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 <asm/uaccess.h>
  23#include <linux/fs.h>
  24#include <linux/personality.h>
  25#include <linux/pagemap.h>
  26#include <linux/syscalls.h>
  27#include <linux/rcupdate.h>
  28#include <linux/audit.h>
  29#include <linux/falloc.h>
  30#include <linux/fs_struct.h>
  31#include <linux/ima.h>
  32#include <linux/dnotify.h>
  33#include <linux/compat.h>
  34
  35#include "internal.h"
  36
  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 on truncate too */
  55        ret = should_remove_suid(dentry);
  56        if (ret)
  57                newattrs.ia_valid |= ret | ATTR_FORCE;
  58
  59        mutex_lock(&dentry->d_inode->i_mutex);
  60        ret = notify_change(dentry, &newattrs);
  61        mutex_unlock(&dentry->d_inode->i_mutex);
  62        return ret;
  63}
  64
  65long vfs_truncate(struct path *path, loff_t length)
  66{
  67        struct inode *inode;
  68        long error;
  69
  70        inode = path->dentry->d_inode;
  71
  72        /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
  73        if (S_ISDIR(inode->i_mode))
  74                return -EISDIR;
  75        if (!S_ISREG(inode->i_mode))
  76                return -EINVAL;
  77
  78        error = mnt_want_write(path->mnt);
  79        if (error)
  80                goto out;
  81
  82        error = inode_permission(inode, MAY_WRITE);
  83        if (error)
  84                goto mnt_drop_write_and_out;
  85
  86        error = -EPERM;
  87        if (IS_APPEND(inode))
  88                goto mnt_drop_write_and_out;
  89
  90        error = get_write_access(inode);
  91        if (error)
  92                goto mnt_drop_write_and_out;
  93
  94        /*
  95         * Make sure that there are no leases.  get_write_access() protects
  96         * against the truncate racing with a lease-granting setlease().
  97         */
  98        error = break_lease(inode, O_WRONLY);
  99        if (error)
 100                goto put_write_and_out;
 101
 102        error = locks_verify_truncate(inode, NULL, length);
 103        if (!error)
 104                error = security_path_truncate(path);
 105        if (!error)
 106                error = do_truncate(path->dentry, length, 0, NULL);
 107
 108put_write_and_out:
 109        put_write_access(inode);
 110mnt_drop_write_and_out:
 111        mnt_drop_write(path->mnt);
 112out:
 113        return error;
 114}
 115EXPORT_SYMBOL_GPL(vfs_truncate);
 116
 117static long do_sys_truncate(const char __user *pathname, loff_t length)
 118{
 119        unsigned int lookup_flags = LOOKUP_FOLLOW;
 120        struct path path;
 121        int error;
 122
 123        if (length < 0) /* sorry, but loff_t says... */
 124                return -EINVAL;
 125
 126retry:
 127        error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
 128        if (!error) {
 129                error = vfs_truncate(&path, length);
 130                path_put(&path);
 131        }
 132        if (retry_estale(error, lookup_flags)) {
 133                lookup_flags |= LOOKUP_REVAL;
 134                goto retry;
 135        }
 136        return error;
 137}
 138
 139SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 140{
 141        return do_sys_truncate(path, length);
 142}
 143
 144#ifdef CONFIG_COMPAT
 145COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
 146{
 147        return do_sys_truncate(path, length);
 148}
 149#endif
 150
 151static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 152{
 153        struct inode *inode;
 154        struct dentry *dentry;
 155        struct fd f;
 156        int error;
 157
 158        error = -EINVAL;
 159        if (length < 0)
 160                goto out;
 161        error = -EBADF;
 162        f = fdget(fd);
 163        if (!f.file)
 164                goto out;
 165
 166        /* explicitly opened as large or we are on 64-bit box */
 167        if (f.file->f_flags & O_LARGEFILE)
 168                small = 0;
 169
 170        dentry = f.file->f_path.dentry;
 171        inode = dentry->d_inode;
 172        error = -EINVAL;
 173        if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
 174                goto out_putf;
 175
 176        error = -EINVAL;
 177        /* Cannot ftruncate over 2^31 bytes without large file support */
 178        if (small && length > MAX_NON_LFS)
 179                goto out_putf;
 180
 181        error = -EPERM;
 182        if (IS_APPEND(inode))
 183                goto out_putf;
 184
 185        sb_start_write(inode->i_sb);
 186        error = locks_verify_truncate(inode, f.file, length);
 187        if (!error)
 188                error = security_path_truncate(&f.file->f_path);
 189        if (!error)
 190                error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
 191        sb_end_write(inode->i_sb);
 192out_putf:
 193        fdput(f);
 194out:
 195        return error;
 196}
 197
 198SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 199{
 200        long ret = do_sys_ftruncate(fd, length, 1);
 201        /* avoid REGPARM breakage on x86: */
 202        asmlinkage_protect(2, ret, fd, length);
 203        return ret;
 204}
 205
 206#ifdef CONFIG_COMPAT
 207COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
 208{
 209        return do_sys_ftruncate(fd, length, 1);
 210}
 211#endif
 212
 213/* LFS versions of truncate are only needed on 32 bit machines */
 214#if BITS_PER_LONG == 32
 215SYSCALL_DEFINE(truncate64)(const char __user * path, loff_t length)
 216{
 217        return do_sys_truncate(path, length);
 218}
 219#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 220asmlinkage long SyS_truncate64(long path, loff_t length)
 221{
 222        return SYSC_truncate64((const char __user *) path, length);
 223}
 224SYSCALL_ALIAS(sys_truncate64, SyS_truncate64);
 225#endif
 226
 227SYSCALL_DEFINE(ftruncate64)(unsigned int fd, loff_t length)
 228{
 229        long ret = do_sys_ftruncate(fd, length, 0);
 230        /* avoid REGPARM breakage on x86: */
 231        asmlinkage_protect(2, ret, fd, length);
 232        return ret;
 233}
 234#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 235asmlinkage long SyS_ftruncate64(long fd, loff_t length)
 236{
 237        return SYSC_ftruncate64((unsigned int) fd, length);
 238}
 239SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
 240#endif
 241#endif /* BITS_PER_LONG == 32 */
 242
 243
 244int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 245{
 246        struct inode *inode = file_inode(file);
 247        long ret;
 248
 249        if (offset < 0 || len <= 0)
 250                return -EINVAL;
 251
 252        /* Return error if mode is not supported */
 253        if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
 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        if (!(file->f_mode & FMODE_WRITE))
 262                return -EBADF;
 263
 264        /* It's not possible punch hole on append only file */
 265        if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
 266                return -EPERM;
 267
 268        if (IS_IMMUTABLE(inode))
 269                return -EPERM;
 270
 271        /*
 272         * Revalidate the write permissions, in case security policy has
 273         * changed since the files were opened.
 274         */
 275        ret = security_file_permission(file, MAY_WRITE);
 276        if (ret)
 277                return ret;
 278
 279        if (S_ISFIFO(inode->i_mode))
 280                return -ESPIPE;
 281
 282        /*
 283         * Let individual file system decide if it supports preallocation
 284         * for directories or not.
 285         */
 286        if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 287                return -ENODEV;
 288
 289        /* Check for wrap through zero too */
 290        if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 291                return -EFBIG;
 292
 293        if (!file->f_op->fallocate)
 294                return -EOPNOTSUPP;
 295
 296        sb_start_write(inode->i_sb);
 297        ret = file->f_op->fallocate(file, mode, offset, len);
 298        sb_end_write(inode->i_sb);
 299        return ret;
 300}
 301
 302SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)
 303{
 304        struct fd f = fdget(fd);
 305        int error = -EBADF;
 306
 307        if (f.file) {
 308                error = do_fallocate(f.file, mode, offset, len);
 309                fdput(f);
 310        }
 311        return error;
 312}
 313
 314#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 315asmlinkage long SyS_fallocate(long fd, long mode, loff_t offset, loff_t len)
 316{
 317        return SYSC_fallocate((int)fd, (int)mode, offset, len);
 318}
 319SYSCALL_ALIAS(sys_fallocate, SyS_fallocate);
 320#endif
 321
 322/*
 323 * access() needs to use the real uid/gid, not the effective uid/gid.
 324 * We do this by temporarily clearing all FS-related capabilities and
 325 * switching the fsuid/fsgid around to the real ones.
 326 */
 327SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 328{
 329        const struct cred *old_cred;
 330        struct cred *override_cred;
 331        struct path path;
 332        struct inode *inode;
 333        int res;
 334        unsigned int lookup_flags = LOOKUP_FOLLOW;
 335
 336        if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 337                return -EINVAL;
 338
 339        override_cred = prepare_creds();
 340        if (!override_cred)
 341                return -ENOMEM;
 342
 343        override_cred->fsuid = override_cred->uid;
 344        override_cred->fsgid = override_cred->gid;
 345
 346        if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 347                /* Clear the capabilities if we switch to a non-root user */
 348                kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 349                if (!uid_eq(override_cred->uid, root_uid))
 350                        cap_clear(override_cred->cap_effective);
 351                else
 352                        override_cred->cap_effective =
 353                                override_cred->cap_permitted;
 354        }
 355
 356        old_cred = override_creds(override_cred);
 357retry:
 358        res = user_path_at(dfd, filename, lookup_flags, &path);
 359        if (res)
 360                goto out;
 361
 362        inode = path.dentry->d_inode;
 363
 364        if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 365                /*
 366                 * MAY_EXEC on regular files is denied if the fs is mounted
 367                 * with the "noexec" flag.
 368                 */
 369                res = -EACCES;
 370                if (path.mnt->mnt_flags & MNT_NOEXEC)
 371                        goto out_path_release;
 372        }
 373
 374        res = inode_permission(inode, mode | MAY_ACCESS);
 375        /* SuS v2 requires we report a read only fs too */
 376        if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 377                goto out_path_release;
 378        /*
 379         * This is a rare case where using __mnt_is_readonly()
 380         * is OK without a mnt_want/drop_write() pair.  Since
 381         * no actual write to the fs is performed here, we do
 382         * not need to telegraph to that to anyone.
 383         *
 384         * By doing this, we accept that this access is
 385         * inherently racy and know that the fs may change
 386         * state before we even see this result.
 387         */
 388        if (__mnt_is_readonly(path.mnt))
 389                res = -EROFS;
 390
 391out_path_release:
 392        path_put(&path);
 393        if (retry_estale(res, lookup_flags)) {
 394                lookup_flags |= LOOKUP_REVAL;
 395                goto retry;
 396        }
 397out:
 398        revert_creds(old_cred);
 399        put_cred(override_cred);
 400        return res;
 401}
 402
 403SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 404{
 405        return sys_faccessat(AT_FDCWD, filename, mode);
 406}
 407
 408SYSCALL_DEFINE1(chdir, const char __user *, filename)
 409{
 410        struct path path;
 411        int error;
 412        unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 413retry:
 414        error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 415        if (error)
 416                goto out;
 417
 418        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 419        if (error)
 420                goto dput_and_out;
 421
 422        set_fs_pwd(current->fs, &path);
 423
 424dput_and_out:
 425        path_put(&path);
 426        if (retry_estale(error, lookup_flags)) {
 427                lookup_flags |= LOOKUP_REVAL;
 428                goto retry;
 429        }
 430out:
 431        return error;
 432}
 433
 434SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 435{
 436        struct fd f = fdget_raw(fd);
 437        struct inode *inode;
 438        int error = -EBADF;
 439
 440        error = -EBADF;
 441        if (!f.file)
 442                goto out;
 443
 444        inode = file_inode(f.file);
 445
 446        error = -ENOTDIR;
 447        if (!S_ISDIR(inode->i_mode))
 448                goto out_putf;
 449
 450        error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
 451        if (!error)
 452                set_fs_pwd(current->fs, &f.file->f_path);
 453out_putf:
 454        fdput(f);
 455out:
 456        return error;
 457}
 458
 459SYSCALL_DEFINE1(chroot, const char __user *, filename)
 460{
 461        struct path path;
 462        int error;
 463        unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
 464retry:
 465        error = user_path_at(AT_FDCWD, filename, lookup_flags, &path);
 466        if (error)
 467                goto out;
 468
 469        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 470        if (error)
 471                goto dput_and_out;
 472
 473        error = -EPERM;
 474        if (!nsown_capable(CAP_SYS_CHROOT))
 475                goto dput_and_out;
 476        error = security_path_chroot(&path);
 477        if (error)
 478                goto dput_and_out;
 479
 480        set_fs_root(current->fs, &path);
 481        error = 0;
 482dput_and_out:
 483        path_put(&path);
 484        if (retry_estale(error, lookup_flags)) {
 485                lookup_flags |= LOOKUP_REVAL;
 486                goto retry;
 487        }
 488out:
 489        return error;
 490}
 491
 492static int chmod_common(struct path *path, umode_t mode)
 493{
 494        struct inode *inode = path->dentry->d_inode;
 495        struct iattr newattrs;
 496        int error;
 497
 498        error = mnt_want_write(path->mnt);
 499        if (error)
 500                return error;
 501        mutex_lock(&inode->i_mutex);
 502        error = security_path_chmod(path, mode);
 503        if (error)
 504                goto out_unlock;
 505        newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 506        newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 507        error = notify_change(path->dentry, &newattrs);
 508out_unlock:
 509        mutex_unlock(&inode->i_mutex);
 510        mnt_drop_write(path->mnt);
 511        return error;
 512}
 513
 514SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 515{
 516        struct file * file;
 517        int err = -EBADF;
 518
 519        file = fget(fd);
 520        if (file) {
 521                audit_inode(NULL, file->f_path.dentry, 0);
 522                err = chmod_common(&file->f_path, mode);
 523                fput(file);
 524        }
 525        return err;
 526}
 527
 528SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
 529{
 530        struct path path;
 531        int error;
 532        unsigned int lookup_flags = LOOKUP_FOLLOW;
 533retry:
 534        error = user_path_at(dfd, filename, lookup_flags, &path);
 535        if (!error) {
 536                error = chmod_common(&path, mode);
 537                path_put(&path);
 538                if (retry_estale(error, lookup_flags)) {
 539                        lookup_flags |= LOOKUP_REVAL;
 540                        goto retry;
 541                }
 542        }
 543        return error;
 544}
 545
 546SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 547{
 548        return sys_fchmodat(AT_FDCWD, filename, mode);
 549}
 550
 551static int chown_common(struct path *path, uid_t user, gid_t group)
 552{
 553        struct inode *inode = path->dentry->d_inode;
 554        int error;
 555        struct iattr newattrs;
 556        kuid_t uid;
 557        kgid_t gid;
 558
 559        uid = make_kuid(current_user_ns(), user);
 560        gid = make_kgid(current_user_ns(), group);
 561
 562        newattrs.ia_valid =  ATTR_CTIME;
 563        if (user != (uid_t) -1) {
 564                if (!uid_valid(uid))
 565                        return -EINVAL;
 566                newattrs.ia_valid |= ATTR_UID;
 567                newattrs.ia_uid = uid;
 568        }
 569        if (group != (gid_t) -1) {
 570                if (!gid_valid(gid))
 571                        return -EINVAL;
 572                newattrs.ia_valid |= ATTR_GID;
 573                newattrs.ia_gid = gid;
 574        }
 575        if (!S_ISDIR(inode->i_mode))
 576                newattrs.ia_valid |=
 577                        ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 578        mutex_lock(&inode->i_mutex);
 579        error = security_path_chown(path, uid, gid);
 580        if (!error)
 581                error = notify_change(path->dentry, &newattrs);
 582        mutex_unlock(&inode->i_mutex);
 583
 584        return error;
 585}
 586
 587SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 588                gid_t, group, int, flag)
 589{
 590        struct path path;
 591        int error = -EINVAL;
 592        int lookup_flags;
 593
 594        if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 595                goto out;
 596
 597        lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 598        if (flag & AT_EMPTY_PATH)
 599                lookup_flags |= LOOKUP_EMPTY;
 600retry:
 601        error = user_path_at(dfd, filename, lookup_flags, &path);
 602        if (error)
 603                goto out;
 604        error = mnt_want_write(path.mnt);
 605        if (error)
 606                goto out_release;
 607        error = chown_common(&path, user, group);
 608        mnt_drop_write(path.mnt);
 609out_release:
 610        path_put(&path);
 611        if (retry_estale(error, lookup_flags)) {
 612                lookup_flags |= LOOKUP_REVAL;
 613                goto retry;
 614        }
 615out:
 616        return error;
 617}
 618
 619SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 620{
 621        return sys_fchownat(AT_FDCWD, filename, user, group, 0);
 622}
 623
 624SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 625{
 626        return sys_fchownat(AT_FDCWD, filename, user, group,
 627                            AT_SYMLINK_NOFOLLOW);
 628}
 629
 630SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 631{
 632        struct fd f = fdget(fd);
 633        int error = -EBADF;
 634
 635        if (!f.file)
 636                goto out;
 637
 638        error = mnt_want_write_file(f.file);
 639        if (error)
 640                goto out_fput;
 641        audit_inode(NULL, f.file->f_path.dentry, 0);
 642        error = chown_common(&f.file->f_path, user, group);
 643        mnt_drop_write_file(f.file);
 644out_fput:
 645        fdput(f);
 646out:
 647        return error;
 648}
 649
 650/*
 651 * You have to be very careful that these write
 652 * counts get cleaned up in error cases and
 653 * upon __fput().  This should probably never
 654 * be called outside of __dentry_open().
 655 */
 656static inline int __get_file_write_access(struct inode *inode,
 657                                          struct vfsmount *mnt)
 658{
 659        int error;
 660        error = get_write_access(inode);
 661        if (error)
 662                return error;
 663        /*
 664         * Do not take mount writer counts on
 665         * special files since no writes to
 666         * the mount itself will occur.
 667         */
 668        if (!special_file(inode->i_mode)) {
 669                /*
 670                 * Balanced in __fput()
 671                 */
 672                error = __mnt_want_write(mnt);
 673                if (error)
 674                        put_write_access(inode);
 675        }
 676        return error;
 677}
 678
 679int open_check_o_direct(struct file *f)
 680{
 681        /* NB: we're sure to have correct a_ops only after f_op->open */
 682        if (f->f_flags & O_DIRECT) {
 683                if (!f->f_mapping->a_ops ||
 684                    ((!f->f_mapping->a_ops->direct_IO) &&
 685                    (!f->f_mapping->a_ops->get_xip_mem))) {
 686                        return -EINVAL;
 687                }
 688        }
 689        return 0;
 690}
 691
 692static int do_dentry_open(struct file *f,
 693                          int (*open)(struct inode *, struct file *),
 694                          const struct cred *cred)
 695{
 696        static const struct file_operations empty_fops = {};
 697        struct inode *inode;
 698        int error;
 699
 700        f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 701                                FMODE_PREAD | FMODE_PWRITE;
 702
 703        if (unlikely(f->f_flags & O_PATH))
 704                f->f_mode = FMODE_PATH;
 705
 706        path_get(&f->f_path);
 707        inode = f->f_inode = f->f_path.dentry->d_inode;
 708        if (f->f_mode & FMODE_WRITE) {
 709                error = __get_file_write_access(inode, f->f_path.mnt);
 710                if (error)
 711                        goto cleanup_file;
 712                if (!special_file(inode->i_mode))
 713                        file_take_write(f);
 714        }
 715
 716        f->f_mapping = inode->i_mapping;
 717        file_sb_list_add(f, inode->i_sb);
 718
 719        if (unlikely(f->f_mode & FMODE_PATH)) {
 720                f->f_op = &empty_fops;
 721                return 0;
 722        }
 723
 724        f->f_op = fops_get(inode->i_fop);
 725
 726        error = security_file_open(f, cred);
 727        if (error)
 728                goto cleanup_all;
 729
 730        error = break_lease(inode, f->f_flags);
 731        if (error)
 732                goto cleanup_all;
 733
 734        if (!open && f->f_op)
 735                open = f->f_op->open;
 736        if (open) {
 737                error = open(inode, f);
 738                if (error)
 739                        goto cleanup_all;
 740        }
 741        if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 742                i_readcount_inc(inode);
 743
 744        f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 745
 746        file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 747
 748        return 0;
 749
 750cleanup_all:
 751        fops_put(f->f_op);
 752        file_sb_list_del(f);
 753        if (f->f_mode & FMODE_WRITE) {
 754                put_write_access(inode);
 755                if (!special_file(inode->i_mode)) {
 756                        /*
 757                         * We don't consider this a real
 758                         * mnt_want/drop_write() pair
 759                         * because it all happenend right
 760                         * here, so just reset the state.
 761                         */
 762                        file_reset_write(f);
 763                        __mnt_drop_write(f->f_path.mnt);
 764                }
 765        }
 766cleanup_file:
 767        path_put(&f->f_path);
 768        f->f_path.mnt = NULL;
 769        f->f_path.dentry = NULL;
 770        f->f_inode = NULL;
 771        return error;
 772}
 773
 774/**
 775 * finish_open - finish opening a file
 776 * @od: opaque open data
 777 * @dentry: pointer to dentry
 778 * @open: open callback
 779 *
 780 * This can be used to finish opening a file passed to i_op->atomic_open().
 781 *
 782 * If the open callback is set to NULL, then the standard f_op->open()
 783 * filesystem callback is substituted.
 784 */
 785int finish_open(struct file *file, struct dentry *dentry,
 786                int (*open)(struct inode *, struct file *),
 787                int *opened)
 788{
 789        int error;
 790        BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
 791
 792        file->f_path.dentry = dentry;
 793        error = do_dentry_open(file, open, current_cred());
 794        if (!error)
 795                *opened |= FILE_OPENED;
 796
 797        return error;
 798}
 799EXPORT_SYMBOL(finish_open);
 800
 801/**
 802 * finish_no_open - finish ->atomic_open() without opening the file
 803 *
 804 * @od: opaque open data
 805 * @dentry: dentry or NULL (as returned from ->lookup())
 806 *
 807 * This can be used to set the result of a successful lookup in ->atomic_open().
 808 * The filesystem's atomic_open() method shall return NULL after calling this.
 809 */
 810int finish_no_open(struct file *file, struct dentry *dentry)
 811{
 812        file->f_path.dentry = dentry;
 813        return 1;
 814}
 815EXPORT_SYMBOL(finish_no_open);
 816
 817struct file *dentry_open(const struct path *path, int flags,
 818                         const struct cred *cred)
 819{
 820        int error;
 821        struct file *f;
 822
 823        validate_creds(cred);
 824
 825        /* We must always pass in a valid mount pointer. */
 826        BUG_ON(!path->mnt);
 827
 828        f = get_empty_filp();
 829        if (!IS_ERR(f)) {
 830                f->f_flags = flags;
 831                f->f_path = *path;
 832                error = do_dentry_open(f, NULL, cred);
 833                if (!error) {
 834                        /* from now on we need fput() to dispose of f */
 835                        error = open_check_o_direct(f);
 836                        if (error) {
 837                                fput(f);
 838                                f = ERR_PTR(error);
 839                        }
 840                } else { 
 841                        put_filp(f);
 842                        f = ERR_PTR(error);
 843                }
 844        }
 845        return f;
 846}
 847EXPORT_SYMBOL(dentry_open);
 848
 849static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
 850{
 851        int lookup_flags = 0;
 852        int acc_mode;
 853
 854        if (flags & O_CREAT)
 855                op->mode = (mode & S_IALLUGO) | S_IFREG;
 856        else
 857                op->mode = 0;
 858
 859        /* Must never be set by userspace */
 860        flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;
 861
 862        /*
 863         * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
 864         * check for O_DSYNC if the need any syncing at all we enforce it's
 865         * always set instead of having to deal with possibly weird behaviour
 866         * for malicious applications setting only __O_SYNC.
 867         */
 868        if (flags & __O_SYNC)
 869                flags |= O_DSYNC;
 870
 871        /*
 872         * If we have O_PATH in the open flag. Then we
 873         * cannot have anything other than the below set of flags
 874         */
 875        if (flags & O_PATH) {
 876                flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
 877                acc_mode = 0;
 878        } else {
 879                acc_mode = MAY_OPEN | ACC_MODE(flags);
 880        }
 881
 882        op->open_flag = flags;
 883
 884        /* O_TRUNC implies we need access checks for write permissions */
 885        if (flags & O_TRUNC)
 886                acc_mode |= MAY_WRITE;
 887
 888        /* Allow the LSM permission hook to distinguish append
 889           access from general write access. */
 890        if (flags & O_APPEND)
 891                acc_mode |= MAY_APPEND;
 892
 893        op->acc_mode = acc_mode;
 894
 895        op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
 896
 897        if (flags & O_CREAT) {
 898                op->intent |= LOOKUP_CREATE;
 899                if (flags & O_EXCL)
 900                        op->intent |= LOOKUP_EXCL;
 901        }
 902
 903        if (flags & O_DIRECTORY)
 904                lookup_flags |= LOOKUP_DIRECTORY;
 905        if (!(flags & O_NOFOLLOW))
 906                lookup_flags |= LOOKUP_FOLLOW;
 907        return lookup_flags;
 908}
 909
 910/**
 911 * file_open_name - open file and return file pointer
 912 *
 913 * @name:       struct filename containing path to open
 914 * @flags:      open flags as per the open(2) second argument
 915 * @mode:       mode for the new file if O_CREAT is set, else ignored
 916 *
 917 * This is the helper to open a file from kernelspace if you really
 918 * have to.  But in generally you should not do this, so please move
 919 * along, nothing to see here..
 920 */
 921struct file *file_open_name(struct filename *name, int flags, umode_t mode)
 922{
 923        struct open_flags op;
 924        int lookup = build_open_flags(flags, mode, &op);
 925        return do_filp_open(AT_FDCWD, name, &op, lookup);
 926}
 927
 928/**
 929 * filp_open - open file and return file pointer
 930 *
 931 * @filename:   path to open
 932 * @flags:      open flags as per the open(2) second argument
 933 * @mode:       mode for the new file if O_CREAT is set, else ignored
 934 *
 935 * This is the helper to open a file from kernelspace if you really
 936 * have to.  But in generally you should not do this, so please move
 937 * along, nothing to see here..
 938 */
 939struct file *filp_open(const char *filename, int flags, umode_t mode)
 940{
 941        struct filename name = {.name = filename};
 942        return file_open_name(&name, flags, mode);
 943}
 944EXPORT_SYMBOL(filp_open);
 945
 946struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
 947                            const char *filename, int flags)
 948{
 949        struct open_flags op;
 950        int lookup = build_open_flags(flags, 0, &op);
 951        if (flags & O_CREAT)
 952                return ERR_PTR(-EINVAL);
 953        if (!filename && (flags & O_DIRECTORY))
 954                if (!dentry->d_inode->i_op->lookup)
 955                        return ERR_PTR(-ENOTDIR);
 956        return do_file_open_root(dentry, mnt, filename, &op, lookup);
 957}
 958EXPORT_SYMBOL(file_open_root);
 959
 960long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
 961{
 962        struct open_flags op;
 963        int lookup = build_open_flags(flags, mode, &op);
 964        struct filename *tmp = getname(filename);
 965        int fd = PTR_ERR(tmp);
 966
 967        if (!IS_ERR(tmp)) {
 968                fd = get_unused_fd_flags(flags);
 969                if (fd >= 0) {
 970                        struct file *f = do_filp_open(dfd, tmp, &op, lookup);
 971                        if (IS_ERR(f)) {
 972                                put_unused_fd(fd);
 973                                fd = PTR_ERR(f);
 974                        } else {
 975                                fsnotify_open(f);
 976                                fd_install(fd, f);
 977                        }
 978                }
 979                putname(tmp);
 980        }
 981        return fd;
 982}
 983
 984SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
 985{
 986        long ret;
 987
 988        if (force_o_largefile())
 989                flags |= O_LARGEFILE;
 990
 991        ret = do_sys_open(AT_FDCWD, filename, flags, mode);
 992        /* avoid REGPARM breakage on x86: */
 993        asmlinkage_protect(3, ret, filename, flags, mode);
 994        return ret;
 995}
 996
 997SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
 998                umode_t, mode)
 999{
1000        long ret;
1001
1002        if (force_o_largefile())
1003                flags |= O_LARGEFILE;
1004
1005        ret = do_sys_open(dfd, filename, flags, mode);
1006        /* avoid REGPARM breakage on x86: */
1007        asmlinkage_protect(4, ret, dfd, filename, flags, mode);
1008        return ret;
1009}
1010
1011#ifndef __alpha__
1012
1013/*
1014 * For backward compatibility?  Maybe this should be moved
1015 * into arch/i386 instead?
1016 */
1017SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1018{
1019        return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1020}
1021
1022#endif
1023
1024/*
1025 * "id" is the POSIX thread ID. We use the
1026 * files pointer for this..
1027 */
1028int filp_close(struct file *filp, fl_owner_t id)
1029{
1030        int retval = 0;
1031
1032        if (!file_count(filp)) {
1033                printk(KERN_ERR "VFS: Close: file count is 0\n");
1034                return 0;
1035        }
1036
1037        if (filp->f_op && filp->f_op->flush)
1038                retval = filp->f_op->flush(filp, id);
1039
1040        if (likely(!(filp->f_mode & FMODE_PATH))) {
1041                dnotify_flush(filp, id);
1042                locks_remove_posix(filp, id);
1043        }
1044        fput(filp);
1045        return retval;
1046}
1047
1048EXPORT_SYMBOL(filp_close);
1049
1050/*
1051 * Careful here! We test whether the file pointer is NULL before
1052 * releasing the fd. This ensures that one clone task can't release
1053 * an fd while another clone is opening it.
1054 */
1055SYSCALL_DEFINE1(close, unsigned int, fd)
1056{
1057        int retval = __close_fd(current->files, fd);
1058
1059        /* can't restart close syscall because file table entry was cleared */
1060        if (unlikely(retval == -ERESTARTSYS ||
1061                     retval == -ERESTARTNOINTR ||
1062                     retval == -ERESTARTNOHAND ||
1063                     retval == -ERESTART_RESTARTBLOCK))
1064                retval = -EINTR;
1065
1066        return retval;
1067}
1068EXPORT_SYMBOL(sys_close);
1069
1070/*
1071 * This routine simulates a hangup on the tty, to arrange that users
1072 * are given clean terminals at login time.
1073 */
1074SYSCALL_DEFINE0(vhangup)
1075{
1076        if (capable(CAP_SYS_TTY_CONFIG)) {
1077                tty_vhangup_self();
1078                return 0;
1079        }
1080        return -EPERM;
1081}
1082
1083/*
1084 * Called when an inode is about to be open.
1085 * We use this to disallow opening large files on 32bit systems if
1086 * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1087 * on this flag in sys_open.
1088 */
1089int generic_file_open(struct inode * inode, struct file * filp)
1090{
1091        if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1092                return -EOVERFLOW;
1093        return 0;
1094}
1095
1096EXPORT_SYMBOL(generic_file_open);
1097
1098/*
1099 * This is used by subsystems that don't want seekable
1100 * file descriptors. The function is not supposed to ever fail, the only
1101 * reason it returns an 'int' and not 'void' is so that it can be plugged
1102 * directly into file_operations structure.
1103 */
1104int nonseekable_open(struct inode *inode, struct file *filp)
1105{
1106        filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1107        return 0;
1108}
1109
1110EXPORT_SYMBOL(nonseekable_open);
1111
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