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