fs/open.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/fs/open.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  */
   7
   8 #include <linux/string.h>
   9 #include <linux/mm.h>
  10 #include <linux/file.h>
  11 #include <linux/fdtable.h>
  12 #include <linux/fsnotify.h>
  13 #include <linux/module.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/securebits.h>
  19 #include <linux/security.h>
  20 #include <linux/mount.h>
  21 #include <linux/fcntl.h>
  22 #include <linux/slab.h>
  23 #include <linux/uaccess.h>
  24 #include <linux/fs.h>
  25 #include <linux/personality.h>
  26 #include <linux/pagemap.h>
  27 #include <linux/syscalls.h>
  28 #include <linux/rcupdate.h>
  29 #include <linux/audit.h>
  30 #include <linux/falloc.h>
  31 #include <linux/fs_struct.h>
  32 #include <linux/ima.h>
  33 #include <linux/dnotify.h>
  34 #include <linux/compat.h>
  35
  36 #include "internal.h"
  37
  38 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
  39         struct file *filp)
  40 {
  41         int ret;
  42         struct iattr newattrs;
  43
  44         /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
  45         if (length < 0)
  46                 return -EINVAL;
  47
  48         newattrs.ia_size = length;
  49         newattrs.ia_valid = ATTR_SIZE | time_attrs;
  50         if (filp) {
  51                 newattrs.ia_file = filp;
  52                 newattrs.ia_valid |= ATTR_FILE;
  53         }
  54
  55         /* Remove suid, sgid, and file capabilities on truncate too */
  56         ret = dentry_needs_remove_privs(dentry);
  57         if (ret < 0)
  58                 return ret;
  59         if (ret)
  60                 newattrs.ia_valid |= ret | ATTR_FORCE;
  61
  62         inode_lock(dentry->d_inode);
  63         /* Note any delegations or leases have already been broken: */
  64         ret = notify_change(dentry, &newattrs, NULL);
  65         inode_unlock(dentry->d_inode);
  66         return ret;
  67 }
  68 EXPORT_SYMBOL_GPL(do_truncate);
  69
  70 long vfs_truncate(const struct path *path, loff_t length)
  71 {
  72         struct inode *inode;
  73         long error;
  74
  75         inode = path->dentry->d_inode;
  76
  77         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
  78         if (S_ISDIR(inode->i_mode))
  79                 return -EISDIR;
  80         if (!S_ISREG(inode->i_mode))
  81                 return -EINVAL;
  82
  83         error = mnt_want_write(path->mnt);
  84         if (error)
  85                 goto out;
  86
  87         error = inode_permission(inode, MAY_WRITE);
  88         if (error)
  89                 goto mnt_drop_write_and_out;
  90
  91         error = -EPERM;
  92         if (IS_APPEND(inode))
  93                 goto mnt_drop_write_and_out;
  94
  95         error = get_write_access(inode);
  96         if (error)
  97                 goto mnt_drop_write_and_out;
  98
  99         /*
 100          * Make sure that there are no leases.  get_write_access() protects
 101          * against the truncate racing with a lease-granting setlease().
 102          */
 103         error = break_lease(inode, O_WRONLY);
 104         if (error)
 105                 goto put_write_and_out;
 106
 107         error = locks_verify_truncate(inode, NULL, length);
 108         if (!error)
 109                 error = security_path_truncate(path);
 110         if (!error)
 111                 error = do_truncate(path->dentry, length, 0, NULL);
 112
 113 put_write_and_out:
 114         put_write_access(inode);
 115 mnt_drop_write_and_out:
 116         mnt_drop_write(path->mnt);
 117 out:
 118         return error;
 119 }
 120 EXPORT_SYMBOL_GPL(vfs_truncate);
 121
 122 long do_sys_truncate(const char __user *pathname, loff_t length)
 123 {
 124         unsigned int lookup_flags = LOOKUP_FOLLOW;
 125         struct path path;
 126         int error;
 127
 128         if (length < 0) /* sorry, but loff_t says... */
 129                 return -EINVAL;
 130
 131 retry:
 132         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 133         if (!error) {
 134                 error = vfs_truncate(&path, length);
 135                 path_put(&path);
 136         }
 137         if (retry_estale(error, lookup_flags)) {
 138                 lookup_flags |= LOOKUP_REVAL;
 139                 goto retry;
 140         }
 141         return error;
 142 }
 143
 144 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 145 {
 146         return do_sys_truncate(path, length);
 147 }
 148
 149 #ifdef CONFIG_COMPAT
 150 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
 151 {
 152         return do_sys_truncate(path, length);
 153 }
 154 #endif
 155
 156 long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 157 {
 158         struct inode *inode;
 159         struct dentry *dentry;
 160         struct fd f;
 161         int error;
 162
 163         error = -EINVAL;
 164         if (length < 0)
 165                 goto out;
 166         error = -EBADF;
 167         f = fdget(fd);
 168         if (!f.file)
 169                 goto out;
 170
 171         /* explicitly opened as large or we are on 64-bit box */
 172         if (f.file->f_flags & O_LARGEFILE)
 173                 small = 0;
 174
 175         dentry = f.file->f_path.dentry;
 176         inode = dentry->d_inode;
 177         error = -EINVAL;
 178         if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
 179                 goto out_putf;
 180
 181         error = -EINVAL;
 182         /* Cannot ftruncate over 2^31 bytes without large file support */
 183         if (small && length > MAX_NON_LFS)
 184                 goto out_putf;
 185
 186         error = -EPERM;
 187         /* Check IS_APPEND on real upper inode */
 188         if (IS_APPEND(file_inode(f.file)))
 189                 goto out_putf;
 190
 191         sb_start_write(inode->i_sb);
 192         error = locks_verify_truncate(inode, f.file, length);
 193         if (!error)
 194                 error = security_path_truncate(&f.file->f_path);
 195         if (!error)
 196                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
 197         sb_end_write(inode->i_sb);
 198 out_putf:
 199         fdput(f);
 200 out:
 201         return error;
 202 }
 203
 204 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 205 {
 206         return do_sys_ftruncate(fd, length, 1);
 207 }
 208
 209 #ifdef CONFIG_COMPAT
 210 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
 211 {
 212         return do_sys_ftruncate(fd, length, 1);
 213 }
 214 #endif
 215
 216 /* LFS versions of truncate are only needed on 32 bit machines */
 217 #if BITS_PER_LONG == 32
 218 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
 219 {
 220         return do_sys_truncate(path, length);
 221 }
 222
 223 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
 224 {
 225         return do_sys_ftruncate(fd, length, 0);
 226 }
 227 #endif /* BITS_PER_LONG == 32 */
 228
 229
 230 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 231 {
 232         struct inode *inode = file_inode(file);
 233         long ret;
 234
 235         if (offset < 0 || len <= 0)
 236                 return -EINVAL;
 237
 238         /* Return error if mode is not supported */
 239         if (mode & ~FALLOC_FL_SUPPORTED_MASK)
 240                 return -EOPNOTSUPP;
 241
 242         /* Punch hole and zero range are mutually exclusive */
 243         if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
 244             (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
 245                 return -EOPNOTSUPP;
 246
 247         /* Punch hole must have keep size set */
 248         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
 249             !(mode & FALLOC_FL_KEEP_SIZE))
 250                 return -EOPNOTSUPP;
 251
 252         /* Collapse range should only be used exclusively. */
 253         if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
 254             (mode & ~FALLOC_FL_COLLAPSE_RANGE))
 255                 return -EINVAL;
 256
 257         /* Insert range should only be used exclusively. */
 258         if ((mode & FALLOC_FL_INSERT_RANGE) &&
 259             (mode & ~FALLOC_FL_INSERT_RANGE))
 260                 return -EINVAL;
 261
 262         /* Unshare range should only be used with allocate mode. */
 263         if ((mode & FALLOC_FL_UNSHARE_RANGE) &&
 264             (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))
 265                 return -EINVAL;
 266
 267         if (!(file->f_mode & FMODE_WRITE))
 268                 return -EBADF;
 269
 270         /*
 271          * We can only allow pure fallocate on append only files
 272          */
 273         if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
 274                 return -EPERM;
 275
 276         if (IS_IMMUTABLE(inode))
 277                 return -EPERM;
 278
 279         /*
 280          * We cannot allow any fallocate operation on an active swapfile
 281          */
 282         if (IS_SWAPFILE(inode))
 283                 return -ETXTBSY;
 284
 285         /*
 286          * Revalidate the write permissions, in case security policy has
 287          * changed since the files were opened.
 288          */
 289         ret = security_file_permission(file, MAY_WRITE);
 290         if (ret)
 291                 return ret;
 292
 293         if (S_ISFIFO(inode->i_mode))
 294                 return -ESPIPE;
 295
 296         if (S_ISDIR(inode->i_mode))
 297                 return -EISDIR;
 298
 299         if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
 300                 return -ENODEV;
 301
 302         /* Check for wrap through zero too */
 303         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 304                 return -EFBIG;
 305
 306         if (!file->f_op->fallocate)
 307                 return -EOPNOTSUPP;
 308
 309         file_start_write(file);
 310         ret = file->f_op->fallocate(file, mode, offset, len);
 311
 312         /*
 313          * Create inotify and fanotify events.
 314          *
 315          * To keep the logic simple always create events if fallocate succeeds.
 316          * This implies that events are even created if the file size remains
 317          * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
 318          */
 319         if (ret == 0)
 320                 fsnotify_modify(file);
 321
 322         file_end_write(file);
 323         return ret;
 324 }
 325 EXPORT_SYMBOL_GPL(vfs_fallocate);
 326
 327 int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
 328 {
 329         struct fd f = fdget(fd);
 330         int error = -EBADF;
 331
 332         if (f.file) {
 333                 error = vfs_fallocate(f.file, mode, offset, len);
 334                 fdput(f);
 335         }
 336         return error;
 337 }
 338
 339 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
 340 {
 341         return ksys_fallocate(fd, mode, offset, len);
 342 }
 343
 344 /*
 345  * access() needs to use the real uid/gid, not the effective uid/gid.
 346  * We do this by temporarily clearing all FS-related capabilities and
 347  * switching the fsuid/fsgid around to the real ones.
 348  */
 349 static const struct cred *access_override_creds(void)
 350 {
 351         const struct cred *old_cred;
 352         struct cred *override_cred;
 353
 354         override_cred = prepare_creds();
 355         if (!override_cred)
 356                 return NULL;
 357
 358         override_cred->fsuid = override_cred->uid;
 359         override_cred->fsgid = override_cred->gid;
 360
 361         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 362                 /* Clear the capabilities if we switch to a non-root user */
 363                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 364                 if (!uid_eq(override_cred->uid, root_uid))
 365                         cap_clear(override_cred->cap_effective);
 366                 else
 367                         override_cred->cap_effective =
 368                                 override_cred->cap_permitted;
 369         }
 370
 371         /*
 372          * The new set of credentials can *only* be used in
 373          * task-synchronous circumstances, and does not need
 374          * RCU freeing, unless somebody then takes a separate
 375          * reference to it.
 376          *
 377          * NOTE! This is _only_ true because this credential
 378          * is used purely for override_creds() that installs
 379          * it as the subjective cred. Other threads will be
 380          * accessing ->real_cred, not the subjective cred.
 381          *
 382          * If somebody _does_ make a copy of this (using the
 383          * 'get_current_cred()' function), that will clear the
 384          * non_rcu field, because now that other user may be
 385          * expecting RCU freeing. But normal thread-synchronous
 386          * cred accesses will keep things non-RCY.
 387          */
 388         override_cred->non_rcu = 1;
 389
 390         old_cred = override_creds(override_cred);
 391
 392         /* override_cred() gets its own ref */
 393         put_cred(override_cred);
 394
 395         return old_cred;
 396 }
 397
 398 static long do_faccessat(int dfd, const char __user *filename, int mode, int flags)
 399 {
 400         struct path path;
 401         struct inode *inode;
 402         int res;
 403         unsigned int lookup_flags = LOOKUP_FOLLOW;
 404         const struct cred *old_cred = NULL;
 405
 406         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 407                 return -EINVAL;
 408
 409         if (flags & ~(AT_EACCESS | AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
 410                 return -EINVAL;
 411
 412         if (flags & AT_SYMLINK_NOFOLLOW)
 413                 lookup_flags &= ~LOOKUP_FOLLOW;
 414         if (flags & AT_EMPTY_PATH)
 415                 lookup_flags |= LOOKUP_EMPTY;
 416
 417         if (!(flags & AT_EACCESS)) {
 418                 old_cred = access_override_creds();
 419                 if (!old_cred)
 420                         return -ENOMEM;
 421         }
 422
 423 retry:
 424         res = user_path_at(dfd, filename, lookup_flags, &path);
 425         if (res)
 426                 goto out;
 427
 428         inode = d_backing_inode(path.dentry);
 429
 430         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 431                 /*
 432                  * MAY_EXEC on regular files is denied if the fs is mounted
 433                  * with the "noexec" flag.
 434                  */
 435                 res = -EACCES;
 436                 if (path_noexec(&path))
 437                         goto out_path_release;
 438         }
 439
 440         res = inode_permission(inode, mode | MAY_ACCESS);
 441         /* SuS v2 requires we report a read only fs too */
 442         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 443                 goto out_path_release;
 444         /*
 445          * This is a rare case where using __mnt_is_readonly()
 446          * is OK without a mnt_want/drop_write() pair.  Since
 447          * no actual write to the fs is performed here, we do
 448          * not need to telegraph to that to anyone.
 449          *
 450          * By doing this, we accept that this access is
 451          * inherently racy and know that the fs may change
 452          * state before we even see this result.
 453          */
 454         if (__mnt_is_readonly(path.mnt))
 455                 res = -EROFS;
 456
 457 out_path_release:
 458         path_put(&path);
 459         if (retry_estale(res, lookup_flags)) {
 460                 lookup_flags |= LOOKUP_REVAL;
 461                 goto retry;
 462         }
 463 out:
 464         if (old_cred)
 465                 revert_creds(old_cred);
 466
 467         return res;
 468 }
 469
 470 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 471 {
 472         return do_faccessat(dfd, filename, mode, 0);
 473 }
 474
 475 SYSCALL_DEFINE4(faccessat2, int, dfd, const char __user *, filename, int, mode,
 476                 int, flags)
 477 {
 478         return do_faccessat(dfd, filename, mode, flags);
 479 }
 480
 481 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 482 {
 483         return do_faccessat(AT_FDCWD, filename, mode, 0);
 484 }
 485
 486 SYSCALL_DEFINE1(chdir, const char __user *, filename)
 487 {
 488         struct path path;
 489         int error;
 490         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 491 retry:
 492         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 493         if (error)
 494                 goto out;
 495
 496         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 497         if (error)
 498                 goto dput_and_out;
 499
 500         set_fs_pwd(current->fs, &path);
 501
 502 dput_and_out:
 503         path_put(&path);
 504         if (retry_estale(error, lookup_flags)) {
 505                 lookup_flags |= LOOKUP_REVAL;
 506                 goto retry;
 507         }
 508 out:
 509         return error;
 510 }
 511
 512 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 513 {
 514         struct fd f = fdget_raw(fd);
 515         int error;
 516
 517         error = -EBADF;
 518         if (!f.file)
 519                 goto out;
 520
 521         error = -ENOTDIR;
 522         if (!d_can_lookup(f.file->f_path.dentry))
 523                 goto out_putf;
 524
 525         error = inode_permission(file_inode(f.file), MAY_EXEC | MAY_CHDIR);
 526         if (!error)
 527                 set_fs_pwd(current->fs, &f.file->f_path);
 528 out_putf:
 529         fdput(f);
 530 out:
 531         return error;
 532 }
 533
 534 SYSCALL_DEFINE1(chroot, const char __user *, filename)
 535 {
 536         struct path path;
 537         int error;
 538         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 539 retry:
 540         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 541         if (error)
 542                 goto out;
 543
 544         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 545         if (error)
 546                 goto dput_and_out;
 547
 548         error = -EPERM;
 549         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
 550                 goto dput_and_out;
 551         error = security_path_chroot(&path);
 552         if (error)
 553                 goto dput_and_out;
 554
 555         set_fs_root(current->fs, &path);
 556         error = 0;
 557 dput_and_out:
 558         path_put(&path);
 559         if (retry_estale(error, lookup_flags)) {
 560                 lookup_flags |= LOOKUP_REVAL;
 561                 goto retry;
 562         }
 563 out:
 564         return error;
 565 }
 566
 567 int chmod_common(const struct path *path, umode_t mode)
 568 {
 569         struct inode *inode = path->dentry->d_inode;
 570         struct inode *delegated_inode = NULL;
 571         struct iattr newattrs;
 572         int error;
 573
 574         error = mnt_want_write(path->mnt);
 575         if (error)
 576                 return error;
 577 retry_deleg:
 578         inode_lock(inode);
 579         error = security_path_chmod(path, mode);
 580         if (error)
 581                 goto out_unlock;
 582         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 583         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 584         error = notify_change(path->dentry, &newattrs, &delegated_inode);
 585 out_unlock:
 586         inode_unlock(inode);
 587         if (delegated_inode) {
 588                 error = break_deleg_wait(&delegated_inode);
 589                 if (!error)
 590                         goto retry_deleg;
 591         }
 592         mnt_drop_write(path->mnt);
 593         return error;
 594 }
 595
 596 int vfs_fchmod(struct file *file, umode_t mode)
 597 {
 598         audit_file(file);
 599         return chmod_common(&file->f_path, mode);
 600 }
 601
 602 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 603 {
 604         struct fd f = fdget(fd);
 605         int err = -EBADF;
 606
 607         if (f.file) {
 608                 err = vfs_fchmod(f.file, mode);
 609                 fdput(f);
 610         }
 611         return err;
 612 }
 613
 614 static int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
 615 {
 616         struct path path;
 617         int error;
 618         unsigned int lookup_flags = LOOKUP_FOLLOW;
 619 retry:
 620         error = user_path_at(dfd, filename, lookup_flags, &path);
 621         if (!error) {
 622                 error = chmod_common(&path, mode);
 623                 path_put(&path);
 624                 if (retry_estale(error, lookup_flags)) {
 625                         lookup_flags |= LOOKUP_REVAL;
 626                         goto retry;
 627                 }
 628         }
 629         return error;
 630 }
 631
 632 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
 633                 umode_t, mode)
 634 {
 635         return do_fchmodat(dfd, filename, mode);
 636 }
 637
 638 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 639 {
 640         return do_fchmodat(AT_FDCWD, filename, mode);
 641 }
 642
 643 int chown_common(const struct path *path, uid_t user, gid_t group)
 644 {
 645         struct inode *inode = path->dentry->d_inode;
 646         struct inode *delegated_inode = NULL;
 647         int error;
 648         struct iattr newattrs;
 649         kuid_t uid;
 650         kgid_t gid;
 651
 652         uid = make_kuid(current_user_ns(), user);
 653         gid = make_kgid(current_user_ns(), group);
 654
 655 retry_deleg:
 656         newattrs.ia_valid =  ATTR_CTIME;
 657         if (user != (uid_t) -1) {
 658                 if (!uid_valid(uid))
 659                         return -EINVAL;
 660                 newattrs.ia_valid |= ATTR_UID;
 661                 newattrs.ia_uid = uid;
 662         }
 663         if (group != (gid_t) -1) {
 664                 if (!gid_valid(gid))
 665                         return -EINVAL;
 666                 newattrs.ia_valid |= ATTR_GID;
 667                 newattrs.ia_gid = gid;
 668         }
 669         if (!S_ISDIR(inode->i_mode))
 670                 newattrs.ia_valid |=
 671                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 672         inode_lock(inode);
 673         error = security_path_chown(path, uid, gid);
 674         if (!error)
 675                 error = notify_change(path->dentry, &newattrs, &delegated_inode);
 676         inode_unlock(inode);
 677         if (delegated_inode) {
 678                 error = break_deleg_wait(&delegated_inode);
 679                 if (!error)
 680                         goto retry_deleg;
 681         }
 682         return error;
 683 }
 684
 685 int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
 686                 int flag)
 687 {
 688         struct path path;
 689         int error = -EINVAL;
 690         int lookup_flags;
 691
 692         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 693                 goto out;
 694
 695         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 696         if (flag & AT_EMPTY_PATH)
 697                 lookup_flags |= LOOKUP_EMPTY;
 698 retry:
 699         error = user_path_at(dfd, filename, lookup_flags, &path);
 700         if (error)
 701                 goto out;
 702         error = mnt_want_write(path.mnt);
 703         if (error)
 704                 goto out_release;
 705         error = chown_common(&path, user, group);
 706         mnt_drop_write(path.mnt);
 707 out_release:
 708         path_put(&path);
 709         if (retry_estale(error, lookup_flags)) {
 710                 lookup_flags |= LOOKUP_REVAL;
 711                 goto retry;
 712         }
 713 out:
 714         return error;
 715 }
 716
 717 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 718                 gid_t, group, int, flag)
 719 {
 720         return do_fchownat(dfd, filename, user, group, flag);
 721 }
 722
 723 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 724 {
 725         return do_fchownat(AT_FDCWD, filename, user, group, 0);
 726 }
 727
 728 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 729 {
 730         return do_fchownat(AT_FDCWD, filename, user, group,
 731                            AT_SYMLINK_NOFOLLOW);
 732 }
 733
 734 int vfs_fchown(struct file *file, uid_t user, gid_t group)
 735 {
 736         int error;
 737
 738         error = mnt_want_write_file(file);
 739         if (error)
 740                 return error;
 741         audit_file(file);
 742         error = chown_common(&file->f_path, user, group);
 743         mnt_drop_write_file(file);
 744         return error;
 745 }
 746
 747 int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
 748 {
 749         struct fd f = fdget(fd);
 750         int error = -EBADF;
 751
 752         if (f.file) {
 753                 error = vfs_fchown(f.file, user, group);
 754                 fdput(f);
 755         }
 756         return error;
 757 }
 758
 759 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 760 {
 761         return ksys_fchown(fd, user, group);
 762 }
 763
 764 static int do_dentry_open(struct file *f,
 765                           struct inode *inode,
 766                           int (*open)(struct inode *, struct file *))
 767 {
 768         static const struct file_operations empty_fops = {};
 769         int error;
 770
 771         path_get(&f->f_path);
 772         f->f_inode = inode;
 773         f->f_mapping = inode->i_mapping;
 774         f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
 775         f->f_sb_err = file_sample_sb_err(f);
 776
 777         if (unlikely(f->f_flags & O_PATH)) {
 778                 f->f_mode = FMODE_PATH | FMODE_OPENED;
 779                 f->f_op = &empty_fops;
 780                 return 0;
 781         }
 782
 783         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
 784                 error = get_write_access(inode);
 785                 if (unlikely(error))
 786                         goto cleanup_file;
 787                 error = __mnt_want_write(f->f_path.mnt);
 788                 if (unlikely(error)) {
 789                         put_write_access(inode);
 790                         goto cleanup_file;
 791                 }
 792                 f->f_mode |= FMODE_WRITER;
 793         }
 794
 795         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
 796         if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
 797                 f->f_mode |= FMODE_ATOMIC_POS;
 798
 799         f->f_op = fops_get(inode->i_fop);
 800         if (WARN_ON(!f->f_op)) {
 801                 error = -ENODEV;
 802                 goto cleanup_all;
 803         }
 804
 805         error = security_file_open(f);
 806         if (error)
 807                 goto cleanup_all;
 808
 809         error = break_lease(locks_inode(f), f->f_flags);
 810         if (error)
 811                 goto cleanup_all;
 812
 813         /* normally all 3 are set; ->open() can clear them if needed */
 814         f->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
 815         if (!open)
 816                 open = f->f_op->open;
 817         if (open) {
 818                 error = open(inode, f);
 819                 if (error)
 820                         goto cleanup_all;
 821         }
 822         f->f_mode |= FMODE_OPENED;
 823         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 824                 i_readcount_inc(inode);
 825         if ((f->f_mode & FMODE_READ) &&
 826              likely(f->f_op->read || f->f_op->read_iter))
 827                 f->f_mode |= FMODE_CAN_READ;
 828         if ((f->f_mode & FMODE_WRITE) &&
 829              likely(f->f_op->write || f->f_op->write_iter))
 830                 f->f_mode |= FMODE_CAN_WRITE;
 831
 832         f->f_write_hint = WRITE_LIFE_NOT_SET;
 833         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 834
 835         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 836
 837         /* NB: we're sure to have correct a_ops only after f_op->open */
 838         if (f->f_flags & O_DIRECT) {
 839                 if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
 840                         return -EINVAL;
 841         }
 842
 843         /*
 844          * XXX: Huge page cache doesn't support writing yet. Drop all page
 845          * cache for this file before processing writes.
 846          */
 847         if ((f->f_mode & FMODE_WRITE) && filemap_nr_thps(inode->i_mapping))
 848                 truncate_pagecache(inode, 0);
 849
 850         return 0;
 851
 852 cleanup_all:
 853         if (WARN_ON_ONCE(error > 0))
 854                 error = -EINVAL;
 855         fops_put(f->f_op);
 856         if (f->f_mode & FMODE_WRITER) {
 857                 put_write_access(inode);
 858                 __mnt_drop_write(f->f_path.mnt);
 859         }
 860 cleanup_file:
 861         path_put(&f->f_path);
 862         f->f_path.mnt = NULL;
 863         f->f_path.dentry = NULL;
 864         f->f_inode = NULL;
 865         return error;
 866 }
 867
 868 /**
 869  * finish_open - finish opening a file
 870  * @file: file pointer
 871  * @dentry: pointer to dentry
 872  * @open: open callback
 873  * @opened: state of open
 874  *
 875  * This can be used to finish opening a file passed to i_op->atomic_open().
 876  *
 877  * If the open callback is set to NULL, then the standard f_op->open()
 878  * filesystem callback is substituted.
 879  *
 880  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
 881  * the return value of d_splice_alias(), then the caller needs to perform dput()
 882  * on it after finish_open().
 883  *
 884  * Returns zero on success or -errno if the open failed.
 885  */
 886 int finish_open(struct file *file, struct dentry *dentry,
 887                 int (*open)(struct inode *, struct file *))
 888 {
 889         BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */
 890
 891         file->f_path.dentry = dentry;
 892         return do_dentry_open(file, d_backing_inode(dentry), open);
 893 }
 894 EXPORT_SYMBOL(finish_open);
 895
 896 /**
 897  * finish_no_open - finish ->atomic_open() without opening the file
 898  *
 899  * @file: file pointer
 900  * @dentry: dentry or NULL (as returned from ->lookup())
 901  *
 902  * This can be used to set the result of a successful lookup in ->atomic_open().
 903  *
 904  * NB: unlike finish_open() this function does consume the dentry reference and
 905  * the caller need not dput() it.
 906  *
 907  * Returns "0" which must be the return value of ->atomic_open() after having
 908  * called this function.
 909  */
 910 int finish_no_open(struct file *file, struct dentry *dentry)
 911 {
 912         file->f_path.dentry = dentry;
 913         return 0;
 914 }
 915 EXPORT_SYMBOL(finish_no_open);
 916
 917 char *file_path(struct file *filp, char *buf, int buflen)
 918 {
 919         return d_path(&filp->f_path, buf, buflen);
 920 }
 921 EXPORT_SYMBOL(file_path);
 922
 923 /**
 924  * vfs_open - open the file at the given path
 925  * @path: path to open
 926  * @file: newly allocated file with f_flag initialized
 927  * @cred: credentials to use
 928  */
 929 int vfs_open(const struct path *path, struct file *file)
 930 {
 931         file->f_path = *path;
 932         return do_dentry_open(file, d_backing_inode(path->dentry), NULL);
 933 }
 934
 935 struct file *dentry_open(const struct path *path, int flags,
 936                          const struct cred *cred)
 937 {
 938         int error;
 939         struct file *f;
 940
 941         validate_creds(cred);
 942
 943         /* We must always pass in a valid mount pointer. */
 944         BUG_ON(!path->mnt);
 945
 946         f = alloc_empty_file(flags, cred);
 947         if (!IS_ERR(f)) {
 948                 error = vfs_open(path, f);
 949                 if (error) {
 950                         fput(f);
 951                         f = ERR_PTR(error);
 952                 }
 953         }
 954         return f;
 955 }
 956 EXPORT_SYMBOL(dentry_open);
 957
 958 struct file *open_with_fake_path(const struct path *path, int flags,
 959                                 struct inode *inode, const struct cred *cred)
 960 {
 961         struct file *f = alloc_empty_file_noaccount(flags, cred);
 962         if (!IS_ERR(f)) {
 963                 int error;
 964
 965                 f->f_path = *path;
 966                 error = do_dentry_open(f, inode, NULL);
 967                 if (error) {
 968                         fput(f);
 969                         f = ERR_PTR(error);
 970                 }
 971         }
 972         return f;
 973 }
 974 EXPORT_SYMBOL(open_with_fake_path);
 975
 976 #define WILL_CREATE(flags)      (flags & (O_CREAT | __O_TMPFILE))
 977 #define O_PATH_FLAGS            (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC)
 978
 979 inline struct open_how build_open_how(int flags, umode_t mode)
 980 {
 981         struct open_how how = {
 982                 .flags = flags & VALID_OPEN_FLAGS,
 983                 .mode = mode & S_IALLUGO,
 984         };
 985
 986         /* O_PATH beats everything else. */
 987         if (how.flags & O_PATH)
 988                 how.flags &= O_PATH_FLAGS;
 989         /* Modes should only be set for create-like flags. */
 990         if (!WILL_CREATE(how.flags))
 991                 how.mode = 0;
 992         return how;
 993 }
 994
 995 inline int build_open_flags(const struct open_how *how, struct open_flags *op)
 996 {
 997         int flags = how->flags;
 998         int lookup_flags = 0;
 999         int acc_mode = ACC_MODE(flags);
1000
1001         /* Must never be set by userspace */
1002         flags &= ~(FMODE_NONOTIFY | O_CLOEXEC);
1003
1004         /*
1005          * Older syscalls implicitly clear all of the invalid flags or argument
1006          * values before calling build_open_flags(), but openat2(2) checks all
1007          * of its arguments.
1008          */
1009         if (flags & ~VALID_OPEN_FLAGS)
1010                 return -EINVAL;
1011         if (how->resolve & ~VALID_RESOLVE_FLAGS)
1012                 return -EINVAL;
1013
1014         /* Scoping flags are mutually exclusive. */
1015         if ((how->resolve & RESOLVE_BENEATH) && (how->resolve & RESOLVE_IN_ROOT))
1016                 return -EINVAL;
1017
1018         /* Deal with the mode. */
1019         if (WILL_CREATE(flags)) {
1020                 if (how->mode & ~S_IALLUGO)
1021                         return -EINVAL;
1022                 op->mode = how->mode | S_IFREG;
1023         } else {
1024                 if (how->mode != 0)
1025                         return -EINVAL;
1026                 op->mode = 0;
1027         }
1028
1029         /*
1030          * In order to ensure programs get explicit errors when trying to use
1031          * O_TMPFILE on old kernels, O_TMPFILE is implemented such that it
1032          * looks like (O_DIRECTORY|O_RDWR & ~O_CREAT) to old kernels. But we
1033          * have to require userspace to explicitly set it.
1034          */
1035         if (flags & __O_TMPFILE) {
1036                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
1037                         return -EINVAL;
1038                 if (!(acc_mode & MAY_WRITE))
1039                         return -EINVAL;
1040         }
1041         if (flags & O_PATH) {
1042                 /* O_PATH only permits certain other flags to be set. */
1043                 if (flags & ~O_PATH_FLAGS)
1044                         return -EINVAL;
1045                 acc_mode = 0;
1046         }
1047
1048         /*
1049          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
1050          * check for O_DSYNC if the need any syncing at all we enforce it's
1051          * always set instead of having to deal with possibly weird behaviour
1052          * for malicious applications setting only __O_SYNC.
1053          */
1054         if (flags & __O_SYNC)
1055                 flags |= O_DSYNC;
1056
1057         op->open_flag = flags;
1058
1059         /* O_TRUNC implies we need access checks for write permissions */
1060         if (flags & O_TRUNC)
1061                 acc_mode |= MAY_WRITE;
1062
1063         /* Allow the LSM permission hook to distinguish append
1064            access from general write access. */
1065         if (flags & O_APPEND)
1066                 acc_mode |= MAY_APPEND;
1067
1068         op->acc_mode = acc_mode;
1069
1070         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
1071
1072         if (flags & O_CREAT) {
1073                 op->intent |= LOOKUP_CREATE;
1074                 if (flags & O_EXCL) {
1075                         op->intent |= LOOKUP_EXCL;
1076                         flags |= O_NOFOLLOW;
1077                 }
1078         }
1079
1080         if (flags & O_DIRECTORY)
1081                 lookup_flags |= LOOKUP_DIRECTORY;
1082         if (!(flags & O_NOFOLLOW))
1083                 lookup_flags |= LOOKUP_FOLLOW;
1084
1085         if (how->resolve & RESOLVE_NO_XDEV)
1086                 lookup_flags |= LOOKUP_NO_XDEV;
1087         if (how->resolve & RESOLVE_NO_MAGICLINKS)
1088                 lookup_flags |= LOOKUP_NO_MAGICLINKS;
1089         if (how->resolve & RESOLVE_NO_SYMLINKS)
1090                 lookup_flags |= LOOKUP_NO_SYMLINKS;
1091         if (how->resolve & RESOLVE_BENEATH)
1092                 lookup_flags |= LOOKUP_BENEATH;
1093         if (how->resolve & RESOLVE_IN_ROOT)
1094                 lookup_flags |= LOOKUP_IN_ROOT;
1095
1096         op->lookup_flags = lookup_flags;
1097         return 0;
1098 }
1099
1100 /**
1101  * file_open_name - open file and return file pointer
1102  *
1103  * @name:       struct filename containing path to open
1104  * @flags:      open flags as per the open(2) second argument
1105  * @mode:       mode for the new file if O_CREAT is set, else ignored
1106  *
1107  * This is the helper to open a file from kernelspace if you really
1108  * have to.  But in generally you should not do this, so please move
1109  * along, nothing to see here..
1110  */
1111 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
1112 {
1113         struct open_flags op;
1114         struct open_how how = build_open_how(flags, mode);
1115         int err = build_open_flags(&how, &op);
1116         if (err)
1117                 return ERR_PTR(err);
1118         return do_filp_open(AT_FDCWD, name, &op);
1119 }
1120
1121 /**
1122  * filp_open - open file and return file pointer
1123  *
1124  * @filename:   path to open
1125  * @flags:      open flags as per the open(2) second argument
1126  * @mode:       mode for the new file if O_CREAT is set, else ignored
1127  *
1128  * This is the helper to open a file from kernelspace if you really
1129  * have to.  But in generally you should not do this, so please move
1130  * along, nothing to see here..
1131  */
1132 struct file *filp_open(const char *filename, int flags, umode_t mode)
1133 {
1134         struct filename *name = getname_kernel(filename);
1135         struct file *file = ERR_CAST(name);
1136
1137         if (!IS_ERR(name)) {
1138                 file = file_open_name(name, flags, mode);
1139                 putname(name);
1140         }
1141         return file;
1142 }
1143 EXPORT_SYMBOL(filp_open);
1144
1145 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
1146                             const char *filename, int flags, umode_t mode)
1147 {
1148         struct open_flags op;
1149         struct open_how how = build_open_how(flags, mode);
1150         int err = build_open_flags(&how, &op);
1151         if (err)
1152                 return ERR_PTR(err);
1153         return do_file_open_root(dentry, mnt, filename, &op);
1154 }
1155 EXPORT_SYMBOL(file_open_root);
1156
1157 static long do_sys_openat2(int dfd, const char __user *filename,
1158                            struct open_how *how)
1159 {
1160         struct open_flags op;
1161         int fd = build_open_flags(how, &op);
1162         struct filename *tmp;
1163
1164         if (fd)
1165                 return fd;
1166
1167         tmp = getname(filename);
1168         if (IS_ERR(tmp))
1169                 return PTR_ERR(tmp);
1170
1171         fd = get_unused_fd_flags(how->flags);
1172         if (fd >= 0) {
1173                 struct file *f = do_filp_open(dfd, tmp, &op);
1174                 if (IS_ERR(f)) {
1175                         put_unused_fd(fd);
1176                         fd = PTR_ERR(f);
1177                 } else {
1178                         fsnotify_open(f);
1179                         fd_install(fd, f);
1180                 }
1181         }
1182         putname(tmp);
1183         return fd;
1184 }
1185
1186 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1187 {
1188         struct open_how how = build_open_how(flags, mode);
1189         return do_sys_openat2(dfd, filename, &how);
1190 }
1191
1192
1193 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1194 {
1195         if (force_o_largefile())
1196                 flags |= O_LARGEFILE;
1197         return do_sys_open(AT_FDCWD, filename, flags, mode);
1198 }
1199
1200 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1201                 umode_t, mode)
1202 {
1203         if (force_o_largefile())
1204                 flags |= O_LARGEFILE;
1205         return do_sys_open(dfd, filename, flags, mode);
1206 }
1207
1208 SYSCALL_DEFINE4(openat2, int, dfd, const char __user *, filename,
1209                 struct open_how __user *, how, size_t, usize)
1210 {
1211         int err;
1212         struct open_how tmp;
1213
1214         BUILD_BUG_ON(sizeof(struct open_how) < OPEN_HOW_SIZE_VER0);
1215         BUILD_BUG_ON(sizeof(struct open_how) != OPEN_HOW_SIZE_LATEST);
1216
1217         if (unlikely(usize < OPEN_HOW_SIZE_VER0))
1218                 return -EINVAL;
1219
1220         err = copy_struct_from_user(&tmp, sizeof(tmp), how, usize);
1221         if (err)
1222                 return err;
1223
1224         /* O_LARGEFILE is only allowed for non-O_PATH. */
1225         if (!(tmp.flags & O_PATH) && force_o_largefile())
1226                 tmp.flags |= O_LARGEFILE;
1227
1228         return do_sys_openat2(dfd, filename, &tmp);
1229 }
1230
1231 #ifdef CONFIG_COMPAT
1232 /*
1233  * Exactly like sys_open(), except that it doesn't set the
1234  * O_LARGEFILE flag.
1235  */
1236 COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1237 {
1238         return do_sys_open(AT_FDCWD, filename, flags, mode);
1239 }
1240
1241 /*
1242  * Exactly like sys_openat(), except that it doesn't set the
1243  * O_LARGEFILE flag.
1244  */
1245 COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
1246 {
1247         return do_sys_open(dfd, filename, flags, mode);
1248 }
1249 #endif
1250
1251 #ifndef __alpha__
1252
1253 /*
1254  * For backward compatibility?  Maybe this should be moved
1255  * into arch/i386 instead?
1256  */
1257 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1258 {
1259         int flags = O_CREAT | O_WRONLY | O_TRUNC;
1260
1261         if (force_o_largefile())
1262                 flags |= O_LARGEFILE;
1263         return do_sys_open(AT_FDCWD, pathname, flags, mode);
1264 }
1265 #endif
1266
1267 /*
1268  * "id" is the POSIX thread ID. We use the
1269  * files pointer for this..
1270  */
1271 int filp_close(struct file *filp, fl_owner_t id)
1272 {
1273         int retval = 0;
1274
1275         if (!file_count(filp)) {
1276                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1277                 return 0;
1278         }
1279
1280         if (filp->f_op->flush)
1281                 retval = filp->f_op->flush(filp, id);
1282
1283         if (likely(!(filp->f_mode & FMODE_PATH))) {
1284                 dnotify_flush(filp, id);
1285                 locks_remove_posix(filp, id);
1286         }
1287         fput(filp);
1288         return retval;
1289 }
1290
1291 EXPORT_SYMBOL(filp_close);
1292
1293 /*
1294  * Careful here! We test whether the file pointer is NULL before
1295  * releasing the fd. This ensures that one clone task can't release
1296  * an fd while another clone is opening it.
1297  */
1298 SYSCALL_DEFINE1(close, unsigned int, fd)
1299 {
1300         int retval = close_fd(fd);
1301
1302         /* can't restart close syscall because file table entry was cleared */
1303         if (unlikely(retval == -ERESTARTSYS ||
1304                      retval == -ERESTARTNOINTR ||
1305                      retval == -ERESTARTNOHAND ||
1306                      retval == -ERESTART_RESTARTBLOCK))
1307                 retval = -EINTR;
1308
1309         return retval;
1310 }
1311
1312 /**
1313  * close_range() - Close all file descriptors in a given range.
1314  *
1315  * @fd:     starting file descriptor to close
1316  * @max_fd: last file descriptor to close
1317  * @flags:  reserved for future extensions
1318  *
1319  * This closes a range of file descriptors. All file descriptors
1320  * from @fd up to and including @max_fd are closed.
1321  * Currently, errors to close a given file descriptor are ignored.
1322  */
1323 SYSCALL_DEFINE3(close_range, unsigned int, fd, unsigned int, max_fd,
1324                 unsigned int, flags)
1325 {
1326         return __close_range(fd, max_fd, flags);
1327 }
1328
1329 /*
1330  * This routine simulates a hangup on the tty, to arrange that users
1331  * are given clean terminals at login time.
1332  */
1333 SYSCALL_DEFINE0(vhangup)
1334 {
1335         if (capable(CAP_SYS_TTY_CONFIG)) {
1336                 tty_vhangup_self();
1337                 return 0;
1338         }
1339         return -EPERM;
1340 }
1341
1342 /*
1343  * Called when an inode is about to be open.
1344  * We use this to disallow opening large files on 32bit systems if
1345  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1346  * on this flag in sys_open.
1347  */
1348 int generic_file_open(struct inode * inode, struct file * filp)
1349 {
1350         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1351                 return -EOVERFLOW;
1352         return 0;
1353 }
1354
1355 EXPORT_SYMBOL(generic_file_open);
1356
1357 /*
1358  * This is used by subsystems that don't want seekable
1359  * file descriptors. The function is not supposed to ever fail, the only
1360  * reason it returns an 'int' and not 'void' is so that it can be plugged
1361  * directly into file_operations structure.
1362  */
1363 int nonseekable_open(struct inode *inode, struct file *filp)
1364 {
1365         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1366         return 0;
1367 }
1368
1369 EXPORT_SYMBOL(nonseekable_open);
1370
1371 /*
1372  * stream_open is used by subsystems that want stream-like file descriptors.
1373  * Such file descriptors are not seekable and don't have notion of position
1374  * (file.f_pos is always 0 and ppos passed to .read()/.write() is always NULL).
1375  * Contrary to file descriptors of other regular files, .read() and .write()
1376  * can run simultaneously.
1377  *
1378  * stream_open never fails and is marked to return int so that it could be
1379  * directly used as file_operations.open .
1380  */
1381 int stream_open(struct inode *inode, struct file *filp)
1382 {
1383         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE | FMODE_ATOMIC_POS);
1384         filp->f_mode |= FMODE_STREAM;
1385         return 0;
1386 }
1387
1388 EXPORT_SYMBOL(stream_open);