fs/open.c

   1 /*
   2  *  linux/fs/open.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 #include <linux/string.h>
   8 #include <linux/mm.h>
   9 #include <linux/file.h>
  10 #include <linux/fdtable.h>
  11 #include <linux/fsnotify.h>
  12 #include <linux/module.h>
  13 #include <linux/tty.h>
  14 #include <linux/namei.h>
  15 #include <linux/backing-dev.h>
  16 #include <linux/capability.h>
  17 #include <linux/securebits.h>
  18 #include <linux/security.h>
  19 #include <linux/mount.h>
  20 #include <linux/fcntl.h>
  21 #include <linux/slab.h>
  22 #include <asm/uaccess.h>
  23 #include <linux/fs.h>
  24 #include <linux/personality.h>
  25 #include <linux/pagemap.h>
  26 #include <linux/syscalls.h>
  27 #include <linux/rcupdate.h>
  28 #include <linux/audit.h>
  29 #include <linux/falloc.h>
  30 #include <linux/fs_struct.h>
  31 #include <linux/ima.h>
  32 #include <linux/dnotify.h>
  33 #include <linux/compat.h>
  34
  35 #include "internal.h"
  36
  37 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
  38         struct file *filp)
  39 {
  40         int ret;
  41         struct iattr newattrs;
  42
  43         /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
  44         if (length < 0)
  45                 return -EINVAL;
  46
  47         newattrs.ia_size = length;
  48         newattrs.ia_valid = ATTR_SIZE | time_attrs;
  49         if (filp) {
  50                 newattrs.ia_file = filp;
  51                 newattrs.ia_valid |= ATTR_FILE;
  52         }
  53
  54         /* Remove suid/sgid on truncate too */
  55         ret = should_remove_suid(dentry);
  56         if (ret)
  57                 newattrs.ia_valid |= ret | ATTR_FORCE;
  58
  59         mutex_lock(&dentry->d_inode->i_mutex);
  60         /* Note any delegations or leases have already been broken: */
  61         ret = notify_change(dentry, &newattrs, NULL);
  62         mutex_unlock(&dentry->d_inode->i_mutex);
  63         return ret;
  64 }
  65
  66 long vfs_truncate(struct path *path, loff_t length)
  67 {
  68         struct inode *inode;
  69         long error;
  70
  71         inode = path->dentry->d_inode;
  72
  73         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
  74         if (S_ISDIR(inode->i_mode))
  75                 return -EISDIR;
  76         if (!S_ISREG(inode->i_mode))
  77                 return -EINVAL;
  78
  79         error = mnt_want_write(path->mnt);
  80         if (error)
  81                 goto out;
  82
  83         error = inode_permission(inode, MAY_WRITE);
  84         if (error)
  85                 goto mnt_drop_write_and_out;
  86
  87         error = -EPERM;
  88         if (IS_APPEND(inode))
  89                 goto mnt_drop_write_and_out;
  90
  91         error = get_write_access(inode);
  92         if (error)
  93                 goto mnt_drop_write_and_out;
  94
  95         /*
  96          * Make sure that there are no leases.  get_write_access() protects
  97          * against the truncate racing with a lease-granting setlease().
  98          */
  99         error = break_lease(inode, O_WRONLY);
 100         if (error)
 101                 goto put_write_and_out;
 102
 103         error = locks_verify_truncate(inode, NULL, length);
 104         if (!error)
 105                 error = security_path_truncate(path);
 106         if (!error)
 107                 error = do_truncate(path->dentry, length, 0, NULL);
 108
 109 put_write_and_out:
 110         put_write_access(inode);
 111 mnt_drop_write_and_out:
 112         mnt_drop_write(path->mnt);
 113 out:
 114         return error;
 115 }
 116 EXPORT_SYMBOL_GPL(vfs_truncate);
 117
 118 static long do_sys_truncate(const char __user *pathname, loff_t length)
 119 {
 120         unsigned int lookup_flags = LOOKUP_FOLLOW;
 121         struct path path;
 122         int error;
 123
 124         if (length < 0) /* sorry, but loff_t says... */
 125                 return -EINVAL;
 126
 127 retry:
 128         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 129         if (!error) {
 130                 error = vfs_truncate(&path, length);
 131                 path_put(&path);
 132         }
 133         if (retry_estale(error, lookup_flags)) {
 134                 lookup_flags |= LOOKUP_REVAL;
 135                 goto retry;
 136         }
 137         return error;
 138 }
 139
 140 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 141 {
 142         return do_sys_truncate(path, length);
 143 }
 144
 145 #ifdef CONFIG_COMPAT
 146 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
 147 {
 148         return do_sys_truncate(path, length);
 149 }
 150 #endif
 151
 152 static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 153 {
 154         struct inode *inode;
 155         struct dentry *dentry;
 156         struct fd f;
 157         int error;
 158
 159         error = -EINVAL;
 160         if (length < 0)
 161                 goto out;
 162         error = -EBADF;
 163         f = fdget(fd);
 164         if (!f.file)
 165                 goto out;
 166
 167         /* explicitly opened as large or we are on 64-bit box */
 168         if (f.file->f_flags & O_LARGEFILE)
 169                 small = 0;
 170
 171         dentry = f.file->f_path.dentry;
 172         inode = dentry->d_inode;
 173         error = -EINVAL;
 174         if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
 175                 goto out_putf;
 176
 177         error = -EINVAL;
 178         /* Cannot ftruncate over 2^31 bytes without large file support */
 179         if (small && length > MAX_NON_LFS)
 180                 goto out_putf;
 181
 182         error = -EPERM;
 183         if (IS_APPEND(inode))
 184                 goto out_putf;
 185
 186         sb_start_write(inode->i_sb);
 187         error = locks_verify_truncate(inode, f.file, length);
 188         if (!error)
 189                 error = security_path_truncate(&f.file->f_path);
 190         if (!error)
 191                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
 192         sb_end_write(inode->i_sb);
 193 out_putf:
 194         fdput(f);
 195 out:
 196         return error;
 197 }
 198
 199 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 200 {
 201         return do_sys_ftruncate(fd, length, 1);
 202 }
 203
 204 #ifdef CONFIG_COMPAT
 205 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
 206 {
 207         return do_sys_ftruncate(fd, length, 1);
 208 }
 209 #endif
 210
 211 /* LFS versions of truncate are only needed on 32 bit machines */
 212 #if BITS_PER_LONG == 32
 213 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
 214 {
 215         return do_sys_truncate(path, length);
 216 }
 217
 218 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
 219 {
 220         return do_sys_ftruncate(fd, length, 0);
 221 }
 222 #endif /* BITS_PER_LONG == 32 */
 223
 224
 225 int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 226 {
 227         struct inode *inode = file_inode(file);
 228         long ret;
 229
 230         if (offset < 0 || len <= 0)
 231                 return -EINVAL;
 232
 233         /* Return error if mode is not supported */
 234         if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
 235                 return -EOPNOTSUPP;
 236
 237         /* Punch hole must have keep size set */
 238         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
 239             !(mode & FALLOC_FL_KEEP_SIZE))
 240                 return -EOPNOTSUPP;
 241
 242         if (!(file->f_mode & FMODE_WRITE))
 243                 return -EBADF;
 244
 245         /* It's not possible punch hole on append only file */
 246         if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
 247                 return -EPERM;
 248
 249         if (IS_IMMUTABLE(inode))
 250                 return -EPERM;
 251
 252         /*
 253          * Revalidate the write permissions, in case security policy has
 254          * changed since the files were opened.
 255          */
 256         ret = security_file_permission(file, MAY_WRITE);
 257         if (ret)
 258                 return ret;
 259
 260         if (S_ISFIFO(inode->i_mode))
 261                 return -ESPIPE;
 262
 263         /*
 264          * Let individual file system decide if it supports preallocation
 265          * for directories or not.
 266          */
 267         if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 268                 return -ENODEV;
 269
 270         /* Check for wrap through zero too */
 271         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 272                 return -EFBIG;
 273
 274         if (!file->f_op->fallocate)
 275                 return -EOPNOTSUPP;
 276
 277         sb_start_write(inode->i_sb);
 278         ret = file->f_op->fallocate(file, mode, offset, len);
 279         sb_end_write(inode->i_sb);
 280         return ret;
 281 }
 282
 283 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
 284 {
 285         struct fd f = fdget(fd);
 286         int error = -EBADF;
 287
 288         if (f.file) {
 289                 error = do_fallocate(f.file, mode, offset, len);
 290                 fdput(f);
 291         }
 292         return error;
 293 }
 294
 295 /*
 296  * access() needs to use the real uid/gid, not the effective uid/gid.
 297  * We do this by temporarily clearing all FS-related capabilities and
 298  * switching the fsuid/fsgid around to the real ones.
 299  */
 300 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 301 {
 302         const struct cred *old_cred;
 303         struct cred *override_cred;
 304         struct path path;
 305         struct inode *inode;
 306         int res;
 307         unsigned int lookup_flags = LOOKUP_FOLLOW;
 308
 309         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 310                 return -EINVAL;
 311
 312         override_cred = prepare_creds();
 313         if (!override_cred)
 314                 return -ENOMEM;
 315
 316         override_cred->fsuid = override_cred->uid;
 317         override_cred->fsgid = override_cred->gid;
 318
 319         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 320                 /* Clear the capabilities if we switch to a non-root user */
 321                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 322                 if (!uid_eq(override_cred->uid, root_uid))
 323                         cap_clear(override_cred->cap_effective);
 324                 else
 325                         override_cred->cap_effective =
 326                                 override_cred->cap_permitted;
 327         }
 328
 329         old_cred = override_creds(override_cred);
 330 retry:
 331         res = user_path_at(dfd, filename, lookup_flags, &path);
 332         if (res)
 333                 goto out;
 334
 335         inode = path.dentry->d_inode;
 336
 337         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 338                 /*
 339                  * MAY_EXEC on regular files is denied if the fs is mounted
 340                  * with the "noexec" flag.
 341                  */
 342                 res = -EACCES;
 343                 if (path.mnt->mnt_flags & MNT_NOEXEC)
 344                         goto out_path_release;
 345         }
 346
 347         res = inode_permission(inode, mode | MAY_ACCESS);
 348         /* SuS v2 requires we report a read only fs too */
 349         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 350                 goto out_path_release;
 351         /*
 352          * This is a rare case where using __mnt_is_readonly()
 353          * is OK without a mnt_want/drop_write() pair.  Since
 354          * no actual write to the fs is performed here, we do
 355          * not need to telegraph to that to anyone.
 356          *
 357          * By doing this, we accept that this access is
 358          * inherently racy and know that the fs may change
 359          * state before we even see this result.
 360          */
 361         if (__mnt_is_readonly(path.mnt))
 362                 res = -EROFS;
 363
 364 out_path_release:
 365         path_put(&path);
 366         if (retry_estale(res, lookup_flags)) {
 367                 lookup_flags |= LOOKUP_REVAL;
 368                 goto retry;
 369         }
 370 out:
 371         revert_creds(old_cred);
 372         put_cred(override_cred);
 373         return res;
 374 }
 375
 376 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 377 {
 378         return sys_faccessat(AT_FDCWD, filename, mode);
 379 }
 380
 381 SYSCALL_DEFINE1(chdir, const char __user *, filename)
 382 {
 383         struct path path;
 384         int error;
 385         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 386 retry:
 387         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 388         if (error)
 389                 goto out;
 390
 391         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 392         if (error)
 393                 goto dput_and_out;
 394
 395         set_fs_pwd(current->fs, &path);
 396
 397 dput_and_out:
 398         path_put(&path);
 399         if (retry_estale(error, lookup_flags)) {
 400                 lookup_flags |= LOOKUP_REVAL;
 401                 goto retry;
 402         }
 403 out:
 404         return error;
 405 }
 406
 407 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 408 {
 409         struct fd f = fdget_raw(fd);
 410         struct inode *inode;
 411         int error = -EBADF;
 412
 413         error = -EBADF;
 414         if (!f.file)
 415                 goto out;
 416
 417         inode = file_inode(f.file);
 418
 419         error = -ENOTDIR;
 420         if (!S_ISDIR(inode->i_mode))
 421                 goto out_putf;
 422
 423         error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
 424         if (!error)
 425                 set_fs_pwd(current->fs, &f.file->f_path);
 426 out_putf:
 427         fdput(f);
 428 out:
 429         return error;
 430 }
 431
 432 SYSCALL_DEFINE1(chroot, const char __user *, filename)
 433 {
 434         struct path path;
 435         int error;
 436         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 437 retry:
 438         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 439         if (error)
 440                 goto out;
 441
 442         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 443         if (error)
 444                 goto dput_and_out;
 445
 446         error = -EPERM;
 447         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
 448                 goto dput_and_out;
 449         error = security_path_chroot(&path);
 450         if (error)
 451                 goto dput_and_out;
 452
 453         set_fs_root(current->fs, &path);
 454         error = 0;
 455 dput_and_out:
 456         path_put(&path);
 457         if (retry_estale(error, lookup_flags)) {
 458                 lookup_flags |= LOOKUP_REVAL;
 459                 goto retry;
 460         }
 461 out:
 462         return error;
 463 }
 464
 465 static int chmod_common(struct path *path, umode_t mode)
 466 {
 467         struct inode *inode = path->dentry->d_inode;
 468         struct inode *delegated_inode = NULL;
 469         struct iattr newattrs;
 470         int error;
 471
 472         error = mnt_want_write(path->mnt);
 473         if (error)
 474                 return error;
 475 retry_deleg:
 476         mutex_lock(&inode->i_mutex);
 477         error = security_path_chmod(path, mode);
 478         if (error)
 479                 goto out_unlock;
 480         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 481         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 482         error = notify_change(path->dentry, &newattrs, &delegated_inode);
 483 out_unlock:
 484         mutex_unlock(&inode->i_mutex);
 485         if (delegated_inode) {
 486                 error = break_deleg_wait(&delegated_inode);
 487                 if (!error)
 488                         goto retry_deleg;
 489         }
 490         mnt_drop_write(path->mnt);
 491         return error;
 492 }
 493
 494 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 495 {
 496         struct fd f = fdget(fd);
 497         int err = -EBADF;
 498
 499         if (f.file) {
 500                 audit_inode(NULL, f.file->f_path.dentry, 0);
 501                 err = chmod_common(&f.file->f_path, mode);
 502                 fdput(f);
 503         }
 504         return err;
 505 }
 506
 507 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
 508 {
 509         struct path path;
 510         int error;
 511         unsigned int lookup_flags = LOOKUP_FOLLOW;
 512 retry:
 513         error = user_path_at(dfd, filename, lookup_flags, &path);
 514         if (!error) {
 515                 error = chmod_common(&path, mode);
 516                 path_put(&path);
 517                 if (retry_estale(error, lookup_flags)) {
 518                         lookup_flags |= LOOKUP_REVAL;
 519                         goto retry;
 520                 }
 521         }
 522         return error;
 523 }
 524
 525 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 526 {
 527         return sys_fchmodat(AT_FDCWD, filename, mode);
 528 }
 529
 530 static int chown_common(struct path *path, uid_t user, gid_t group)
 531 {
 532         struct inode *inode = path->dentry->d_inode;
 533         struct inode *delegated_inode = NULL;
 534         int error;
 535         struct iattr newattrs;
 536         kuid_t uid;
 537         kgid_t gid;
 538
 539         uid = make_kuid(current_user_ns(), user);
 540         gid = make_kgid(current_user_ns(), group);
 541
 542         newattrs.ia_valid =  ATTR_CTIME;
 543         if (user != (uid_t) -1) {
 544                 if (!uid_valid(uid))
 545                         return -EINVAL;
 546                 newattrs.ia_valid |= ATTR_UID;
 547                 newattrs.ia_uid = uid;
 548         }
 549         if (group != (gid_t) -1) {
 550                 if (!gid_valid(gid))
 551                         return -EINVAL;
 552                 newattrs.ia_valid |= ATTR_GID;
 553                 newattrs.ia_gid = gid;
 554         }
 555         if (!S_ISDIR(inode->i_mode))
 556                 newattrs.ia_valid |=
 557                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 558 retry_deleg:
 559         mutex_lock(&inode->i_mutex);
 560         error = security_path_chown(path, uid, gid);
 561         if (!error)
 562                 error = notify_change(path->dentry, &newattrs, &delegated_inode);
 563         mutex_unlock(&inode->i_mutex);
 564         if (delegated_inode) {
 565                 error = break_deleg_wait(&delegated_inode);
 566                 if (!error)
 567                         goto retry_deleg;
 568         }
 569         return error;
 570 }
 571
 572 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 573                 gid_t, group, int, flag)
 574 {
 575         struct path path;
 576         int error = -EINVAL;
 577         int lookup_flags;
 578
 579         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 580                 goto out;
 581
 582         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 583         if (flag & AT_EMPTY_PATH)
 584                 lookup_flags |= LOOKUP_EMPTY;
 585 retry:
 586         error = user_path_at(dfd, filename, lookup_flags, &path);
 587         if (error)
 588                 goto out;
 589         error = mnt_want_write(path.mnt);
 590         if (error)
 591                 goto out_release;
 592         error = chown_common(&path, user, group);
 593         mnt_drop_write(path.mnt);
 594 out_release:
 595         path_put(&path);
 596         if (retry_estale(error, lookup_flags)) {
 597                 lookup_flags |= LOOKUP_REVAL;
 598                 goto retry;
 599         }
 600 out:
 601         return error;
 602 }
 603
 604 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 605 {
 606         return sys_fchownat(AT_FDCWD, filename, user, group, 0);
 607 }
 608
 609 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 610 {
 611         return sys_fchownat(AT_FDCWD, filename, user, group,
 612                             AT_SYMLINK_NOFOLLOW);
 613 }
 614
 615 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 616 {
 617         struct fd f = fdget(fd);
 618         int error = -EBADF;
 619
 620         if (!f.file)
 621                 goto out;
 622
 623         error = mnt_want_write_file(f.file);
 624         if (error)
 625                 goto out_fput;
 626         audit_inode(NULL, f.file->f_path.dentry, 0);
 627         error = chown_common(&f.file->f_path, user, group);
 628         mnt_drop_write_file(f.file);
 629 out_fput:
 630         fdput(f);
 631 out:
 632         return error;
 633 }
 634
 635 /*
 636  * You have to be very careful that these write
 637  * counts get cleaned up in error cases and
 638  * upon __fput().  This should probably never
 639  * be called outside of __dentry_open().
 640  */
 641 static inline int __get_file_write_access(struct inode *inode,
 642                                           struct vfsmount *mnt)
 643 {
 644         int error = get_write_access(inode);
 645         if (error)
 646                 return error;
 647         error = __mnt_want_write(mnt);
 648         if (error)
 649                 put_write_access(inode);
 650         return error;
 651 }
 652
 653 int open_check_o_direct(struct file *f)
 654 {
 655         /* NB: we're sure to have correct a_ops only after f_op->open */
 656         if (f->f_flags & O_DIRECT) {
 657                 if (!f->f_mapping->a_ops ||
 658                     ((!f->f_mapping->a_ops->direct_IO) &&
 659                     (!f->f_mapping->a_ops->get_xip_mem))) {
 660                         return -EINVAL;
 661                 }
 662         }
 663         return 0;
 664 }
 665
 666 static int do_dentry_open(struct file *f,
 667                           int (*open)(struct inode *, struct file *),
 668                           const struct cred *cred)
 669 {
 670         static const struct file_operations empty_fops = {};
 671         struct inode *inode;
 672         int error;
 673
 674         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 675                                 FMODE_PREAD | FMODE_PWRITE;
 676
 677         if (unlikely(f->f_flags & O_PATH))
 678                 f->f_mode = FMODE_PATH;
 679
 680         path_get(&f->f_path);
 681         inode = f->f_inode = f->f_path.dentry->d_inode;
 682         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
 683                 error = __get_file_write_access(inode, f->f_path.mnt);
 684                 if (error)
 685                         goto cleanup_file;
 686                 file_take_write(f);
 687         }
 688
 689         f->f_mapping = inode->i_mapping;
 690
 691         if (unlikely(f->f_mode & FMODE_PATH)) {
 692                 f->f_op = &empty_fops;
 693                 return 0;
 694         }
 695
 696         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
 697         if (S_ISREG(inode->i_mode))
 698                 f->f_mode |= FMODE_ATOMIC_POS;
 699
 700         f->f_op = fops_get(inode->i_fop);
 701         if (unlikely(WARN_ON(!f->f_op))) {
 702                 error = -ENODEV;
 703                 goto cleanup_all;
 704         }
 705
 706         error = security_file_open(f, cred);
 707         if (error)
 708                 goto cleanup_all;
 709
 710         error = break_lease(inode, f->f_flags);
 711         if (error)
 712                 goto cleanup_all;
 713
 714         if (!open)
 715                 open = f->f_op->open;
 716         if (open) {
 717                 error = open(inode, f);
 718                 if (error)
 719                         goto cleanup_all;
 720         }
 721         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 722                 i_readcount_inc(inode);
 723
 724         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 725
 726         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 727
 728         return 0;
 729
 730 cleanup_all:
 731         fops_put(f->f_op);
 732         if (f->f_mode & FMODE_WRITE) {
 733                 if (!special_file(inode->i_mode)) {
 734                         /*
 735                          * We don't consider this a real
 736                          * mnt_want/drop_write() pair
 737                          * because it all happenend right
 738                          * here, so just reset the state.
 739                          */
 740                         put_write_access(inode);
 741                         file_reset_write(f);
 742                         __mnt_drop_write(f->f_path.mnt);
 743                 }
 744         }
 745 cleanup_file:
 746         path_put(&f->f_path);
 747         f->f_path.mnt = NULL;
 748         f->f_path.dentry = NULL;
 749         f->f_inode = NULL;
 750         return error;
 751 }
 752
 753 /**
 754  * finish_open - finish opening a file
 755  * @file: file pointer
 756  * @dentry: pointer to dentry
 757  * @open: open callback
 758  * @opened: state of open
 759  *
 760  * This can be used to finish opening a file passed to i_op->atomic_open().
 761  *
 762  * If the open callback is set to NULL, then the standard f_op->open()
 763  * filesystem callback is substituted.
 764  *
 765  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
 766  * the return value of d_splice_alias(), then the caller needs to perform dput()
 767  * on it after finish_open().
 768  *
 769  * On successful return @file is a fully instantiated open file.  After this, if
 770  * an error occurs in ->atomic_open(), it needs to clean up with fput().
 771  *
 772  * Returns zero on success or -errno if the open failed.
 773  */
 774 int finish_open(struct file *file, struct dentry *dentry,
 775                 int (*open)(struct inode *, struct file *),
 776                 int *opened)
 777 {
 778         int error;
 779         BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
 780
 781         file->f_path.dentry = dentry;
 782         error = do_dentry_open(file, open, current_cred());
 783         if (!error)
 784                 *opened |= FILE_OPENED;
 785
 786         return error;
 787 }
 788 EXPORT_SYMBOL(finish_open);
 789
 790 /**
 791  * finish_no_open - finish ->atomic_open() without opening the file
 792  *
 793  * @file: file pointer
 794  * @dentry: dentry or NULL (as returned from ->lookup())
 795  *
 796  * This can be used to set the result of a successful lookup in ->atomic_open().
 797  *
 798  * NB: unlike finish_open() this function does consume the dentry reference and
 799  * the caller need not dput() it.
 800  *
 801  * Returns "1" which must be the return value of ->atomic_open() after having
 802  * called this function.
 803  */
 804 int finish_no_open(struct file *file, struct dentry *dentry)
 805 {
 806         file->f_path.dentry = dentry;
 807         return 1;
 808 }
 809 EXPORT_SYMBOL(finish_no_open);
 810
 811 struct file *dentry_open(const struct path *path, int flags,
 812                          const struct cred *cred)
 813 {
 814         int error;
 815         struct file *f;
 816
 817         validate_creds(cred);
 818
 819         /* We must always pass in a valid mount pointer. */
 820         BUG_ON(!path->mnt);
 821
 822         f = get_empty_filp();
 823         if (!IS_ERR(f)) {
 824                 f->f_flags = flags;
 825                 f->f_path = *path;
 826                 error = do_dentry_open(f, NULL, cred);
 827                 if (!error) {
 828                         /* from now on we need fput() to dispose of f */
 829                         error = open_check_o_direct(f);
 830                         if (error) {
 831                                 fput(f);
 832                                 f = ERR_PTR(error);
 833                         }
 834                 } else {
 835                         put_filp(f);
 836                         f = ERR_PTR(error);
 837                 }
 838         }
 839         return f;
 840 }
 841 EXPORT_SYMBOL(dentry_open);
 842
 843 static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
 844 {
 845         int lookup_flags = 0;
 846         int acc_mode;
 847
 848         if (flags & (O_CREAT | __O_TMPFILE))
 849                 op->mode = (mode & S_IALLUGO) | S_IFREG;
 850         else
 851                 op->mode = 0;
 852
 853         /* Must never be set by userspace */
 854         flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
 855
 856         /*
 857          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
 858          * check for O_DSYNC if the need any syncing at all we enforce it's
 859          * always set instead of having to deal with possibly weird behaviour
 860          * for malicious applications setting only __O_SYNC.
 861          */
 862         if (flags & __O_SYNC)
 863                 flags |= O_DSYNC;
 864
 865         if (flags & __O_TMPFILE) {
 866                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
 867                         return -EINVAL;
 868                 acc_mode = MAY_OPEN | ACC_MODE(flags);
 869                 if (!(acc_mode & MAY_WRITE))
 870                         return -EINVAL;
 871         } else if (flags & O_PATH) {
 872                 /*
 873                  * If we have O_PATH in the open flag. Then we
 874                  * cannot have anything other than the below set of flags
 875                  */
 876                 flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
 877                 acc_mode = 0;
 878         } else {
 879                 acc_mode = MAY_OPEN | ACC_MODE(flags);
 880         }
 881
 882         op->open_flag = flags;
 883
 884         /* O_TRUNC implies we need access checks for write permissions */
 885         if (flags & O_TRUNC)
 886                 acc_mode |= MAY_WRITE;
 887
 888         /* Allow the LSM permission hook to distinguish append
 889            access from general write access. */
 890         if (flags & O_APPEND)
 891                 acc_mode |= MAY_APPEND;
 892
 893         op->acc_mode = acc_mode;
 894
 895         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
 896
 897         if (flags & O_CREAT) {
 898                 op->intent |= LOOKUP_CREATE;
 899                 if (flags & O_EXCL)
 900                         op->intent |= LOOKUP_EXCL;
 901         }
 902
 903         if (flags & O_DIRECTORY)
 904                 lookup_flags |= LOOKUP_DIRECTORY;
 905         if (!(flags & O_NOFOLLOW))
 906                 lookup_flags |= LOOKUP_FOLLOW;
 907         op->lookup_flags = lookup_flags;
 908         return 0;
 909 }
 910
 911 /**
 912  * file_open_name - open file and return file pointer
 913  *
 914  * @name:       struct filename containing path to open
 915  * @flags:      open flags as per the open(2) second argument
 916  * @mode:       mode for the new file if O_CREAT is set, else ignored
 917  *
 918  * This is the helper to open a file from kernelspace if you really
 919  * have to.  But in generally you should not do this, so please move
 920  * along, nothing to see here..
 921  */
 922 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
 923 {
 924         struct open_flags op;
 925         int err = build_open_flags(flags, mode, &op);
 926         return err ? ERR_PTR(err) : do_filp_open(AT_FDCWD, name, &op);
 927 }
 928
 929 /**
 930  * filp_open - open file and return file pointer
 931  *
 932  * @filename:   path to open
 933  * @flags:      open flags as per the open(2) second argument
 934  * @mode:       mode for the new file if O_CREAT is set, else ignored
 935  *
 936  * This is the helper to open a file from kernelspace if you really
 937  * have to.  But in generally you should not do this, so please move
 938  * along, nothing to see here..
 939  */
 940 struct file *filp_open(const char *filename, int flags, umode_t mode)
 941 {
 942         struct filename name = {.name = filename};
 943         return file_open_name(&name, flags, mode);
 944 }
 945 EXPORT_SYMBOL(filp_open);
 946
 947 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
 948                             const char *filename, int flags)
 949 {
 950         struct open_flags op;
 951         int err = build_open_flags(flags, 0, &op);
 952         if (err)
 953                 return ERR_PTR(err);
 954         if (flags & O_CREAT)
 955                 return ERR_PTR(-EINVAL);
 956         if (!filename && (flags & O_DIRECTORY))
 957                 if (!dentry->d_inode->i_op->lookup)
 958                         return ERR_PTR(-ENOTDIR);
 959         return do_file_open_root(dentry, mnt, filename, &op);
 960 }
 961 EXPORT_SYMBOL(file_open_root);
 962
 963 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
 964 {
 965         struct open_flags op;
 966         int fd = build_open_flags(flags, mode, &op);
 967         struct filename *tmp;
 968
 969         if (fd)
 970                 return fd;
 971
 972         tmp = getname(filename);
 973         if (IS_ERR(tmp))
 974                 return PTR_ERR(tmp);
 975
 976         fd = get_unused_fd_flags(flags);
 977         if (fd >= 0) {
 978                 struct file *f = do_filp_open(dfd, tmp, &op);
 979                 if (IS_ERR(f)) {
 980                         put_unused_fd(fd);
 981                         fd = PTR_ERR(f);
 982                 } else {
 983                         fsnotify_open(f);
 984                         fd_install(fd, f);
 985                 }
 986         }
 987         putname(tmp);
 988         return fd;
 989 }
 990
 991 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
 992 {
 993         if (force_o_largefile())
 994                 flags |= O_LARGEFILE;
 995
 996         return do_sys_open(AT_FDCWD, filename, flags, mode);
 997 }
 998
 999 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1000                 umode_t, mode)
1001 {
1002         if (force_o_largefile())
1003                 flags |= O_LARGEFILE;
1004
1005         return do_sys_open(dfd, filename, flags, mode);
1006 }
1007
1008 #ifndef __alpha__
1009
1010 /*
1011  * For backward compatibility?  Maybe this should be moved
1012  * into arch/i386 instead?
1013  */
1014 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1015 {
1016         return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1017 }
1018
1019 #endif
1020
1021 /*
1022  * "id" is the POSIX thread ID. We use the
1023  * files pointer for this..
1024  */
1025 int filp_close(struct file *filp, fl_owner_t id)
1026 {
1027         int retval = 0;
1028
1029         if (!file_count(filp)) {
1030                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1031                 return 0;
1032         }
1033
1034         if (filp->f_op->flush)
1035                 retval = filp->f_op->flush(filp, id);
1036
1037         if (likely(!(filp->f_mode & FMODE_PATH))) {
1038                 dnotify_flush(filp, id);
1039                 locks_remove_posix(filp, id);
1040         }
1041         fput(filp);
1042         return retval;
1043 }
1044
1045 EXPORT_SYMBOL(filp_close);
1046
1047 /*
1048  * Careful here! We test whether the file pointer is NULL before
1049  * releasing the fd. This ensures that one clone task can't release
1050  * an fd while another clone is opening it.
1051  */
1052 SYSCALL_DEFINE1(close, unsigned int, fd)
1053 {
1054         int retval = __close_fd(current->files, fd);
1055
1056         /* can't restart close syscall because file table entry was cleared */
1057         if (unlikely(retval == -ERESTARTSYS ||
1058                      retval == -ERESTARTNOINTR ||
1059                      retval == -ERESTARTNOHAND ||
1060                      retval == -ERESTART_RESTARTBLOCK))
1061                 retval = -EINTR;
1062
1063         return retval;
1064 }
1065 EXPORT_SYMBOL(sys_close);
1066
1067 /*
1068  * This routine simulates a hangup on the tty, to arrange that users
1069  * are given clean terminals at login time.
1070  */
1071 SYSCALL_DEFINE0(vhangup)
1072 {
1073         if (capable(CAP_SYS_TTY_CONFIG)) {
1074                 tty_vhangup_self();
1075                 return 0;
1076         }
1077         return -EPERM;
1078 }
1079
1080 /*
1081  * Called when an inode is about to be open.
1082  * We use this to disallow opening large files on 32bit systems if
1083  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1084  * on this flag in sys_open.
1085  */
1086 int generic_file_open(struct inode * inode, struct file * filp)
1087 {
1088         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1089                 return -EOVERFLOW;
1090         return 0;
1091 }
1092
1093 EXPORT_SYMBOL(generic_file_open);
1094
1095 /*
1096  * This is used by subsystems that don't want seekable
1097  * file descriptors. The function is not supposed to ever fail, the only
1098  * reason it returns an 'int' and not 'void' is so that it can be plugged
1099  * directly into file_operations structure.
1100  */
1101 int nonseekable_open(struct inode *inode, struct file *filp)
1102 {
1103         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1104         return 0;
1105 }
1106
1107 EXPORT_SYMBOL(nonseekable_open);