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 = locks_verify_truncate(inode, NULL, length);
 109         if (!error)
 110                 error = security_path_truncate(path);
 111         if (!error)
 112                 error = do_truncate(mnt_userns, path->dentry, length, 0, NULL);
 113
 114 put_write_and_out:
 115         put_write_access(inode);
 116 mnt_drop_write_and_out:
 117         mnt_drop_write(path->mnt);
 118 out:
 119         return error;
 120 }
 121 EXPORT_SYMBOL_GPL(vfs_truncate);
 122
 123 long do_sys_truncate(const char __user *pathname, loff_t length)
 124 {
 125         unsigned int lookup_flags = LOOKUP_FOLLOW;
 126         struct path path;
 127         int error;
 128
 129         if (length < 0) /* sorry, but loff_t says... */
 130                 return -EINVAL;
 131
 132 retry:
 133         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 134         if (!error) {
 135                 error = vfs_truncate(&path, length);
 136                 path_put(&path);
 137         }
 138         if (retry_estale(error, lookup_flags)) {
 139                 lookup_flags |= LOOKUP_REVAL;
 140                 goto retry;
 141         }
 142         return error;
 143 }
 144
 145 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 146 {
 147         return do_sys_truncate(path, length);
 148 }
 149
 150 #ifdef CONFIG_COMPAT
 151 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
 152 {
 153         return do_sys_truncate(path, length);
 154 }
 155 #endif
 156
 157 long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 158 {
 159         struct inode *inode;
 160         struct dentry *dentry;
 161         struct fd f;
 162         int error;
 163
 164         error = -EINVAL;
 165         if (length < 0)
 166                 goto out;
 167         error = -EBADF;
 168         f = fdget(fd);
 169         if (!f.file)
 170                 goto out;
 171
 172         /* explicitly opened as large or we are on 64-bit box */
 173         if (f.file->f_flags & O_LARGEFILE)
 174                 small = 0;
 175
 176         dentry = f.file->f_path.dentry;
 177         inode = dentry->d_inode;
 178         error = -EINVAL;
 179         if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
 180                 goto out_putf;
 181
 182         error = -EINVAL;
 183         /* Cannot ftruncate over 2^31 bytes without large file support */
 184         if (small && length > MAX_NON_LFS)
 185                 goto out_putf;
 186
 187         error = -EPERM;
 188         /* Check IS_APPEND on real upper inode */
 189         if (IS_APPEND(file_inode(f.file)))
 190                 goto out_putf;
 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(file_mnt_user_ns(f.file), dentry, length,
 197                                     ATTR_MTIME | ATTR_CTIME, f.file);
 198         sb_end_write(inode->i_sb);
 199 out_putf:
 200         fdput(f);
 201 out:
 202         return error;
 203 }
 204
 205 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 206 {
 207         return do_sys_ftruncate(fd, length, 1);
 208 }
 209
 210 #ifdef CONFIG_COMPAT
 211 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
 212 {
 213         return do_sys_ftruncate(fd, length, 1);
 214 }
 215 #endif
 216
 217 /* LFS versions of truncate are only needed on 32 bit machines */
 218 #if BITS_PER_LONG == 32
 219 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
 220 {
 221         return do_sys_truncate(path, length);
 222 }
 223
 224 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
 225 {
 226         return do_sys_ftruncate(fd, length, 0);
 227 }
 228 #endif /* BITS_PER_LONG == 32 */
 229
 230
 231 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 232 {
 233         struct inode *inode = file_inode(file);
 234         long ret;
 235
 236         if (offset < 0 || len <= 0)
 237                 return -EINVAL;
 238
 239         /* Return error if mode is not supported */
 240         if (mode & ~FALLOC_FL_SUPPORTED_MASK)
 241                 return -EOPNOTSUPP;
 242
 243         /* Punch hole and zero range are mutually exclusive */
 244         if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
 245             (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
 246                 return -EOPNOTSUPP;
 247
 248         /* Punch hole must have keep size set */
 249         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
 250             !(mode & FALLOC_FL_KEEP_SIZE))
 251                 return -EOPNOTSUPP;
 252
 253         /* Collapse range should only be used exclusively. */
 254         if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
 255             (mode & ~FALLOC_FL_COLLAPSE_RANGE))
 256                 return -EINVAL;
 257
 258         /* Insert range should only be used exclusively. */
 259         if ((mode & FALLOC_FL_INSERT_RANGE) &&
 260             (mode & ~FALLOC_FL_INSERT_RANGE))
 261                 return -EINVAL;
 262
 263         /* Unshare range should only be used with allocate mode. */
 264         if ((mode & FALLOC_FL_UNSHARE_RANGE) &&
 265             (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))
 266                 return -EINVAL;
 267
 268         if (!(file->f_mode & FMODE_WRITE))
 269                 return -EBADF;
 270
 271         /*
 272          * We can only allow pure fallocate on append only files
 273          */
 274         if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
 275                 return -EPERM;
 276
 277         if (IS_IMMUTABLE(inode))
 278                 return -EPERM;
 279
 280         /*
 281          * We cannot allow any fallocate operation on an active swapfile
 282          */
 283         if (IS_SWAPFILE(inode))
 284                 return -ETXTBSY;
 285
 286         /*
 287          * Revalidate the write permissions, in case security policy has
 288          * changed since the files were opened.
 289          */
 290         ret = security_file_permission(file, MAY_WRITE);
 291         if (ret)
 292                 return ret;
 293
 294         if (S_ISFIFO(inode->i_mode))
 295                 return -ESPIPE;
 296
 297         if (S_ISDIR(inode->i_mode))
 298                 return -EISDIR;
 299
 300         if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
 301                 return -ENODEV;
 302
 303         /* Check for wrap through zero too */
 304         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 305                 return -EFBIG;
 306
 307         if (!file->f_op->fallocate)
 308                 return -EOPNOTSUPP;
 309
 310         file_start_write(file);
 311         ret = file->f_op->fallocate(file, mode, offset, len);
 312
 313         /*
 314          * Create inotify and fanotify events.
 315          *
 316          * To keep the logic simple always create events if fallocate succeeds.
 317          * This implies that events are even created if the file size remains
 318          * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
 319          */
 320         if (ret == 0)
 321                 fsnotify_modify(file);
 322
 323         file_end_write(file);
 324         return ret;
 325 }
 326 EXPORT_SYMBOL_GPL(vfs_fallocate);
 327
 328 int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
 329 {
 330         struct fd f = fdget(fd);
 331         int error = -EBADF;
 332
 333         if (f.file) {
 334                 error = vfs_fallocate(f.file, mode, offset, len);
 335                 fdput(f);
 336         }
 337         return error;
 338 }
 339
 340 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
 341 {
 342         return ksys_fallocate(fd, mode, offset, len);
 343 }
 344
 345 /*
 346  * access() needs to use the real uid/gid, not the effective uid/gid.
 347  * We do this by temporarily clearing all FS-related capabilities and
 348  * switching the fsuid/fsgid around to the real ones.
 349  */
 350 static const struct cred *access_override_creds(void)
 351 {
 352         const struct cred *old_cred;
 353         struct cred *override_cred;
 354
 355         override_cred = prepare_creds();
 356         if (!override_cred)
 357                 return NULL;
 358
 359         override_cred->fsuid = override_cred->uid;
 360         override_cred->fsgid = override_cred->gid;
 361
 362         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 363                 /* Clear the capabilities if we switch to a non-root user */
 364                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 365                 if (!uid_eq(override_cred->uid, root_uid))
 366                         cap_clear(override_cred->cap_effective);
 367                 else
 368                         override_cred->cap_effective =
 369                                 override_cred->cap_permitted;
 370         }
 371
 372         /*
 373          * The new set of credentials can *only* be used in
 374          * task-synchronous circumstances, and does not need
 375          * RCU freeing, unless somebody then takes a separate
 376          * reference to it.
 377          *
 378          * NOTE! This is _only_ true because this credential
 379          * is used purely for override_creds() that installs
 380          * it as the subjective cred. Other threads will be
 381          * accessing ->real_cred, not the subjective cred.
 382          *
 383          * If somebody _does_ make a copy of this (using the
 384          * 'get_current_cred()' function), that will clear the
 385          * non_rcu field, because now that other user may be
 386          * expecting RCU freeing. But normal thread-synchronous
 387          * cred accesses will keep things non-RCY.
 388          */
 389         override_cred->non_rcu = 1;
 390
 391         old_cred = override_creds(override_cred);
 392
 393         /* override_cred() gets its own ref */
 394         put_cred(override_cred);
 395
 396         return old_cred;
 397 }
 398
 399 static long do_faccessat(int dfd, const char __user *filename, int mode, int flags)
 400 {
 401         struct path path;
 402         struct inode *inode;
 403         int res;
 404         unsigned int lookup_flags = LOOKUP_FOLLOW;
 405         const struct cred *old_cred = NULL;
 406
 407         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 408                 return -EINVAL;
 409
 410         if (flags & ~(AT_EACCESS | AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
 411                 return -EINVAL;
 412
 413         if (flags & AT_SYMLINK_NOFOLLOW)
 414                 lookup_flags &= ~LOOKUP_FOLLOW;
 415         if (flags & AT_EMPTY_PATH)
 416                 lookup_flags |= LOOKUP_EMPTY;
 417
 418         if (!(flags & AT_EACCESS)) {
 419                 old_cred = access_override_creds();
 420                 if (!old_cred)
 421                         return -ENOMEM;
 422         }
 423
 424 retry:
 425         res = user_path_at(dfd, filename, lookup_flags, &path);
 426         if (res)
 427                 goto out;
 428
 429         inode = d_backing_inode(path.dentry);
 430
 431         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 432                 /*
 433                  * MAY_EXEC on regular files is denied if the fs is mounted
 434                  * with the "noexec" flag.
 435                  */
 436                 res = -EACCES;
 437                 if (path_noexec(&path))
 438                         goto out_path_release;
 439         }
 440
 441         res = inode_permission(mnt_user_ns(path.mnt), inode, mode | MAY_ACCESS);
 442         /* SuS v2 requires we report a read only fs too */
 443         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 444                 goto out_path_release;
 445         /*
 446          * This is a rare case where using __mnt_is_readonly()
 447          * is OK without a mnt_want/drop_write() pair.  Since
 448          * no actual write to the fs is performed here, we do
 449          * not need to telegraph to that to anyone.
 450          *
 451          * By doing this, we accept that this access is
 452          * inherently racy and know that the fs may change
 453          * state before we even see this result.
 454          */
 455         if (__mnt_is_readonly(path.mnt))
 456                 res = -EROFS;
 457
 458 out_path_release:
 459         path_put(&path);
 460         if (retry_estale(res, lookup_flags)) {
 461                 lookup_flags |= LOOKUP_REVAL;
 462                 goto retry;
 463         }
 464 out:
 465         if (old_cred)
 466                 revert_creds(old_cred);
 467
 468         return res;
 469 }
 470
 471 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 472 {
 473         return do_faccessat(dfd, filename, mode, 0);
 474 }
 475
 476 SYSCALL_DEFINE4(faccessat2, int, dfd, const char __user *, filename, int, mode,
 477                 int, flags)
 478 {
 479         return do_faccessat(dfd, filename, mode, flags);
 480 }
 481
 482 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 483 {
 484         return do_faccessat(AT_FDCWD, filename, mode, 0);
 485 }
 486
 487 SYSCALL_DEFINE1(chdir, const char __user *, filename)
 488 {
 489         struct path path;
 490         int error;
 491         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 492 retry:
 493         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 494         if (error)
 495                 goto out;
 496
 497         error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
 498         if (error)
 499                 goto dput_and_out;
 500
 501         set_fs_pwd(current->fs, &path);
 502
 503 dput_and_out:
 504         path_put(&path);
 505         if (retry_estale(error, lookup_flags)) {
 506                 lookup_flags |= LOOKUP_REVAL;
 507                 goto retry;
 508         }
 509 out:
 510         return error;
 511 }
 512
 513 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 514 {
 515         struct fd f = fdget_raw(fd);
 516         int error;
 517
 518         error = -EBADF;
 519         if (!f.file)
 520                 goto out;
 521
 522         error = -ENOTDIR;
 523         if (!d_can_lookup(f.file->f_path.dentry))
 524                 goto out_putf;
 525
 526         error = file_permission(f.file, MAY_EXEC | MAY_CHDIR);
 527         if (!error)
 528                 set_fs_pwd(current->fs, &f.file->f_path);
 529 out_putf:
 530         fdput(f);
 531 out:
 532         return error;
 533 }
 534
 535 SYSCALL_DEFINE1(chroot, const char __user *, filename)
 536 {
 537         struct path path;
 538         int error;
 539         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 540 retry:
 541         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 542         if (error)
 543                 goto out;
 544
 545         error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
 546         if (error)
 547                 goto dput_and_out;
 548
 549         error = -EPERM;
 550         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
 551                 goto dput_and_out;
 552         error = security_path_chroot(&path);
 553         if (error)
 554                 goto dput_and_out;
 555
 556         set_fs_root(current->fs, &path);
 557         error = 0;
 558 dput_and_out:
 559         path_put(&path);
 560         if (retry_estale(error, lookup_flags)) {
 561                 lookup_flags |= LOOKUP_REVAL;
 562                 goto retry;
 563         }
 564 out:
 565         return error;
 566 }
 567
 568 int chmod_common(const struct path *path, umode_t mode)
 569 {
 570         struct inode *inode = path->dentry->d_inode;
 571         struct inode *delegated_inode = NULL;
 572         struct iattr newattrs;
 573         int error;
 574
 575         error = mnt_want_write(path->mnt);
 576         if (error)
 577                 return error;
 578 retry_deleg:
 579         inode_lock(inode);
 580         error = security_path_chmod(path, mode);
 581         if (error)
 582                 goto out_unlock;
 583         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 584         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 585         error = notify_change(mnt_user_ns(path->mnt), path->dentry,
 586                               &newattrs, &delegated_inode);
 587 out_unlock:
 588         inode_unlock(inode);
 589         if (delegated_inode) {
 590                 error = break_deleg_wait(&delegated_inode);
 591                 if (!error)
 592                         goto retry_deleg;
 593         }
 594         mnt_drop_write(path->mnt);
 595         return error;
 596 }
 597
 598 int vfs_fchmod(struct file *file, umode_t mode)
 599 {
 600         audit_file(file);
 601         return chmod_common(&file->f_path, mode);
 602 }
 603
 604 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 605 {
 606         struct fd f = fdget(fd);
 607         int err = -EBADF;
 608
 609         if (f.file) {
 610                 err = vfs_fchmod(f.file, mode);
 611                 fdput(f);
 612         }
 613         return err;
 614 }
 615
 616 static int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
 617 {
 618         struct path path;
 619         int error;
 620         unsigned int lookup_flags = LOOKUP_FOLLOW;
 621 retry:
 622         error = user_path_at(dfd, filename, lookup_flags, &path);
 623         if (!error) {
 624                 error = chmod_common(&path, mode);
 625                 path_put(&path);
 626                 if (retry_estale(error, lookup_flags)) {
 627                         lookup_flags |= LOOKUP_REVAL;
 628                         goto retry;
 629                 }
 630         }
 631         return error;
 632 }
 633
 634 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
 635                 umode_t, mode)
 636 {
 637         return do_fchmodat(dfd, filename, mode);
 638 }
 639
 640 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 641 {
 642         return do_fchmodat(AT_FDCWD, filename, mode);
 643 }
 644
 645 int chown_common(const struct path *path, uid_t user, gid_t group)
 646 {
 647         struct user_namespace *mnt_userns;
 648         struct inode *inode = path->dentry->d_inode;
 649         struct inode *delegated_inode = NULL;
 650         int error;
 651         struct iattr newattrs;
 652         kuid_t uid;
 653         kgid_t gid;
 654
 655         uid = make_kuid(current_user_ns(), user);
 656         gid = make_kgid(current_user_ns(), group);
 657
 658         mnt_userns = mnt_user_ns(path->mnt);
 659         uid = kuid_from_mnt(mnt_userns, uid);
 660         gid = kgid_from_mnt(mnt_userns, gid);
 661
 662 retry_deleg:
 663         newattrs.ia_valid =  ATTR_CTIME;
 664         if (user != (uid_t) -1) {
 665                 if (!uid_valid(uid))
 666                         return -EINVAL;
 667                 newattrs.ia_valid |= ATTR_UID;
 668                 newattrs.ia_uid = uid;
 669         }
 670         if (group != (gid_t) -1) {
 671                 if (!gid_valid(gid))
 672                         return -EINVAL;
 673                 newattrs.ia_valid |= ATTR_GID;
 674                 newattrs.ia_gid = gid;
 675         }
 676         if (!S_ISDIR(inode->i_mode))
 677                 newattrs.ia_valid |=
 678                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 679         inode_lock(inode);
 680         error = security_path_chown(path, uid, gid);
 681         if (!error)
 682                 error = notify_change(mnt_userns, path->dentry, &newattrs,
 683                                       &delegated_inode);
 684         inode_unlock(inode);
 685         if (delegated_inode) {
 686                 error = break_deleg_wait(&delegated_inode);
 687                 if (!error)
 688                         goto retry_deleg;
 689         }
 690         return error;
 691 }
 692
 693 int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
 694                 int flag)
 695 {
 696         struct path path;
 697         int error = -EINVAL;
 698         int lookup_flags;
 699
 700         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 701                 goto out;
 702
 703         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 704         if (flag & AT_EMPTY_PATH)
 705                 lookup_flags |= LOOKUP_EMPTY;
 706 retry:
 707         error = user_path_at(dfd, filename, lookup_flags, &path);
 708         if (error)
 709                 goto out;
 710         error = mnt_want_write(path.mnt);
 711         if (error)
 712                 goto out_release;
 713         error = chown_common(&path, user, group);
 714         mnt_drop_write(path.mnt);
 715 out_release:
 716         path_put(&path);
 717         if (retry_estale(error, lookup_flags)) {
 718                 lookup_flags |= LOOKUP_REVAL;
 719                 goto retry;
 720         }
 721 out:
 722         return error;
 723 }
 724
 725 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 726                 gid_t, group, int, flag)
 727 {
 728         return do_fchownat(dfd, filename, user, group, flag);
 729 }
 730
 731 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 732 {
 733         return do_fchownat(AT_FDCWD, filename, user, group, 0);
 734 }
 735
 736 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 737 {
 738         return do_fchownat(AT_FDCWD, filename, user, group,
 739                            AT_SYMLINK_NOFOLLOW);
 740 }
 741
 742 int vfs_fchown(struct file *file, uid_t user, gid_t group)
 743 {
 744         int error;
 745
 746         error = mnt_want_write_file(file);
 747         if (error)
 748                 return error;
 749         audit_file(file);
 750         error = chown_common(&file->f_path, user, group);
 751         mnt_drop_write_file(file);
 752         return error;
 753 }
 754
 755 int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
 756 {
 757         struct fd f = fdget(fd);
 758         int error = -EBADF;
 759
 760         if (f.file) {
 761                 error = vfs_fchown(f.file, user, group);
 762                 fdput(f);
 763         }
 764         return error;
 765 }
 766
 767 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 768 {
 769         return ksys_fchown(fd, user, group);
 770 }
 771
 772 static int do_dentry_open(struct file *f,
 773                           struct inode *inode,
 774                           int (*open)(struct inode *, struct file *))
 775 {
 776         static const struct file_operations empty_fops = {};
 777         int error;
 778
 779         path_get(&f->f_path);
 780         f->f_inode = inode;
 781         f->f_mapping = inode->i_mapping;
 782         f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
 783         f->f_sb_err = file_sample_sb_err(f);
 784
 785         if (unlikely(f->f_flags & O_PATH)) {
 786                 f->f_mode = FMODE_PATH | FMODE_OPENED;
 787                 f->f_op = &empty_fops;
 788                 return 0;
 789         }
 790
 791         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
 792                 error = get_write_access(inode);
 793                 if (unlikely(error))
 794                         goto cleanup_file;
 795                 error = __mnt_want_write(f->f_path.mnt);
 796                 if (unlikely(error)) {
 797                         put_write_access(inode);
 798                         goto cleanup_file;
 799                 }
 800                 f->f_mode |= FMODE_WRITER;
 801         }
 802
 803         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
 804         if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
 805                 f->f_mode |= FMODE_ATOMIC_POS;
 806
 807         f->f_op = fops_get(inode->i_fop);
 808         if (WARN_ON(!f->f_op)) {
 809                 error = -ENODEV;
 810                 goto cleanup_all;
 811         }
 812
 813         error = security_file_open(f);
 814         if (error)
 815                 goto cleanup_all;
 816
 817         error = break_lease(locks_inode(f), f->f_flags);
 818         if (error)
 819                 goto cleanup_all;
 820
 821         /* normally all 3 are set; ->open() can clear them if needed */
 822         f->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
 823         if (!open)
 824                 open = f->f_op->open;
 825         if (open) {
 826                 error = open(inode, f);
 827                 if (error)
 828                         goto cleanup_all;
 829         }
 830         f->f_mode |= FMODE_OPENED;
 831         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 832                 i_readcount_inc(inode);
 833         if ((f->f_mode & FMODE_READ) &&
 834              likely(f->f_op->read || f->f_op->read_iter))
 835                 f->f_mode |= FMODE_CAN_READ;
 836         if ((f->f_mode & FMODE_WRITE) &&
 837              likely(f->f_op->write || f->f_op->write_iter))
 838                 f->f_mode |= FMODE_CAN_WRITE;
 839
 840         f->f_write_hint = WRITE_LIFE_NOT_SET;
 841         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 842
 843         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 844
 845         /* NB: we're sure to have correct a_ops only after f_op->open */
 846         if (f->f_flags & O_DIRECT) {
 847                 if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
 848                         return -EINVAL;
 849         }
 850
 851         /*
 852          * XXX: Huge page cache doesn't support writing yet. Drop all page
 853          * cache for this file before processing writes.
 854          */
 855         if (f->f_mode & FMODE_WRITE) {
 856                 /*
 857                  * Paired with smp_mb() in collapse_file() to ensure nr_thps
 858                  * is up to date and the update to i_writecount by
 859                  * get_write_access() is visible. Ensures subsequent insertion
 860                  * of THPs into the page cache will fail.
 861                  */
 862                 smp_mb();
 863                 if (filemap_nr_thps(inode->i_mapping))
 864                         truncate_pagecache(inode, 0);
 865         }
 866
 867         return 0;
 868
 869 cleanup_all:
 870         if (WARN_ON_ONCE(error > 0))
 871                 error = -EINVAL;
 872         fops_put(f->f_op);
 873         if (f->f_mode & FMODE_WRITER) {
 874                 put_write_access(inode);
 875                 __mnt_drop_write(f->f_path.mnt);
 876         }
 877 cleanup_file:
 878         path_put(&f->f_path);
 879         f->f_path.mnt = NULL;
 880         f->f_path.dentry = NULL;
 881         f->f_inode = NULL;
 882         return error;
 883 }
 884
 885 /**
 886  * finish_open - finish opening a file
 887  * @file: file pointer
 888  * @dentry: pointer to dentry
 889  * @open: open callback
 890  * @opened: state of open
 891  *
 892  * This can be used to finish opening a file passed to i_op->atomic_open().
 893  *
 894  * If the open callback is set to NULL, then the standard f_op->open()
 895  * filesystem callback is substituted.
 896  *
 897  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
 898  * the return value of d_splice_alias(), then the caller needs to perform dput()
 899  * on it after finish_open().
 900  *
 901  * Returns zero on success or -errno if the open failed.
 902  */
 903 int finish_open(struct file *file, struct dentry *dentry,
 904                 int (*open)(struct inode *, struct file *))
 905 {
 906         BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */
 907
 908         file->f_path.dentry = dentry;
 909         return do_dentry_open(file, d_backing_inode(dentry), open);
 910 }
 911 EXPORT_SYMBOL(finish_open);
 912
 913 /**
 914  * finish_no_open - finish ->atomic_open() without opening the file
 915  *
 916  * @file: file pointer
 917  * @dentry: dentry or NULL (as returned from ->lookup())
 918  *
 919  * This can be used to set the result of a successful lookup in ->atomic_open().
 920  *
 921  * NB: unlike finish_open() this function does consume the dentry reference and
 922  * the caller need not dput() it.
 923  *
 924  * Returns "0" which must be the return value of ->atomic_open() after having
 925  * called this function.
 926  */
 927 int finish_no_open(struct file *file, struct dentry *dentry)
 928 {
 929         file->f_path.dentry = dentry;
 930         return 0;
 931 }
 932 EXPORT_SYMBOL(finish_no_open);
 933
 934 char *file_path(struct file *filp, char *buf, int buflen)
 935 {
 936         return d_path(&filp->f_path, buf, buflen);
 937 }
 938 EXPORT_SYMBOL(file_path);
 939
 940 /**
 941  * vfs_open - open the file at the given path
 942  * @path: path to open
 943  * @file: newly allocated file with f_flag initialized
 944  * @cred: credentials to use
 945  */
 946 int vfs_open(const struct path *path, struct file *file)
 947 {
 948         file->f_path = *path;
 949         return do_dentry_open(file, d_backing_inode(path->dentry), NULL);
 950 }
 951
 952 struct file *dentry_open(const struct path *path, int flags,
 953                          const struct cred *cred)
 954 {
 955         int error;
 956         struct file *f;
 957
 958         validate_creds(cred);
 959
 960         /* We must always pass in a valid mount pointer. */
 961         BUG_ON(!path->mnt);
 962
 963         f = alloc_empty_file(flags, cred);
 964         if (!IS_ERR(f)) {
 965                 error = vfs_open(path, f);
 966                 if (error) {
 967                         fput(f);
 968                         f = ERR_PTR(error);
 969                 }
 970         }
 971         return f;
 972 }
 973 EXPORT_SYMBOL(dentry_open);
 974
 975 struct file *open_with_fake_path(const struct path *path, int flags,
 976                                 struct inode *inode, const struct cred *cred)
 977 {
 978         struct file *f = alloc_empty_file_noaccount(flags, cred);
 979         if (!IS_ERR(f)) {
 980                 int error;
 981
 982                 f->f_path = *path;
 983                 error = do_dentry_open(f, inode, NULL);
 984                 if (error) {
 985                         fput(f);
 986                         f = ERR_PTR(error);
 987                 }
 988         }
 989         return f;
 990 }
 991 EXPORT_SYMBOL(open_with_fake_path);
 992
 993 #define WILL_CREATE(flags)      (flags & (O_CREAT | __O_TMPFILE))
 994 #define O_PATH_FLAGS            (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC)
 995
 996 inline struct open_how build_open_how(int flags, umode_t mode)
 997 {
 998         struct open_how how = {
 999                 .flags = flags & VALID_OPEN_FLAGS,
1000                 .mode = mode & S_IALLUGO,
1001         };
1002
1003         /* O_PATH beats everything else. */
1004         if (how.flags & O_PATH)
1005                 how.flags &= O_PATH_FLAGS;
1006         /* Modes should only be set for create-like flags. */
1007         if (!WILL_CREATE(how.flags))
1008                 how.mode = 0;
1009         return how;
1010 }
1011
1012 inline int build_open_flags(const struct open_how *how, struct open_flags *op)
1013 {
1014         u64 flags = how->flags;
1015         u64 strip = FMODE_NONOTIFY | O_CLOEXEC;
1016         int lookup_flags = 0;
1017         int acc_mode = ACC_MODE(flags);
1018
1019         BUILD_BUG_ON_MSG(upper_32_bits(VALID_OPEN_FLAGS),
1020                          "struct open_flags doesn't yet handle flags > 32 bits");
1021
1022         /*
1023          * Strip flags that either shouldn't be set by userspace like
1024          * FMODE_NONOTIFY or that aren't relevant in determining struct
1025          * open_flags like O_CLOEXEC.
1026          */
1027         flags &= ~strip;
1028
1029         /*
1030          * Older syscalls implicitly clear all of the invalid flags or argument
1031          * values before calling build_open_flags(), but openat2(2) checks all
1032          * of its arguments.
1033          */
1034         if (flags & ~VALID_OPEN_FLAGS)
1035                 return -EINVAL;
1036         if (how->resolve & ~VALID_RESOLVE_FLAGS)
1037                 return -EINVAL;
1038
1039         /* Scoping flags are mutually exclusive. */
1040         if ((how->resolve & RESOLVE_BENEATH) && (how->resolve & RESOLVE_IN_ROOT))
1041                 return -EINVAL;
1042
1043         /* Deal with the mode. */
1044         if (WILL_CREATE(flags)) {
1045                 if (how->mode & ~S_IALLUGO)
1046                         return -EINVAL;
1047                 op->mode = how->mode | S_IFREG;
1048         } else {
1049                 if (how->mode != 0)
1050                         return -EINVAL;
1051                 op->mode = 0;
1052         }
1053
1054         /*
1055          * In order to ensure programs get explicit errors when trying to use
1056          * O_TMPFILE on old kernels, O_TMPFILE is implemented such that it
1057          * looks like (O_DIRECTORY|O_RDWR & ~O_CREAT) to old kernels. But we
1058          * have to require userspace to explicitly set it.
1059          */
1060         if (flags & __O_TMPFILE) {
1061                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
1062                         return -EINVAL;
1063                 if (!(acc_mode & MAY_WRITE))
1064                         return -EINVAL;
1065         }
1066         if (flags & O_PATH) {
1067                 /* O_PATH only permits certain other flags to be set. */
1068                 if (flags & ~O_PATH_FLAGS)
1069                         return -EINVAL;
1070                 acc_mode = 0;
1071         }
1072
1073         /*
1074          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
1075          * check for O_DSYNC if the need any syncing at all we enforce it's
1076          * always set instead of having to deal with possibly weird behaviour
1077          * for malicious applications setting only __O_SYNC.
1078          */
1079         if (flags & __O_SYNC)
1080                 flags |= O_DSYNC;
1081
1082         op->open_flag = flags;
1083
1084         /* O_TRUNC implies we need access checks for write permissions */
1085         if (flags & O_TRUNC)
1086                 acc_mode |= MAY_WRITE;
1087
1088         /* Allow the LSM permission hook to distinguish append
1089            access from general write access. */
1090         if (flags & O_APPEND)
1091                 acc_mode |= MAY_APPEND;
1092
1093         op->acc_mode = acc_mode;
1094
1095         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
1096
1097         if (flags & O_CREAT) {
1098                 op->intent |= LOOKUP_CREATE;
1099                 if (flags & O_EXCL) {
1100                         op->intent |= LOOKUP_EXCL;
1101                         flags |= O_NOFOLLOW;
1102                 }
1103         }
1104
1105         if (flags & O_DIRECTORY)
1106                 lookup_flags |= LOOKUP_DIRECTORY;
1107         if (!(flags & O_NOFOLLOW))
1108                 lookup_flags |= LOOKUP_FOLLOW;
1109
1110         if (how->resolve & RESOLVE_NO_XDEV)
1111                 lookup_flags |= LOOKUP_NO_XDEV;
1112         if (how->resolve & RESOLVE_NO_MAGICLINKS)
1113                 lookup_flags |= LOOKUP_NO_MAGICLINKS;
1114         if (how->resolve & RESOLVE_NO_SYMLINKS)
1115                 lookup_flags |= LOOKUP_NO_SYMLINKS;
1116         if (how->resolve & RESOLVE_BENEATH)
1117                 lookup_flags |= LOOKUP_BENEATH;
1118         if (how->resolve & RESOLVE_IN_ROOT)
1119                 lookup_flags |= LOOKUP_IN_ROOT;
1120         if (how->resolve & RESOLVE_CACHED) {
1121                 /* Don't bother even trying for create/truncate/tmpfile open */
1122                 if (flags & (O_TRUNC | O_CREAT | O_TMPFILE))
1123                         return -EAGAIN;
1124                 lookup_flags |= LOOKUP_CACHED;
1125         }
1126
1127         op->lookup_flags = lookup_flags;
1128         return 0;
1129 }
1130
1131 /**
1132  * file_open_name - open file and return file pointer
1133  *
1134  * @name:       struct filename containing path to open
1135  * @flags:      open flags as per the open(2) second argument
1136  * @mode:       mode for the new file if O_CREAT is set, else ignored
1137  *
1138  * This is the helper to open a file from kernelspace if you really
1139  * have to.  But in generally you should not do this, so please move
1140  * along, nothing to see here..
1141  */
1142 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
1143 {
1144         struct open_flags op;
1145         struct open_how how = build_open_how(flags, mode);
1146         int err = build_open_flags(&how, &op);
1147         if (err)
1148                 return ERR_PTR(err);
1149         return do_filp_open(AT_FDCWD, name, &op);
1150 }
1151
1152 /**
1153  * filp_open - open file and return file pointer
1154  *
1155  * @filename:   path to open
1156  * @flags:      open flags as per the open(2) second argument
1157  * @mode:       mode for the new file if O_CREAT is set, else ignored
1158  *
1159  * This is the helper to open a file from kernelspace if you really
1160  * have to.  But in generally you should not do this, so please move
1161  * along, nothing to see here..
1162  */
1163 struct file *filp_open(const char *filename, int flags, umode_t mode)
1164 {
1165         struct filename *name = getname_kernel(filename);
1166         struct file *file = ERR_CAST(name);
1167
1168         if (!IS_ERR(name)) {
1169                 file = file_open_name(name, flags, mode);
1170                 putname(name);
1171         }
1172         return file;
1173 }
1174 EXPORT_SYMBOL(filp_open);
1175
1176 struct file *file_open_root(const struct path *root,
1177                             const char *filename, int flags, umode_t mode)
1178 {
1179         struct open_flags op;
1180         struct open_how how = build_open_how(flags, mode);
1181         int err = build_open_flags(&how, &op);
1182         if (err)
1183                 return ERR_PTR(err);
1184         return do_file_open_root(root, filename, &op);
1185 }
1186 EXPORT_SYMBOL(file_open_root);
1187
1188 static long do_sys_openat2(int dfd, const char __user *filename,
1189                            struct open_how *how)
1190 {
1191         struct open_flags op;
1192         int fd = build_open_flags(how, &op);
1193         struct filename *tmp;
1194
1195         if (fd)
1196                 return fd;
1197
1198         tmp = getname(filename);
1199         if (IS_ERR(tmp))
1200                 return PTR_ERR(tmp);
1201
1202         fd = get_unused_fd_flags(how->flags);
1203         if (fd >= 0) {
1204                 struct file *f = do_filp_open(dfd, tmp, &op);
1205                 if (IS_ERR(f)) {
1206                         put_unused_fd(fd);
1207                         fd = PTR_ERR(f);
1208                 } else {
1209                         fsnotify_open(f);
1210                         fd_install(fd, f);
1211                 }
1212         }
1213         putname(tmp);
1214         return fd;
1215 }
1216
1217 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1218 {
1219         struct open_how how = build_open_how(flags, mode);
1220         return do_sys_openat2(dfd, filename, &how);
1221 }
1222
1223
1224 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1225 {
1226         if (force_o_largefile())
1227                 flags |= O_LARGEFILE;
1228         return do_sys_open(AT_FDCWD, filename, flags, mode);
1229 }
1230
1231 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1232                 umode_t, mode)
1233 {
1234         if (force_o_largefile())
1235                 flags |= O_LARGEFILE;
1236         return do_sys_open(dfd, filename, flags, mode);
1237 }
1238
1239 SYSCALL_DEFINE4(openat2, int, dfd, const char __user *, filename,
1240                 struct open_how __user *, how, size_t, usize)
1241 {
1242         int err;
1243         struct open_how tmp;
1244
1245         BUILD_BUG_ON(sizeof(struct open_how) < OPEN_HOW_SIZE_VER0);
1246         BUILD_BUG_ON(sizeof(struct open_how) != OPEN_HOW_SIZE_LATEST);
1247
1248         if (unlikely(usize < OPEN_HOW_SIZE_VER0))
1249                 return -EINVAL;
1250
1251         err = copy_struct_from_user(&tmp, sizeof(tmp), how, usize);
1252         if (err)
1253                 return err;
1254
1255         /* O_LARGEFILE is only allowed for non-O_PATH. */
1256         if (!(tmp.flags & O_PATH) && force_o_largefile())
1257                 tmp.flags |= O_LARGEFILE;
1258
1259         return do_sys_openat2(dfd, filename, &tmp);
1260 }
1261
1262 #ifdef CONFIG_COMPAT
1263 /*
1264  * Exactly like sys_open(), except that it doesn't set the
1265  * O_LARGEFILE flag.
1266  */
1267 COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1268 {
1269         return do_sys_open(AT_FDCWD, filename, flags, mode);
1270 }
1271
1272 /*
1273  * Exactly like sys_openat(), except that it doesn't set the
1274  * O_LARGEFILE flag.
1275  */
1276 COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
1277 {
1278         return do_sys_open(dfd, filename, flags, mode);
1279 }
1280 #endif
1281
1282 #ifndef __alpha__
1283
1284 /*
1285  * For backward compatibility?  Maybe this should be moved
1286  * into arch/i386 instead?
1287  */
1288 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1289 {
1290         int flags = O_CREAT | O_WRONLY | O_TRUNC;
1291
1292         if (force_o_largefile())
1293                 flags |= O_LARGEFILE;
1294         return do_sys_open(AT_FDCWD, pathname, flags, mode);
1295 }
1296 #endif
1297
1298 /*
1299  * "id" is the POSIX thread ID. We use the
1300  * files pointer for this..
1301  */
1302 int filp_close(struct file *filp, fl_owner_t id)
1303 {
1304         int retval = 0;
1305
1306         if (!file_count(filp)) {
1307                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1308                 return 0;
1309         }
1310
1311         if (filp->f_op->flush)
1312                 retval = filp->f_op->flush(filp, id);
1313
1314         if (likely(!(filp->f_mode & FMODE_PATH))) {
1315                 dnotify_flush(filp, id);
1316                 locks_remove_posix(filp, id);
1317         }
1318         fput(filp);
1319         return retval;
1320 }
1321
1322 EXPORT_SYMBOL(filp_close);
1323
1324 /*
1325  * Careful here! We test whether the file pointer is NULL before
1326  * releasing the fd. This ensures that one clone task can't release
1327  * an fd while another clone is opening it.
1328  */
1329 SYSCALL_DEFINE1(close, unsigned int, fd)
1330 {
1331         int retval = close_fd(fd);
1332
1333         /* can't restart close syscall because file table entry was cleared */
1334         if (unlikely(retval == -ERESTARTSYS ||
1335                      retval == -ERESTARTNOINTR ||
1336                      retval == -ERESTARTNOHAND ||
1337                      retval == -ERESTART_RESTARTBLOCK))
1338                 retval = -EINTR;
1339
1340         return retval;
1341 }
1342
1343 /**
1344  * close_range() - Close all file descriptors in a given range.
1345  *
1346  * @fd:     starting file descriptor to close
1347  * @max_fd: last file descriptor to close
1348  * @flags:  reserved for future extensions
1349  *
1350  * This closes a range of file descriptors. All file descriptors
1351  * from @fd up to and including @max_fd are closed.
1352  * Currently, errors to close a given file descriptor are ignored.
1353  */
1354 SYSCALL_DEFINE3(close_range, unsigned int, fd, unsigned int, max_fd,
1355                 unsigned int, flags)
1356 {
1357         return __close_range(fd, max_fd, flags);
1358 }
1359
1360 /*
1361  * This routine simulates a hangup on the tty, to arrange that users
1362  * are given clean terminals at login time.
1363  */
1364 SYSCALL_DEFINE0(vhangup)
1365 {
1366         if (capable(CAP_SYS_TTY_CONFIG)) {
1367                 tty_vhangup_self();
1368                 return 0;
1369         }
1370         return -EPERM;
1371 }
1372
1373 /*
1374  * Called when an inode is about to be open.
1375  * We use this to disallow opening large files on 32bit systems if
1376  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1377  * on this flag in sys_open.
1378  */
1379 int generic_file_open(struct inode * inode, struct file * filp)
1380 {
1381         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1382                 return -EOVERFLOW;
1383         return 0;
1384 }
1385
1386 EXPORT_SYMBOL(generic_file_open);
1387
1388 /*
1389  * This is used by subsystems that don't want seekable
1390  * file descriptors. The function is not supposed to ever fail, the only
1391  * reason it returns an 'int' and not 'void' is so that it can be plugged
1392  * directly into file_operations structure.
1393  */
1394 int nonseekable_open(struct inode *inode, struct file *filp)
1395 {
1396         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1397         return 0;
1398 }
1399
1400 EXPORT_SYMBOL(nonseekable_open);
1401
1402 /*
1403  * stream_open is used by subsystems that want stream-like file descriptors.
1404  * Such file descriptors are not seekable and don't have notion of position
1405  * (file.f_pos is always 0 and ppos passed to .read()/.write() is always NULL).
1406  * Contrary to file descriptors of other regular files, .read() and .write()
1407  * can run simultaneously.
1408  *
1409  * stream_open never fails and is marked to return int so that it could be
1410  * directly used as file_operations.open .
1411  */
1412 int stream_open(struct inode *inode, struct file *filp)
1413 {
1414         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE | FMODE_ATOMIC_POS);
1415         filp->f_mode |= FMODE_STREAM;
1416         return 0;
1417 }
1418
1419 EXPORT_SYMBOL(stream_open);