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                 if (override_cred->uid)
 320                         cap_clear(override_cred->cap_effective);
 321                 else
 322                         override_cred->cap_effective =
 323                                 override_cred->cap_permitted;
 324         }
 325
 326         old_cred = override_creds(override_cred);
 327
 328         res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
 329         if (res)
 330                 goto out;
 331
 332         inode = path.dentry->d_inode;
 333
 334         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 335                 /*
 336                  * MAY_EXEC on regular files is denied if the fs is mounted
 337                  * with the "noexec" flag.
 338                  */
 339                 res = -EACCES;
 340                 if (path.mnt->mnt_flags & MNT_NOEXEC)
 341                         goto out_path_release;
 342         }
 343
 344         res = inode_permission(inode, mode | MAY_ACCESS);
 345         /* SuS v2 requires we report a read only fs too */
 346         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 347                 goto out_path_release;
 348         /*
 349          * This is a rare case where using __mnt_is_readonly()
 350          * is OK without a mnt_want/drop_write() pair.  Since
 351          * no actual write to the fs is performed here, we do
 352          * not need to telegraph to that to anyone.
 353          *
 354          * By doing this, we accept that this access is
 355          * inherently racy and know that the fs may change
 356          * state before we even see this result.
 357          */
 358         if (__mnt_is_readonly(path.mnt))
 359                 res = -EROFS;
 360
 361 out_path_release:
 362         path_put(&path);
 363 out:
 364         revert_creds(old_cred);
 365         put_cred(override_cred);
 366         return res;
 367 }
 368
 369 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 370 {
 371         return sys_faccessat(AT_FDCWD, filename, mode);
 372 }
 373
 374 SYSCALL_DEFINE1(chdir, const char __user *, filename)
 375 {
 376         struct path path;
 377         int error;
 378
 379         error = user_path_dir(filename, &path);
 380         if (error)
 381                 goto out;
 382
 383         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 384         if (error)
 385                 goto dput_and_out;
 386
 387         set_fs_pwd(current->fs, &path);
 388
 389 dput_and_out:
 390         path_put(&path);
 391 out:
 392         return error;
 393 }
 394
 395 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 396 {
 397         struct file *file;
 398         struct inode *inode;
 399         int error;
 400
 401         error = -EBADF;
 402         file = fget(fd);
 403         if (!file)
 404                 goto out;
 405
 406         inode = file->f_path.dentry->d_inode;
 407
 408         error = -ENOTDIR;
 409         if (!S_ISDIR(inode->i_mode))
 410                 goto out_putf;
 411
 412         error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
 413         if (!error)
 414                 set_fs_pwd(current->fs, &file->f_path);
 415 out_putf:
 416         fput(file);
 417 out:
 418         return error;
 419 }
 420
 421 SYSCALL_DEFINE1(chroot, const char __user *, filename)
 422 {
 423         struct path path;
 424         int error;
 425
 426         error = user_path_dir(filename, &path);
 427         if (error)
 428                 goto out;
 429
 430         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 431         if (error)
 432                 goto dput_and_out;
 433
 434         error = -EPERM;
 435         if (!capable(CAP_SYS_CHROOT))
 436                 goto dput_and_out;
 437         error = security_path_chroot(&path);
 438         if (error)
 439                 goto dput_and_out;
 440
 441         set_fs_root(current->fs, &path);
 442         error = 0;
 443 dput_and_out:
 444         path_put(&path);
 445 out:
 446         return error;
 447 }
 448
 449 SYSCALL_DEFINE2(fchmod, unsigned int, fd, mode_t, mode)
 450 {
 451         struct inode * inode;
 452         struct dentry * dentry;
 453         struct file * file;
 454         int err = -EBADF;
 455         struct iattr newattrs;
 456
 457         file = fget(fd);
 458         if (!file)
 459                 goto out;
 460
 461         dentry = file->f_path.dentry;
 462         inode = dentry->d_inode;
 463
 464         audit_inode(NULL, dentry);
 465
 466         err = mnt_want_write_file(file);
 467         if (err)
 468                 goto out_putf;
 469         mutex_lock(&inode->i_mutex);
 470         err = security_path_chmod(dentry, file->f_vfsmnt, mode);
 471         if (err)
 472                 goto out_unlock;
 473         if (mode == (mode_t) -1)
 474                 mode = inode->i_mode;
 475         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 476         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 477         err = notify_change(dentry, &newattrs);
 478 out_unlock:
 479         mutex_unlock(&inode->i_mutex);
 480         mnt_drop_write(file->f_path.mnt);
 481 out_putf:
 482         fput(file);
 483 out:
 484         return err;
 485 }
 486
 487 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, mode_t, mode)
 488 {
 489         struct path path;
 490         struct inode *inode;
 491         int error;
 492         struct iattr newattrs;
 493
 494         error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
 495         if (error)
 496                 goto out;
 497         inode = path.dentry->d_inode;
 498
 499         error = mnt_want_write(path.mnt);
 500         if (error)
 501                 goto dput_and_out;
 502         mutex_lock(&inode->i_mutex);
 503         error = security_path_chmod(path.dentry, path.mnt, mode);
 504         if (error)
 505                 goto out_unlock;
 506         if (mode == (mode_t) -1)
 507                 mode = inode->i_mode;
 508         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 509         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 510         error = notify_change(path.dentry, &newattrs);
 511 out_unlock:
 512         mutex_unlock(&inode->i_mutex);
 513         mnt_drop_write(path.mnt);
 514 dput_and_out:
 515         path_put(&path);
 516 out:
 517         return error;
 518 }
 519
 520 SYSCALL_DEFINE2(chmod, const char __user *, filename, mode_t, mode)
 521 {
 522         return sys_fchmodat(AT_FDCWD, filename, mode);
 523 }
 524
 525 static int chown_common(struct path *path, uid_t user, gid_t group)
 526 {
 527         struct inode *inode = path->dentry->d_inode;
 528         int error;
 529         struct iattr newattrs;
 530
 531         newattrs.ia_valid =  ATTR_CTIME;
 532         if (user != (uid_t) -1) {
 533                 newattrs.ia_valid |= ATTR_UID;
 534                 newattrs.ia_uid = user;
 535         }
 536         if (group != (gid_t) -1) {
 537                 newattrs.ia_valid |= ATTR_GID;
 538                 newattrs.ia_gid = group;
 539         }
 540         if (!S_ISDIR(inode->i_mode))
 541                 newattrs.ia_valid |=
 542                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 543         mutex_lock(&inode->i_mutex);
 544         error = security_path_chown(path, user, group);
 545         if (!error)
 546                 error = notify_change(path->dentry, &newattrs);
 547         mutex_unlock(&inode->i_mutex);
 548
 549         return error;
 550 }
 551
 552 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 553 {
 554         struct path path;
 555         int error;
 556
 557         error = user_path(filename, &path);
 558         if (error)
 559                 goto out;
 560         error = mnt_want_write(path.mnt);
 561         if (error)
 562                 goto out_release;
 563         error = chown_common(&path, user, group);
 564         mnt_drop_write(path.mnt);
 565 out_release:
 566         path_put(&path);
 567 out:
 568         return error;
 569 }
 570
 571 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 572                 gid_t, group, int, flag)
 573 {
 574         struct path path;
 575         int error = -EINVAL;
 576         int lookup_flags;
 577
 578         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 579                 goto out;
 580
 581         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 582         if (flag & AT_EMPTY_PATH)
 583                 lookup_flags |= LOOKUP_EMPTY;
 584         error = user_path_at(dfd, filename, lookup_flags, &path);
 585         if (error)
 586                 goto out;
 587         error = mnt_want_write(path.mnt);
 588         if (error)
 589                 goto out_release;
 590         error = chown_common(&path, user, group);
 591         mnt_drop_write(path.mnt);
 592 out_release:
 593         path_put(&path);
 594 out:
 595         return error;
 596 }
 597
 598 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 599 {
 600         struct path path;
 601         int error;
 602
 603         error = user_lpath(filename, &path);
 604         if (error)
 605                 goto out;
 606         error = mnt_want_write(path.mnt);
 607         if (error)
 608                 goto out_release;
 609         error = chown_common(&path, user, group);
 610         mnt_drop_write(path.mnt);
 611 out_release:
 612         path_put(&path);
 613 out:
 614         return error;
 615 }
 616
 617 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 618 {
 619         struct file * file;
 620         int error = -EBADF;
 621         struct dentry * dentry;
 622
 623         file = fget(fd);
 624         if (!file)
 625                 goto out;
 626
 627         error = mnt_want_write_file(file);
 628         if (error)
 629                 goto out_fput;
 630         dentry = file->f_path.dentry;
 631         audit_inode(NULL, dentry);
 632         error = chown_common(&file->f_path, user, group);
 633         mnt_drop_write(file->f_path.mnt);
 634 out_fput:
 635         fput(file);
 636 out:
 637         return error;
 638 }
 639
 640 /*
 641  * You have to be very careful that these write
 642  * counts get cleaned up in error cases and
 643  * upon __fput().  This should probably never
 644  * be called outside of __dentry_open().
 645  */
 646 static inline int __get_file_write_access(struct inode *inode,
 647                                           struct vfsmount *mnt)
 648 {
 649         int error;
 650         error = get_write_access(inode);
 651         if (error)
 652                 return error;
 653         /*
 654          * Do not take mount writer counts on
 655          * special files since no writes to
 656          * the mount itself will occur.
 657          */
 658         if (!special_file(inode->i_mode)) {
 659                 /*
 660                  * Balanced in __fput()
 661                  */
 662                 error = mnt_want_write(mnt);
 663                 if (error)
 664                         put_write_access(inode);
 665         }
 666         return error;
 667 }
 668
 669 static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 670                                         struct file *f,
 671                                         int (*open)(struct inode *, struct file *),
 672                                         const struct cred *cred)
 673 {
 674         static const struct file_operations empty_fops = {};
 675         struct inode *inode;
 676         int error;
 677
 678         f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 679                                 FMODE_PREAD | FMODE_PWRITE;
 680
 681         if (unlikely(f->f_flags & O_PATH))
 682                 f->f_mode = FMODE_PATH;
 683
 684         inode = dentry->d_inode;
 685         if (f->f_mode & FMODE_WRITE) {
 686                 error = __get_file_write_access(inode, mnt);
 687                 if (error)
 688                         goto cleanup_file;
 689                 if (!special_file(inode->i_mode))
 690                         file_take_write(f);
 691         }
 692
 693         f->f_mapping = inode->i_mapping;
 694         f->f_path.dentry = dentry;
 695         f->f_path.mnt = mnt;
 696         f->f_pos = 0;
 697         file_sb_list_add(f, inode->i_sb);
 698
 699         if (unlikely(f->f_mode & FMODE_PATH)) {
 700                 f->f_op = &empty_fops;
 701                 return f;
 702         }
 703
 704         f->f_op = fops_get(inode->i_fop);
 705
 706         error = security_dentry_open(f, cred);
 707         if (error)
 708                 goto cleanup_all;
 709
 710         if (!open && f->f_op)
 711                 open = f->f_op->open;
 712         if (open) {
 713                 error = open(inode, f);
 714                 if (error)
 715                         goto cleanup_all;
 716         }
 717         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 718                 i_readcount_inc(inode);
 719
 720         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 721
 722         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 723
 724         /* NB: we're sure to have correct a_ops only after f_op->open */
 725         if (f->f_flags & O_DIRECT) {
 726                 if (!f->f_mapping->a_ops ||
 727                     ((!f->f_mapping->a_ops->direct_IO) &&
 728                     (!f->f_mapping->a_ops->get_xip_mem))) {
 729                         fput(f);
 730                         f = ERR_PTR(-EINVAL);
 731                 }
 732         }
 733
 734         return f;
 735
 736 cleanup_all:
 737         fops_put(f->f_op);
 738         if (f->f_mode & FMODE_WRITE) {
 739                 put_write_access(inode);
 740                 if (!special_file(inode->i_mode)) {
 741                         /*
 742                          * We don't consider this a real
 743                          * mnt_want/drop_write() pair
 744                          * because it all happenend right
 745                          * here, so just reset the state.
 746                          */
 747                         file_reset_write(f);
 748                         mnt_drop_write(mnt);
 749                 }
 750         }
 751         file_sb_list_del(f);
 752         f->f_path.dentry = NULL;
 753         f->f_path.mnt = NULL;
 754 cleanup_file:
 755         put_filp(f);
 756         dput(dentry);
 757         mntput(mnt);
 758         return ERR_PTR(error);
 759 }
 760
 761 /**
 762  * lookup_instantiate_filp - instantiates the open intent filp
 763  * @nd: pointer to nameidata
 764  * @dentry: pointer to dentry
 765  * @open: open callback
 766  *
 767  * Helper for filesystems that want to use lookup open intents and pass back
 768  * a fully instantiated struct file to the caller.
 769  * This function is meant to be called from within a filesystem's
 770  * lookup method.
 771  * Beware of calling it for non-regular files! Those ->open methods might block
 772  * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
 773  * leading to a deadlock, as nobody can open that fifo anymore, because
 774  * another process to open fifo will block on locked parent when doing lookup).
 775  * Note that in case of error, nd->intent.open.file is destroyed, but the
 776  * path information remains valid.
 777  * If the open callback is set to NULL, then the standard f_op->open()
 778  * filesystem callback is substituted.
 779  */
 780 struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
 781                 int (*open)(struct inode *, struct file *))
 782 {
 783         const struct cred *cred = current_cred();
 784
 785         if (IS_ERR(nd->intent.open.file))
 786                 goto out;
 787         if (IS_ERR(dentry))
 788                 goto out_err;
 789         nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
 790                                              nd->intent.open.file,
 791                                              open, cred);
 792 out:
 793         return nd->intent.open.file;
 794 out_err:
 795         release_open_intent(nd);
 796         nd->intent.open.file = (struct file *)dentry;
 797         goto out;
 798 }
 799 EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
 800
 801 /**
 802  * nameidata_to_filp - convert a nameidata to an open filp.
 803  * @nd: pointer to nameidata
 804  * @flags: open flags
 805  *
 806  * Note that this function destroys the original nameidata
 807  */
 808 struct file *nameidata_to_filp(struct nameidata *nd)
 809 {
 810         const struct cred *cred = current_cred();
 811         struct file *filp;
 812
 813         /* Pick up the filp from the open intent */
 814         filp = nd->intent.open.file;
 815         nd->intent.open.file = NULL;
 816
 817         /* Has the filesystem initialised the file for us? */
 818         if (filp->f_path.dentry == NULL) {
 819                 path_get(&nd->path);
 820                 filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
 821                                      NULL, cred);
 822         }
 823         return filp;
 824 }
 825
 826 /*
 827  * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
 828  * error.
 829  */
 830 struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
 831                          const struct cred *cred)
 832 {
 833         int error;
 834         struct file *f;
 835
 836         validate_creds(cred);
 837
 838         /*
 839          * We must always pass in a valid mount pointer.   Historically
 840          * callers got away with not passing it, but we must enforce this at
 841          * the earliest possible point now to avoid strange problems deep in the
 842          * filesystem stack.
 843          */
 844         if (!mnt) {
 845                 printk(KERN_WARNING "%s called with NULL vfsmount\n", __func__);
 846                 dump_stack();
 847                 return ERR_PTR(-EINVAL);
 848         }
 849
 850         error = -ENFILE;
 851         f = get_empty_filp();
 852         if (f == NULL) {
 853                 dput(dentry);
 854                 mntput(mnt);
 855                 return ERR_PTR(error);
 856         }
 857
 858         f->f_flags = flags;
 859         return __dentry_open(dentry, mnt, f, NULL, cred);
 860 }
 861 EXPORT_SYMBOL(dentry_open);
 862
 863 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 864 {
 865         struct fdtable *fdt = files_fdtable(files);
 866         __FD_CLR(fd, fdt->open_fds);
 867         if (fd < files->next_fd)
 868                 files->next_fd = fd;
 869 }
 870
 871 void put_unused_fd(unsigned int fd)
 872 {
 873         struct files_struct *files = current->files;
 874         spin_lock(&files->file_lock);
 875         __put_unused_fd(files, fd);
 876         spin_unlock(&files->file_lock);
 877 }
 878
 879 EXPORT_SYMBOL(put_unused_fd);
 880
 881 /*
 882  * Install a file pointer in the fd array.
 883  *
 884  * The VFS is full of places where we drop the files lock between
 885  * setting the open_fds bitmap and installing the file in the file
 886  * array.  At any such point, we are vulnerable to a dup2() race
 887  * installing a file in the array before us.  We need to detect this and
 888  * fput() the struct file we are about to overwrite in this case.
 889  *
 890  * It should never happen - if we allow dup2() do it, _really_ bad things
 891  * will follow.
 892  */
 893
 894 void fd_install(unsigned int fd, struct file *file)
 895 {
 896         struct files_struct *files = current->files;
 897         struct fdtable *fdt;
 898         spin_lock(&files->file_lock);
 899         fdt = files_fdtable(files);
 900         BUG_ON(fdt->fd[fd] != NULL);
 901         rcu_assign_pointer(fdt->fd[fd], file);
 902         spin_unlock(&files->file_lock);
 903 }
 904
 905 EXPORT_SYMBOL(fd_install);
 906
 907 static inline int build_open_flags(int flags, int mode, struct open_flags *op)
 908 {
 909         int lookup_flags = 0;
 910         int acc_mode;
 911
 912         if (!(flags & O_CREAT))
 913                 mode = 0;
 914         op->mode = mode;
 915
 916         /* Must never be set by userspace */
 917         flags &= ~FMODE_NONOTIFY;
 918
 919         /*
 920          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
 921          * check for O_DSYNC if the need any syncing at all we enforce it's
 922          * always set instead of having to deal with possibly weird behaviour
 923          * for malicious applications setting only __O_SYNC.
 924          */
 925         if (flags & __O_SYNC)
 926                 flags |= O_DSYNC;
 927
 928         /*
 929          * If we have O_PATH in the open flag. Then we
 930          * cannot have anything other than the below set of flags
 931          */
 932         if (flags & O_PATH) {
 933                 flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
 934                 acc_mode = 0;
 935         } else {
 936                 acc_mode = MAY_OPEN | ACC_MODE(flags);
 937         }
 938
 939         op->open_flag = flags;
 940
 941         /* O_TRUNC implies we need access checks for write permissions */
 942         if (flags & O_TRUNC)
 943                 acc_mode |= MAY_WRITE;
 944
 945         /* Allow the LSM permission hook to distinguish append
 946            access from general write access. */
 947         if (flags & O_APPEND)
 948                 acc_mode |= MAY_APPEND;
 949
 950         op->acc_mode = acc_mode;
 951
 952         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
 953
 954         if (flags & O_CREAT) {
 955                 op->intent |= LOOKUP_CREATE;
 956                 if (flags & O_EXCL)
 957                         op->intent |= LOOKUP_EXCL;
 958         }
 959
 960         if (flags & O_DIRECTORY)
 961                 lookup_flags |= LOOKUP_DIRECTORY;
 962         if (!(flags & O_NOFOLLOW))
 963                 lookup_flags |= LOOKUP_FOLLOW;
 964         return lookup_flags;
 965 }
 966
 967 /**
 968  * filp_open - open file and return file pointer
 969  *
 970  * @filename:   path to open
 971  * @flags:      open flags as per the open(2) second argument
 972  * @mode:       mode for the new file if O_CREAT is set, else ignored
 973  *
 974  * This is the helper to open a file from kernelspace if you really
 975  * have to.  But in generally you should not do this, so please move
 976  * along, nothing to see here..
 977  */
 978 struct file *filp_open(const char *filename, int flags, int mode)
 979 {
 980         struct open_flags op;
 981         int lookup = build_open_flags(flags, mode, &op);
 982         return do_filp_open(AT_FDCWD, filename, &op, lookup);
 983 }
 984 EXPORT_SYMBOL(filp_open);
 985
 986 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
 987                             const char *filename, int flags)
 988 {
 989         struct open_flags op;
 990         int lookup = build_open_flags(flags, 0, &op);
 991         if (flags & O_CREAT)
 992                 return ERR_PTR(-EINVAL);
 993         if (!filename && (flags & O_DIRECTORY))
 994                 if (!dentry->d_inode->i_op->lookup)
 995                         return ERR_PTR(-ENOTDIR);
 996         return do_file_open_root(dentry, mnt, filename, &op, lookup);
 997 }
 998 EXPORT_SYMBOL(file_open_root);
 999
1000 long do_sys_open(int dfd, const char __user *filename, int flags, int mode)
1001 {
1002         struct open_flags op;
1003         int lookup = build_open_flags(flags, mode, &op);
1004         char *tmp = getname(filename);
1005         int fd = PTR_ERR(tmp);
1006
1007         if (!IS_ERR(tmp)) {
1008                 fd = get_unused_fd_flags(flags);
1009                 if (fd >= 0) {
1010                         struct file *f = do_filp_open(dfd, tmp, &op, lookup);
1011                         if (IS_ERR(f)) {
1012                                 put_unused_fd(fd);
1013                                 fd = PTR_ERR(f);
1014                         } else {
1015                                 fsnotify_open(f);
1016                                 fd_install(fd, f);
1017                         }
1018                 }
1019                 putname(tmp);
1020         }
1021         return fd;
1022 }
1023
1024 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, int, mode)
1025 {
1026         long ret;
1027
1028         if (force_o_largefile())
1029                 flags |= O_LARGEFILE;
1030
1031         ret = do_sys_open(AT_FDCWD, filename, flags, mode);
1032         /* avoid REGPARM breakage on x86: */
1033         asmlinkage_protect(3, ret, filename, flags, mode);
1034         return ret;
1035 }
1036
1037 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1038                 int, mode)
1039 {
1040         long ret;
1041
1042         if (force_o_largefile())
1043                 flags |= O_LARGEFILE;
1044
1045         ret = do_sys_open(dfd, filename, flags, mode);
1046         /* avoid REGPARM breakage on x86: */
1047         asmlinkage_protect(4, ret, dfd, filename, flags, mode);
1048         return ret;
1049 }
1050
1051 #ifndef __alpha__
1052
1053 /*
1054  * For backward compatibility?  Maybe this should be moved
1055  * into arch/i386 instead?
1056  */
1057 SYSCALL_DEFINE2(creat, const char __user *, pathname, int, mode)
1058 {
1059         return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1060 }
1061
1062 #endif
1063
1064 /*
1065  * "id" is the POSIX thread ID. We use the
1066  * files pointer for this..
1067  */
1068 int filp_close(struct file *filp, fl_owner_t id)
1069 {
1070         int retval = 0;
1071
1072         if (!file_count(filp)) {
1073                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1074                 return 0;
1075         }
1076
1077         if (filp->f_op && filp->f_op->flush)
1078                 retval = filp->f_op->flush(filp, id);
1079
1080         if (likely(!(filp->f_mode & FMODE_PATH))) {
1081                 dnotify_flush(filp, id);
1082                 locks_remove_posix(filp, id);
1083         }
1084         fput(filp);
1085         return retval;
1086 }
1087
1088 EXPORT_SYMBOL(filp_close);
1089
1090 /*
1091  * Careful here! We test whether the file pointer is NULL before
1092  * releasing the fd. This ensures that one clone task can't release
1093  * an fd while another clone is opening it.
1094  */
1095 SYSCALL_DEFINE1(close, unsigned int, fd)
1096 {
1097         struct file * filp;
1098         struct files_struct *files = current->files;
1099         struct fdtable *fdt;
1100         int retval;
1101
1102         spin_lock(&files->file_lock);
1103         fdt = files_fdtable(files);
1104         if (fd >= fdt->max_fds)
1105                 goto out_unlock;
1106         filp = fdt->fd[fd];
1107         if (!filp)
1108                 goto out_unlock;
1109         rcu_assign_pointer(fdt->fd[fd], NULL);
1110         FD_CLR(fd, fdt->close_on_exec);
1111         __put_unused_fd(files, fd);
1112         spin_unlock(&files->file_lock);
1113         retval = filp_close(filp, files);
1114
1115         /* can't restart close syscall because file table entry was cleared */
1116         if (unlikely(retval == -ERESTARTSYS ||
1117                      retval == -ERESTARTNOINTR ||
1118                      retval == -ERESTARTNOHAND ||
1119                      retval == -ERESTART_RESTARTBLOCK))
1120                 retval = -EINTR;
1121
1122         return retval;
1123
1124 out_unlock:
1125         spin_unlock(&files->file_lock);
1126         return -EBADF;
1127 }
1128 EXPORT_SYMBOL(sys_close);
1129
1130 /*
1131  * This routine simulates a hangup on the tty, to arrange that users
1132  * are given clean terminals at login time.
1133  */
1134 SYSCALL_DEFINE0(vhangup)
1135 {
1136         if (capable(CAP_SYS_TTY_CONFIG)) {
1137                 tty_vhangup_self();
1138                 return 0;
1139         }
1140         return -EPERM;
1141 }
1142
1143 /*
1144  * Called when an inode is about to be open.
1145  * We use this to disallow opening large files on 32bit systems if
1146  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1147  * on this flag in sys_open.
1148  */
1149 int generic_file_open(struct inode * inode, struct file * filp)
1150 {
1151         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1152                 return -EOVERFLOW;
1153         return 0;
1154 }
1155
1156 EXPORT_SYMBOL(generic_file_open);
1157
1158 /*
1159  * This is used by subsystems that don't want seekable
1160  * file descriptors. The function is not supposed to ever fail, the only
1161  * reason it returns an 'int' and not 'void' is so that it can be plugged
1162  * directly into file_operations structure.
1163  */
1164 int nonseekable_open(struct inode *inode, struct file *filp)
1165 {
1166         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1167         return 0;
1168 }
1169
1170 EXPORT_SYMBOL(nonseekable_open);