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        sb_start_write(inode->i_sb);
 168        error = locks_verify_truncate(inode, file, length);
 169        if (!error)
 170                error = security_path_truncate(&file->f_path);
 171        if (!error)
 172                error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, file);
 173        sb_end_write(inode->i_sb);
 174out_putf:
 175        fput(file);
 176out:
 177        return error;
 178}
 179
 180SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
 181{
 182        long ret = do_sys_ftruncate(fd, length, 1);
 183        /* avoid REGPARM breakage on x86: */
 184        asmlinkage_protect(2, ret, fd, length);
 185        return ret;
 186}
 187
 188/* LFS versions of truncate are only needed on 32 bit machines */
 189#if BITS_PER_LONG == 32
 190SYSCALL_DEFINE(truncate64)(const char __user * path, loff_t length)
 191{
 192        return do_sys_truncate(path, length);
 193}
 194#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 195asmlinkage long SyS_truncate64(long path, loff_t length)
 196{
 197        return SYSC_truncate64((const char __user *) path, length);
 198}
 199SYSCALL_ALIAS(sys_truncate64, SyS_truncate64);
 200#endif
 201
 202SYSCALL_DEFINE(ftruncate64)(unsigned int fd, loff_t length)
 203{
 204        long ret = do_sys_ftruncate(fd, length, 0);
 205        /* avoid REGPARM breakage on x86: */
 206        asmlinkage_protect(2, ret, fd, length);
 207        return ret;
 208}
 209#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 210asmlinkage long SyS_ftruncate64(long fd, loff_t length)
 211{
 212        return SYSC_ftruncate64((unsigned int) fd, length);
 213}
 214SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
 215#endif
 216#endif /* BITS_PER_LONG == 32 */
 217
 218
 219int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 220{
 221        struct inode *inode = file->f_path.dentry->d_inode;
 222        long ret;
 223
 224        if (offset < 0 || len <= 0)
 225                return -EINVAL;
 226
 227        /* Return error if mode is not supported */
 228        if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
 229                return -EOPNOTSUPP;
 230
 231        /* Punch hole must have keep size set */
 232        if ((mode & FALLOC_FL_PUNCH_HOLE) &&
 233            !(mode & FALLOC_FL_KEEP_SIZE))
 234                return -EOPNOTSUPP;
 235
 236        if (!(file->f_mode & FMODE_WRITE))
 237                return -EBADF;
 238
 239        /* It's not possible punch hole on append only file */
 240        if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
 241                return -EPERM;
 242
 243        if (IS_IMMUTABLE(inode))
 244                return -EPERM;
 245
 246        /*
 247         * Revalidate the write permissions, in case security policy has
 248         * changed since the files were opened.
 249         */
 250        ret = security_file_permission(file, MAY_WRITE);
 251        if (ret)
 252                return ret;
 253
 254        if (S_ISFIFO(inode->i_mode))
 255                return -ESPIPE;
 256
 257        /*
 258         * Let individual file system decide if it supports preallocation
 259         * for directories or not.
 260         */
 261        if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
 262                return -ENODEV;
 263
 264        /* Check for wrap through zero too */
 265        if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
 266                return -EFBIG;
 267
 268        if (!file->f_op->fallocate)
 269                return -EOPNOTSUPP;
 270
 271        sb_start_write(inode->i_sb);
 272        ret = file->f_op->fallocate(file, mode, offset, len);
 273        sb_end_write(inode->i_sb);
 274        return ret;
 275}
 276
 277SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)
 278{
 279        struct file *file;
 280        int error = -EBADF;
 281
 282        file = fget(fd);
 283        if (file) {
 284                error = do_fallocate(file, mode, offset, len);
 285                fput(file);
 286        }
 287
 288        return error;
 289}
 290
 291#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
 292asmlinkage long SyS_fallocate(long fd, long mode, loff_t offset, loff_t len)
 293{
 294        return SYSC_fallocate((int)fd, (int)mode, offset, len);
 295}
 296SYSCALL_ALIAS(sys_fallocate, SyS_fallocate);
 297#endif
 298
 299/*
 300 * access() needs to use the real uid/gid, not the effective uid/gid.
 301 * We do this by temporarily clearing all FS-related capabilities and
 302 * switching the fsuid/fsgid around to the real ones.
 303 */
 304SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 305{
 306        const struct cred *old_cred;
 307        struct cred *override_cred;
 308        struct path path;
 309        struct inode *inode;
 310        int res;
 311
 312        if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
 313                return -EINVAL;
 314
 315        override_cred = prepare_creds();
 316        if (!override_cred)
 317                return -ENOMEM;
 318
 319        override_cred->fsuid = override_cred->uid;
 320        override_cred->fsgid = override_cred->gid;
 321
 322        if (!issecure(SECURE_NO_SETUID_FIXUP)) {
 323                /* Clear the capabilities if we switch to a non-root user */
 324                kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
 325                if (!uid_eq(override_cred->uid, root_uid))
 326                        cap_clear(override_cred->cap_effective);
 327                else
 328                        override_cred->cap_effective =
 329                                override_cred->cap_permitted;
 330        }
 331
 332        old_cred = override_creds(override_cred);
 333
 334        res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
 335        if (res)
 336                goto out;
 337
 338        inode = path.dentry->d_inode;
 339
 340        if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
 341                /*
 342                 * MAY_EXEC on regular files is denied if the fs is mounted
 343                 * with the "noexec" flag.
 344                 */
 345                res = -EACCES;
 346                if (path.mnt->mnt_flags & MNT_NOEXEC)
 347                        goto out_path_release;
 348        }
 349
 350        res = inode_permission(inode, mode | MAY_ACCESS);
 351        /* SuS v2 requires we report a read only fs too */
 352        if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
 353                goto out_path_release;
 354        /*
 355         * This is a rare case where using __mnt_is_readonly()
 356         * is OK without a mnt_want/drop_write() pair.  Since
 357         * no actual write to the fs is performed here, we do
 358         * not need to telegraph to that to anyone.
 359         *
 360         * By doing this, we accept that this access is
 361         * inherently racy and know that the fs may change
 362         * state before we even see this result.
 363         */
 364        if (__mnt_is_readonly(path.mnt))
 365                res = -EROFS;
 366
 367out_path_release:
 368        path_put(&path);
 369out:
 370        revert_creds(old_cred);
 371        put_cred(override_cred);
 372        return res;
 373}
 374
 375SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
 376{
 377        return sys_faccessat(AT_FDCWD, filename, mode);
 378}
 379
 380SYSCALL_DEFINE1(chdir, const char __user *, filename)
 381{
 382        struct path path;
 383        int error;
 384
 385        error = user_path_dir(filename, &path);
 386        if (error)
 387                goto out;
 388
 389        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 390        if (error)
 391                goto dput_and_out;
 392
 393        set_fs_pwd(current->fs, &path);
 394
 395dput_and_out:
 396        path_put(&path);
 397out:
 398        return error;
 399}
 400
 401SYSCALL_DEFINE1(fchdir, unsigned int, fd)
 402{
 403        struct file *file;
 404        struct inode *inode;
 405        int error, fput_needed;
 406
 407        error = -EBADF;
 408        file = fget_raw_light(fd, &fput_needed);
 409        if (!file)
 410                goto out;
 411
 412        inode = file->f_path.dentry->d_inode;
 413
 414        error = -ENOTDIR;
 415        if (!S_ISDIR(inode->i_mode))
 416                goto out_putf;
 417
 418        error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
 419        if (!error)
 420                set_fs_pwd(current->fs, &file->f_path);
 421out_putf:
 422        fput_light(file, fput_needed);
 423out:
 424        return error;
 425}
 426
 427SYSCALL_DEFINE1(chroot, const char __user *, filename)
 428{
 429        struct path path;
 430        int error;
 431
 432        error = user_path_dir(filename, &path);
 433        if (error)
 434                goto out;
 435
 436        error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
 437        if (error)
 438                goto dput_and_out;
 439
 440        error = -EPERM;
 441        if (!capable(CAP_SYS_CHROOT))
 442                goto dput_and_out;
 443        error = security_path_chroot(&path);
 444        if (error)
 445                goto dput_and_out;
 446
 447        set_fs_root(current->fs, &path);
 448        error = 0;
 449dput_and_out:
 450        path_put(&path);
 451out:
 452        return error;
 453}
 454
 455static int chmod_common(struct path *path, umode_t mode)
 456{
 457        struct inode *inode = path->dentry->d_inode;
 458        struct iattr newattrs;
 459        int error;
 460
 461        error = mnt_want_write(path->mnt);
 462        if (error)
 463                return error;
 464        mutex_lock(&inode->i_mutex);
 465        error = security_path_chmod(path, mode);
 466        if (error)
 467                goto out_unlock;
 468        newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
 469        newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
 470        error = notify_change(path->dentry, &newattrs);
 471out_unlock:
 472        mutex_unlock(&inode->i_mutex);
 473        mnt_drop_write(path->mnt);
 474        return error;
 475}
 476
 477SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
 478{
 479        struct file * file;
 480        int err = -EBADF;
 481
 482        file = fget(fd);
 483        if (file) {
 484                audit_inode(NULL, file->f_path.dentry);
 485                err = chmod_common(&file->f_path, mode);
 486                fput(file);
 487        }
 488        return err;
 489}
 490
 491SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
 492{
 493        struct path path;
 494        int error;
 495
 496        error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
 497        if (!error) {
 498                error = chmod_common(&path, mode);
 499                path_put(&path);
 500        }
 501        return error;
 502}
 503
 504SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 505{
 506        return sys_fchmodat(AT_FDCWD, filename, mode);
 507}
 508
 509static int chown_common(struct path *path, uid_t user, gid_t group)
 510{
 511        struct inode *inode = path->dentry->d_inode;
 512        int error;
 513        struct iattr newattrs;
 514        kuid_t uid;
 515        kgid_t gid;
 516
 517        uid = make_kuid(current_user_ns(), user);
 518        gid = make_kgid(current_user_ns(), group);
 519
 520        newattrs.ia_valid =  ATTR_CTIME;
 521        if (user != (uid_t) -1) {
 522                if (!uid_valid(uid))
 523                        return -EINVAL;
 524                newattrs.ia_valid |= ATTR_UID;
 525                newattrs.ia_uid = uid;
 526        }
 527        if (group != (gid_t) -1) {
 528                if (!gid_valid(gid))
 529                        return -EINVAL;
 530                newattrs.ia_valid |= ATTR_GID;
 531                newattrs.ia_gid = gid;
 532        }
 533        if (!S_ISDIR(inode->i_mode))
 534                newattrs.ia_valid |=
 535                        ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
 536        mutex_lock(&inode->i_mutex);
 537        error = security_path_chown(path, user, group);
 538        if (!error)
 539                error = notify_change(path->dentry, &newattrs);
 540        mutex_unlock(&inode->i_mutex);
 541
 542        return error;
 543}
 544
 545SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
 546                gid_t, group, int, flag)
 547{
 548        struct path path;
 549        int error = -EINVAL;
 550        int lookup_flags;
 551
 552        if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
 553                goto out;
 554
 555        lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
 556        if (flag & AT_EMPTY_PATH)
 557                lookup_flags |= LOOKUP_EMPTY;
 558        error = user_path_at(dfd, filename, lookup_flags, &path);
 559        if (error)
 560                goto out;
 561        error = mnt_want_write(path.mnt);
 562        if (error)
 563                goto out_release;
 564        error = chown_common(&path, user, group);
 565        mnt_drop_write(path.mnt);
 566out_release:
 567        path_put(&path);
 568out:
 569        return error;
 570}
 571
 572SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
 573{
 574        return sys_fchownat(AT_FDCWD, filename, user, group, 0);
 575}
 576
 577SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
 578{
 579        return sys_fchownat(AT_FDCWD, filename, user, group,
 580                            AT_SYMLINK_NOFOLLOW);
 581}
 582
 583SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
 584{
 585        struct file * file;
 586        int error = -EBADF;
 587        struct dentry * dentry;
 588
 589        file = fget(fd);
 590        if (!file)
 591                goto out;
 592
 593        error = mnt_want_write_file(file);
 594        if (error)
 595                goto out_fput;
 596        dentry = file->f_path.dentry;
 597        audit_inode(NULL, dentry);
 598        error = chown_common(&file->f_path, user, group);
 599        mnt_drop_write_file(file);
 600out_fput:
 601        fput(file);
 602out:
 603        return error;
 604}
 605
 606/*
 607 * You have to be very careful that these write
 608 * counts get cleaned up in error cases and
 609 * upon __fput().  This should probably never
 610 * be called outside of __dentry_open().
 611 */
 612static inline int __get_file_write_access(struct inode *inode,
 613                                          struct vfsmount *mnt)
 614{
 615        int error;
 616        error = get_write_access(inode);
 617        if (error)
 618                return error;
 619        /*
 620         * Do not take mount writer counts on
 621         * special files since no writes to
 622         * the mount itself will occur.
 623         */
 624        if (!special_file(inode->i_mode)) {
 625                /*
 626                 * Balanced in __fput()
 627                 */
 628                error = __mnt_want_write(mnt);
 629                if (error)
 630                        put_write_access(inode);
 631        }
 632        return error;
 633}
 634
 635int open_check_o_direct(struct file *f)
 636{
 637        /* NB: we're sure to have correct a_ops only after f_op->open */
 638        if (f->f_flags & O_DIRECT) {
 639                if (!f->f_mapping->a_ops ||
 640                    ((!f->f_mapping->a_ops->direct_IO) &&
 641                    (!f->f_mapping->a_ops->get_xip_mem))) {
 642                        return -EINVAL;
 643                }
 644        }
 645        return 0;
 646}
 647
 648static int do_dentry_open(struct file *f,
 649                          int (*open)(struct inode *, struct file *),
 650                          const struct cred *cred)
 651{
 652        static const struct file_operations empty_fops = {};
 653        struct inode *inode;
 654        int error;
 655
 656        f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
 657                                FMODE_PREAD | FMODE_PWRITE;
 658
 659        if (unlikely(f->f_flags & O_PATH))
 660                f->f_mode = FMODE_PATH;
 661
 662        path_get(&f->f_path);
 663        inode = f->f_path.dentry->d_inode;
 664        if (f->f_mode & FMODE_WRITE) {
 665                error = __get_file_write_access(inode, f->f_path.mnt);
 666                if (error)
 667                        goto cleanup_file;
 668                if (!special_file(inode->i_mode))
 669                        file_take_write(f);
 670        }
 671
 672        f->f_mapping = inode->i_mapping;
 673        f->f_pos = 0;
 674        file_sb_list_add(f, inode->i_sb);
 675
 676        if (unlikely(f->f_mode & FMODE_PATH)) {
 677                f->f_op = &empty_fops;
 678                return 0;
 679        }
 680
 681        f->f_op = fops_get(inode->i_fop);
 682
 683        error = security_file_open(f, cred);
 684        if (error)
 685                goto cleanup_all;
 686
 687        error = break_lease(inode, f->f_flags);
 688        if (error)
 689                goto cleanup_all;
 690
 691        if (!open && f->f_op)
 692                open = f->f_op->open;
 693        if (open) {
 694                error = open(inode, f);
 695                if (error)
 696                        goto cleanup_all;
 697        }
 698        if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
 699                i_readcount_inc(inode);
 700
 701        f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 702
 703        file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
 704
 705        return 0;
 706
 707cleanup_all:
 708        fops_put(f->f_op);
 709        file_sb_list_del(f);
 710        if (f->f_mode & FMODE_WRITE) {
 711                put_write_access(inode);
 712                if (!special_file(inode->i_mode)) {
 713                        /*
 714                         * We don't consider this a real
 715                         * mnt_want/drop_write() pair
 716                         * because it all happenend right
 717                         * here, so just reset the state.
 718                         */
 719                        file_reset_write(f);
 720                        __mnt_drop_write(f->f_path.mnt);
 721                }
 722        }
 723cleanup_file:
 724        path_put(&f->f_path);
 725        f->f_path.mnt = NULL;
 726        f->f_path.dentry = NULL;
 727        return error;
 728}
 729
 730/**
 731 * finish_open - finish opening a file
 732 * @od: opaque open data
 733 * @dentry: pointer to dentry
 734 * @open: open callback
 735 *
 736 * This can be used to finish opening a file passed to i_op->atomic_open().
 737 *
 738 * If the open callback is set to NULL, then the standard f_op->open()
 739 * filesystem callback is substituted.
 740 */
 741int finish_open(struct file *file, struct dentry *dentry,
 742                int (*open)(struct inode *, struct file *),
 743                int *opened)
 744{
 745        int error;
 746        BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */
 747
 748        file->f_path.dentry = dentry;
 749        error = do_dentry_open(file, open, current_cred());
 750        if (!error)
 751                *opened |= FILE_OPENED;
 752
 753        return error;
 754}
 755EXPORT_SYMBOL(finish_open);
 756
 757/**
 758 * finish_no_open - finish ->atomic_open() without opening the file
 759 *
 760 * @od: opaque open data
 761 * @dentry: dentry or NULL (as returned from ->lookup())
 762 *
 763 * This can be used to set the result of a successful lookup in ->atomic_open().
 764 * The filesystem's atomic_open() method shall return NULL after calling this.
 765 */
 766int finish_no_open(struct file *file, struct dentry *dentry)
 767{
 768        file->f_path.dentry = dentry;
 769        return 1;
 770}
 771EXPORT_SYMBOL(finish_no_open);
 772
 773struct file *dentry_open(const struct path *path, int flags,
 774                         const struct cred *cred)
 775{
 776        int error;
 777        struct file *f;
 778
 779        validate_creds(cred);
 780
 781        /* We must always pass in a valid mount pointer. */
 782        BUG_ON(!path->mnt);
 783
 784        error = -ENFILE;
 785        f = get_empty_filp();
 786        if (f == NULL)
 787                return ERR_PTR(error);
 788
 789        f->f_flags = flags;
 790        f->f_path = *path;
 791        error = do_dentry_open(f, NULL, cred);
 792        if (!error) {
 793                error = open_check_o_direct(f);
 794                if (error) {
 795                        fput(f);
 796                        f = ERR_PTR(error);
 797                }
 798        } else { 
 799                put_filp(f);
 800                f = ERR_PTR(error);
 801        }
 802        return f;
 803}
 804EXPORT_SYMBOL(dentry_open);
 805
 806static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 807{
 808        struct fdtable *fdt = files_fdtable(files);
 809        __clear_open_fd(fd, fdt);
 810        if (fd < files->next_fd)
 811                files->next_fd = fd;
 812}
 813
 814void put_unused_fd(unsigned int fd)
 815{
 816        struct files_struct *files = current->files;
 817        spin_lock(&files->file_lock);
 818        __put_unused_fd(files, fd);
 819        spin_unlock(&files->file_lock);
 820}
 821
 822EXPORT_SYMBOL(put_unused_fd);
 823
 824/*
 825 * Install a file pointer in the fd array.
 826 *
 827 * The VFS is full of places where we drop the files lock between
 828 * setting the open_fds bitmap and installing the file in the file
 829 * array.  At any such point, we are vulnerable to a dup2() race
 830 * installing a file in the array before us.  We need to detect this and
 831 * fput() the struct file we are about to overwrite in this case.
 832 *
 833 * It should never happen - if we allow dup2() do it, _really_ bad things
 834 * will follow.
 835 */
 836
 837void fd_install(unsigned int fd, struct file *file)
 838{
 839        struct files_struct *files = current->files;
 840        struct fdtable *fdt;
 841        spin_lock(&files->file_lock);
 842        fdt = files_fdtable(files);
 843        BUG_ON(fdt->fd[fd] != NULL);
 844        rcu_assign_pointer(fdt->fd[fd], file);
 845        spin_unlock(&files->file_lock);
 846}
 847
 848EXPORT_SYMBOL(fd_install);
 849
 850static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
 851{
 852        int lookup_flags = 0;
 853        int acc_mode;
 854
 855        if (flags & O_CREAT)
 856                op->mode = (mode & S_IALLUGO) | S_IFREG;
 857        else
 858                op->mode = 0;
 859
 860        /* Must never be set by userspace */
 861        flags &= ~FMODE_NONOTIFY;
 862
 863        /*
 864         * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
 865         * check for O_DSYNC if the need any syncing at all we enforce it's
 866         * always set instead of having to deal with possibly weird behaviour
 867         * for malicious applications setting only __O_SYNC.
 868         */
 869        if (flags & __O_SYNC)
 870                flags |= O_DSYNC;
 871
 872        /*
 873         * If we have O_PATH in the open flag. Then we
 874         * cannot have anything other than the below set of flags
 875         */
 876        if (flags & O_PATH) {
 877                flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
 878                acc_mode = 0;
 879        } else {
 880                acc_mode = MAY_OPEN | ACC_MODE(flags);
 881        }
 882
 883        op->open_flag = flags;
 884
 885        /* O_TRUNC implies we need access checks for write permissions */
 886        if (flags & O_TRUNC)
 887                acc_mode |= MAY_WRITE;
 888
 889        /* Allow the LSM permission hook to distinguish append
 890           access from general write access. */
 891        if (flags & O_APPEND)
 892                acc_mode |= MAY_APPEND;
 893
 894        op->acc_mode = acc_mode;
 895
 896        op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;
 897
 898        if (flags & O_CREAT) {
 899                op->intent |= LOOKUP_CREATE;
 900                if (flags & O_EXCL)
 901                        op->intent |= LOOKUP_EXCL;
 902        }
 903
 904        if (flags & O_DIRECTORY)
 905                lookup_flags |= LOOKUP_DIRECTORY;
 906        if (!(flags & O_NOFOLLOW))
 907                lookup_flags |= LOOKUP_FOLLOW;
 908        return lookup_flags;
 909}
 910
 911/**
 912 * filp_open - open file and return file pointer
 913 *
 914 * @filename:   path to open
 915 * @flags:      open flags as per the open(2) second argument
 916 * @mode:       mode for the new file if O_CREAT is set, else ignored
 917 *
 918 * This is the helper to open a file from kernelspace if you really
 919 * have to.  But in generally you should not do this, so please move
 920 * along, nothing to see here..
 921 */
 922struct file *filp_open(const char *filename, int flags, umode_t mode)
 923{
 924        struct open_flags op;
 925        int lookup = build_open_flags(flags, mode, &op);
 926        return do_filp_open(AT_FDCWD, filename, &op, lookup);
 927}
 928EXPORT_SYMBOL(filp_open);
 929
 930struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
 931                            const char *filename, int flags)
 932{
 933        struct open_flags op;
 934        int lookup = build_open_flags(flags, 0, &op);
 935        if (flags & O_CREAT)
 936                return ERR_PTR(-EINVAL);
 937        if (!filename && (flags & O_DIRECTORY))
 938                if (!dentry->d_inode->i_op->lookup)
 939                        return ERR_PTR(-ENOTDIR);
 940        return do_file_open_root(dentry, mnt, filename, &op, lookup);
 941}
 942EXPORT_SYMBOL(file_open_root);
 943
 944long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
 945{
 946        struct open_flags op;
 947        int lookup = build_open_flags(flags, mode, &op);
 948        char *tmp = getname(filename);
 949        int fd = PTR_ERR(tmp);
 950
 951        if (!IS_ERR(tmp)) {
 952                fd = get_unused_fd_flags(flags);
 953                if (fd >= 0) {
 954                        struct file *f = do_filp_open(dfd, tmp, &op, lookup);
 955                        if (IS_ERR(f)) {
 956                                put_unused_fd(fd);
 957                                fd = PTR_ERR(f);
 958                        } else {
 959                                fsnotify_open(f);
 960                                fd_install(fd, f);
 961                        }
 962                }
 963                putname(tmp);
 964        }
 965        return fd;
 966}
 967
 968SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
 969{
 970        long ret;
 971
 972        if (force_o_largefile())
 973                flags |= O_LARGEFILE;
 974
 975        ret = do_sys_open(AT_FDCWD, filename, flags, mode);
 976        /* avoid REGPARM breakage on x86: */
 977        asmlinkage_protect(3, ret, filename, flags, mode);
 978        return ret;
 979}
 980
 981SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
 982                umode_t, mode)
 983{
 984        long ret;
 985
 986        if (force_o_largefile())
 987                flags |= O_LARGEFILE;
 988
 989        ret = do_sys_open(dfd, filename, flags, mode);
 990        /* avoid REGPARM breakage on x86: */
 991        asmlinkage_protect(4, ret, dfd, filename, flags, mode);
 992        return ret;
 993}
 994
 995#ifndef __alpha__
 996
 997/*
 998 * For backward compatibility?  Maybe this should be moved
 999 * into arch/i386 instead?
1000 */
1001SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
1002{
1003        return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
1004}
1005
1006#endif
1007
1008/*
1009 * "id" is the POSIX thread ID. We use the
1010 * files pointer for this..
1011 */
1012int filp_close(struct file *filp, fl_owner_t id)
1013{
1014        int retval = 0;
1015
1016        if (!file_count(filp)) {
1017                printk(KERN_ERR "VFS: Close: file count is 0\n");
1018                return 0;
1019        }
1020
1021        if (filp->f_op && filp->f_op->flush)
1022                retval = filp->f_op->flush(filp, id);
1023
1024        if (likely(!(filp->f_mode & FMODE_PATH))) {
1025                dnotify_flush(filp, id);
1026                locks_remove_posix(filp, id);
1027        }
1028        fput(filp);
1029        return retval;
1030}
1031
1032EXPORT_SYMBOL(filp_close);
1033
1034/*
1035 * Careful here! We test whether the file pointer is NULL before
1036 * releasing the fd. This ensures that one clone task can't release
1037 * an fd while another clone is opening it.
1038 */
1039SYSCALL_DEFINE1(close, unsigned int, fd)
1040{
1041        struct file * filp;
1042        struct files_struct *files = current->files;
1043        struct fdtable *fdt;
1044        int retval;
1045
1046        spin_lock(&files->file_lock);
1047        fdt = files_fdtable(files);
1048        if (fd >= fdt->max_fds)
1049                goto out_unlock;
1050        filp = fdt->fd[fd];
1051        if (!filp)
1052                goto out_unlock;
1053        rcu_assign_pointer(fdt->fd[fd], NULL);
1054        __clear_close_on_exec(fd, fdt);
1055        __put_unused_fd(files, fd);
1056        spin_unlock(&files->file_lock);
1057        retval = filp_close(filp, files);
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
1068out_unlock:
1069        spin_unlock(&files->file_lock);
1070        return -EBADF;
1071}
1072EXPORT_SYMBOL(sys_close);
1073
1074/*
1075 * This routine simulates a hangup on the tty, to arrange that users
1076 * are given clean terminals at login time.
1077 */
1078SYSCALL_DEFINE0(vhangup)
1079{
1080        if (capable(CAP_SYS_TTY_CONFIG)) {
1081                tty_vhangup_self();
1082                return 0;
1083        }
1084        return -EPERM;
1085}
1086
1087/*
1088 * Called when an inode is about to be open.
1089 * We use this to disallow opening large files on 32bit systems if
1090 * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
1091 * on this flag in sys_open.
1092 */
1093int generic_file_open(struct inode * inode, struct file * filp)
1094{
1095        if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
1096                return -EOVERFLOW;
1097        return 0;
1098}
1099
1100EXPORT_SYMBOL(generic_file_open);
1101
1102/*
1103 * This is used by subsystems that don't want seekable
1104 * file descriptors. The function is not supposed to ever fail, the only
1105 * reason it returns an 'int' and not 'void' is so that it can be plugged
1106 * directly into file_operations structure.
1107 */
1108int nonseekable_open(struct inode *inode, struct file *filp)
1109{
1110        filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
1111        return 0;
1112}
1113
1114EXPORT_SYMBOL(nonseekable_open);
1115
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