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