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
  34#include "internal.h"
  35
  36int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
  37        struct file *filp)
  38{
  39        int ret;
  40        struct iattr newattrs;
  41
  42        /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
  43        if (length < 0)
  44                return -EINVAL;
  45
  46        newattrs.ia_size = length;
  47        newattrs.ia_valid = ATTR_SIZE | time_attrs;
  48        if (filp) {
  49                newattrs.ia_file = filp;
  50                newattrs.ia_valid |= ATTR_FILE;
  51        }
  52
  53        /* Remove suid/sgid on truncate too */
  54        ret = should_remove_suid(dentry);
  55        if (ret)
  56                newattrs.ia_valid |= ret | ATTR_FORCE;
  57
  58        mutex_lock(&dentry->d_inode->i_mutex);
  59        ret = notify_change(dentry, &newattrs);
  60        mutex_unlock(&dentry->d_inode->i_mutex);
  61        return ret;
  62}
  63
  64static long do_sys_truncate(const char __user *pathname, loff_t length)
  65{
  66        struct path path;
  67        struct inode *inode;
  68        int error;
  69
  70        error = -EINVAL;
  71        if (length < 0) /* sorry, but loff_t says... */
  72                goto out;
  73
  74        error = user_path(pathname, &path);
  75        if (error)
  76                goto out;
  77        inode = path.dentry->d_inode;
  78
  79        /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
  80        error = -EISDIR;
  81        if (S_ISDIR(inode->i_mode))
  82                goto dput_and_out;
  83
  84        error = -EINVAL;
  85        if (!S_ISREG(inode->i_mode))
  86                goto dput_and_out;
  87
  88        error = mnt_want_write(path.mnt);
  89        if (error)
  90                goto dput_and_out;
  91
  92        error = inode_permission(inode, MAY_WRITE);
  93        if (error)
  94                goto mnt_drop_write_and_out;
  95
  96        error = -EPERM;
  97        if (IS_APPEND(inode))
  98                goto mnt_drop_write_and_out;
  99
 100        error = get_write_access(inode);
 101        if (error)
 102                goto mnt_drop_write_and_out;
 103
 104        /*
 105         * Make sure that there are no leases.  get_write_access() protects
 106         * against the truncate racing with a lease-granting setlease().
 107         */
 108        error = break_lease(inode, O_WRONLY);
 109        if (error)
 110                goto put_write_and_out;
 111
 112        error = locks_verify_truncate(inode, NULL, length);
 113        if (!error)
 114                error = security_path_truncate(&path);
 115        if (!error)
 116                error = do_truncate(path.dentry, length, 0, NULL);
 117
 118put_write_and_out:
 119        put_write_access(inode);
 120mnt_drop_write_and_out:
 121        mnt_drop_write(path.mnt);
 122dput_and_out:
 123        path_put(&path);
 124out:
 125        return error;
 126}
 127
 128SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
 129{
 130        return do_sys_truncate(path, length);
 131}
 132
 133static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
 134{
 135        struct inode * inode;
 136        struct dentry *dentry;
 137        struct file * file;
 138        int error;
 139
 140        error = -EINVAL;
 141        if (length < 0)
 142                goto out;
 143        error = -EBADF;
 144        file = fget(fd);
 145        if (!file)
 146                goto out;
 147
 148        /* explicitly opened as large or we are on 64-bit box */
 149        if (file->f_flags & O_LARGEFILE)
 150                small = 0;
 151
 152        dentry = file->f_path.dentry;
 153        inode = dentry->d_inode;
 154        error = -EINVAL;
 155        if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
 156                goto out_putf;
 157
 158        error = -EINVAL;
 159        /* Cannot ftruncate over 2^31 bytes without large file support */
 160        if (small && length > MAX_NON_LFS)
 161                goto out_putf;
 162
 163        error = -EPERM;
 164        if (IS_APPEND(inode))
 165                goto out_putf;
 166
 167        error = locks_verify_truncate(inode, file, length);
 168        if (!error)
 169                error = security_path_truncate(&file->f_path);
 170        if (!error)
 171                error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
 172out_putf:
 173        fput(file);
 174out:
 175        return error;
 176}
 177
 178SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 179{
 180        long ret = do_sys_ftruncate(fd, length, 1);
 181        /* avoid REGPARM breakage on x86: */
 182        asmlinkage_protect(2, ret, fd, length);
 183        return ret;
 184}
 185
 186/* LFS versions of truncate are only needed on 32 bit machines */
 187#if BITS_PER_LONG == 32
 188SYSCALL_DEFINE(truncate64)(const char __user * path, loff_t length)
 189{
 190        return do_sys_truncate(path, length);
 191}
 192#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 193asmlinkage long SyS_truncate64(long path, loff_t length)
 194{
 195        return SYSC_truncate64((const char __user *) path, length);
 196}
 197SYSCALL_ALIAS(sys_truncate64, SyS_truncate64);
 198#endif
 199
 200SYSCALL_DEFINE(ftruncate64)(unsigned int fd, loff_t length)
 201{
 202        long ret = do_sys_ftruncate(fd, length, 0);
 203        /* avoid REGPARM breakage on x86: */
 204        asmlinkage_protect(2, ret, fd, length);
 205        return ret;
 206}
 207#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 208asmlinkage long SyS_ftruncate64(long fd, loff_t length)
 209{
 210        return SYSC_ftruncate64((unsigned int) fd, length);
 211}
 212SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
 213#endif
 214#endif /* BITS_PER_LONG == 32 */
 215
 216
 217int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 218{
 219        struct inode *inode = file->f_path.dentry->d_inode;
 220        long ret;
 221
 222        if (offset < 0 || len <= 0)
 223                return -EINVAL;
 224
 225        /* Return error if mode is not supported */
 226        if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
 227                return -EOPNOTSUPP;
 228
 229        /* Punch hole must have keep size set */
 230        if ((mode & FALLOC_FL_PUNCH_HOLE) &&
 231            !(mode & FALLOC_FL_KEEP_SIZE))
 232                return -EOPNOTSUPP;
 233
 234        if (!(file->f_mode & FMODE_WRITE))
 235                return -EBADF;
 236
 237        /* It's not possible punch hole on append only file */
 238        if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
 239                return -EPERM;
 240
 241        if (IS_IMMUTABLE(inode))
 242                return -EPERM;
 243
 244        /*
 245         * Revalidate the write permissions, in case security policy has
 246         * changed since the files were opened.
 247         */
 248        ret = security_file_permission(file, MAY_WRITE);
 249        if (ret)
 250                return ret;
 251
 252        if (S_ISFIFO(inode->i_mode))
 253                return -ESPIPE;
 254
 255        /*
 256         * Let individual file system decide if it supports preallocation
 257         * for directories or not.
 258         */
 259        if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 260                return -ENODEV;
 261
 262        /* Check for wrap through zero too */
 263        if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 264                return -EFBIG;
 265
 266        if (!file->f_op->fallocate)
 267                return -EOPNOTSUPP;
 268
 269        return file->f_op->fallocate(file, mode, offset, len);
 270}
 271
 272SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)
 273{
 274        struct file *file;
 275        int error = -EBADF;
 276
 277        file = fget(fd);
 278        if (file) {
 279                error = do_fallocate(file, mode, offset, len);
 280                fput(file);
 281        }
 282
 283        return error;
 284}
 285
 286#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 287asmlinkage long SyS_fallocate(long fd, long mode, loff_t offset, loff_t len)
 288{
 289        return SYSC_fallocate((int)fd, (int)mode, offset, len);
 290}
 291SYSCALL_ALIAS(sys_fallocate, SyS_fallocate);
 292#endif
 293
 294/*
 295 * access() needs to use the real uid/gid, not the effective uid/gid.
 296 * We do this by temporarily clearing all FS-related capabilities and
 297 * switching the fsuid/fsgid around to the real ones.
 298 */
 299SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 300{
 301        const struct cred *old_cred;
 302        struct cred *override_cred;
 303        struct path path;
 304        struct inode *inode;
 305        int res;
 306
 307        if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 308                return -EINVAL;
 309
 310        override_cred = prepare_creds();
 311        if (!override_cred)
 312                return -ENOMEM;
 313
 314        override_cred->fsuid = override_cred->uid;
 315        override_cred->fsgid = override_cred->gid;
 316
 317        if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 318                /* Clear the capabilities if we switch to a non-root user */
 319                kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 320                if (!uid_eq(override_cred->uid, root_uid))
 321                        cap_clear(override_cred->cap_effective);
 322                else
 323                        override_cred->cap_effective =
 324                                override_cred->cap_permitted;
 325        }
 326
 327        old_cred = override_creds(override_cred);
 328
 329        res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
 330        if (res)
 331                goto out;
 332
 333        inode = path.dentry->d_inode;
 334
 335        if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 336                /*
 337                 * MAY_EXEC on regular files is denied if the fs is mounted
 338                 * with the "noexec" flag.
 339                 */
 340                res = -EACCES;
 341                if (path.mnt->mnt_flags & MNT_NOEXEC)
 342                        goto out_path_release;
 343        }
 344
 345        res = inode_permission(inode, mode | MAY_ACCESS);
 346        /* SuS v2 requires we report a read only fs too */
 347        if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 348                goto out_path_release;
 349        /*
 350         * This is a rare case where using __mnt_is_readonly()
 351         * is OK without a mnt_want/drop_write() pair.  Since
 352         * no actual write to the fs is performed here, we do
 353         * not need to telegraph to that to anyone.
 354         *
 355         * By doing this, we accept that this access is
 356         * inherently racy and know that the fs may change
 357         * state before we even see this result.
 358         */
 359        if (__mnt_is_readonly(path.mnt))
 360                res = -EROFS;
 361
 362out_path_release:
 363        path_put(&path);
 364out:
 365        revert_creds(old_cred);
 366        put_cred(override_cred);
 367        return res;
 368}
 369
 370SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 371{
 372        return sys_faccessat(AT_FDCWD, filename, mode);
 373}
 374
 375SYSCALL_DEFINE1(chdir, const char __user *, filename)
 376{
 377        struct path path;
 378        int error;
 379
 380        error = user_path_dir(filename, &path);
 381        if (error)
 382                goto out;
 383
 384        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 385        if (error)
 386                goto dput_and_out;
 387
 388        set_fs_pwd(current->fs, &path);
 389
 390dput_and_out:
 391        path_put(&path);
 392out:
 393        return error;
 394}
 395
 396SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 397{
 398        struct file *file;
 399        struct inode *inode;
 400        int error, fput_needed;
 401
 402        error = -EBADF;
 403        file = fget_raw_light(fd, &fput_needed);
 404        if (!file)
 405                goto out;
 406
 407        inode = file->f_path.dentry->d_inode;
 408
 409        error = -ENOTDIR;
 410        if (!S_ISDIR(inode->i_mode))
 411                goto out_putf;
 412
 413        error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
 414        if (!error)
 415                set_fs_pwd(current->fs, &file->f_path);
 416out_putf:
 417        fput_light(file, fput_needed);
 418out:
 419        return error;
 420}
 421
 422SYSCALL_DEFINE1(chroot, const char __user *, filename)
 423{
 424        struct path path;
 425        int error;
 426
 427        error = user_path_dir(filename, &path);
 428        if (error)
 429                goto out;
 430
 431        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 432        if (error)
 433                goto dput_and_out;
 434
 435        error = -EPERM;
 436        if (!capable(CAP_SYS_CHROOT))
 437                goto dput_and_out;
 438        error = security_path_chroot(&path);
 439        if (error)
 440                goto dput_and_out;
 441
 442        set_fs_root(current->fs, &path);
 443        error = 0;
 444dput_and_out:
 445        path_put(&path);
 446out:
 447        return error;
 448}
 449
 450static int chmod_common(struct path *path, umode_t mode)
 451{
 452        struct inode *inode = path->dentry->d_inode;
 453        struct iattr newattrs;
 454        int error;
 455
 456        error = mnt_want_write(path->mnt);
 457        if (error)
 458                return error;
 459        mutex_lock(&inode->i_mutex);
 460        error = security_path_chmod(path, mode);
 461        if (error)
 462                goto out_unlock;
 463        newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 464        newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 465        error = notify_change(path->dentry, &newattrs);
 466out_unlock:
 467        mutex_unlock(&inode->i_mutex);
 468        mnt_drop_write(path->mnt);
 469        return error;
 470}
 471
 472SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 473{
 474        struct file * file;
 475        int err = -EBADF;
 476
 477        file = fget(fd);
 478        if (file) {
 479                audit_inode(NULL, file->f_path.dentry);
 480                err = chmod_common(&file->f_path, mode);
 481                fput(file);
 482        }
 483        return err;
 484}
 485
 486SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
 487{
 488        struct path path;
 489        int error;
 490
 491        error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
 492        if (!error) {
 493                error = chmod_common(&path, mode);
 494                path_put(&path);
 495        }
 496        return error;
 497}
 498
 499SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 500{
 501        return sys_fchmodat(AT_FDCWD, filename, mode);
 502}
 503
 504static int chown_common(struct path *path, uid_t user, gid_t group)
 505{
 506        struct inode *inode = path->dentry->d_inode;
 507        int error;
 508        struct iattr newattrs;
 509        kuid_t uid;
 510        kgid_t gid;
 511
 512        uid = make_kuid(current_user_ns(), user);
 513        gid = make_kgid(current_user_ns(), group);
 514
 515        newattrs.ia_valid =  ATTR_CTIME;
 516        if (user != (uid_t) -1) {
 517                if (!uid_valid(uid))
 518                        return -EINVAL;
 519                newattrs.ia_valid |= ATTR_UID;
 520                newattrs.ia_uid = uid;
 521        }
 522        if (group != (gid_t) -1) {
 523                if (!gid_valid(gid))
 524                        return -EINVAL;
 525                newattrs.ia_valid |= ATTR_GID;
 526                newattrs.ia_gid = gid;
 527        }
 528        if (!S_ISDIR(inode->i_mode))
 529                newattrs.ia_valid |=
 530                        ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 531        mutex_lock(&inode->i_mutex);
 532        error = security_path_chown(path, user, group);
 533        if (!error)
 534                error = notify_change(path->dentry, &newattrs);
 535        mutex_unlock(&inode->i_mutex);
 536
 537        return error;
 538}
 539
 540SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 541{
 542        struct path path;
 543        int error;
 544
 545        error = user_path(filename, &path);
 546        if (error)
 547                goto out;
 548        error = mnt_want_write(path.mnt);
 549        if (error)
 550                goto out_release;
 551        error = chown_common(&path, user, group);
 552        mnt_drop_write(path.mnt);
 553out_release:
 554        path_put(&path);
 555out:
 556        return error;
 557}
 558
 559SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 560                gid_t, group, int, flag)
 561{
 562        struct path path;
 563        int error = -EINVAL;
 564        int lookup_flags;
 565
 566        if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 567                goto out;
 568
 569        lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 570        if (flag & AT_EMPTY_PATH)
 571                lookup_flags |= LOOKUP_EMPTY;
 572        error = user_path_at(dfd, filename, lookup_flags, &path);
 573        if (error)
 574                goto out;
 575        error = mnt_want_write(path.mnt);
 576        if (error)
 577                goto out_release;
 578        error = chown_common(&path, user, group);
 579        mnt_drop_write(path.mnt);
 580out_release:
 581        path_put(&path);
 582out:
 583        return error;
 584}
 585
 586SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 587{
 588        struct path path;
 589        int error;
 590
 591        error = user_lpath(filename, &path);
 592        if (error)
 593                goto out;
 594        error = mnt_want_write(path.mnt);
 595        if (error)
 596                goto out_release;
 597        error = chown_common(&path, user, group);
 598        mnt_drop_write(path.mnt);
 599out_release:
 600        path_put(&path);
 601out:
 602        return error;
 603}
 604
 605SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 606{
 607        struct file * file;
 608        int error = -EBADF;
 609        struct dentry * dentry;
 610
 611        file = fget(fd);
 612        if (!file)
 613                goto out;
 614
 615        error = mnt_want_write_file(file);
 616        if (error)
 617                goto out_fput;
 618        dentry = file->f_path.dentry;
 619        audit_inode(NULL, dentry);
 620        error = chown_common(&file->f_path, user, group);
 621        mnt_drop_write_file(file);
 622out_fput:
 623        fput(file);
 624out:
 625        return error;
 626}
 627
 628/*
 629 * You have to be very careful that these write
 630 * counts get cleaned up in error cases and
 631 * upon __fput().  This should probably never
 632 * be called outside of __dentry_open().
 633 */
 634static inline int __get_file_write_access(struct inode *inode,
 635                                          struct vfsmount *mnt)
 636{
 637        int error;
 638        error = get_write_access(inode);
 639        if (error)
 640                return error;
 641        /*
 642         * Do not take mount writer counts on
 643         * special files since no writes to
 644         * the mount itself will occur.
 645         */
 646        if (!special_file(inode->i_mode)) {
 647                /*
 648                 * Balanced in __fput()
 649                 */
 650                error = mnt_want_write(mnt);
 651                if (error)
 652                        put_write_access(inode);
 653        }
 654        return error;
 655}
 656
 657int open_check_o_direct(struct file *f)
 658{
 659        /* NB: we're sure to have correct a_ops only after f_op->open */
 660        if (f->f_flags & O_DIRECT) {
 661                if (!f->f_mapping->a_ops ||
 662                    ((!f->f_mapping->a_ops->direct_IO) &&
 663                    (!f->f_mapping->a_ops->get_xip_mem))) {
 664                        return -EINVAL;
 665                }
 666        }
 667        return 0;
 668}
 669
 670static struct file *do_dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 671                                   struct file *f,
 672                                   int (*open)(struct inode *, struct file *),
 673                                   const struct cred *cred)
 674{
 675        static const struct file_operations empty_fops = {};
 676        struct inode *inode;
 677        int error;
 678
 679        f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 680                                FMODE_PREAD | FMODE_PWRITE;
 681
 682        if (unlikely(f->f_flags & O_PATH))
 683                f->f_mode = FMODE_PATH;
 684
 685        inode = dentry->d_inode;
 686        if (f->f_mode & FMODE_WRITE) {
 687                error = __get_file_write_access(inode, mnt);
 688                if (error)
 689                        goto cleanup_file;
 690                if (!special_file(inode->i_mode))
 691                        file_take_write(f);
 692        }
 693
 694        f->f_mapping = inode->i_mapping;
 695        f->f_path.dentry = dentry;
 696        f->f_path.mnt = mnt;
 697        f->f_pos = 0;
 698        file_sb_list_add(f, inode->i_sb);
 699
 700        if (unlikely(f->f_mode & FMODE_PATH)) {
 701                f->f_op = &empty_fops;
 702                return f;
 703        }
 704
 705        f->f_op = fops_get(inode->i_fop);
 706
 707        error = security_file_open(f, cred);
 708        if (error)
 709                goto cleanup_all;
 710
 711        error = break_lease(inode, f->f_flags);
 712        if (error)
 713                goto cleanup_all;
 714
 715        if (!open && f->f_op)
 716                open = f->f_op->open;
 717        if (open) {
 718                error = open(inode, f);
 719                if (error)
 720                        goto cleanup_all;
 721        }
 722        if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 723                i_readcount_inc(inode);
 724
 725        f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 726
 727        file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 728
 729        return f;
 730
 731cleanup_all:
 732        fops_put(f->f_op);
 733        if (f->f_mode & FMODE_WRITE) {
 734                put_write_access(inode);
 735                if (!special_file(inode->i_mode)) {
 736                        /*
 737                         * We don't consider this a real
 738                         * mnt_want/drop_write() pair
 739                         * because it all happenend right
 740                         * here, so just reset the state.
 741                         */
 742                        file_reset_write(f);
 743                        mnt_drop_write(mnt);
 744                }
 745        }
 746        file_sb_list_del(f);
 747        f->f_path.dentry = NULL;
 748        f->f_path.mnt = NULL;
 749cleanup_file:
 750        dput(dentry);
 751        mntput(mnt);
 752        return ERR_PTR(error);
 753}
 754
 755static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
 756                                struct file *f,
 757                                int (*open)(struct inode *, struct file *),
 758                                const struct cred *cred)
 759{
 760        struct file *res = do_dentry_open(dentry, mnt, f, open, cred);
 761        if (!IS_ERR(res)) {
 762                int error = open_check_o_direct(f);
 763                if (error) {
 764                        fput(res);
 765                        res = ERR_PTR(error);
 766                }
 767        } else {
 768                put_filp(f);
 769        }
 770        return res;
 771}
 772
 773/**
 774 * lookup_instantiate_filp - instantiates the open intent filp
 775 * @nd: pointer to nameidata
 776 * @dentry: pointer to dentry
 777 * @open: open callback
 778 *
 779 * Helper for filesystems that want to use lookup open intents and pass back
 780 * a fully instantiated struct file to the caller.
 781 * This function is meant to be called from within a filesystem's
 782 * lookup method.
 783 * Beware of calling it for non-regular files! Those ->open methods might block
 784 * (e.g. in fifo_open), leaving you with parent locked (and in case of fifo,
 785 * leading to a deadlock, as nobody can open that fifo anymore, because
 786 * another process to open fifo will block on locked parent when doing lookup).
 787 * Note that in case of error, nd->intent.open.file is destroyed, but the
 788 * path information remains valid.
 789 * If the open callback is set to NULL, then the standard f_op->open()
 790 * filesystem callback is substituted.
 791 */
 792struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
 793                int (*open)(struct inode *, struct file *))
 794{
 795        const struct cred *cred = current_cred();
 796
 797        if (IS_ERR(nd->intent.open.file))
 798                goto out;
 799        if (IS_ERR(dentry))
 800                goto out_err;
 801        nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
 802                                             nd->intent.open.file,
 803                                             open, cred);
 804out:
 805        return nd->intent.open.file;
 806out_err:
 807        release_open_intent(nd);
 808        nd->intent.open.file = ERR_CAST(dentry);
 809        goto out;
 810}
 811EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
 812
 813/**
 814 * nameidata_to_filp - convert a nameidata to an open filp.
 815 * @nd: pointer to nameidata
 816 * @flags: open flags
 817 *
 818 * Note that this function destroys the original nameidata
 819 */
 820struct file *nameidata_to_filp(struct nameidata *nd)
 821{
 822        const struct cred *cred = current_cred();
 823        struct file *filp;
 824
 825        /* Pick up the filp from the open intent */
 826        filp = nd->intent.open.file;
 827
 828        /* Has the filesystem initialised the file for us? */
 829        if (filp->f_path.dentry != NULL) {
 830                nd->intent.open.file = NULL;
 831        } else {
 832                struct file *res;
 833
 834                path_get(&nd->path);
 835                res = do_dentry_open(nd->path.dentry, nd->path.mnt,
 836                                     filp, NULL, cred);
 837                if (!IS_ERR(res)) {
 838                        int error;
 839
 840                        nd->intent.open.file = NULL;
 841                        BUG_ON(res != filp);
 842
 843                        error = open_check_o_direct(filp);
 844                        if (error) {
 845                                fput(filp);
 846                                filp = ERR_PTR(error);
 847                        }
 848                } else {
 849                        /* Allow nd->intent.open.file to be recycled */
 850                        filp = res;
 851                }
 852        }
 853        return filp;
 854}
 855
 856/*
 857 * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
 858 * error.
 859 */
 860struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
 861                         const struct cred *cred)
 862{
 863        int error;
 864        struct file *f;
 865
 866        validate_creds(cred);
 867
 868        /* We must always pass in a valid mount pointer. */
 869        BUG_ON(!mnt);
 870
 871        error = -ENFILE;
 872        f = get_empty_filp();
 873        if (f == NULL) {
 874                dput(dentry);
 875                mntput(mnt);
 876                return ERR_PTR(error);
 877        }
 878
 879        f->f_flags = flags;
 880        return __dentry_open(dentry, mnt, f, NULL, cred);
 881}
 882EXPORT_SYMBOL(dentry_open);
 883
 884static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 885{
 886        struct fdtable *fdt = files_fdtable(files);
 887        __clear_open_fd(fd, fdt);
 888        if (fd < files->next_fd)
 889                files->next_fd = fd;
 890}
 891
 892void put_unused_fd(unsigned int fd)
 893{
 894        struct files_struct *files = current->files;
 895        spin_lock(&files->file_lock);
 896        __put_unused_fd(files, fd);
 897        spin_unlock(&files->file_lock);
 898}
 899
 900EXPORT_SYMBOL(put_unused_fd);
 901
 902/*
 903 * Install a file pointer in the fd array.
 904 *
 905 * The VFS is full of places where we drop the files lock between
 906 * setting the open_fds bitmap and installing the file in the file
 907 * array.  At any such point, we are vulnerable to a dup2() race
 908 * installing a file in the array before us.  We need to detect this and
 909 * fput() the struct file we are about to overwrite in this case.
 910 *
 911 * It should never happen - if we allow dup2() do it, _really_ bad things
 912 * will follow.
 913 */
 914
 915void fd_install(unsigned int fd, struct file *file)
 916{
 917        struct files_struct *files = current->files;
 918        struct fdtable *fdt;
 919        spin_lock(&files->file_lock);
 920        fdt = files_fdtable(files);
 921        BUG_ON(fdt->fd[fd] != NULL);
 922        rcu_assign_pointer(fdt->fd[fd], file);
 923        spin_unlock(&files->file_lock);
 924}
 925
 926EXPORT_SYMBOL(fd_install);
 927
 928static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
 929{
 930        int lookup_flags = 0;
 931        int acc_mode;
 932
 933        if (flags & O_CREAT)
 934                op->mode = (mode & S_IALLUGO) | S_IFREG;
 935        else
 936                op->mode = 0;
 937
 938        /* Must never be set by userspace */
 939        flags &= ~FMODE_NONOTIFY;
 940
 941        /*
 942         * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
 943         * check for O_DSYNC if the need any syncing at all we enforce it's
 944         * always set instead of having to deal with possibly weird behaviour
 945         * for malicious applications setting only __O_SYNC.
 946         */
 947        if (flags & __O_SYNC)
 948                flags |= O_DSYNC;
 949
 950        /*
 951         * If we have O_PATH in the open flag. Then we
 952         * cannot have anything other than the below set of flags
 953         */
 954        if (flags & O_PATH) {
 955                flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
 956                acc_mode = 0;
 957        } else {
 958                acc_mode = MAY_OPEN | ACC_MODE(flags);
 959        }
 960
 961        op->open_flag = flags;
 962
 963        /* O_TRUNC implies we need access checks for write permissions */
 964        if (flags & O_TRUNC)
 965                acc_mode |= MAY_WRITE;
 966
 967        /* Allow the LSM permission hook to distinguish append
 968           access from general write access. */
 969        if (flags & O_APPEND)
 970                acc_mode |= MAY_APPEND;
 971
 972        op->acc_mode = acc_mode;
 973
 974        op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
 975
 976        if (flags & O_CREAT) {
 977                op->intent |= LOOKUP_CREATE;
 978                if (flags & O_EXCL)
 979                        op->intent |= LOOKUP_EXCL;
 980        }
 981
 982        if (flags & O_DIRECTORY)
 983                lookup_flags |= LOOKUP_DIRECTORY;
 984        if (!(flags & O_NOFOLLOW))
 985                lookup_flags |= LOOKUP_FOLLOW;
 986        return lookup_flags;
 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 open_flags op;
1003        int lookup = build_open_flags(flags, mode, &op);
1004        return do_filp_open(AT_FDCWD, filename, &op, lookup);
1005}
1006EXPORT_SYMBOL(filp_open);
1007
1008struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
1009                            const char *filename, int flags)
1010{
1011        struct open_flags op;
1012        int lookup = build_open_flags(flags, 0, &op);
1013        if (flags & O_CREAT)
1014                return ERR_PTR(-EINVAL);
1015        if (!filename && (flags & O_DIRECTORY))
1016                if (!dentry->d_inode->i_op->lookup)
1017                        return ERR_PTR(-ENOTDIR);
1018        return do_file_open_root(dentry, mnt, filename, &op, lookup);
1019}
1020EXPORT_SYMBOL(file_open_root);
1021
1022long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
1023{
1024        struct open_flags op;
1025        int lookup = build_open_flags(flags, mode, &op);
1026        char *tmp = getname(filename);
1027        int fd = PTR_ERR(tmp);
1028
1029        if (!IS_ERR(tmp)) {
1030                fd = get_unused_fd_flags(flags);
1031                if (fd >= 0) {
1032                        struct file *f = do_filp_open(dfd, tmp, &op, lookup);
1033                        if (IS_ERR(f)) {
1034                                put_unused_fd(fd);
1035                                fd = PTR_ERR(f);
1036                        } else {
1037                                fsnotify_open(f);
1038                                fd_install(fd, f);
1039                        }
1040                }
1041                putname(tmp);
1042        }
1043        return fd;
1044}
1045
1046SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
1047{
1048        long ret;
1049
1050        if (force_o_largefile())
1051                flags |= O_LARGEFILE;
1052
1053        ret = do_sys_open(AT_FDCWD, filename, flags, mode);
1054        /* avoid REGPARM breakage on x86: */
1055        asmlinkage_protect(3, ret, filename, flags, mode);
1056        return ret;
1057}
1058
1059SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
1060                umode_t, mode)
1061{
1062        long ret;
1063
1064        if (force_o_largefile())
1065                flags |= O_LARGEFILE;
1066
1067        ret = do_sys_open(dfd, filename, flags, mode);
1068        /* avoid REGPARM breakage on x86: */
1069        asmlinkage_protect(4, ret, dfd, filename, flags, mode);
1070        return ret;
1071}
1072
1073#ifndef __alpha__
1074
1075/*
1076 * For backward compatibility?  Maybe this should be moved
1077 * into arch/i386 instead?
1078 */
1079SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1080{
1081        return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1082}
1083
1084#endif
1085
1086/*
1087 * "id" is the POSIX thread ID. We use the
1088 * files pointer for this..
1089 */
1090int filp_close(struct file *filp, fl_owner_t id)
1091{
1092        int retval = 0;
1093
1094        if (!file_count(filp)) {
1095                printk(KERN_ERR "VFS: Close: file count is 0\n");
1096                return 0;
1097        }
1098
1099        if (filp->f_op && filp->f_op->flush)
1100                retval = filp->f_op->flush(filp, id);
1101
1102        if (likely(!(filp->f_mode & FMODE_PATH))) {
1103                dnotify_flush(filp, id);
1104                locks_remove_posix(filp, id);
1105        }
1106        fput(filp);
1107        return retval;
1108}
1109
1110EXPORT_SYMBOL(filp_close);
1111
1112/*
1113 * Careful here! We test whether the file pointer is NULL before
1114 * releasing the fd. This ensures that one clone task can't release
1115 * an fd while another clone is opening it.
1116 */
1117SYSCALL_DEFINE1(close, unsigned int, fd)
1118{
1119        struct file * filp;
1120        struct files_struct *files = current->files;
1121        struct fdtable *fdt;
1122        int retval;
1123
1124        spin_lock(&files->file_lock);
1125        fdt = files_fdtable(files);
1126        if (fd >= fdt->max_fds)
1127                goto out_unlock;
1128        filp = fdt->fd[fd];
1129        if (!filp)
1130                goto out_unlock;
1131        rcu_assign_pointer(fdt->fd[fd], NULL);
1132        __clear_close_on_exec(fd, fdt);
1133        __put_unused_fd(files, fd);
1134        spin_unlock(&files->file_lock);
1135        retval = filp_close(filp, files);
1136
1137        /* can't restart close syscall because file table entry was cleared */
1138        if (unlikely(retval == -ERESTARTSYS ||
1139                     retval == -ERESTARTNOINTR ||
1140                     retval == -ERESTARTNOHAND ||
1141                     retval == -ERESTART_RESTARTBLOCK))
1142                retval = -EINTR;
1143
1144        return retval;
1145
1146out_unlock:
1147        spin_unlock(&files->file_lock);
1148        return -EBADF;
1149}
1150EXPORT_SYMBOL(sys_close);
1151
1152/*
1153 * This routine simulates a hangup on the tty, to arrange that users
1154 * are given clean terminals at login time.
1155 */
1156SYSCALL_DEFINE0(vhangup)
1157{
1158        if (capable(CAP_SYS_TTY_CONFIG)) {
1159                tty_vhangup_self();
1160                return 0;
1161        }
1162        return -EPERM;
1163}
1164
1165/*
1166 * Called when an inode is about to be open.
1167 * We use this to disallow opening large files on 32bit systems if
1168 * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1169 * on this flag in sys_open.
1170 */
1171int generic_file_open(struct inode * inode, struct file * filp)
1172{
1173        if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1174                return -EOVERFLOW;
1175        return 0;
1176}
1177
1178EXPORT_SYMBOL(generic_file_open);
1179
1180/*
1181 * This is used by subsystems that don't want seekable
1182 * file descriptors. The function is not supposed to ever fail, the only
1183 * reason it returns an 'int' and not 'void' is so that it can be plugged
1184 * directly into file_operations structure.
1185 */
1186int nonseekable_open(struct inode *inode, struct file *filp)
1187{
1188        filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1189        return 0;
1190}
1191
1192EXPORT_SYMBOL(nonseekable_open);
1193
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