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
  34 #include "internal.h"
  35
  36 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
  37         struct file *filp)
  38 {
  39         int ret;
  40         struct iattr newattrs;
  41
  42         /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
  43         if (length < 0)
  44                 return -EINVAL;
  45
  46         newattrs.ia_size = length;
  47         newattrs.ia_valid = ATTR_SIZE | time_attrs;
  48         if (filp) {
  49                 newattrs.ia_file = filp;
  50                 newattrs.ia_valid |= ATTR_FILE;
  51         }
  52
  53         /* Remove suid/sgid on truncate too */
  54         ret = should_remove_suid(dentry);
  55         if (ret)
  56                 newattrs.ia_valid |= ret | ATTR_FORCE;
  57
  58         mutex_lock(&dentry->d_inode->i_mutex);
  59         ret = notify_change(dentry, &newattrs);
  60         mutex_unlock(&dentry->d_inode->i_mutex);
  61         return ret;
  62 }
  63
  64 static long do_sys_truncate(const char __user *pathname, loff_t length)
  65 {
  66         struct path path;
  67         struct inode *inode;
  68         int error;
  69
  70         error = -EINVAL;
  71         if (length < 0) /* sorry, but loff_t says... */
  72                 goto out;
  73
  74         error = user_path(pathname, &path);
  75         if (error)
  76                 goto out;
  77         inode = path.dentry->d_inode;
  78
  79         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
  80         error = -EISDIR;
  81         if (S_ISDIR(inode->i_mode))
  82                 goto dput_and_out;
  83
  84         error = -EINVAL;
  85         if (!S_ISREG(inode->i_mode))
  86                 goto dput_and_out;
  87
  88         error = mnt_want_write(path.mnt);
  89         if (error)
  90                 goto dput_and_out;
  91
  92         error = inode_permission(inode, MAY_WRITE);
  93         if (error)
  94                 goto mnt_drop_write_and_out;
  95
  96         error = -EPERM;
  97         if (IS_APPEND(inode))
  98                 goto mnt_drop_write_and_out;
  99
 100         error = get_write_access(inode);
 101         if (error)
 102                 goto mnt_drop_write_and_out;
 103
 104         /*
 105          * Make sure that there are no leases.  get_write_access() protects
 106          * against the truncate racing with a lease-granting setlease().
 107          */
 108         error = break_lease(inode, O_WRONLY);
 109         if (error)
 110                 goto put_write_and_out;
 111
 112         error = locks_verify_truncate(inode, NULL, length);
 113         if (!error)
 114                 error = security_path_truncate(&path);
 115         if (!error)
 116                 error = do_truncate(path.dentry, length, 0, NULL);
 117
 118 put_write_and_out:
 119         put_write_access(inode);
 120 mnt_drop_write_and_out:
 121         mnt_drop_write(path.mnt);
 122 dput_and_out:
 123         path_put(&path);
 124 out:
 125         return error;
 126 }
 127
 128 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 129 {
 130         return do_sys_truncate(path, length);
 131 }
 132
 133 static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 134 {
 135         struct inode * inode;
 136         struct dentry *dentry;
 137         struct file * file;
 138         int error;
 139
 140         error = -EINVAL;
 141         if (length < 0)
 142                 goto out;
 143         error = -EBADF;
 144         file = fget(fd);
 145         if (!file)
 146                 goto out;
 147
 148         /* explicitly opened as large or we are on 64-bit box */
 149         if (file->f_flags & O_LARGEFILE)
 150                 small = 0;
 151
 152         dentry = file->f_path.dentry;
 153         inode = dentry->d_inode;
 154         error = -EINVAL;
 155         if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
 156                 goto out_putf;
 157
 158         error = -EINVAL;
 159         /* Cannot ftruncate over 2^31 bytes without large file support */
 160         if (small && length > MAX_NON_LFS)
 161                 goto out_putf;
 162
 163         error = -EPERM;
 164         if (IS_APPEND(inode))
 165                 goto out_putf;
 166
 167         error = locks_verify_truncate(inode, file, length);
 168         if (!error)
 169                 error = security_path_truncate(&file->f_path);
 170         if (!error)
 171                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
 172 out_putf:
 173         fput(file);
 174 out:
 175         return error;
 176 }
 177
 178 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 179 {
 180         long ret = do_sys_ftruncate(fd, length, 1);
 181         /* avoid REGPARM breakage on x86: */
 182         asmlinkage_protect(2, ret, fd, length);
 183         return ret;
 184 }
 185
 186 /* LFS versions of truncate are only needed on 32 bit machines */
 187 #if BITS_PER_LONG == 32
 188 SYSCALL_DEFINE(truncate64)(const char __user * path, loff_t length)
 189 {
 190         return do_sys_truncate(path, length);
 191 }
 192 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 193 asmlinkage long SyS_truncate64(long path, loff_t length)
 194 {
 195         return SYSC_truncate64((const char __user *) path, length);
 196 }
 197 SYSCALL_ALIAS(sys_truncate64, SyS_truncate64);
 198 #endif
 199
 200 SYSCALL_DEFINE(ftruncate64)(unsigned int fd, loff_t length)
 201 {
 202         long ret = do_sys_ftruncate(fd, length, 0);
 203         /* avoid REGPARM breakage on x86: */
 204         asmlinkage_protect(2, ret, fd, length);
 205         return ret;
 206 }
 207 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 208 asmlinkage long SyS_ftruncate64(long fd, loff_t length)
 209 {
 210         return SYSC_ftruncate64((unsigned int) fd, length);
 211 }
 212 SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
 213 #endif
 214 #endif /* BITS_PER_LONG == 32 */
 215
 216
 217 int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 218 {
 219         struct inode *inode = file->f_path.dentry->d_inode;
 220         long ret;
 221
 222         if (offset < 0 || len <= 0)
 223                 return -EINVAL;
 224
 225         /* Return error if mode is not supported */
 226         if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
 227                 return -EOPNOTSUPP;
 228
 229         /* Punch hole must have keep size set */
 230         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
 231             !(mode & FALLOC_FL_KEEP_SIZE))
 232                 return -EOPNOTSUPP;
 233
 234         if (!(file->f_mode & FMODE_WRITE))
 235                 return -EBADF;
 236
 237         /* It's not possible punch hole on append only file */
 238         if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
 239                 return -EPERM;
 240
 241         if (IS_IMMUTABLE(inode))
 242                 return -EPERM;
 243
 244         /*
 245          * Revalidate the write permissions, in case security policy has
 246          * changed since the files were opened.
 247          */
 248         ret = security_file_permission(file, MAY_WRITE);
 249         if (ret)
 250                 return ret;
 251
 252         if (S_ISFIFO(inode->i_mode))
 253                 return -ESPIPE;
 254
 255         /*
 256          * Let individual file system decide if it supports preallocation
 257          * for directories or not.
 258          */
 259         if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 260                 return -ENODEV;
 261
 262         /* Check for wrap through zero too */
 263         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 264                 return -EFBIG;
 265
 266         if (!file->f_op->fallocate)
 267                 return -EOPNOTSUPP;
 268
 269         return file->f_op->fallocate(file, mode, offset, len);
 270 }
 271
 272 SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)
 273 {
 274         struct file *file;
 275         int error = -EBADF;
 276
 277         file = fget(fd);
 278         if (file) {
 279                 error = do_fallocate(file, mode, offset, len);
 280                 fput(file);
 281         }
 282
 283         return error;
 284 }
 285
 286 #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 287 asmlinkage long SyS_fallocate(long fd, long mode, loff_t offset, loff_t len)
 288 {
 289         return SYSC_fallocate((int)fd, (int)mode, offset, len);
 290 }
 291 SYSCALL_ALIAS(sys_fallocate, SyS_fallocate);
 292 #endif
 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
 307         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 308                 return -EINVAL;
 309
 310         override_cred = prepare_creds();
 311         if (!override_cred)
 312                 return -ENOMEM;
 313
 314         override_cred->fsuid = override_cred->uid;
 315         override_cred->fsgid = override_cred->gid;
 316
 317         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 318                 /* Clear the capabilities if we switch to a non-root user */
 319                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 320                 if (!uid_eq(override_cred->uid, root_uid))
 321                         cap_clear(override_cred->cap_effective);
 322                 else
 323                         override_cred->cap_effective =
 324                                 override_cred->cap_permitted;
 325         }
 326
 327         old_cred = override_creds(override_cred);
 328
 329         res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
 330         if (res)
 331                 goto out;
 332
 333         inode = path.dentry->d_inode;
 334
 335         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 336                 /*
 337                  * MAY_EXEC on regular files is denied if the fs is mounted
 338                  * with the "noexec" flag.
 339                  */
 340                 res = -EACCES;
 341                 if (path.mnt->mnt_flags & MNT_NOEXEC)
 342                         goto out_path_release;
 343         }
 344
 345         res = inode_permission(inode, mode | MAY_ACCESS);
 346         /* SuS v2 requires we report a read only fs too */
 347         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 348                 goto out_path_release;
 349         /*
 350          * This is a rare case where using __mnt_is_readonly()
 351          * is OK without a mnt_want/drop_write() pair.  Since
 352          * no actual write to the fs is performed here, we do
 353          * not need to telegraph to that to anyone.
 354          *
 355          * By doing this, we accept that this access is
 356          * inherently racy and know that the fs may change
 357          * state before we even see this result.
 358          */
 359         if (__mnt_is_readonly(path.mnt))
 360                 res = -EROFS;
 361
 362 out_path_release:
 363         path_put(&path);
 364 out:
 365         revert_creds(old_cred);
 366         put_cred(override_cred);
 367         return res;
 368 }
 369
 370 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 371 {
 372         return sys_faccessat(AT_FDCWD, filename, mode);
 373 }
 374
 375 SYSCALL_DEFINE1(chdir, const char __user *, filename)
 376 {
 377         struct path path;
 378         int error;
 379
 380         error = user_path_dir(filename, &path);
 381         if (error)
 382                 goto out;
 383
 384         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 385         if (error)
 386                 goto dput_and_out;
 387
 388         set_fs_pwd(current->fs, &path);
 389
 390 dput_and_out:
 391         path_put(&path);
 392 out:
 393         return error;
 394 }
 395
 396 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 397 {
 398         struct file *file;
 399         struct inode *inode;
 400         int error;
 401
 402         error = -EBADF;
 403         file = fget(fd);
 404         if (!file)
 405                 goto out;
 406
 407         inode = file->f_path.dentry->d_inode;
 408
 409         error = -ENOTDIR;
 410         if (!S_ISDIR(inode->i_mode))
 411                 goto out_putf;
 412
 413         error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
 414         if (!error)
 415                 set_fs_pwd(current->fs, &file->f_path);
 416 out_putf:
 417         fput(file);
 418 out:
 419         return error;
 420 }
 421
 422 SYSCALL_DEFINE1(chroot, const char __user *, filename)
 423 {
 424         struct path path;
 425         int error;
 426
 427         error = user_path_dir(filename, &path);
 428         if (error)
 429                 goto out;
 430
 431         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 432         if (error)
 433                 goto dput_and_out;
 434
 435         error = -EPERM;
 436         if (!capable(CAP_SYS_CHROOT))
 437                 goto dput_and_out;
 438         error = security_path_chroot(&path);
 439         if (error)
 440                 goto dput_and_out;
 441
 442         set_fs_root(current->fs, &path);
 443         error = 0;
 444 dput_and_out:
 445         path_put(&path);
 446 out:
 447         return error;
 448 }
 449
 450 static int chmod_common(struct path *path, umode_t mode)
 451 {
 452         struct inode *inode = path->dentry->d_inode;
 453         struct iattr newattrs;
 454         int error;
 455
 456         error = mnt_want_write(path->mnt);
 457         if (error)
 458                 return error;
 459         mutex_lock(&inode->i_mutex);
 460         error = security_path_chmod(path, mode);
 461         if (error)
 462                 goto out_unlock;
 463         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 464         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 465         error = notify_change(path->dentry, &newattrs);
 466 out_unlock:
 467         mutex_unlock(&inode->i_mutex);
 468         mnt_drop_write(path->mnt);
 469         return error;
 470 }
 471
 472 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 473 {
 474         struct file * file;
 475         int err = -EBADF;
 476
 477         file = fget(fd);
 478         if (file) {
 479                 audit_inode(NULL, file->f_path.dentry);
 480                 err = chmod_common(&file->f_path, mode);
 481                 fput(file);
 482         }
 483         return err;
 484 }
 485
 486 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
 487 {
 488         struct path path;
 489         int error;
 490
 491         error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
 492         if (!error) {
 493                 error = chmod_common(&path, mode);
 494                 path_put(&path);
 495         }
 496         return error;
 497 }
 498
 499 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 500 {
 501         return sys_fchmodat(AT_FDCWD, filename, mode);
 502 }
 503
 504 static int chown_common(struct path *path, uid_t user, gid_t group)
 505 {
 506         struct inode *inode = path->dentry->d_inode;
 507         int error;
 508         struct iattr newattrs;
 509         kuid_t uid;
 510         kgid_t gid;
 511
 512         uid = make_kuid(current_user_ns(), user);
 513         gid = make_kgid(current_user_ns(), group);
 514
 515         newattrs.ia_valid =  ATTR_CTIME;
 516         if (user != (uid_t) -1) {
 517                 if (!uid_valid(uid))
 518                         return -EINVAL;
 519                 newattrs.ia_valid |= ATTR_UID;
 520                 newattrs.ia_uid = uid;
 521         }
 522         if (group != (gid_t) -1) {
 523                 if (!gid_valid(gid))
 524                         return -EINVAL;
 525                 newattrs.ia_valid |= ATTR_GID;
 526                 newattrs.ia_gid = gid;
 527         }
 528         if (!S_ISDIR(inode->i_mode))
 529                 newattrs.ia_valid |=
 530                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 531         mutex_lock(&inode->i_mutex);
 532         error = security_path_chown(path, user, group);
 533         if (!error)
 534                 error = notify_change(path->dentry, &newattrs);
 535         mutex_unlock(&inode->i_mutex);
 536
 537         return error;
 538 }
 539
 540 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 541 {
 542         struct path path;
 543         int error;
 544
 545         error = user_path(filename, &path);
 546         if (error)
 547                 goto out;
 548         error = mnt_want_write(path.mnt);
 549         if (error)
 550                 goto out_release;
 551         error = chown_common(&path, user, group);
 552         mnt_drop_write(path.mnt);
 553 out_release:
 554         path_put(&path);
 555 out:
 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         error = user_path_at(dfd, filename, lookup_flags, &path);
 573         if (error)
 574                 goto out;
 575         error = mnt_want_write(path.mnt);
 576         if (error)
 577                 goto out_release;
 578         error = chown_common(&path, user, group);
 579         mnt_drop_write(path.mnt);
 580 out_release:
 581         path_put(&path);
 582 out:
 583         return error;
 584 }
 585
 586 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 587 {
 588         struct path path;
 589         int error;
 590
 591         error = user_lpath(filename, &path);
 592         if (error)
 593                 goto out;
 594         error = mnt_want_write(path.mnt);
 595         if (error)
 596                 goto out_release;
 597         error = chown_common(&path, user, group);
 598         mnt_drop_write(path.mnt);
 599 out_release:
 600         path_put(&path);
 601 out:
 602         return error;
 603 }
 604
 605 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 606 {
 607         struct file * file;
 608         int error = -EBADF;
 609         struct dentry * dentry;
 610
 611         file = fget(fd);
 612         if (!file)
 613                 goto out;
 614
 615         error = mnt_want_write_file(file);
 616         if (error)
 617                 goto out_fput;
 618         dentry = file->f_path.dentry;
 619         audit_inode(NULL, dentry);
 620         error = chown_common(&file->f_path, user, group);
 621         mnt_drop_write_file(file);
 622 out_fput:
 623         fput(file);
 624 out:
 625         return error;
 626 }
 627
 628 /*
 629  * You have to be very careful that these write
 630  * counts get cleaned up in error cases and
 631  * upon __fput().  This should probably never
 632  * be called outside of __dentry_open().
 633  */
 634 static inline int __get_file_write_access(struct inode *inode,
 635                                           struct vfsmount *mnt)
 636 {
 637         int error;
 638         error = get_write_access(inode);
 639         if (error)
 640                 return error;
 641         /*
 642          * Do not take mount writer counts on
 643          * special files since no writes to
 644          * the mount itself will occur.
 645          */
 646         if (!special_file(inode->i_mode)) {
 647                 /*
 648                  * Balanced in __fput()
 649                  */
 650                 error = mnt_want_write(mnt);
 651                 if (error)
 652                         put_write_access(inode);
 653         }
 654         return error;
 655 }
 656
 657 int open_check_o_direct(struct file *f)
 658 {
 659         /* NB: we're sure to have correct a_ops only after f_op->open */
 660         if (f->f_flags & O_DIRECT) {
 661                 if (!f->f_mapping->a_ops ||
 662                     ((!f->f_mapping->a_ops->direct_IO) &&
 663                     (!f->f_mapping->a_ops->get_xip_mem))) {
 664                         return -EINVAL;
 665                 }
 666         }
 667         return 0;
 668 }
 669
 670 static struct file *do_dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 671                                    struct file *f,
 672                                    int (*open)(struct inode *, struct file *),
 673                                    const struct cred *cred)
 674 {
 675         static const struct file_operations empty_fops = {};
 676         struct inode *inode;
 677         int error;
 678
 679         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 680                                 FMODE_PREAD | FMODE_PWRITE;
 681
 682         if (unlikely(f->f_flags & O_PATH))
 683                 f->f_mode = FMODE_PATH;
 684
 685         inode = dentry->d_inode;
 686         if (f->f_mode & FMODE_WRITE) {
 687                 error = __get_file_write_access(inode, mnt);
 688                 if (error)
 689                         goto cleanup_file;
 690                 if (!special_file(inode->i_mode))
 691                         file_take_write(f);
 692         }
 693
 694         f->f_mapping = inode->i_mapping;
 695         f->f_path.dentry = dentry;
 696         f->f_path.mnt = mnt;
 697         f->f_pos = 0;
 698         file_sb_list_add(f, inode->i_sb);
 699
 700         if (unlikely(f->f_mode & FMODE_PATH)) {
 701                 f->f_op = &empty_fops;
 702                 return f;
 703         }
 704
 705         f->f_op = fops_get(inode->i_fop);
 706
 707         error = security_file_open(f, cred);
 708         if (error)
 709                 goto cleanup_all;
 710
 711         error = break_lease(inode, f->f_flags);
 712         if (error)
 713                 goto cleanup_all;
 714
 715         if (!open && f->f_op)
 716                 open = f->f_op->open;
 717         if (open) {
 718                 error = open(inode, f);
 719                 if (error)
 720                         goto cleanup_all;
 721         }
 722         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 723                 i_readcount_inc(inode);
 724
 725         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 726
 727         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 728
 729         return f;
 730
 731 cleanup_all:
 732         fops_put(f->f_op);
 733         if (f->f_mode & FMODE_WRITE) {
 734                 put_write_access(inode);
 735                 if (!special_file(inode->i_mode)) {
 736                         /*
 737                          * We don't consider this a real
 738                          * mnt_want/drop_write() pair
 739                          * because it all happenend right
 740                          * here, so just reset the state.
 741                          */
 742                         file_reset_write(f);
 743                         mnt_drop_write(mnt);
 744                 }
 745         }
 746         file_sb_list_del(f);
 747         f->f_path.dentry = NULL;
 748         f->f_path.mnt = NULL;
 749 cleanup_file:
 750         dput(dentry);
 751         mntput(mnt);
 752         return ERR_PTR(error);
 753 }
 754
 755 static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 756                                 struct file *f,
 757                                 int (*open)(struct inode *, struct file *),
 758                                 const struct cred *cred)
 759 {
 760         struct file *res = do_dentry_open(dentry, mnt, f, open, cred);
 761         if (!IS_ERR(res)) {
 762                 int error = open_check_o_direct(f);
 763                 if (error) {
 764                         fput(res);
 765                         res = ERR_PTR(error);
 766                 }
 767         } else {
 768                 put_filp(f);
 769         }
 770         return res;
 771 }
 772
 773 /**
 774  * lookup_instantiate_filp - instantiates the open intent filp
 775  * @nd: pointer to nameidata
 776  * @dentry: pointer to dentry
 777  * @open: open callback
 778  *
 779  * Helper for filesystems that want to use lookup open intents and pass back
 780  * a fully instantiated struct file to the caller.
 781  * This function is meant to be called from within a filesystem's
 782  * lookup method.
 783  * Beware of calling it for non-regular files! Those ->open methods might block
 784  * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
 785  * leading to a deadlock, as nobody can open that fifo anymore, because
 786  * another process to open fifo will block on locked parent when doing lookup).
 787  * Note that in case of error, nd->intent.open.file is destroyed, but the
 788  * path information remains valid.
 789  * If the open callback is set to NULL, then the standard f_op->open()
 790  * filesystem callback is substituted.
 791  */
 792 struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
 793                 int (*open)(struct inode *, struct file *))
 794 {
 795         const struct cred *cred = current_cred();
 796
 797         if (IS_ERR(nd->intent.open.file))
 798                 goto out;
 799         if (IS_ERR(dentry))
 800                 goto out_err;
 801         nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
 802                                              nd->intent.open.file,
 803                                              open, cred);
 804 out:
 805         return nd->intent.open.file;
 806 out_err:
 807         release_open_intent(nd);
 808         nd->intent.open.file = ERR_CAST(dentry);
 809         goto out;
 810 }
 811 EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
 812
 813 /**
 814  * nameidata_to_filp - convert a nameidata to an open filp.
 815  * @nd: pointer to nameidata
 816  * @flags: open flags
 817  *
 818  * Note that this function destroys the original nameidata
 819  */
 820 struct file *nameidata_to_filp(struct nameidata *nd)
 821 {
 822         const struct cred *cred = current_cred();
 823         struct file *filp;
 824
 825         /* Pick up the filp from the open intent */
 826         filp = nd->intent.open.file;
 827         nd->intent.open.file = NULL;
 828
 829         /* Has the filesystem initialised the file for us? */
 830         if (filp->f_path.dentry == NULL) {
 831                 path_get(&nd->path);
 832                 filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
 833                                      NULL, cred);
 834         }
 835         return filp;
 836 }
 837
 838 /*
 839  * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
 840  * error.
 841  */
 842 struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
 843                          const struct cred *cred)
 844 {
 845         int error;
 846         struct file *f;
 847
 848         validate_creds(cred);
 849
 850         /* We must always pass in a valid mount pointer. */
 851         BUG_ON(!mnt);
 852
 853         error = -ENFILE;
 854         f = get_empty_filp();
 855         if (f == NULL) {
 856                 dput(dentry);
 857                 mntput(mnt);
 858                 return ERR_PTR(error);
 859         }
 860
 861         f->f_flags = flags;
 862         return __dentry_open(dentry, mnt, f, NULL, cred);
 863 }
 864 EXPORT_SYMBOL(dentry_open);
 865
 866 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 867 {
 868         struct fdtable *fdt = files_fdtable(files);
 869         __clear_open_fd(fd, fdt);
 870         if (fd < files->next_fd)
 871                 files->next_fd = fd;
 872 }
 873
 874 void put_unused_fd(unsigned int fd)
 875 {
 876         struct files_struct *files = current->files;
 877         spin_lock(&files->file_lock);
 878         __put_unused_fd(files, fd);
 879         spin_unlock(&files->file_lock);
 880 }
 881
 882 EXPORT_SYMBOL(put_unused_fd);
 883
 884 /*
 885  * Install a file pointer in the fd array.
 886  *
 887  * The VFS is full of places where we drop the files lock between
 888  * setting the open_fds bitmap and installing the file in the file
 889  * array.  At any such point, we are vulnerable to a dup2() race
 890  * installing a file in the array before us.  We need to detect this and
 891  * fput() the struct file we are about to overwrite in this case.
 892  *
 893  * It should never happen - if we allow dup2() do it, _really_ bad things
 894  * will follow.
 895  */
 896
 897 void fd_install(unsigned int fd, struct file *file)
 898 {
 899         struct files_struct *files = current->files;
 900         struct fdtable *fdt;
 901         spin_lock(&files->file_lock);
 902         fdt = files_fdtable(files);
 903         BUG_ON(fdt->fd[fd] != NULL);
 904         rcu_assign_pointer(fdt->fd[fd], file);
 905         spin_unlock(&files->file_lock);
 906 }
 907
 908 EXPORT_SYMBOL(fd_install);
 909
 910 static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
 911 {
 912         int lookup_flags = 0;
 913         int acc_mode;
 914
 915         if (!(flags & O_CREAT))
 916                 mode = 0;
 917         op->mode = mode;
 918
 919         /* Must never be set by userspace */
 920         flags &= ~FMODE_NONOTIFY;
 921
 922         /*
 923          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
 924          * check for O_DSYNC if the need any syncing at all we enforce it's
 925          * always set instead of having to deal with possibly weird behaviour
 926          * for malicious applications setting only __O_SYNC.
 927          */
 928         if (flags & __O_SYNC)
 929                 flags |= O_DSYNC;
 930
 931         /*
 932          * If we have O_PATH in the open flag. Then we
 933          * cannot have anything other than the below set of flags
 934          */
 935         if (flags & O_PATH) {
 936                 flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
 937                 acc_mode = 0;
 938         } else {
 939                 acc_mode = MAY_OPEN | ACC_MODE(flags);
 940         }
 941
 942         op->open_flag = flags;
 943
 944         /* O_TRUNC implies we need access checks for write permissions */
 945         if (flags & O_TRUNC)
 946                 acc_mode |= MAY_WRITE;
 947
 948         /* Allow the LSM permission hook to distinguish append
 949            access from general write access. */
 950         if (flags & O_APPEND)
 951                 acc_mode |= MAY_APPEND;
 952
 953         op->acc_mode = acc_mode;
 954
 955         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
 956
 957         if (flags & O_CREAT) {
 958                 op->intent |= LOOKUP_CREATE;
 959                 if (flags & O_EXCL)
 960                         op->intent |= LOOKUP_EXCL;
 961         }
 962
 963         if (flags & O_DIRECTORY)
 964                 lookup_flags |= LOOKUP_DIRECTORY;
 965         if (!(flags & O_NOFOLLOW))
 966                 lookup_flags |= LOOKUP_FOLLOW;
 967         return lookup_flags;
 968 }
 969
 970 /**
 971  * filp_open - open file and return file pointer
 972  *
 973  * @filename:   path to open
 974  * @flags:      open flags as per the open(2) second argument
 975  * @mode:       mode for the new file if O_CREAT is set, else ignored
 976  *
 977  * This is the helper to open a file from kernelspace if you really
 978  * have to.  But in generally you should not do this, so please move
 979  * along, nothing to see here..
 980  */
 981 struct file *filp_open(const char *filename, int flags, umode_t mode)
 982 {
 983         struct open_flags op;
 984         int lookup = build_open_flags(flags, mode, &op);
 985         return do_filp_open(AT_FDCWD, filename, &op, lookup);
 986 }
 987 EXPORT_SYMBOL(filp_open);
 988
 989 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
 990                             const char *filename, int flags)
 991 {
 992         struct open_flags op;
 993         int lookup = build_open_flags(flags, 0, &op);
 994         if (flags & O_CREAT)
 995                 return ERR_PTR(-EINVAL);
 996         if (!filename && (flags & O_DIRECTORY))
 997                 if (!dentry->d_inode->i_op->lookup)
 998                         return ERR_PTR(-ENOTDIR);
 999         return do_file_open_root(dentry, mnt, filename, &op, lookup);
1000 }
1001 EXPORT_SYMBOL(file_open_root);
1002
1003 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1004 {
1005         struct open_flags op;
1006         int lookup = build_open_flags(flags, mode, &op);
1007         char *tmp = getname(filename);
1008         int fd = PTR_ERR(tmp);
1009
1010         if (!IS_ERR(tmp)) {
1011                 fd = get_unused_fd_flags(flags);
1012                 if (fd >= 0) {
1013                         struct file *f = do_filp_open(dfd, tmp, &op, lookup);
1014                         if (IS_ERR(f)) {
1015                                 put_unused_fd(fd);
1016                                 fd = PTR_ERR(f);
1017                         } else {
1018                                 fsnotify_open(f);
1019                                 fd_install(fd, f);
1020                         }
1021                 }
1022                 putname(tmp);
1023         }
1024         return fd;
1025 }
1026
1027 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1028 {
1029         long ret;
1030
1031         if (force_o_largefile())
1032                 flags |= O_LARGEFILE;
1033
1034         ret = do_sys_open(AT_FDCWD, filename, flags, mode);
1035         /* avoid REGPARM breakage on x86: */
1036         asmlinkage_protect(3, ret, filename, flags, mode);
1037         return ret;
1038 }
1039
1040 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1041                 umode_t, mode)
1042 {
1043         long ret;
1044
1045         if (force_o_largefile())
1046                 flags |= O_LARGEFILE;
1047
1048         ret = do_sys_open(dfd, filename, flags, mode);
1049         /* avoid REGPARM breakage on x86: */
1050         asmlinkage_protect(4, ret, dfd, filename, flags, mode);
1051         return ret;
1052 }
1053
1054 #ifndef __alpha__
1055
1056 /*
1057  * For backward compatibility?  Maybe this should be moved
1058  * into arch/i386 instead?
1059  */
1060 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1061 {
1062         return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1063 }
1064
1065 #endif
1066
1067 /*
1068  * "id" is the POSIX thread ID. We use the
1069  * files pointer for this..
1070  */
1071 int filp_close(struct file *filp, fl_owner_t id)
1072 {
1073         int retval = 0;
1074
1075         if (!file_count(filp)) {
1076                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1077                 return 0;
1078         }
1079
1080         if (filp->f_op && filp->f_op->flush)
1081                 retval = filp->f_op->flush(filp, id);
1082
1083         if (likely(!(filp->f_mode & FMODE_PATH))) {
1084                 dnotify_flush(filp, id);
1085                 locks_remove_posix(filp, id);
1086         }
1087         fput(filp);
1088         return retval;
1089 }
1090
1091 EXPORT_SYMBOL(filp_close);
1092
1093 /*
1094  * Careful here! We test whether the file pointer is NULL before
1095  * releasing the fd. This ensures that one clone task can't release
1096  * an fd while another clone is opening it.
1097  */
1098 SYSCALL_DEFINE1(close, unsigned int, fd)
1099 {
1100         struct file * filp;
1101         struct files_struct *files = current->files;
1102         struct fdtable *fdt;
1103         int retval;
1104
1105         spin_lock(&files->file_lock);
1106         fdt = files_fdtable(files);
1107         if (fd >= fdt->max_fds)
1108                 goto out_unlock;
1109         filp = fdt->fd[fd];
1110         if (!filp)
1111                 goto out_unlock;
1112         rcu_assign_pointer(fdt->fd[fd], NULL);
1113         __clear_close_on_exec(fd, fdt);
1114         __put_unused_fd(files, fd);
1115         spin_unlock(&files->file_lock);
1116         retval = filp_close(filp, files);
1117
1118         /* can't restart close syscall because file table entry was cleared */
1119         if (unlikely(retval == -ERESTARTSYS ||
1120                      retval == -ERESTARTNOINTR ||
1121                      retval == -ERESTARTNOHAND ||
1122                      retval == -ERESTART_RESTARTBLOCK))
1123                 retval = -EINTR;
1124
1125         return retval;
1126
1127 out_unlock:
1128         spin_unlock(&files->file_lock);
1129         return -EBADF;
1130 }
1131 EXPORT_SYMBOL(sys_close);
1132
1133 /*
1134  * This routine simulates a hangup on the tty, to arrange that users
1135  * are given clean terminals at login time.
1136  */
1137 SYSCALL_DEFINE0(vhangup)
1138 {
1139         if (capable(CAP_SYS_TTY_CONFIG)) {
1140                 tty_vhangup_self();
1141                 return 0;
1142         }
1143         return -EPERM;
1144 }
1145
1146 /*
1147  * Called when an inode is about to be open.
1148  * We use this to disallow opening large files on 32bit systems if
1149  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1150  * on this flag in sys_open.
1151  */
1152 int generic_file_open(struct inode * inode, struct file * filp)
1153 {
1154         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1155                 return -EOVERFLOW;
1156         return 0;
1157 }
1158
1159 EXPORT_SYMBOL(generic_file_open);
1160
1161 /*
1162  * This is used by subsystems that don't want seekable
1163  * file descriptors. The function is not supposed to ever fail, the only
1164  * reason it returns an 'int' and not 'void' is so that it can be plugged
1165  * directly into file_operations structure.
1166  */
1167 int nonseekable_open(struct inode *inode, struct file *filp)
1168 {
1169         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1170         return 0;
1171 }
1172
1173 EXPORT_SYMBOL(nonseekable_open);