 mutex_unlock(&inode->i_mutex); 622 623 dput_and_out: 624 path_release(&nd); 625 out: 626 return error; 627 } 628 629 asmlinkage long sys_chmod(const char __user *filename, mode_t mode) 630 { 631 return sys_fchmodat(AT_FDCWD, filename, mode); 632 } 633 634 static int chown_common(struct dentry * dentry, uid_t user, gid_t group) 635 { 636 struct inode * inode; 637 int error; 638 struct iattr newattrs; 639 640 error = -ENOENT; 641 if (!(inode = dentry->d_inode)) { 642 printk(KERN_ERR "chown_common: NULL inode\n"); 643 goto out; 644 } 645 error = -EROFS; 646 if (IS_RDONLY(inode)) 647 goto out; 648 error = -EPERM; 649 if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) 650 goto out; 651 newattrs.ia_valid = ATTR_CTIME; 652 if (user != (uid_t) -1) { 653 newattrs.ia_valid |= ATTR_UID; 654 newattrs.ia_uid = user; 655 } 656 if (group != (gid_t) -1) { 657 newattrs.ia_valid |= ATTR_GID; 658 newattrs.ia_gid = group; 659 } 660 if (!S_ISDIR(inode->i_mode)) 661 newattrs.ia_valid |= ATTR_KILL_SUID|ATTR_KILL_SGID; 662 mutex_lock(&inode->i_mutex); 663 error = notify_change(dentry, &newattrs); 664 mutex_unlock(&inode->i_mutex); 665 out: 666 return error; 667 } 668 669 asmlinkage long sys_chown(const char __user * filename, uid_t user, gid_t group) 670 { 671 struct nameidata nd; 672 int error; 673 674 error = user_path_walk(filename, &nd); 675 if (error) 676 goto out; 677 error = chown_common(nd.dentry, user, group); 678 path_release(&nd); 679 out: 680 return error; 681 } 682 683 asmlinkage long sys_fchownat(int dfd, const char __user *filename, uid_t user, 684 gid_t group, int flag) 685 { 686 struct nameidata nd; 687 int error = -EINVAL; 688 int follow; 689 690 if ((flag & ~AT_SYMLINK_NOFOLLOW) != 0) 691 goto out; 692 693 follow = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW; 694 error = __user_walk_fd(dfd, filename, follow, &nd); 695 if (error) 696 goto out; 697 error = chown_common(nd.dentry, user, group); 698 path_release(&nd); 699 out: 700 return error; 701 } 702 703 asmlinkage long sys_lchown(const char __user * filename, uid_t user, gid_t group) 704 { 705 struct nameidata nd; 706 int error; 707 708 error = user_path_walk_link(filename, &nd); 709 if (error) 710 goto out; 711 error = chown_common(nd.dentry, user, group); 712 path_release(&nd); 713 out: 714 return error; 715 } 716 717 718 asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group) 719 { 720 struct file * file; 721 int error = -EBADF; 722 struct dentry * dentry; 723 724 file = fget(fd); 725 if (!file) 726 goto out; 727 728 dentry = file->f_path.dentry; 729 audit_inode(NULL, dentry->d_inode); 730 error = chown_common(dentry, user, group); 731 fput(file); 732 out: 733 return error; 734 } 735 736 static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt, 737 int flags, struct file *f, 738 int (*open)(struct inode *, struct file *)) 739 { 740 struct inode *inode; 741 int error; 742 743 f->f_flags = flags; 744 f->f_mode = ((flags+1) & O_ACCMODE) | FMODE_LSEEK | 745 FMODE_PREAD | FMODE_PWRITE; 746 inode = dentry->d_inode; 747 if (f->f_mode & FMODE_WRITE) { 748 error = get_write_access(inode); 749 if (error) 750 goto cleanup_file; 751 } 752 753 f->f_mapping = inode->i_mapping; 754 f->f_path.dentry = dentry; 755 f->f_path.mnt = mnt; 756 f->f_pos = 0; 757 f->f_op = fops_get(inode->i_fop); 758 file_move(f, &inode->i_sb->s_files); 759 760 error = security_dentry_open(f); 761 if (error) 762 goto cleanup_all; 763 764 if (!open && f->f_op) 765 open = f->f_op->open; 766 if (open) { 767 error = open(inode, f); 768 if (error) 769 goto cleanup_all; 770 } 771 772 f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC); 773 774 file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping); 775 776 /* NB: we're sure to have correct a_ops only after f_op->open */ 777 if (f->f_flags & O_DIRECT) { 778 if (!f->f_mapping->a_ops || 779 ((!f->f_mapping->a_ops->direct_IO) && 780 (!f->f_mapping->a_ops->get_xip_page))) { 781 fput(f); 782 f = ERR_PTR(-EINVAL); 783 } 784 } 785 786 return f; 787 788 cleanup_all: 789 fops_put(f->f_op); 790 if (f->f_mode & FMODE_WRITE) 791 put_write_access(inode); 792 file_kill(f); 793 f->f_path.dentry = NULL; 794 f->f_path.mnt = NULL; 795 cleanup_file: 796 put_filp(f); 797 dput(dentry); 798 mntput(mnt); 799 return ERR_PTR(error); 800 } 801 802 /* 803 * Note that while the flag value (low two bits) for sys_open means: 804 * 00 - read-only 805 * 01 - write-only 806 * 10 - read-write 807 * 11 - special 808 * it is changed into 809 * 00 - no permissions needed 810 * 01 - read-permission 811 * 10 - write-permission 812 * 11 - read-write 813 * for the internal routines (ie open_namei()/follow_link() etc). 00 is 814 * used by symlinks. 815 */ 816 static struct file *do_filp_open(int dfd, const char *filename, int flags, 817 int mode) 818 { 819 int namei_flags, error; 820 struct nameidata nd; 821 822 namei_flags = flags; 823 if ((namei_flags+1) & O_ACCMODE) 824 namei_flags++; 825 826 error = open_namei(dfd, filename, namei_flags, mode, &nd); 827 if (!error) 828 return nameidata_to_filp(&nd, flags); 829 830 return ERR_PTR(error); 831 } 832 833 struct file *filp_open(const char *filename, int flags, int mode) 834 { 835 return do_filp_open(AT_FDCWD, filename, flags, mode); 836 } 837 EXPORT_SYMBOL(filp_open); 838 839 /** 840 * lookup_instantiate_filp - instantiates the open intent filp 841 * @nd: pointer to nameidata 842 * @dentry: pointer to dentry 843 * @open: open callback 844 * 845 * Helper for filesystems that want to use lookup open intents and pass back 846 * a fully instantiated struct file to the caller. 847 * This function is meant to be called from within a filesystem's 848 * lookup method. 849 * Beware of calling it for non-regular files! Those ->open methods might block 850 * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo, 851 * leading to a deadlock, as nobody can open that fifo anymore, because 852 * another process to open fifo will block on locked parent when doing lookup). 853 * Note that in case of error, nd->intent.open.file is destroyed, but the 854 * path information remains valid. 855 * If the open callback is set to NULL, then the standard f_op->open() 856 * filesystem callback is substituted. 857 */ 858 struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry, 859 int (*open)(struct inode *, struct file *)) 860 { 861 if (IS_ERR(nd->intent.open.file)) 862 goto out; 863 if (IS_ERR(dentry)) 864 goto out_err; 865 nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->mnt), 866 nd->intent.open.flags - 1, 867 nd->intent.open.file, 868 open); 869 out: 870 return nd->intent.open.file; 871 out_err: 872 release_open_intent(nd); 873 nd->intent.open.file = (struct file *)dentry; 874 goto out; 875 } 876 EXPORT_SYMBOL_GPL(lookup_instantiate_filp); 877 878 /** 879 * nameidata_to_filp - convert a nameidata to an open filp. 880 * @nd: pointer to nameidata 881 * @flags: open flags 882 * 883 * Note that this function destroys the original nameidata 884 */ 885 struct file *nameidata_to_filp(struct nameidata *nd, int flags) 886 { 887 struct file *filp; 888 889 /* Pick up the filp from the open intent */ 890 filp = nd->intent.open.file; 891 /* Has the filesystem initialised the file for us? */ 892 if (filp->f_path.dentry == NULL) 893 filp = __dentry_open(nd->dentry, nd->mnt, flags, filp, NULL); 894 else 895 path_release(nd); 896 return filp; 897 } 898 899 /* 900 * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an 901 * error. 902 */ 903 struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags) 904 { 905 int error; 906 struct file *f; 907 908 error = -ENFILE; 909 f = get_empty_filp(); 910 if (f == NULL) { 911 dput(dentry); 912 mntput(mnt); 913 return ERR_PTR(error); 914 } 915 916 return __dentry_open(dentry, mnt, flags, f, NULL); 917 } 918 EXPORT_SYMBOL(dentry_open); 919 920 /* 921 * Find an empty file descriptor entry, and mark it busy. 922 */ 923 int get_unused_fd_flags(int flags) 924 { 925 struct files_struct * files = current->files; 926 int fd, error; 927 struct fdtable *fdt; 928 929 error = -EMFILE; 930 spin_lock(&files->file_lock); 931 932 repeat: 933 fdt = files_fdtable(files); 934 fd = find_next_zero_bit(fdt->open_fds->fds_bits, fdt->max_fds, 935 files->next_fd); 936 937 /* 938 * N.B. For clone tasks sharing a files structure, this test 939 * will limit the total number of files that can be opened. 940 */ 941 if (fd >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur) 942 goto out; 943 944 /* Do we need to expand the fd array or fd set? */ 945 error = expand_files(files, fd); 946 if (error < 0) 947 goto out; 948 949 if (error) { 950 /* 951 * If we needed to expand the fs array we 952 * might have blocked - try again. 953 */ 954 error = -EMFILE; 955 goto repeat; 956 } 957 958 FD_SET(fd, fdt->open_fds); 959 if (flags & O_CLOEXEC) 960 FD_SET(fd, fdt->close_on_exec); 961 else 962 FD_CLR(fd, fdt->close_on_exec); 963 files->next_fd = fd + 1; 964 #if 1 965 /* Sanity check */ 966 if (fdt->fd[fd] != NULL) { 967 printk(KERN_WARNING "get_unused_fd: slot %d not NULL!\n", fd); 968 fdt->fd[fd] = NULL; 969 } 970 #endif 971 error = fd; 972 973 out: 974 spin_unlock(&files->file_lock); 975 return error; 976 } 977 978 int get_unused_fd(void) 979 { 980 return get_unused_fd_flags(0); 981 } 982 983 EXPORT_SYMBOL(get_unused_fd); 984 985 static void __put_unused_fd(struct files_struct *files, unsigned int fd) 986 { 987 struct fdtable *fdt = files_fdtable(files); 988 __FD_CLR(fd, fdt->open_fds); 989 if (fd < files->next_fd) 990 files->next_fd = fd; 991 } 992 993 void fastcall put_unused_fd(unsigned int fd) 994 { 995 struct files_struct *files = current->files; 996 spin_lock(&files->file_lock); 997 __put_unused_fd(files, fd); 998 spin_unlock(&files->file_lock); 999 } 1000 1001 EXPORT_SYMBOL(put_unused_fd); 1002 1003 /* 1004 * Install a file pointer in the fd array. 1005 * 1006 * The VFS is full of places where we drop the files lock between 1007 * setting the open_fds bitmap and installing the file in the file 1008 * array. At any such point, we are vulnerable to a dup2() race 1009 * installing a file in the array before us. We need to detect this and 1010 * fput() the struct file we are about to overwrite in this case. 1011 * 1012 * It should never happen - if we allow dup2() do it, _really_ bad things 1013 * will follow. 1014 */ 1015 1016 void fastcall fd_install(unsigned int fd, struct file * file) 1017 { 1018 struct files_struct *files = current->files; 1019 struct fdtable *fdt; 1020 spin_lock(&files->file_lock); 1021 fdt = files_fdtable(files); 1022 BUG_ON(fdt->fd[fd] != NULL); 1023 rcu_assign_pointer(fdt->fd[fd], file); 1024 spin_unlock(&files->file_lock); 1025 } 1026 1027 EXPORT_SYMBOL(fd_install); 1028 1029 long do_sys_open(int dfd, const char __user *filename, int flags, int mode) 1030 { 1031 char *tmp = getname(filename); 1032 int fd = PTR_ERR(tmp); 1033 1034 if (!IS_ERR(tmp)) { 1035 fd = get_unused_fd_flags(flags); 1036 if (fd >= 0) { 1037 struct file *f = do_filp_open(dfd, tmp, flags, mode); 1038 if (IS_ERR(f)) { 1039 put_unused_fd(fd); 1040 fd = PTR_ERR(f); 1041 } else { 1042 fsnotify_open(f->f_path.dentry); 1043 fd_install(fd, f); 1044 } 1045 } 1046 putname(tmp); 1047 } 1048 return fd; 1049 } 1050 1051 asmlinkage long sys_open(const char __user *filename, int flags, int mode) 1052 { 1053 long ret; 1054 1055 if (force_o_largefile()) 1056 flags |= O_LARGEFILE; 1057 1058 ret = do_sys_open(AT_FDCWD, filename, flags, mode); 1059 /* avoid REGPARM breakage on x86: */ 1060 prevent_tail_call(ret); 1061 return ret; 1062 } 1063 EXPORT_SYMBOL_GPL(sys_open); 1064 1065 asmlinkage long sys_openat(int dfd, const char __user *filename, int flags, 1066 int mode) 1067 { 1068 long ret; 1069 1070 if (force_o_largefile()) 1071 flags |= O_LARGEFILE; 1072 1073 ret = do_sys_open(dfd, filename, flags, mode); 1074 /* avoid REGPARM breakage on x86: */ 1075 prevent_tail_call(ret); 1076 return ret; 1077 } 1078 1079 #ifndef __alpha__ 1080 1081 /* 1082 * For backward compatibility? Maybe this should be moved 1083 * into arch/i386 instead? 1084 */ 1085 asmlinkage long sys_creat(const char __user * pathname, int mode) 1086 { 1087 return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode); 1088 } 1089 1090 #endif 1091 1092 /* 1093 * "id" is the POSIX thread ID. We use the 1094 * files pointer for this.. 1095 */ 1096 int filp_close(struct file *filp, fl_owner_t id) 1097 { 1098 int retval = 0; 1099 1100 if (!file_count(filp)) { 1101 printk(KERN_ERR "VFS: Close: file count is 0\n"); 1102 return 0; 1103 } 1104 1105 if (filp->f_op && filp->f_op->flush) 1106 retval = filp->f_op->flush(filp, id); 1107 1108 dnotify_flush(filp, id); 1109 locks_remove_posix(filp, id); 1110 fput(filp); 1111 return retval; 1112 } 1113 1114 EXPORT_SYMBOL(filp_close); 1115 1116 /* 1117 * Careful here! We test whether the file pointer is NULL before 1118 * releasing the fd. This ensures that one clone task can't release 1119 * an fd while another clone is opening it. 1120 */ 1121 asmlinkage long sys_close(unsigned int fd) 1122 { 1123 struct file * filp; 1124 struct files_struct *files = current->files; 1125 struct fdtable *fdt; 1126 int retval; 1127 1128 spin_lock(&files->file_lock); 1129 fdt = files_fdtable(files); 1130 if (fd >= fdt->max_fds) 1131 goto out_unlock; 1132 filp = fdt->fd[fd]; 1133 if (!filp) 1134 goto out_unlock; 1135 rcu_assign_pointer(fdt->fd[fd], NULL); 1136 FD_CLR(fd, fdt->close_on_exec); 1137 __put_unused_fd(files, fd); 1138 spin_unlock(&files->file_lock); 1139 retval = filp_close(filp, files); 1140 1141 /* can't restart close syscall because file table entry was cleared */ 1142 if (unlikely(retval == -ERESTARTSYS || 1143 retval == -ERESTARTNOINTR || 1144 retval == -ERESTARTNOHAND || 1145 retval == -ERESTART_RESTARTBLOCK)) 1146 retval = -EINTR; 1147 1148 return retval; 1149 1150 out_unlock: 1151 spin_unlock(&files->file_lock); 1152 return -EBADF; 1153 } 1154 1155 EXPORT_SYMBOL(sys_close); 1156 1157 /* 1158 * This routine simulates a hangup on the tty, to arrange that users 1159 * are given clean terminals at login time. 1160 */ 1161 asmlinkage long sys_vhangup(void) 1162 { 1163 if (capable(CAP_SYS_TTY_CONFIG)) { 1164 /* XXX: this needs locking */ 1165 tty_vhangup(current->signal->tty); 1166 return 0; 1167 } 1168 return -EPERM; 1169 } 1170 1171 /* 1172 * Called when an inode is about to be open. 1173 * We use this to disallow opening large files on 32bit systems if 1174 * the caller didn't specify O_LARGEFILE. On 64bit systems we force 1175 * on this flag in sys_open. 1176 */ 1177 int generic_file_open(struct inode * inode, struct file * filp) 1178 { 1179 if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS) 1180 return -EFBIG; 1181 return 0; 1182 } 1183 1184 EXPORT_SYMBOL(generic_file_open); 1185 1186 /* 1187 * This is used by subsystems that don't want seekable 1188 * file descriptors 1189 */ 1190 int nonseekable_open(struct inode *inode, struct file *filp) 1191 { 1192 filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE); 1193 return 0; 1194 } 1195 1196 EXPORT_SYMBOL(nonseekable_open); 1197