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 user_namespace *mnt_userns, struct dentry *dentry,
  39                 loff_t length, unsigned int time_attrs, 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(mnt_userns, dentry, &newattrs, NULL);
  65         inode_unlock(dentry->d_inode);
  66         return ret;
  67 }
  68
  69 long vfs_truncate(const struct path *path, loff_t length)
  70 {
  71         struct user_namespace *mnt_userns;
  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         mnt_userns = mnt_user_ns(path->mnt);
  88         error = inode_permission(mnt_userns, inode, MAY_WRITE);
  89         if (error)
  90                 goto mnt_drop_write_and_out;
  91
  92         error = -EPERM;
  93         if (IS_APPEND(inode))
  94                 goto mnt_drop_write_and_out;
  95
  96         error = get_write_access(inode);
  97         if (error)
  98                 goto mnt_drop_write_and_out;
  99
 100         /*
 101          * Make sure that there are no leases.  get_write_access() protects
 102          * against the truncate racing with a lease-granting setlease().
 103          */
 104         error = break_lease(inode, O_WRONLY);
 105         if (error)
 106                 goto put_write_and_out;
 107
 108         error = security_path_truncate(path);
 109         if (!error)
 110                 error = do_truncate(mnt_userns, path->dentry, length, 0, NULL);
 111
 112 put_write_and_out:
 113         put_write_access(inode);
 114 mnt_drop_write_and_out:
 115         mnt_drop_write(path->mnt);
 116 out:
 117         return error;
 118 }
 119 EXPORT_SYMBOL_GPL(vfs_truncate);
 120
 121 long do_sys_truncate(const char __user *pathname, loff_t length)
 122 {
 123         unsigned int lookup_flags = LOOKUP_FOLLOW;
 124         struct path path;
 125         int error;
 126
 127         if (length < 0) /* sorry, but loff_t says... */
 128                 return -EINVAL;
 129
 130 retry:
 131         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 132         if (!error) {
 133                 error = vfs_truncate(&path, length);
 134                 path_put(&path);
 135         }
 136         if (retry_estale(error, lookup_flags)) {
 137                 lookup_flags |= LOOKUP_REVAL;
 138                 goto retry;
 139         }
 140         return error;
 141 }
 142
 143 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 144 {
 145         return do_sys_truncate(path, length);
 146 }
 147
 148 #ifdef CONFIG_COMPAT
 149 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
 150 {
 151         return do_sys_truncate(path, length);
 152 }
 153 #endif
 154
 155 long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 156 {
 157         struct inode *inode;
 158         struct dentry *dentry;
 159         struct fd f;
 160         int error;
 161
 162         error = -EINVAL;
 163         if (length < 0)
 164                 goto out;
 165         error = -EBADF;
 166         f = fdget(fd);
 167         if (!f.file)
 168                 goto out;
 169
 170         /* explicitly opened as large or we are on 64-bit box */
 171         if (f.file->f_flags & O_LARGEFILE)
 172                 small = 0;
 173
 174         dentry = f.file->f_path.dentry;
 175         inode = dentry->d_inode;
 176         error = -EINVAL;
 177         if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
 178                 goto out_putf;
 179
 180         error = -EINVAL;
 181         /* Cannot ftruncate over 2^31 bytes without large file support */
 182         if (small && length > MAX_NON_LFS)
 183                 goto out_putf;
 184
 185         error = -EPERM;
 186         /* Check IS_APPEND on real upper inode */
 187         if (IS_APPEND(file_inode(f.file)))
 188                 goto out_putf;
 189         sb_start_write(inode->i_sb);
 190         error = security_path_truncate(&f.file->f_path);
 191         if (!error)
 192                 error = do_truncate(file_mnt_user_ns(f.file), dentry, length,
 193                                     ATTR_MTIME | ATTR_CTIME, f.file);
 194         sb_end_write(inode->i_sb);
 195 out_putf:
 196         fdput(f);
 197 out:
 198         return error;
 199 }
 200
 201 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 202 {
 203         return do_sys_ftruncate(fd, length, 1);
 204 }
 205
 206 #ifdef CONFIG_COMPAT
 207 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
 208 {
 209         return do_sys_ftruncate(fd, length, 1);
 210 }
 211 #endif
 212
 213 /* LFS versions of truncate are only needed on 32 bit machines */
 214 #if BITS_PER_LONG == 32
 215 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
 216 {
 217         return do_sys_truncate(path, length);
 218 }
 219
 220 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
 221 {
 222         return do_sys_ftruncate(fd, length, 0);
 223 }
 224 #endif /* BITS_PER_LONG == 32 */
 225
 226
 227 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 228 {
 229         struct inode *inode = file_inode(file);
 230         long ret;
 231
 232         if (offset < 0 || len <= 0)
 233                 return -EINVAL;
 234
 235         /* Return error if mode is not supported */
 236         if (mode & ~FALLOC_FL_SUPPORTED_MASK)
 237                 return -EOPNOTSUPP;
 238
 239         /* Punch hole and zero range are mutually exclusive */
 240         if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
 241             (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
 242                 return -EOPNOTSUPP;
 243
 244         /* Punch hole must have keep size set */
 245         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
 246             !(mode & FALLOC_FL_KEEP_SIZE))
 247                 return -EOPNOTSUPP;
 248
 249         /* Collapse range should only be used exclusively. */
 250         if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
 251             (mode & ~FALLOC_FL_COLLAPSE_RANGE))
 252                 return -EINVAL;
 253
 254         /* Insert range should only be used exclusively. */
 255         if ((mode & FALLOC_FL_INSERT_RANGE) &&
 256             (mode & ~FALLOC_FL_INSERT_RANGE))
 257                 return -EINVAL;
 258
 259         /* Unshare range should only be used with allocate mode. */
 260         if ((mode & FALLOC_FL_UNSHARE_RANGE) &&
 261             (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))
 262                 return -EINVAL;
 263
 264         if (!(file->f_mode & FMODE_WRITE))
 265                 return -EBADF;
 266
 267         /*
 268          * We can only allow pure fallocate on append only files
 269          */
 270         if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
 271                 return -EPERM;
 272
 273         if (IS_IMMUTABLE(inode))
 274                 return -EPERM;
 275
 276         /*
 277          * We cannot allow any fallocate operation on an active swapfile
 278          */
 279         if (IS_SWAPFILE(inode))
 280                 return -ETXTBSY;
 281
 282         /*
 283          * Revalidate the write permissions, in case security policy has
 284          * changed since the files were opened.
 285          */
 286         ret = security_file_permission(file, MAY_WRITE);
 287         if (ret)
 288                 return ret;
 289
 290         if (S_ISFIFO(inode->i_mode))
 291                 return -ESPIPE;
 292
 293         if (S_ISDIR(inode->i_mode))
 294                 return -EISDIR;
 295
 296         if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
 297                 return -ENODEV;
 298
 299         /* Check for wrap through zero too */
 300         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 301                 return -EFBIG;
 302
 303         if (!file->f_op->fallocate)
 304                 return -EOPNOTSUPP;
 305
 306         file_start_write(file);
 307         ret = file->f_op->fallocate(file, mode, offset, len);
 308
 309         /*
 310          * Create inotify and fanotify events.
 311          *
 312          * To keep the logic simple always create events if fallocate succeeds.
 313          * This implies that events are even created if the file size remains
 314          * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
 315          */
 316         if (ret == 0)
 317                 fsnotify_modify(file);
 318
 319         file_end_write(file);
 320         return ret;
 321 }
 322 EXPORT_SYMBOL_GPL(vfs_fallocate);
 323
 324 int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
 325 {
 326         struct fd f = fdget(fd);
 327         int error = -EBADF;
 328
 329         if (f.file) {
 330                 error = vfs_fallocate(f.file, mode, offset, len);
 331                 fdput(f);
 332         }
 333         return error;
 334 }
 335
 336 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
 337 {
 338         return ksys_fallocate(fd, mode, offset, len);
 339 }
 340
 341 /*
 342  * access() needs to use the real uid/gid, not the effective uid/gid.
 343  * We do this by temporarily clearing all FS-related capabilities and
 344  * switching the fsuid/fsgid around to the real ones.
 345  */
 346 static const struct cred *access_override_creds(void)
 347 {
 348         const struct cred *old_cred;
 349         struct cred *override_cred;
 350
 351         override_cred = prepare_creds();
 352         if (!override_cred)
 353                 return NULL;
 354
 355         override_cred->fsuid = override_cred->uid;
 356         override_cred->fsgid = override_cred->gid;
 357
 358         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 359                 /* Clear the capabilities if we switch to a non-root user */
 360                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 361                 if (!uid_eq(override_cred->uid, root_uid))
 362                         cap_clear(override_cred->cap_effective);
 363                 else
 364                         override_cred->cap_effective =
 365                                 override_cred->cap_permitted;
 366         }
 367
 368         /*
 369          * The new set of credentials can *only* be used in
 370          * task-synchronous circumstances, and does not need
 371          * RCU freeing, unless somebody then takes a separate
 372          * reference to it.
 373          *
 374          * NOTE! This is _only_ true because this credential
 375          * is used purely for override_creds() that installs
 376          * it as the subjective cred. Other threads will be
 377          * accessing ->real_cred, not the subjective cred.
 378          *
 379          * If somebody _does_ make a copy of this (using the
 380          * 'get_current_cred()' function), that will clear the
 381          * non_rcu field, because now that other user may be
 382          * expecting RCU freeing. But normal thread-synchronous
 383          * cred accesses will keep things non-RCY.
 384          */
 385         override_cred->non_rcu = 1;
 386
 387         old_cred = override_creds(override_cred);
 388
 389         /* override_cred() gets its own ref */
 390         put_cred(override_cred);
 391
 392         return old_cred;
 393 }
 394
 395 static long do_faccessat(int dfd, const char __user *filename, int mode, int flags)
 396 {
 397         struct path path;
 398         struct inode *inode;
 399         int res;
 400         unsigned int lookup_flags = LOOKUP_FOLLOW;
 401         const struct cred *old_cred = NULL;
 402
 403         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 404                 return -EINVAL;
 405
 406         if (flags & ~(AT_EACCESS | AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
 407                 return -EINVAL;
 408
 409         if (flags & AT_SYMLINK_NOFOLLOW)
 410                 lookup_flags &= ~LOOKUP_FOLLOW;
 411         if (flags & AT_EMPTY_PATH)
 412                 lookup_flags |= LOOKUP_EMPTY;
 413
 414         if (!(flags & AT_EACCESS)) {
 415                 old_cred = access_override_creds();
 416                 if (!old_cred)
 417                         return -ENOMEM;
 418         }
 419
 420 retry:
 421         res = user_path_at(dfd, filename, lookup_flags, &path);
 422         if (res)
 423                 goto out;
 424
 425         inode = d_backing_inode(path.dentry);
 426
 427         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 428                 /*
 429                  * MAY_EXEC on regular files is denied if the fs is mounted
 430                  * with the "noexec" flag.
 431                  */
 432                 res = -EACCES;
 433                 if (path_noexec(&path))
 434                         goto out_path_release;
 435         }
 436
 437         res = inode_permission(mnt_user_ns(path.mnt), inode, mode | MAY_ACCESS);
 438         /* SuS v2 requires we report a read only fs too */
 439         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 440                 goto out_path_release;
 441         /*
 442          * This is a rare case where using __mnt_is_readonly()
 443          * is OK without a mnt_want/drop_write() pair.  Since
 444          * no actual write to the fs is performed here, we do
 445          * not need to telegraph to that to anyone.
 446          *
 447          * By doing this, we accept that this access is
 448          * inherently racy and know that the fs may change
 449          * state before we even see this result.
 450          */
 451         if (__mnt_is_readonly(path.mnt))
 452                 res = -EROFS;
 453
 454 out_path_release:
 455         path_put(&path);
 456         if (retry_estale(res, lookup_flags)) {
 457                 lookup_flags |= LOOKUP_REVAL;
 458                 goto retry;
 459         }
 460 out:
 461         if (old_cred)
 462                 revert_creds(old_cred);
 463
 464         return res;
 465 }
 466
 467 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 468 {
 469         return do_faccessat(dfd, filename, mode, 0);
 470 }
 471
 472 SYSCALL_DEFINE4(faccessat2, int, dfd, const char __user *, filename, int, mode,
 473                 int, flags)
 474 {
 475         return do_faccessat(dfd, filename, mode, flags);
 476 }
 477
 478 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 479 {
 480         return do_faccessat(AT_FDCWD, filename, mode, 0);
 481 }
 482
 483 SYSCALL_DEFINE1(chdir, const char __user *, filename)
 484 {
 485         struct path path;
 486         int error;
 487         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 488 retry:
 489         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 490         if (error)
 491                 goto out;
 492
 493         error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
 494         if (error)
 495                 goto dput_and_out;
 496
 497         set_fs_pwd(current->fs, &path);
 498
 499 dput_and_out:
 500         path_put(&path);
 501         if (retry_estale(error, lookup_flags)) {
 502                 lookup_flags |= LOOKUP_REVAL;
 503                 goto retry;
 504         }
 505 out:
 506         return error;
 507 }
 508
 509 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 510 {
 511         struct fd f = fdget_raw(fd);
 512         int error;
 513
 514         error = -EBADF;
 515         if (!f.file)
 516                 goto out;
 517
 518         error = -ENOTDIR;
 519         if (!d_can_lookup(f.file->f_path.dentry))
 520                 goto out_putf;
 521
 522         error = file_permission(f.file, MAY_EXEC | MAY_CHDIR);
 523         if (!error)
 524                 set_fs_pwd(current->fs, &f.file->f_path);
 525 out_putf:
 526         fdput(f);
 527 out:
 528         return error;
 529 }
 530
 531 SYSCALL_DEFINE1(chroot, const char __user *, filename)
 532 {
 533         struct path path;
 534         int error;
 535         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 536 retry:
 537         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 538         if (error)
 539                 goto out;
 540
 541         error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
 542         if (error)
 543                 goto dput_and_out;
 544
 545         error = -EPERM;
 546         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
 547                 goto dput_and_out;
 548         error = security_path_chroot(&path);
 549         if (error)
 550                 goto dput_and_out;
 551
 552         set_fs_root(current->fs, &path);
 553         error = 0;
 554 dput_and_out:
 555         path_put(&path);
 556         if (retry_estale(error, lookup_flags)) {
 557                 lookup_flags |= LOOKUP_REVAL;
 558                 goto retry;
 559         }
 560 out:
 561         return error;
 562 }
 563
 564 int chmod_common(const struct path *path, umode_t mode)
 565 {
 566         struct inode *inode = path->dentry->d_inode;
 567         struct inode *delegated_inode = NULL;
 568         struct iattr newattrs;
 569         int error;
 570
 571         error = mnt_want_write(path->mnt);
 572         if (error)
 573                 return error;
 574 retry_deleg:
 575         inode_lock(inode);
 576         error = security_path_chmod(path, mode);
 577         if (error)
 578                 goto out_unlock;
 579         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 580         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 581         error = notify_change(mnt_user_ns(path->mnt), path->dentry,
 582                               &newattrs, &delegated_inode);
 583 out_unlock:
 584         inode_unlock(inode);
 585         if (delegated_inode) {
 586                 error = break_deleg_wait(&delegated_inode);
 587                 if (!error)
 588                         goto retry_deleg;
 589         }
 590         mnt_drop_write(path->mnt);
 591         return error;
 592 }
 593
 594 int vfs_fchmod(struct file *file, umode_t mode)
 595 {
 596         audit_file(file);
 597         return chmod_common(&file->f_path, mode);
 598 }
 599
 600 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 601 {
 602         struct fd f = fdget(fd);
 603         int err = -EBADF;
 604
 605         if (f.file) {
 606                 err = vfs_fchmod(f.file, mode);
 607                 fdput(f);
 608         }
 609         return err;
 610 }
 611
 612 static int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
 613 {
 614         struct path path;
 615         int error;
 616         unsigned int lookup_flags = LOOKUP_FOLLOW;
 617 retry:
 618         error = user_path_at(dfd, filename, lookup_flags, &path);
 619         if (!error) {
 620                 error = chmod_common(&path, mode);
 621                 path_put(&path);
 622                 if (retry_estale(error, lookup_flags)) {
 623                         lookup_flags |= LOOKUP_REVAL;
 624                         goto retry;
 625                 }
 626         }
 627         return error;
 628 }
 629
 630 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
 631                 umode_t, mode)
 632 {
 633         return do_fchmodat(dfd, filename, mode);
 634 }
 635
 636 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 637 {
 638         return do_fchmodat(AT_FDCWD, filename, mode);
 639 }
 640
 641 int chown_common(const struct path *path, uid_t user, gid_t group)
 642 {
 643         struct user_namespace *mnt_userns;
 644         struct inode *inode = path->dentry->d_inode;
 645         struct inode *delegated_inode = NULL;
 646         int error;
 647         struct iattr newattrs;
 648         kuid_t uid;
 649         kgid_t gid;
 650
 651         uid = make_kuid(current_user_ns(), user);
 652         gid = make_kgid(current_user_ns(), group);
 653
 654         mnt_userns = mnt_user_ns(path->mnt);
 655         uid = kuid_from_mnt(mnt_userns, uid);
 656         gid = kgid_from_mnt(mnt_userns, gid);
 657
 658 retry_deleg:
 659         newattrs.ia_valid =  ATTR_CTIME;
 660         if (user != (uid_t) -1) {
 661                 if (!uid_valid(uid))
 662                         return -EINVAL;
 663                 newattrs.ia_valid |= ATTR_UID;
 664                 newattrs.ia_uid = uid;
 665         }
 666         if (group != (gid_t) -1) {
 667                 if (!gid_valid(gid))
 668                         return -EINVAL;
 669                 newattrs.ia_valid |= ATTR_GID;
 670                 newattrs.ia_gid = gid;
 671         }
 672         if (!S_ISDIR(inode->i_mode))
 673                 newattrs.ia_valid |=
 674                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 675         inode_lock(inode);
 676         error = security_path_chown(path, uid, gid);
 677         if (!error)
 678                 error = notify_change(mnt_userns, path->dentry, &newattrs,
 679                                       &delegated_inode);
 680         inode_unlock(inode);
 681         if (delegated_inode) {
 682                 error = break_deleg_wait(&delegated_inode);
 683                 if (!error)
 684                         goto retry_deleg;
 685         }
 686         return error;
 687 }
 688
 689 int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
 690                 int flag)
 691 {
 692         struct path path;
 693         int error = -EINVAL;
 694         int lookup_flags;
 695
 696         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 697                 goto out;
 698
 699         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 700         if (flag & AT_EMPTY_PATH)
 701                 lookup_flags |= LOOKUP_EMPTY;
 702 retry:
 703         error = user_path_at(dfd, filename, lookup_flags, &path);
 704         if (error)
 705                 goto out;
 706         error = mnt_want_write(path.mnt);
 707         if (error)
 708                 goto out_release;
 709         error = chown_common(&path, user, group);
 710         mnt_drop_write(path.mnt);
 711 out_release:
 712         path_put(&path);
 713         if (retry_estale(error, lookup_flags)) {
 714                 lookup_flags |= LOOKUP_REVAL;
 715                 goto retry;
 716         }
 717 out:
 718         return error;
 719 }
 720
 721 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 722                 gid_t, group, int, flag)
 723 {
 724         return do_fchownat(dfd, filename, user, group, flag);
 725 }
 726
 727 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 728 {
 729         return do_fchownat(AT_FDCWD, filename, user, group, 0);
 730 }
 731
 732 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 733 {
 734         return do_fchownat(AT_FDCWD, filename, user, group,
 735                            AT_SYMLINK_NOFOLLOW);
 736 }
 737
 738 int vfs_fchown(struct file *file, uid_t user, gid_t group)
 739 {
 740         int error;
 741
 742         error = mnt_want_write_file(file);
 743         if (error)
 744                 return error;
 745         audit_file(file);
 746         error = chown_common(&file->f_path, user, group);
 747         mnt_drop_write_file(file);
 748         return error;
 749 }
 750
 751 int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
 752 {
 753         struct fd f = fdget(fd);
 754         int error = -EBADF;
 755
 756         if (f.file) {
 757                 error = vfs_fchown(f.file, user, group);
 758                 fdput(f);
 759         }
 760         return error;
 761 }
 762
 763 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 764 {
 765         return ksys_fchown(fd, user, group);
 766 }
 767
 768 static int do_dentry_open(struct file *f,
 769                           struct inode *inode,
 770                           int (*open)(struct inode *, struct file *))
 771 {
 772         static const struct file_operations empty_fops = {};
 773         int error;
 774
 775         path_get(&f->f_path);
 776         f->f_inode = inode;
 777         f->f_mapping = inode->i_mapping;
 778         f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
 779         f->f_sb_err = file_sample_sb_err(f);
 780
 781         if (unlikely(f->f_flags & O_PATH)) {
 782                 f->f_mode = FMODE_PATH | FMODE_OPENED;
 783                 f->f_op = &empty_fops;
 784                 return 0;
 785         }
 786
 787         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
 788                 error = get_write_access(inode);
 789                 if (unlikely(error))
 790                         goto cleanup_file;
 791                 error = __mnt_want_write(f->f_path.mnt);
 792                 if (unlikely(error)) {
 793                         put_write_access(inode);
 794                         goto cleanup_file;
 795                 }
 796                 f->f_mode |= FMODE_WRITER;
 797         }
 798
 799         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
 800         if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
 801                 f->f_mode |= FMODE_ATOMIC_POS;
 802
 803         f->f_op = fops_get(inode->i_fop);
 804         if (WARN_ON(!f->f_op)) {
 805                 error = -ENODEV;
 806                 goto cleanup_all;
 807         }
 808
 809         error = security_file_open(f);
 810         if (error)
 811                 goto cleanup_all;
 812
 813         error = break_lease(locks_inode(f), f->f_flags);
 814         if (error)
 815                 goto cleanup_all;
 816
 817         /* normally all 3 are set; ->open() can clear them if needed */
 818         f->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
 819         if (!open)
 820                 open = f->f_op->open;
 821         if (open) {
 822                 error = open(inode, f);
 823                 if (error)
 824                         goto cleanup_all;
 825         }
 826         f->f_mode |= FMODE_OPENED;
 827         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 828                 i_readcount_inc(inode);
 829         if ((f->f_mode & FMODE_READ) &&
 830              likely(f->f_op->read || f->f_op->read_iter))
 831                 f->f_mode |= FMODE_CAN_READ;
 832         if ((f->f_mode & FMODE_WRITE) &&
 833              likely(f->f_op->write || f->f_op->write_iter))
 834                 f->f_mode |= FMODE_CAN_WRITE;
 835
 836         f->f_write_hint = WRITE_LIFE_NOT_SET;
 837         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 838
 839         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 840
 841         /* NB: we're sure to have correct a_ops only after f_op->open */
 842         if (f->f_flags & O_DIRECT) {
 843                 if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
 844                         return -EINVAL;
 845         }
 846
 847         /*
 848          * XXX: Huge page cache doesn't support writing yet. Drop all page
 849          * cache for this file before processing writes.
 850          */
 851         if (f->f_mode & FMODE_WRITE) {
 852                 /*
 853                  * Paired with smp_mb() in collapse_file() to ensure nr_thps
 854                  * is up to date and the update to i_writecount by
 855                  * get_write_access() is visible. Ensures subsequent insertion
 856                  * of THPs into the page cache will fail.
 857                  */
 858                 smp_mb();
 859                 if (filemap_nr_thps(inode->i_mapping))
 860                         truncate_pagecache(inode, 0);
 861         }
 862
 863         return 0;
 864
 865 cleanup_all:
 866         if (WARN_ON_ONCE(error > 0))
 867                 error = -EINVAL;
 868         fops_put(f->f_op);
 869         if (f->f_mode & FMODE_WRITER) {
 870                 put_write_access(inode);
 871                 __mnt_drop_write(f->f_path.mnt);
 872         }
 873 cleanup_file:
 874         path_put(&f->f_path);
 875         f->f_path.mnt = NULL;
 876         f->f_path.dentry = NULL;
 877         f->f_inode = NULL;
 878         return error;
 879 }
 880
 881 /**
 882  * finish_open - finish opening a file
 883  * @file: file pointer
 884  * @dentry: pointer to dentry
 885  * @open: open callback
 886  * @opened: state of open
 887  *
 888  * This can be used to finish opening a file passed to i_op->atomic_open().
 889  *
 890  * If the open callback is set to NULL, then the standard f_op->open()
 891  * filesystem callback is substituted.
 892  *
 893  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
 894  * the return value of d_splice_alias(), then the caller needs to perform dput()
 895  * on it after finish_open().
 896  *
 897  * Returns zero on success or -errno if the open failed.
 898  */
 899 int finish_open(struct file *file, struct dentry *dentry,
 900                 int (*open)(struct inode *, struct file *))
 901 {
 902         BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */
 903
 904         file->f_path.dentry = dentry;
 905         return do_dentry_open(file, d_backing_inode(dentry), open);
 906 }
 907 EXPORT_SYMBOL(finish_open);
 908
 909 /**
 910  * finish_no_open - finish ->atomic_open() without opening the file
 911  *
 912  * @file: file pointer
 913  * @dentry: dentry or NULL (as returned from ->lookup())
 914  *
 915  * This can be used to set the result of a successful lookup in ->atomic_open().
 916  *
 917  * NB: unlike finish_open() this function does consume the dentry reference and
 918  * the caller need not dput() it.
 919  *
 920  * Returns "0" which must be the return value of ->atomic_open() after having
 921  * called this function.
 922  */
 923 int finish_no_open(struct file *file, struct dentry *dentry)
 924 {
 925         file->f_path.dentry = dentry;
 926         return 0;
 927 }
 928 EXPORT_SYMBOL(finish_no_open);
 929
 930 char *file_path(struct file *filp, char *buf, int buflen)
 931 {
 932         return d_path(&filp->f_path, buf, buflen);
 933 }
 934 EXPORT_SYMBOL(file_path);
 935
 936 /**
 937  * vfs_open - open the file at the given path
 938  * @path: path to open
 939  * @file: newly allocated file with f_flag initialized
 940  * @cred: credentials to use
 941  */
 942 int vfs_open(const struct path *path, struct file *file)
 943 {
 944         file->f_path = *path;
 945         return do_dentry_open(file, d_backing_inode(path->dentry), NULL);
 946 }
 947
 948 struct file *dentry_open(const struct path *path, int flags,
 949                          const struct cred *cred)
 950 {
 951         int error;
 952         struct file *f;
 953
 954         validate_creds(cred);
 955
 956         /* We must always pass in a valid mount pointer. */
 957         BUG_ON(!path->mnt);
 958
 959         f = alloc_empty_file(flags, cred);
 960         if (!IS_ERR(f)) {
 961                 error = vfs_open(path, f);
 962                 if (error) {
 963                         fput(f);
 964                         f = ERR_PTR(error);
 965                 }
 966         }
 967         return f;
 968 }
 969 EXPORT_SYMBOL(dentry_open);
 970
 971 struct file *open_with_fake_path(const struct path *path, int flags,
 972                                 struct inode *inode, const struct cred *cred)
 973 {
 974         struct file *f = alloc_empty_file_noaccount(flags, cred);
 975         if (!IS_ERR(f)) {
 976                 int error;
 977
 978                 f->f_path = *path;
 979                 error = do_dentry_open(f, inode, NULL);
 980                 if (error) {
 981                         fput(f);
 982                         f = ERR_PTR(error);
 983                 }
 984         }
 985         return f;
 986 }
 987 EXPORT_SYMBOL(open_with_fake_path);
 988
 989 #define WILL_CREATE(flags)      (flags & (O_CREAT | __O_TMPFILE))
 990 #define O_PATH_FLAGS            (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC)
 991
 992 inline struct open_how build_open_how(int flags, umode_t mode)
 993 {
 994         struct open_how how = {
 995                 .flags = flags & VALID_OPEN_FLAGS,
 996                 .mode = mode & S_IALLUGO,
 997         };
 998
 999         /* O_PATH beats everything else. */
1000         if (how.flags & O_PATH)
1001                 how.flags &= O_PATH_FLAGS;
1002         /* Modes should only be set for create-like flags. */
1003         if (!WILL_CREATE(how.flags))
1004                 how.mode = 0;
1005         return how;
1006 }
1007
1008 inline int build_open_flags(const struct open_how *how, struct open_flags *op)
1009 {
1010         u64 flags = how->flags;
1011         u64 strip = FMODE_NONOTIFY | O_CLOEXEC;
1012         int lookup_flags = 0;
1013         int acc_mode = ACC_MODE(flags);
1014
1015         BUILD_BUG_ON_MSG(upper_32_bits(VALID_OPEN_FLAGS),
1016                          "struct open_flags doesn't yet handle flags > 32 bits");
1017
1018         /*
1019          * Strip flags that either shouldn't be set by userspace like
1020          * FMODE_NONOTIFY or that aren't relevant in determining struct
1021          * open_flags like O_CLOEXEC.
1022          */
1023         flags &= ~strip;
1024
1025         /*
1026          * Older syscalls implicitly clear all of the invalid flags or argument
1027          * values before calling build_open_flags(), but openat2(2) checks all
1028          * of its arguments.
1029          */
1030         if (flags & ~VALID_OPEN_FLAGS)
1031                 return -EINVAL;
1032         if (how->resolve & ~VALID_RESOLVE_FLAGS)
1033                 return -EINVAL;
1034
1035         /* Scoping flags are mutually exclusive. */
1036         if ((how->resolve & RESOLVE_BENEATH) && (how->resolve & RESOLVE_IN_ROOT))
1037                 return -EINVAL;
1038
1039         /* Deal with the mode. */
1040         if (WILL_CREATE(flags)) {
1041                 if (how->mode & ~S_IALLUGO)
1042                         return -EINVAL;
1043                 op->mode = how->mode | S_IFREG;
1044         } else {
1045                 if (how->mode != 0)
1046                         return -EINVAL;
1047                 op->mode = 0;
1048         }
1049
1050         /*
1051          * In order to ensure programs get explicit errors when trying to use
1052          * O_TMPFILE on old kernels, O_TMPFILE is implemented such that it
1053          * looks like (O_DIRECTORY|O_RDWR & ~O_CREAT) to old kernels. But we
1054          * have to require userspace to explicitly set it.
1055          */
1056         if (flags & __O_TMPFILE) {
1057                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
1058                         return -EINVAL;
1059                 if (!(acc_mode & MAY_WRITE))
1060                         return -EINVAL;
1061         }
1062         if (flags & O_PATH) {
1063                 /* O_PATH only permits certain other flags to be set. */
1064                 if (flags & ~O_PATH_FLAGS)
1065                         return -EINVAL;
1066                 acc_mode = 0;
1067         }
1068
1069         /*
1070          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
1071          * check for O_DSYNC if the need any syncing at all we enforce it's
1072          * always set instead of having to deal with possibly weird behaviour
1073          * for malicious applications setting only __O_SYNC.
1074          */
1075         if (flags & __O_SYNC)
1076                 flags |= O_DSYNC;
1077
1078         op->open_flag = flags;
1079
1080         /* O_TRUNC implies we need access checks for write permissions */
1081         if (flags & O_TRUNC)
1082                 acc_mode |= MAY_WRITE;
1083
1084         /* Allow the LSM permission hook to distinguish append
1085            access from general write access. */
1086         if (flags & O_APPEND)
1087                 acc_mode |= MAY_APPEND;
1088
1089         op->acc_mode = acc_mode;
1090
1091         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
1092
1093         if (flags & O_CREAT) {
1094                 op->intent |= LOOKUP_CREATE;
1095                 if (flags & O_EXCL) {
1096                         op->intent |= LOOKUP_EXCL;
1097                         flags |= O_NOFOLLOW;
1098                 }
1099         }
1100
1101         if (flags & O_DIRECTORY)
1102                 lookup_flags |= LOOKUP_DIRECTORY;
1103         if (!(flags & O_NOFOLLOW))
1104                 lookup_flags |= LOOKUP_FOLLOW;
1105
1106         if (how->resolve & RESOLVE_NO_XDEV)
1107                 lookup_flags |= LOOKUP_NO_XDEV;
1108         if (how->resolve & RESOLVE_NO_MAGICLINKS)
1109                 lookup_flags |= LOOKUP_NO_MAGICLINKS;
1110         if (how->resolve & RESOLVE_NO_SYMLINKS)
1111                 lookup_flags |= LOOKUP_NO_SYMLINKS;
1112         if (how->resolve & RESOLVE_BENEATH)
1113                 lookup_flags |= LOOKUP_BENEATH;
1114         if (how->resolve & RESOLVE_IN_ROOT)
1115                 lookup_flags |= LOOKUP_IN_ROOT;
1116         if (how->resolve & RESOLVE_CACHED) {
1117                 /* Don't bother even trying for create/truncate/tmpfile open */
1118                 if (flags & (O_TRUNC | O_CREAT | O_TMPFILE))
1119                         return -EAGAIN;
1120                 lookup_flags |= LOOKUP_CACHED;
1121         }
1122
1123         op->lookup_flags = lookup_flags;
1124         return 0;
1125 }
1126
1127 /**
1128  * file_open_name - open file and return file pointer
1129  *
1130  * @name:       struct filename containing path to open
1131  * @flags:      open flags as per the open(2) second argument
1132  * @mode:       mode for the new file if O_CREAT is set, else ignored
1133  *
1134  * This is the helper to open a file from kernelspace if you really
1135  * have to.  But in generally you should not do this, so please move
1136  * along, nothing to see here..
1137  */
1138 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
1139 {
1140         struct open_flags op;
1141         struct open_how how = build_open_how(flags, mode);
1142         int err = build_open_flags(&how, &op);
1143         if (err)
1144                 return ERR_PTR(err);
1145         return do_filp_open(AT_FDCWD, name, &op);
1146 }
1147
1148 /**
1149  * filp_open - open file and return file pointer
1150  *
1151  * @filename:   path to open
1152  * @flags:      open flags as per the open(2) second argument
1153  * @mode:       mode for the new file if O_CREAT is set, else ignored
1154  *
1155  * This is the helper to open a file from kernelspace if you really
1156  * have to.  But in generally you should not do this, so please move
1157  * along, nothing to see here..
1158  */
1159 struct file *filp_open(const char *filename, int flags, umode_t mode)
1160 {
1161         struct filename *name = getname_kernel(filename);
1162         struct file *file = ERR_CAST(name);
1163
1164         if (!IS_ERR(name)) {
1165                 file = file_open_name(name, flags, mode);
1166                 putname(name);
1167         }
1168         return file;
1169 }
1170 EXPORT_SYMBOL(filp_open);
1171
1172 struct file *file_open_root(const struct path *root,
1173                             const char *filename, int flags, umode_t mode)
1174 {
1175         struct open_flags op;
1176         struct open_how how = build_open_how(flags, mode);
1177         int err = build_open_flags(&how, &op);
1178         if (err)
1179                 return ERR_PTR(err);
1180         return do_file_open_root(root, filename, &op);
1181 }
1182 EXPORT_SYMBOL(file_open_root);
1183
1184 static long do_sys_openat2(int dfd, const char __user *filename,
1185                            struct open_how *how)
1186 {
1187         struct open_flags op;
1188         int fd = build_open_flags(how, &op);
1189         struct filename *tmp;
1190
1191         if (fd)
1192                 return fd;
1193
1194         tmp = getname(filename);
1195         if (IS_ERR(tmp))
1196                 return PTR_ERR(tmp);
1197
1198         fd = get_unused_fd_flags(how->flags);
1199         if (fd >= 0) {
1200                 struct file *f = do_filp_open(dfd, tmp, &op);
1201                 if (IS_ERR(f)) {
1202                         put_unused_fd(fd);
1203                         fd = PTR_ERR(f);
1204                 } else {
1205                         fsnotify_open(f);
1206                         fd_install(fd, f);
1207                 }
1208         }
1209         putname(tmp);
1210         return fd;
1211 }
1212
1213 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1214 {
1215         struct open_how how = build_open_how(flags, mode);
1216         return do_sys_openat2(dfd, filename, &how);
1217 }
1218
1219
1220 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1221 {
1222         if (force_o_largefile())
1223                 flags |= O_LARGEFILE;
1224         return do_sys_open(AT_FDCWD, filename, flags, mode);
1225 }
1226
1227 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1228                 umode_t, mode)
1229 {
1230         if (force_o_largefile())
1231                 flags |= O_LARGEFILE;
1232         return do_sys_open(dfd, filename, flags, mode);
1233 }
1234
1235 SYSCALL_DEFINE4(openat2, int, dfd, const char __user *, filename,
1236                 struct open_how __user *, how, size_t, usize)
1237 {
1238         int err;
1239         struct open_how tmp;
1240
1241         BUILD_BUG_ON(sizeof(struct open_how) < OPEN_HOW_SIZE_VER0);
1242         BUILD_BUG_ON(sizeof(struct open_how) != OPEN_HOW_SIZE_LATEST);
1243
1244         if (unlikely(usize < OPEN_HOW_SIZE_VER0))
1245                 return -EINVAL;
1246
1247         err = copy_struct_from_user(&tmp, sizeof(tmp), how, usize);
1248         if (err)
1249                 return err;
1250
1251         /* O_LARGEFILE is only allowed for non-O_PATH. */
1252         if (!(tmp.flags & O_PATH) && force_o_largefile())
1253                 tmp.flags |= O_LARGEFILE;
1254
1255         return do_sys_openat2(dfd, filename, &tmp);
1256 }
1257
1258 #ifdef CONFIG_COMPAT
1259 /*
1260  * Exactly like sys_open(), except that it doesn't set the
1261  * O_LARGEFILE flag.
1262  */
1263 COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1264 {
1265         return do_sys_open(AT_FDCWD, filename, flags, mode);
1266 }
1267
1268 /*
1269  * Exactly like sys_openat(), except that it doesn't set the
1270  * O_LARGEFILE flag.
1271  */
1272 COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
1273 {
1274         return do_sys_open(dfd, filename, flags, mode);
1275 }
1276 #endif
1277
1278 #ifndef __alpha__
1279
1280 /*
1281  * For backward compatibility?  Maybe this should be moved
1282  * into arch/i386 instead?
1283  */
1284 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1285 {
1286         int flags = O_CREAT | O_WRONLY | O_TRUNC;
1287
1288         if (force_o_largefile())
1289                 flags |= O_LARGEFILE;
1290         return do_sys_open(AT_FDCWD, pathname, flags, mode);
1291 }
1292 #endif
1293
1294 /*
1295  * "id" is the POSIX thread ID. We use the
1296  * files pointer for this..
1297  */
1298 int filp_close(struct file *filp, fl_owner_t id)
1299 {
1300         int retval = 0;
1301
1302         if (!file_count(filp)) {
1303                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1304                 return 0;
1305         }
1306
1307         if (filp->f_op->flush)
1308                 retval = filp->f_op->flush(filp, id);
1309
1310         if (likely(!(filp->f_mode & FMODE_PATH))) {
1311                 dnotify_flush(filp, id);
1312                 locks_remove_posix(filp, id);
1313         }
1314         fput(filp);
1315         return retval;
1316 }
1317
1318 EXPORT_SYMBOL(filp_close);
1319
1320 /*
1321  * Careful here! We test whether the file pointer is NULL before
1322  * releasing the fd. This ensures that one clone task can't release
1323  * an fd while another clone is opening it.
1324  */
1325 SYSCALL_DEFINE1(close, unsigned int, fd)
1326 {
1327         int retval = close_fd(fd);
1328
1329         /* can't restart close syscall because file table entry was cleared */
1330         if (unlikely(retval == -ERESTARTSYS ||
1331                      retval == -ERESTARTNOINTR ||
1332                      retval == -ERESTARTNOHAND ||
1333                      retval == -ERESTART_RESTARTBLOCK))
1334                 retval = -EINTR;
1335
1336         return retval;
1337 }
1338
1339 /**
1340  * close_range() - Close all file descriptors in a given range.
1341  *
1342  * @fd:     starting file descriptor to close
1343  * @max_fd: last file descriptor to close
1344  * @flags:  reserved for future extensions
1345  *
1346  * This closes a range of file descriptors. All file descriptors
1347  * from @fd up to and including @max_fd are closed.
1348  * Currently, errors to close a given file descriptor are ignored.
1349  */
1350 SYSCALL_DEFINE3(close_range, unsigned int, fd, unsigned int, max_fd,
1351                 unsigned int, flags)
1352 {
1353         return __close_range(fd, max_fd, flags);
1354 }
1355
1356 /*
1357  * This routine simulates a hangup on the tty, to arrange that users
1358  * are given clean terminals at login time.
1359  */
1360 SYSCALL_DEFINE0(vhangup)
1361 {
1362         if (capable(CAP_SYS_TTY_CONFIG)) {
1363                 tty_vhangup_self();
1364                 return 0;
1365         }
1366         return -EPERM;
1367 }
1368
1369 /*
1370  * Called when an inode is about to be open.
1371  * We use this to disallow opening large files on 32bit systems if
1372  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1373  * on this flag in sys_open.
1374  */
1375 int generic_file_open(struct inode * inode, struct file * filp)
1376 {
1377         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1378                 return -EOVERFLOW;
1379         return 0;
1380 }
1381
1382 EXPORT_SYMBOL(generic_file_open);
1383
1384 /*
1385  * This is used by subsystems that don't want seekable
1386  * file descriptors. The function is not supposed to ever fail, the only
1387  * reason it returns an 'int' and not 'void' is so that it can be plugged
1388  * directly into file_operations structure.
1389  */
1390 int nonseekable_open(struct inode *inode, struct file *filp)
1391 {
1392         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1393         return 0;
1394 }
1395
1396 EXPORT_SYMBOL(nonseekable_open);
1397
1398 /*
1399  * stream_open is used by subsystems that want stream-like file descriptors.
1400  * Such file descriptors are not seekable and don't have notion of position
1401  * (file.f_pos is always 0 and ppos passed to .read()/.write() is always NULL).
1402  * Contrary to file descriptors of other regular files, .read() and .write()
1403  * can run simultaneously.
1404  *
1405  * stream_open never fails and is marked to return int so that it could be
1406  * directly used as file_operations.open .
1407  */
1408 int stream_open(struct inode *inode, struct file *filp)
1409 {
1410         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE | FMODE_ATOMIC_POS);
1411         filp->f_mode |= FMODE_STREAM;
1412         return 0;
1413 }
1414
1415 EXPORT_SYMBOL(stream_open);