fs/open.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  linux/fs/open.c
   4  *
   5  *  Copyright (C) 1991, 1992  Linus Torvalds
   6  */
   7
   8 #include <linux/string.h>
   9 #include <linux/mm.h>
  10 #include <linux/file.h>
  11 #include <linux/fdtable.h>
  12 #include <linux/fsnotify.h>
  13 #include <linux/module.h>
  14 #include <linux/tty.h>
  15 #include <linux/namei.h>
  16 #include <linux/backing-dev.h>
  17 #include <linux/capability.h>
  18 #include <linux/securebits.h>
  19 #include <linux/security.h>
  20 #include <linux/mount.h>
  21 #include <linux/fcntl.h>
  22 #include <linux/slab.h>
  23 #include <linux/uaccess.h>
  24 #include <linux/fs.h>
  25 #include <linux/personality.h>
  26 #include <linux/pagemap.h>
  27 #include <linux/syscalls.h>
  28 #include <linux/rcupdate.h>
  29 #include <linux/audit.h>
  30 #include <linux/falloc.h>
  31 #include <linux/fs_struct.h>
  32 #include <linux/ima.h>
  33 #include <linux/dnotify.h>
  34 #include <linux/compat.h>
  35
  36 #include "internal.h"
  37
  38 int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
  39         struct file *filp)
  40 {
  41         int ret;
  42         struct iattr newattrs;
  43
  44         /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
  45         if (length < 0)
  46                 return -EINVAL;
  47
  48         newattrs.ia_size = length;
  49         newattrs.ia_valid = ATTR_SIZE | time_attrs;
  50         if (filp) {
  51                 newattrs.ia_file = filp;
  52                 newattrs.ia_valid |= ATTR_FILE;
  53         }
  54
  55         /* Remove suid, sgid, and file capabilities on truncate too */
  56         ret = dentry_needs_remove_privs(dentry);
  57         if (ret < 0)
  58                 return ret;
  59         if (ret)
  60                 newattrs.ia_valid |= ret | ATTR_FORCE;
  61
  62         inode_lock(dentry->d_inode);
  63         /* Note any delegations or leases have already been broken: */
  64         ret = notify_change(dentry, &newattrs, NULL);
  65         inode_unlock(dentry->d_inode);
  66         return ret;
  67 }
  68
  69 long vfs_truncate(const struct path *path, loff_t length)
  70 {
  71         struct inode *inode;
  72         long error;
  73
  74         inode = path->dentry->d_inode;
  75
  76         /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
  77         if (S_ISDIR(inode->i_mode))
  78                 return -EISDIR;
  79         if (!S_ISREG(inode->i_mode))
  80                 return -EINVAL;
  81
  82         error = mnt_want_write(path->mnt);
  83         if (error)
  84                 goto out;
  85
  86         error = inode_permission(inode, MAY_WRITE);
  87         if (error)
  88                 goto mnt_drop_write_and_out;
  89
  90         error = -EPERM;
  91         if (IS_APPEND(inode))
  92                 goto mnt_drop_write_and_out;
  93
  94         error = get_write_access(inode);
  95         if (error)
  96                 goto mnt_drop_write_and_out;
  97
  98         /*
  99          * Make sure that there are no leases.  get_write_access() protects
 100          * against the truncate racing with a lease-granting setlease().
 101          */
 102         error = break_lease(inode, O_WRONLY);
 103         if (error)
 104                 goto put_write_and_out;
 105
 106         error = locks_verify_truncate(inode, NULL, length);
 107         if (!error)
 108                 error = security_path_truncate(path);
 109         if (!error)
 110                 error = do_truncate(path->dentry, length, 0, NULL);
 111
 112 put_write_and_out:
 113         put_write_access(inode);
 114 mnt_drop_write_and_out:
 115         mnt_drop_write(path->mnt);
 116 out:
 117         return error;
 118 }
 119 EXPORT_SYMBOL_GPL(vfs_truncate);
 120
 121 long do_sys_truncate(const char __user *pathname, loff_t length)
 122 {
 123         unsigned int lookup_flags = LOOKUP_FOLLOW;
 124         struct path path;
 125         int error;
 126
 127         if (length < 0) /* sorry, but loff_t says... */
 128                 return -EINVAL;
 129
 130 retry:
 131         error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 132         if (!error) {
 133                 error = vfs_truncate(&path, length);
 134                 path_put(&path);
 135         }
 136         if (retry_estale(error, lookup_flags)) {
 137                 lookup_flags |= LOOKUP_REVAL;
 138                 goto retry;
 139         }
 140         return error;
 141 }
 142
 143 SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 144 {
 145         return do_sys_truncate(path, length);
 146 }
 147
 148 #ifdef CONFIG_COMPAT
 149 COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
 150 {
 151         return do_sys_truncate(path, length);
 152 }
 153 #endif
 154
 155 long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 156 {
 157         struct inode *inode;
 158         struct dentry *dentry;
 159         struct fd f;
 160         int error;
 161
 162         error = -EINVAL;
 163         if (length < 0)
 164                 goto out;
 165         error = -EBADF;
 166         f = fdget(fd);
 167         if (!f.file)
 168                 goto out;
 169
 170         /* explicitly opened as large or we are on 64-bit box */
 171         if (f.file->f_flags & O_LARGEFILE)
 172                 small = 0;
 173
 174         dentry = f.file->f_path.dentry;
 175         inode = dentry->d_inode;
 176         error = -EINVAL;
 177         if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
 178                 goto out_putf;
 179
 180         error = -EINVAL;
 181         /* Cannot ftruncate over 2^31 bytes without large file support */
 182         if (small && length > MAX_NON_LFS)
 183                 goto out_putf;
 184
 185         error = -EPERM;
 186         /* Check IS_APPEND on real upper inode */
 187         if (IS_APPEND(file_inode(f.file)))
 188                 goto out_putf;
 189
 190         sb_start_write(inode->i_sb);
 191         error = locks_verify_truncate(inode, f.file, length);
 192         if (!error)
 193                 error = security_path_truncate(&f.file->f_path);
 194         if (!error)
 195                 error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
 196         sb_end_write(inode->i_sb);
 197 out_putf:
 198         fdput(f);
 199 out:
 200         return error;
 201 }
 202
 203 SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 204 {
 205         return do_sys_ftruncate(fd, length, 1);
 206 }
 207
 208 #ifdef CONFIG_COMPAT
 209 COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
 210 {
 211         return do_sys_ftruncate(fd, length, 1);
 212 }
 213 #endif
 214
 215 /* LFS versions of truncate are only needed on 32 bit machines */
 216 #if BITS_PER_LONG == 32
 217 SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
 218 {
 219         return do_sys_truncate(path, length);
 220 }
 221
 222 SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
 223 {
 224         return do_sys_ftruncate(fd, length, 0);
 225 }
 226 #endif /* BITS_PER_LONG == 32 */
 227
 228
 229 int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 230 {
 231         struct inode *inode = file_inode(file);
 232         long ret;
 233
 234         if (offset < 0 || len <= 0)
 235                 return -EINVAL;
 236
 237         /* Return error if mode is not supported */
 238         if (mode & ~FALLOC_FL_SUPPORTED_MASK)
 239                 return -EOPNOTSUPP;
 240
 241         /* Punch hole and zero range are mutually exclusive */
 242         if ((mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE)) ==
 243             (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_ZERO_RANGE))
 244                 return -EOPNOTSUPP;
 245
 246         /* Punch hole must have keep size set */
 247         if ((mode & FALLOC_FL_PUNCH_HOLE) &&
 248             !(mode & FALLOC_FL_KEEP_SIZE))
 249                 return -EOPNOTSUPP;
 250
 251         /* Collapse range should only be used exclusively. */
 252         if ((mode & FALLOC_FL_COLLAPSE_RANGE) &&
 253             (mode & ~FALLOC_FL_COLLAPSE_RANGE))
 254                 return -EINVAL;
 255
 256         /* Insert range should only be used exclusively. */
 257         if ((mode & FALLOC_FL_INSERT_RANGE) &&
 258             (mode & ~FALLOC_FL_INSERT_RANGE))
 259                 return -EINVAL;
 260
 261         /* Unshare range should only be used with allocate mode. */
 262         if ((mode & FALLOC_FL_UNSHARE_RANGE) &&
 263             (mode & ~(FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_KEEP_SIZE)))
 264                 return -EINVAL;
 265
 266         if (!(file->f_mode & FMODE_WRITE))
 267                 return -EBADF;
 268
 269         /*
 270          * We can only allow pure fallocate on append only files
 271          */
 272         if ((mode & ~FALLOC_FL_KEEP_SIZE) && IS_APPEND(inode))
 273                 return -EPERM;
 274
 275         if (IS_IMMUTABLE(inode))
 276                 return -EPERM;
 277
 278         /*
 279          * We cannot allow any fallocate operation on an active swapfile
 280          */
 281         if (IS_SWAPFILE(inode))
 282                 return -ETXTBSY;
 283
 284         /*
 285          * Revalidate the write permissions, in case security policy has
 286          * changed since the files were opened.
 287          */
 288         ret = security_file_permission(file, MAY_WRITE);
 289         if (ret)
 290                 return ret;
 291
 292         if (S_ISFIFO(inode->i_mode))
 293                 return -ESPIPE;
 294
 295         if (S_ISDIR(inode->i_mode))
 296                 return -EISDIR;
 297
 298         if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
 299                 return -ENODEV;
 300
 301         /* Check for wrap through zero too */
 302         if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 303                 return -EFBIG;
 304
 305         if (!file->f_op->fallocate)
 306                 return -EOPNOTSUPP;
 307
 308         file_start_write(file);
 309         ret = file->f_op->fallocate(file, mode, offset, len);
 310
 311         /*
 312          * Create inotify and fanotify events.
 313          *
 314          * To keep the logic simple always create events if fallocate succeeds.
 315          * This implies that events are even created if the file size remains
 316          * unchanged, e.g. when using flag FALLOC_FL_KEEP_SIZE.
 317          */
 318         if (ret == 0)
 319                 fsnotify_modify(file);
 320
 321         file_end_write(file);
 322         return ret;
 323 }
 324 EXPORT_SYMBOL_GPL(vfs_fallocate);
 325
 326 int ksys_fallocate(int fd, int mode, loff_t offset, loff_t len)
 327 {
 328         struct fd f = fdget(fd);
 329         int error = -EBADF;
 330
 331         if (f.file) {
 332                 error = vfs_fallocate(f.file, mode, offset, len);
 333                 fdput(f);
 334         }
 335         return error;
 336 }
 337
 338 SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
 339 {
 340         return ksys_fallocate(fd, mode, offset, len);
 341 }
 342
 343 /*
 344  * access() needs to use the real uid/gid, not the effective uid/gid.
 345  * We do this by temporarily clearing all FS-related capabilities and
 346  * switching the fsuid/fsgid around to the real ones.
 347  */
 348 long do_faccessat(int dfd, const char __user *filename, int mode)
 349 {
 350         const struct cred *old_cred;
 351         struct cred *override_cred;
 352         struct path path;
 353         struct inode *inode;
 354         int res;
 355         unsigned int lookup_flags = LOOKUP_FOLLOW;
 356
 357         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 358                 return -EINVAL;
 359
 360         override_cred = prepare_creds();
 361         if (!override_cred)
 362                 return -ENOMEM;
 363
 364         override_cred->fsuid = override_cred->uid;
 365         override_cred->fsgid = override_cred->gid;
 366
 367         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 368                 /* Clear the capabilities if we switch to a non-root user */
 369                 kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 370                 if (!uid_eq(override_cred->uid, root_uid))
 371                         cap_clear(override_cred->cap_effective);
 372                 else
 373                         override_cred->cap_effective =
 374                                 override_cred->cap_permitted;
 375         }
 376
 377         /*
 378          * The new set of credentials can *only* be used in
 379          * task-synchronous circumstances, and does not need
 380          * RCU freeing, unless somebody then takes a separate
 381          * reference to it.
 382          *
 383          * NOTE! This is _only_ true because this credential
 384          * is used purely for override_creds() that installs
 385          * it as the subjective cred. Other threads will be
 386          * accessing ->real_cred, not the subjective cred.
 387          *
 388          * If somebody _does_ make a copy of this (using the
 389          * 'get_current_cred()' function), that will clear the
 390          * non_rcu field, because now that other user may be
 391          * expecting RCU freeing. But normal thread-synchronous
 392          * cred accesses will keep things non-RCY.
 393          */
 394         override_cred->non_rcu = 1;
 395
 396         old_cred = override_creds(override_cred);
 397 retry:
 398         res = user_path_at(dfd, filename, lookup_flags, &path);
 399         if (res)
 400                 goto out;
 401
 402         inode = d_backing_inode(path.dentry);
 403
 404         if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 405                 /*
 406                  * MAY_EXEC on regular files is denied if the fs is mounted
 407                  * with the "noexec" flag.
 408                  */
 409                 res = -EACCES;
 410                 if (path_noexec(&path))
 411                         goto out_path_release;
 412         }
 413
 414         res = inode_permission(inode, mode | MAY_ACCESS);
 415         /* SuS v2 requires we report a read only fs too */
 416         if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 417                 goto out_path_release;
 418         /*
 419          * This is a rare case where using __mnt_is_readonly()
 420          * is OK without a mnt_want/drop_write() pair.  Since
 421          * no actual write to the fs is performed here, we do
 422          * not need to telegraph to that to anyone.
 423          *
 424          * By doing this, we accept that this access is
 425          * inherently racy and know that the fs may change
 426          * state before we even see this result.
 427          */
 428         if (__mnt_is_readonly(path.mnt))
 429                 res = -EROFS;
 430
 431 out_path_release:
 432         path_put(&path);
 433         if (retry_estale(res, lookup_flags)) {
 434                 lookup_flags |= LOOKUP_REVAL;
 435                 goto retry;
 436         }
 437 out:
 438         revert_creds(old_cred);
 439         put_cred(override_cred);
 440         return res;
 441 }
 442
 443 SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 444 {
 445         return do_faccessat(dfd, filename, mode);
 446 }
 447
 448 SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 449 {
 450         return do_faccessat(AT_FDCWD, filename, mode);
 451 }
 452
 453 int ksys_chdir(const char __user *filename)
 454 {
 455         struct path path;
 456         int error;
 457         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 458 retry:
 459         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 460         if (error)
 461                 goto out;
 462
 463         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 464         if (error)
 465                 goto dput_and_out;
 466
 467         set_fs_pwd(current->fs, &path);
 468
 469 dput_and_out:
 470         path_put(&path);
 471         if (retry_estale(error, lookup_flags)) {
 472                 lookup_flags |= LOOKUP_REVAL;
 473                 goto retry;
 474         }
 475 out:
 476         return error;
 477 }
 478
 479 SYSCALL_DEFINE1(chdir, const char __user *, filename)
 480 {
 481         return ksys_chdir(filename);
 482 }
 483
 484 SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 485 {
 486         struct fd f = fdget_raw(fd);
 487         int error;
 488
 489         error = -EBADF;
 490         if (!f.file)
 491                 goto out;
 492
 493         error = -ENOTDIR;
 494         if (!d_can_lookup(f.file->f_path.dentry))
 495                 goto out_putf;
 496
 497         error = inode_permission(file_inode(f.file), MAY_EXEC | MAY_CHDIR);
 498         if (!error)
 499                 set_fs_pwd(current->fs, &f.file->f_path);
 500 out_putf:
 501         fdput(f);
 502 out:
 503         return error;
 504 }
 505
 506 int ksys_chroot(const char __user *filename)
 507 {
 508         struct path path;
 509         int error;
 510         unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 511 retry:
 512         error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 513         if (error)
 514                 goto out;
 515
 516         error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 517         if (error)
 518                 goto dput_and_out;
 519
 520         error = -EPERM;
 521         if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
 522                 goto dput_and_out;
 523         error = security_path_chroot(&path);
 524         if (error)
 525                 goto dput_and_out;
 526
 527         set_fs_root(current->fs, &path);
 528         error = 0;
 529 dput_and_out:
 530         path_put(&path);
 531         if (retry_estale(error, lookup_flags)) {
 532                 lookup_flags |= LOOKUP_REVAL;
 533                 goto retry;
 534         }
 535 out:
 536         return error;
 537 }
 538
 539 SYSCALL_DEFINE1(chroot, const char __user *, filename)
 540 {
 541         return ksys_chroot(filename);
 542 }
 543
 544 static int chmod_common(const struct path *path, umode_t mode)
 545 {
 546         struct inode *inode = path->dentry->d_inode;
 547         struct inode *delegated_inode = NULL;
 548         struct iattr newattrs;
 549         int error;
 550
 551         error = mnt_want_write(path->mnt);
 552         if (error)
 553                 return error;
 554 retry_deleg:
 555         inode_lock(inode);
 556         error = security_path_chmod(path, mode);
 557         if (error)
 558                 goto out_unlock;
 559         newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 560         newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 561         error = notify_change(path->dentry, &newattrs, &delegated_inode);
 562 out_unlock:
 563         inode_unlock(inode);
 564         if (delegated_inode) {
 565                 error = break_deleg_wait(&delegated_inode);
 566                 if (!error)
 567                         goto retry_deleg;
 568         }
 569         mnt_drop_write(path->mnt);
 570         return error;
 571 }
 572
 573 int ksys_fchmod(unsigned int fd, umode_t mode)
 574 {
 575         struct fd f = fdget(fd);
 576         int err = -EBADF;
 577
 578         if (f.file) {
 579                 audit_file(f.file);
 580                 err = chmod_common(&f.file->f_path, mode);
 581                 fdput(f);
 582         }
 583         return err;
 584 }
 585
 586 SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 587 {
 588         return ksys_fchmod(fd, mode);
 589 }
 590
 591 int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
 592 {
 593         struct path path;
 594         int error;
 595         unsigned int lookup_flags = LOOKUP_FOLLOW;
 596 retry:
 597         error = user_path_at(dfd, filename, lookup_flags, &path);
 598         if (!error) {
 599                 error = chmod_common(&path, mode);
 600                 path_put(&path);
 601                 if (retry_estale(error, lookup_flags)) {
 602                         lookup_flags |= LOOKUP_REVAL;
 603                         goto retry;
 604                 }
 605         }
 606         return error;
 607 }
 608
 609 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
 610                 umode_t, mode)
 611 {
 612         return do_fchmodat(dfd, filename, mode);
 613 }
 614
 615 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 616 {
 617         return do_fchmodat(AT_FDCWD, filename, mode);
 618 }
 619
 620 static int chown_common(const struct path *path, uid_t user, gid_t group)
 621 {
 622         struct inode *inode = path->dentry->d_inode;
 623         struct inode *delegated_inode = NULL;
 624         int error;
 625         struct iattr newattrs;
 626         kuid_t uid;
 627         kgid_t gid;
 628
 629         uid = make_kuid(current_user_ns(), user);
 630         gid = make_kgid(current_user_ns(), group);
 631
 632 retry_deleg:
 633         newattrs.ia_valid =  ATTR_CTIME;
 634         if (user != (uid_t) -1) {
 635                 if (!uid_valid(uid))
 636                         return -EINVAL;
 637                 newattrs.ia_valid |= ATTR_UID;
 638                 newattrs.ia_uid = uid;
 639         }
 640         if (group != (gid_t) -1) {
 641                 if (!gid_valid(gid))
 642                         return -EINVAL;
 643                 newattrs.ia_valid |= ATTR_GID;
 644                 newattrs.ia_gid = gid;
 645         }
 646         if (!S_ISDIR(inode->i_mode))
 647                 newattrs.ia_valid |=
 648                         ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 649         inode_lock(inode);
 650         error = security_path_chown(path, uid, gid);
 651         if (!error)
 652                 error = notify_change(path->dentry, &newattrs, &delegated_inode);
 653         inode_unlock(inode);
 654         if (delegated_inode) {
 655                 error = break_deleg_wait(&delegated_inode);
 656                 if (!error)
 657                         goto retry_deleg;
 658         }
 659         return error;
 660 }
 661
 662 int do_fchownat(int dfd, const char __user *filename, uid_t user, gid_t group,
 663                 int flag)
 664 {
 665         struct path path;
 666         int error = -EINVAL;
 667         int lookup_flags;
 668
 669         if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 670                 goto out;
 671
 672         lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 673         if (flag & AT_EMPTY_PATH)
 674                 lookup_flags |= LOOKUP_EMPTY;
 675 retry:
 676         error = user_path_at(dfd, filename, lookup_flags, &path);
 677         if (error)
 678                 goto out;
 679         error = mnt_want_write(path.mnt);
 680         if (error)
 681                 goto out_release;
 682         error = chown_common(&path, user, group);
 683         mnt_drop_write(path.mnt);
 684 out_release:
 685         path_put(&path);
 686         if (retry_estale(error, lookup_flags)) {
 687                 lookup_flags |= LOOKUP_REVAL;
 688                 goto retry;
 689         }
 690 out:
 691         return error;
 692 }
 693
 694 SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 695                 gid_t, group, int, flag)
 696 {
 697         return do_fchownat(dfd, filename, user, group, flag);
 698 }
 699
 700 SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 701 {
 702         return do_fchownat(AT_FDCWD, filename, user, group, 0);
 703 }
 704
 705 SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 706 {
 707         return do_fchownat(AT_FDCWD, filename, user, group,
 708                            AT_SYMLINK_NOFOLLOW);
 709 }
 710
 711 int ksys_fchown(unsigned int fd, uid_t user, gid_t group)
 712 {
 713         struct fd f = fdget(fd);
 714         int error = -EBADF;
 715
 716         if (!f.file)
 717                 goto out;
 718
 719         error = mnt_want_write_file(f.file);
 720         if (error)
 721                 goto out_fput;
 722         audit_file(f.file);
 723         error = chown_common(&f.file->f_path, user, group);
 724         mnt_drop_write_file(f.file);
 725 out_fput:
 726         fdput(f);
 727 out:
 728         return error;
 729 }
 730
 731 SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 732 {
 733         return ksys_fchown(fd, user, group);
 734 }
 735
 736 static int do_dentry_open(struct file *f,
 737                           struct inode *inode,
 738                           int (*open)(struct inode *, struct file *))
 739 {
 740         static const struct file_operations empty_fops = {};
 741         int error;
 742
 743         path_get(&f->f_path);
 744         f->f_inode = inode;
 745         f->f_mapping = inode->i_mapping;
 746
 747         /* Ensure that we skip any errors that predate opening of the file */
 748         f->f_wb_err = filemap_sample_wb_err(f->f_mapping);
 749
 750         if (unlikely(f->f_flags & O_PATH)) {
 751                 f->f_mode = FMODE_PATH | FMODE_OPENED;
 752                 f->f_op = &empty_fops;
 753                 return 0;
 754         }
 755
 756         /* Any file opened for execve()/uselib() has to be a regular file. */
 757         if (unlikely(f->f_flags & FMODE_EXEC && !S_ISREG(inode->i_mode))) {
 758                 error = -EACCES;
 759                 goto cleanup_file;
 760         }
 761
 762         if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
 763                 error = get_write_access(inode);
 764                 if (unlikely(error))
 765                         goto cleanup_file;
 766                 error = __mnt_want_write(f->f_path.mnt);
 767                 if (unlikely(error)) {
 768                         put_write_access(inode);
 769                         goto cleanup_file;
 770                 }
 771                 f->f_mode |= FMODE_WRITER;
 772         }
 773
 774         /* POSIX.1-2008/SUSv4 Section XSI 2.9.7 */
 775         if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))
 776                 f->f_mode |= FMODE_ATOMIC_POS;
 777
 778         f->f_op = fops_get(inode->i_fop);
 779         if (WARN_ON(!f->f_op)) {
 780                 error = -ENODEV;
 781                 goto cleanup_all;
 782         }
 783
 784         error = security_file_open(f);
 785         if (error)
 786                 goto cleanup_all;
 787
 788         error = break_lease(locks_inode(f), f->f_flags);
 789         if (error)
 790                 goto cleanup_all;
 791
 792         /* normally all 3 are set; ->open() can clear them if needed */
 793         f->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
 794         if (!open)
 795                 open = f->f_op->open;
 796         if (open) {
 797                 error = open(inode, f);
 798                 if (error)
 799                         goto cleanup_all;
 800         }
 801         f->f_mode |= FMODE_OPENED;
 802         if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 803                 i_readcount_inc(inode);
 804         if ((f->f_mode & FMODE_READ) &&
 805              likely(f->f_op->read || f->f_op->read_iter))
 806                 f->f_mode |= FMODE_CAN_READ;
 807         if ((f->f_mode & FMODE_WRITE) &&
 808              likely(f->f_op->write || f->f_op->write_iter))
 809                 f->f_mode |= FMODE_CAN_WRITE;
 810
 811         f->f_write_hint = WRITE_LIFE_NOT_SET;
 812         f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 813
 814         file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 815
 816         /* NB: we're sure to have correct a_ops only after f_op->open */
 817         if (f->f_flags & O_DIRECT) {
 818                 if (!f->f_mapping->a_ops || !f->f_mapping->a_ops->direct_IO)
 819                         return -EINVAL;
 820         }
 821
 822         /*
 823          * XXX: Huge page cache doesn't support writing yet. Drop all page
 824          * cache for this file before processing writes.
 825          */
 826         if ((f->f_mode & FMODE_WRITE) && filemap_nr_thps(inode->i_mapping))
 827                 truncate_pagecache(inode, 0);
 828
 829         return 0;
 830
 831 cleanup_all:
 832         if (WARN_ON_ONCE(error > 0))
 833                 error = -EINVAL;
 834         fops_put(f->f_op);
 835         if (f->f_mode & FMODE_WRITER) {
 836                 put_write_access(inode);
 837                 __mnt_drop_write(f->f_path.mnt);
 838         }
 839 cleanup_file:
 840         path_put(&f->f_path);
 841         f->f_path.mnt = NULL;
 842         f->f_path.dentry = NULL;
 843         f->f_inode = NULL;
 844         return error;
 845 }
 846
 847 /**
 848  * finish_open - finish opening a file
 849  * @file: file pointer
 850  * @dentry: pointer to dentry
 851  * @open: open callback
 852  * @opened: state of open
 853  *
 854  * This can be used to finish opening a file passed to i_op->atomic_open().
 855  *
 856  * If the open callback is set to NULL, then the standard f_op->open()
 857  * filesystem callback is substituted.
 858  *
 859  * NB: the dentry reference is _not_ consumed.  If, for example, the dentry is
 860  * the return value of d_splice_alias(), then the caller needs to perform dput()
 861  * on it after finish_open().
 862  *
 863  * On successful return @file is a fully instantiated open file.  After this, if
 864  * an error occurs in ->atomic_open(), it needs to clean up with fput().
 865  *
 866  * Returns zero on success or -errno if the open failed.
 867  */
 868 int finish_open(struct file *file, struct dentry *dentry,
 869                 int (*open)(struct inode *, struct file *))
 870 {
 871         BUG_ON(file->f_mode & FMODE_OPENED); /* once it's opened, it's opened */
 872
 873         file->f_path.dentry = dentry;
 874         return do_dentry_open(file, d_backing_inode(dentry), open);
 875 }
 876 EXPORT_SYMBOL(finish_open);
 877
 878 /**
 879  * finish_no_open - finish ->atomic_open() without opening the file
 880  *
 881  * @file: file pointer
 882  * @dentry: dentry or NULL (as returned from ->lookup())
 883  *
 884  * This can be used to set the result of a successful lookup in ->atomic_open().
 885  *
 886  * NB: unlike finish_open() this function does consume the dentry reference and
 887  * the caller need not dput() it.
 888  *
 889  * Returns "0" which must be the return value of ->atomic_open() after having
 890  * called this function.
 891  */
 892 int finish_no_open(struct file *file, struct dentry *dentry)
 893 {
 894         file->f_path.dentry = dentry;
 895         return 0;
 896 }
 897 EXPORT_SYMBOL(finish_no_open);
 898
 899 char *file_path(struct file *filp, char *buf, int buflen)
 900 {
 901         return d_path(&filp->f_path, buf, buflen);
 902 }
 903 EXPORT_SYMBOL(file_path);
 904
 905 /**
 906  * vfs_open - open the file at the given path
 907  * @path: path to open
 908  * @file: newly allocated file with f_flag initialized
 909  * @cred: credentials to use
 910  */
 911 int vfs_open(const struct path *path, struct file *file)
 912 {
 913         file->f_path = *path;
 914         return do_dentry_open(file, d_backing_inode(path->dentry), NULL);
 915 }
 916
 917 struct file *dentry_open(const struct path *path, int flags,
 918                          const struct cred *cred)
 919 {
 920         int error;
 921         struct file *f;
 922
 923         validate_creds(cred);
 924
 925         /* We must always pass in a valid mount pointer. */
 926         BUG_ON(!path->mnt);
 927
 928         f = alloc_empty_file(flags, cred);
 929         if (!IS_ERR(f)) {
 930                 error = vfs_open(path, f);
 931                 if (error) {
 932                         fput(f);
 933                         f = ERR_PTR(error);
 934                 }
 935         }
 936         return f;
 937 }
 938 EXPORT_SYMBOL(dentry_open);
 939
 940 struct file *open_with_fake_path(const struct path *path, int flags,
 941                                 struct inode *inode, const struct cred *cred)
 942 {
 943         struct file *f = alloc_empty_file_noaccount(flags, cred);
 944         if (!IS_ERR(f)) {
 945                 int error;
 946
 947                 f->f_path = *path;
 948                 error = do_dentry_open(f, inode, NULL);
 949                 if (error) {
 950                         fput(f);
 951                         f = ERR_PTR(error);
 952                 }
 953         }
 954         return f;
 955 }
 956 EXPORT_SYMBOL(open_with_fake_path);
 957
 958 #define WILL_CREATE(flags)      (flags & (O_CREAT | __O_TMPFILE))
 959 #define O_PATH_FLAGS            (O_DIRECTORY | O_NOFOLLOW | O_PATH | O_CLOEXEC)
 960
 961 inline struct open_how build_open_how(int flags, umode_t mode)
 962 {
 963         struct open_how how = {
 964                 .flags = flags & VALID_OPEN_FLAGS,
 965                 .mode = mode & S_IALLUGO,
 966         };
 967
 968         /* O_PATH beats everything else. */
 969         if (how.flags & O_PATH)
 970                 how.flags &= O_PATH_FLAGS;
 971         /* Modes should only be set for create-like flags. */
 972         if (!WILL_CREATE(how.flags))
 973                 how.mode = 0;
 974         return how;
 975 }
 976
 977 inline int build_open_flags(const struct open_how *how, struct open_flags *op)
 978 {
 979         int flags = how->flags;
 980         int lookup_flags = 0;
 981         int acc_mode = ACC_MODE(flags);
 982
 983         /* Must never be set by userspace */
 984         flags &= ~(FMODE_NONOTIFY | O_CLOEXEC);
 985
 986         /*
 987          * Older syscalls implicitly clear all of the invalid flags or argument
 988          * values before calling build_open_flags(), but openat2(2) checks all
 989          * of its arguments.
 990          */
 991         if (flags & ~VALID_OPEN_FLAGS)
 992                 return -EINVAL;
 993         if (how->resolve & ~VALID_RESOLVE_FLAGS)
 994                 return -EINVAL;
 995
 996         /* Deal with the mode. */
 997         if (WILL_CREATE(flags)) {
 998                 if (how->mode & ~S_IALLUGO)
 999                         return -EINVAL;
1000                 op->mode = how->mode | S_IFREG;
1001         } else {
1002                 if (how->mode != 0)
1003                         return -EINVAL;
1004                 op->mode = 0;
1005         }
1006
1007         /*
1008          * In order to ensure programs get explicit errors when trying to use
1009          * O_TMPFILE on old kernels, O_TMPFILE is implemented such that it
1010          * looks like (O_DIRECTORY|O_RDWR & ~O_CREAT) to old kernels. But we
1011          * have to require userspace to explicitly set it.
1012          */
1013         if (flags & __O_TMPFILE) {
1014                 if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
1015                         return -EINVAL;
1016                 if (!(acc_mode & MAY_WRITE))
1017                         return -EINVAL;
1018         }
1019         if (flags & O_PATH) {
1020                 /* O_PATH only permits certain other flags to be set. */
1021                 if (flags & ~O_PATH_FLAGS)
1022                         return -EINVAL;
1023                 acc_mode = 0;
1024         }
1025
1026         /*
1027          * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
1028          * check for O_DSYNC if the need any syncing at all we enforce it's
1029          * always set instead of having to deal with possibly weird behaviour
1030          * for malicious applications setting only __O_SYNC.
1031          */
1032         if (flags & __O_SYNC)
1033                 flags |= O_DSYNC;
1034
1035         op->open_flag = flags;
1036
1037         /* O_TRUNC implies we need access checks for write permissions */
1038         if (flags & O_TRUNC)
1039                 acc_mode |= MAY_WRITE;
1040
1041         /* Allow the LSM permission hook to distinguish append
1042            access from general write access. */
1043         if (flags & O_APPEND)
1044                 acc_mode |= MAY_APPEND;
1045
1046         op->acc_mode = acc_mode;
1047
1048         op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
1049
1050         if (flags & O_CREAT) {
1051                 op->intent |= LOOKUP_CREATE;
1052                 if (flags & O_EXCL)
1053                         op->intent |= LOOKUP_EXCL;
1054         }
1055
1056         if (flags & O_DIRECTORY)
1057                 lookup_flags |= LOOKUP_DIRECTORY;
1058         if (!(flags & O_NOFOLLOW))
1059                 lookup_flags |= LOOKUP_FOLLOW;
1060
1061         if (how->resolve & RESOLVE_NO_XDEV)
1062                 lookup_flags |= LOOKUP_NO_XDEV;
1063         if (how->resolve & RESOLVE_NO_MAGICLINKS)
1064                 lookup_flags |= LOOKUP_NO_MAGICLINKS;
1065         if (how->resolve & RESOLVE_NO_SYMLINKS)
1066                 lookup_flags |= LOOKUP_NO_SYMLINKS;
1067         if (how->resolve & RESOLVE_BENEATH)
1068                 lookup_flags |= LOOKUP_BENEATH;
1069         if (how->resolve & RESOLVE_IN_ROOT)
1070                 lookup_flags |= LOOKUP_IN_ROOT;
1071
1072         op->lookup_flags = lookup_flags;
1073         return 0;
1074 }
1075
1076 /**
1077  * file_open_name - open file and return file pointer
1078  *
1079  * @name:       struct filename containing path to open
1080  * @flags:      open flags as per the open(2) second argument
1081  * @mode:       mode for the new file if O_CREAT is set, else ignored
1082  *
1083  * This is the helper to open a file from kernelspace if you really
1084  * have to.  But in generally you should not do this, so please move
1085  * along, nothing to see here..
1086  */
1087 struct file *file_open_name(struct filename *name, int flags, umode_t mode)
1088 {
1089         struct open_flags op;
1090         struct open_how how = build_open_how(flags, mode);
1091         int err = build_open_flags(&how, &op);
1092         if (err)
1093                 return ERR_PTR(err);
1094         return do_filp_open(AT_FDCWD, name, &op);
1095 }
1096
1097 /**
1098  * filp_open - open file and return file pointer
1099  *
1100  * @filename:   path to open
1101  * @flags:      open flags as per the open(2) second argument
1102  * @mode:       mode for the new file if O_CREAT is set, else ignored
1103  *
1104  * This is the helper to open a file from kernelspace if you really
1105  * have to.  But in generally you should not do this, so please move
1106  * along, nothing to see here..
1107  */
1108 struct file *filp_open(const char *filename, int flags, umode_t mode)
1109 {
1110         struct filename *name = getname_kernel(filename);
1111         struct file *file = ERR_CAST(name);
1112
1113         if (!IS_ERR(name)) {
1114                 file = file_open_name(name, flags, mode);
1115                 putname(name);
1116         }
1117         return file;
1118 }
1119 EXPORT_SYMBOL(filp_open);
1120
1121 struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
1122                             const char *filename, int flags, umode_t mode)
1123 {
1124         struct open_flags op;
1125         struct open_how how = build_open_how(flags, mode);
1126         int err = build_open_flags(&how, &op);
1127         if (err)
1128                 return ERR_PTR(err);
1129         return do_file_open_root(dentry, mnt, filename, &op);
1130 }
1131 EXPORT_SYMBOL(file_open_root);
1132
1133 static long do_sys_openat2(int dfd, const char __user *filename,
1134                            struct open_how *how)
1135 {
1136         struct open_flags op;
1137         int fd = build_open_flags(how, &op);
1138         struct filename *tmp;
1139
1140         if (fd)
1141                 return fd;
1142
1143         tmp = getname(filename);
1144         if (IS_ERR(tmp))
1145                 return PTR_ERR(tmp);
1146
1147         fd = get_unused_fd_flags(how->flags);
1148         if (fd >= 0) {
1149                 struct file *f = do_filp_open(dfd, tmp, &op);
1150                 if (IS_ERR(f)) {
1151                         put_unused_fd(fd);
1152                         fd = PTR_ERR(f);
1153                 } else {
1154                         fsnotify_open(f);
1155                         fd_install(fd, f);
1156                 }
1157         }
1158         putname(tmp);
1159         return fd;
1160 }
1161
1162 long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1163 {
1164         struct open_how how = build_open_how(flags, mode);
1165         return do_sys_openat2(dfd, filename, &how);
1166 }
1167
1168
1169 SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1170 {
1171         return ksys_open(filename, flags, mode);
1172 }
1173
1174 SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1175                 umode_t, mode)
1176 {
1177         if (force_o_largefile())
1178                 flags |= O_LARGEFILE;
1179         return do_sys_open(dfd, filename, flags, mode);
1180 }
1181
1182 SYSCALL_DEFINE4(openat2, int, dfd, const char __user *, filename,
1183                 struct open_how __user *, how, size_t, usize)
1184 {
1185         int err;
1186         struct open_how tmp;
1187
1188         BUILD_BUG_ON(sizeof(struct open_how) < OPEN_HOW_SIZE_VER0);
1189         BUILD_BUG_ON(sizeof(struct open_how) != OPEN_HOW_SIZE_LATEST);
1190
1191         if (unlikely(usize < OPEN_HOW_SIZE_VER0))
1192                 return -EINVAL;
1193
1194         err = copy_struct_from_user(&tmp, sizeof(tmp), how, usize);
1195         if (err)
1196                 return err;
1197
1198         /* O_LARGEFILE is only allowed for non-O_PATH. */
1199         if (!(tmp.flags & O_PATH) && force_o_largefile())
1200                 tmp.flags |= O_LARGEFILE;
1201
1202         return do_sys_openat2(dfd, filename, &tmp);
1203 }
1204
1205 #ifdef CONFIG_COMPAT
1206 /*
1207  * Exactly like sys_open(), except that it doesn't set the
1208  * O_LARGEFILE flag.
1209  */
1210 COMPAT_SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1211 {
1212         return do_sys_open(AT_FDCWD, filename, flags, mode);
1213 }
1214
1215 /*
1216  * Exactly like sys_openat(), except that it doesn't set the
1217  * O_LARGEFILE flag.
1218  */
1219 COMPAT_SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags, umode_t, mode)
1220 {
1221         return do_sys_open(dfd, filename, flags, mode);
1222 }
1223 #endif
1224
1225 #ifndef __alpha__
1226
1227 /*
1228  * For backward compatibility?  Maybe this should be moved
1229  * into arch/i386 instead?
1230  */
1231 SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1232 {
1233         return ksys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1234 }
1235
1236 #endif
1237
1238 /*
1239  * "id" is the POSIX thread ID. We use the
1240  * files pointer for this..
1241  */
1242 int filp_close(struct file *filp, fl_owner_t id)
1243 {
1244         int retval = 0;
1245
1246         if (!file_count(filp)) {
1247                 printk(KERN_ERR "VFS: Close: file count is 0\n");
1248                 return 0;
1249         }
1250
1251         if (filp->f_op->flush)
1252                 retval = filp->f_op->flush(filp, id);
1253
1254         if (likely(!(filp->f_mode & FMODE_PATH))) {
1255                 dnotify_flush(filp, id);
1256                 locks_remove_posix(filp, id);
1257         }
1258         fput(filp);
1259         return retval;
1260 }
1261
1262 EXPORT_SYMBOL(filp_close);
1263
1264 /*
1265  * Careful here! We test whether the file pointer is NULL before
1266  * releasing the fd. This ensures that one clone task can't release
1267  * an fd while another clone is opening it.
1268  */
1269 SYSCALL_DEFINE1(close, unsigned int, fd)
1270 {
1271         int retval = __close_fd(current->files, fd);
1272
1273         /* can't restart close syscall because file table entry was cleared */
1274         if (unlikely(retval == -ERESTARTSYS ||
1275                      retval == -ERESTARTNOINTR ||
1276                      retval == -ERESTARTNOHAND ||
1277                      retval == -ERESTART_RESTARTBLOCK))
1278                 retval = -EINTR;
1279
1280         return retval;
1281 }
1282
1283 /*
1284  * This routine simulates a hangup on the tty, to arrange that users
1285  * are given clean terminals at login time.
1286  */
1287 SYSCALL_DEFINE0(vhangup)
1288 {
1289         if (capable(CAP_SYS_TTY_CONFIG)) {
1290                 tty_vhangup_self();
1291                 return 0;
1292         }
1293         return -EPERM;
1294 }
1295
1296 /*
1297  * Called when an inode is about to be open.
1298  * We use this to disallow opening large files on 32bit systems if
1299  * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1300  * on this flag in sys_open.
1301  */
1302 int generic_file_open(struct inode * inode, struct file * filp)
1303 {
1304         if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1305                 return -EOVERFLOW;
1306         return 0;
1307 }
1308
1309 EXPORT_SYMBOL(generic_file_open);
1310
1311 /*
1312  * This is used by subsystems that don't want seekable
1313  * file descriptors. The function is not supposed to ever fail, the only
1314  * reason it returns an 'int' and not 'void' is so that it can be plugged
1315  * directly into file_operations structure.
1316  */
1317 int nonseekable_open(struct inode *inode, struct file *filp)
1318 {
1319         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1320         return 0;
1321 }
1322
1323 EXPORT_SYMBOL(nonseekable_open);
1324
1325 /*
1326  * stream_open is used by subsystems that want stream-like file descriptors.
1327  * Such file descriptors are not seekable and don't have notion of position
1328  * (file.f_pos is always 0 and ppos passed to .read()/.write() is always NULL).
1329  * Contrary to file descriptors of other regular files, .read() and .write()
1330  * can run simultaneously.
1331  *
1332  * stream_open never fails and is marked to return int so that it could be
1333  * directly used as file_operations.open .
1334  */
1335 int stream_open(struct inode *inode, struct file *filp)
1336 {
1337         filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE | FMODE_ATOMIC_POS);
1338         filp->f_mode |= FMODE_STREAM;
1339         return 0;
1340 }
1341
1342 EXPORT_SYMBOL(stream_open);