open.c

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/*
 *  linux/fs/open.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/string.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/fsnotify.h>
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/capability.h>
#include <linux/securebits.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/fcntl.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <linux/fs.h>
#include <linux/personality.h>
#include <linux/pagemap.h>
#include <linux/syscalls.h>
#include <linux/rcupdate.h>
#include <linux/audit.h>
#include <linux/falloc.h>
#include <linux/fs_struct.h>
#include <linux/ima.h>
#include <linux/dnotify.h>

#include "internal.h"

int do_truncate(struct dentry *dentry, loff_t length, unsigned int time_attrs,
    struct file *filp)
{
    int ret;
    struct iattr newattrs;

    /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
    if (length < 0)
        return -EINVAL;

    newattrs.ia_size = length;
    newattrs.ia_valid = ATTR_SIZE | time_attrs;
    if (filp) {
        newattrs.ia_file = filp;
        newattrs.ia_valid |= ATTR_FILE;
    }

    /* Remove suid/sgid on truncate too */
    ret = should_remove_suid(dentry);
    if (ret)
        newattrs.ia_valid |= ret | ATTR_FORCE;

    mutex_lock(&dentry->d_inode->i_mutex);
    ret = notify_change(dentry, &newattrs);
    mutex_unlock(&dentry->d_inode->i_mutex);
    return ret;
}

static long do_sys_truncate(const char __user *pathname, loff_t length)
{
    struct path path;
    struct inode *inode;
    int error;

    error = -EINVAL;
    if (length < 0) /* sorry, but loff_t says... */
        goto out;

    error = user_path(pathname, &path);
    if (error)
        goto out;
    inode = path.dentry->d_inode;

    /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
    error = -EISDIR;
    if (S_ISDIR(inode->i_mode))
        goto dput_and_out;

    error = -EINVAL;
    if (!S_ISREG(inode->i_mode))
        goto dput_and_out;

    error = mnt_want_write(path.mnt);
    if (error)
        goto dput_and_out;

    error = inode_permission(inode, MAY_WRITE);
    if (error)
        goto mnt_drop_write_and_out;

    error = -EPERM;
    if (IS_APPEND(inode))
        goto mnt_drop_write_and_out;

    error = get_write_access(inode);
    if (error)
        goto mnt_drop_write_and_out;

    /*
     * Make sure that there are no leases.  get_write_access() protects
     * against the truncate racing with a lease-granting setlease().
     */
    error = break_lease(inode, O_WRONLY);
    if (error)
        goto put_write_and_out;

    error = locks_verify_truncate(inode, NULL, length);
    if (!error)
        error = security_path_truncate(&path);
    if (!error)
        error = do_truncate(path.dentry, length, 0, NULL);

put_write_and_out:
    put_write_access(inode);
mnt_drop_write_and_out:
    mnt_drop_write(path.mnt);
dput_and_out:
    path_put(&path);
out:
    return error;
}

SYSCALL_DEFINE2(truncate, const char __user *, path, long, length)
{
    return do_sys_truncate(path, length);
}

static long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
    struct inode *inode;
    struct dentry *dentry;
    struct fd f;
    int error;

    error = -EINVAL;
    if (length < 0)
        goto out;
    error = -EBADF;
    f = fdget(fd);
    if (!f.file)
        goto out;

    /* explicitly opened as large or we are on 64-bit box */
    if (f.file->f_flags & O_LARGEFILE)
        small = 0;

    dentry = f.file->f_path.dentry;
    inode = dentry->d_inode;
    error = -EINVAL;
    if (!S_ISREG(inode->i_mode) || !(f.file->f_mode & FMODE_WRITE))
        goto out_putf;

    error = -EINVAL;
    /* Cannot ftruncate over 2^31 bytes without large file support */
    if (small && length > MAX_NON_LFS)
        goto out_putf;

    error = -EPERM;
    if (IS_APPEND(inode))
        goto out_putf;

    sb_start_write(inode->i_sb);
    error = locks_verify_truncate(inode, f.file, length);
    if (!error)
        error = security_path_truncate(&f.file->f_path);
    if (!error)
        error = do_truncate(dentry, length, ATTR_MTIME|ATTR_CTIME, f.file);
    sb_end_write(inode->i_sb);
out_putf:
    fdput(f);
out:
    return error;
}

SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
{
    long ret = do_sys_ftruncate(fd, length, 1);
    /* avoid REGPARM breakage on x86: */
    asmlinkage_protect(2, ret, fd, length);
    return ret;
}

/* LFS versions of truncate are only needed on 32 bit machines */
#if BITS_PER_LONG == 32
SYSCALL_DEFINE(truncate64)(const char __user * path, loff_t length)
{
    return do_sys_truncate(path, length);
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_truncate64(long path, loff_t length)
{
    return SYSC_truncate64((const char __user *) path, length);
}
SYSCALL_ALIAS(sys_truncate64, SyS_truncate64);
#endif

SYSCALL_DEFINE(ftruncate64)(unsigned int fd, loff_t length)
{
    long ret = do_sys_ftruncate(fd, length, 0);
    /* avoid REGPARM breakage on x86: */
    asmlinkage_protect(2, ret, fd, length);
    return ret;
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_ftruncate64(long fd, loff_t length)
{
    return SYSC_ftruncate64((unsigned int) fd, length);
}
SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
#endif
#endif /* BITS_PER_LONG == 32 */


int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    long ret;

    if (offset < 0 || len <= 0)
        return -EINVAL;

    /* Return error if mode is not supported */
    if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
        return -EOPNOTSUPP;

    /* Punch hole must have keep size set */
    if ((mode & FALLOC_FL_PUNCH_HOLE) &&
        !(mode & FALLOC_FL_KEEP_SIZE))
        return -EOPNOTSUPP;

    if (!(file->f_mode & FMODE_WRITE))
        return -EBADF;

    /* It's not possible punch hole on append only file */
    if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
        return -EPERM;

    if (IS_IMMUTABLE(inode))
        return -EPERM;

    /*
     * Revalidate the write permissions, in case security policy has
     * changed since the files were opened.
     */
    ret = security_file_permission(file, MAY_WRITE);
    if (ret)
        return ret;

    if (S_ISFIFO(inode->i_mode))
        return -ESPIPE;

    /*
     * Let individual file system decide if it supports preallocation
     * for directories or not.
     */
    if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
        return -ENODEV;

    /* Check for wrap through zero too */
    if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
        return -EFBIG;

    if (!file->f_op->fallocate)
        return -EOPNOTSUPP;

    sb_start_write(inode->i_sb);
    ret = file->f_op->fallocate(file, mode, offset, len);
    sb_end_write(inode->i_sb);
    return ret;
}

SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)
{
    struct fd f = fdget(fd);
    int error = -EBADF;

    if (f.file) {
        error = do_fallocate(f.file, mode, offset, len);
        fdput(f);
    }
    return error;
}

#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_fallocate(long fd, long mode, loff_t offset, loff_t len)
{
    return SYSC_fallocate((int)fd, (int)mode, offset, len);
}
SYSCALL_ALIAS(sys_fallocate, SyS_fallocate);
#endif

/*
 * access() needs to use the real uid/gid, not the effective uid/gid.
 * We do this by temporarily clearing all FS-related capabilities and
 * switching the fsuid/fsgid around to the real ones.
 */
SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
{
    const struct cred *old_cred;
    struct cred *override_cred;
    struct path path;
    struct inode *inode;
    int res;

    if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
        return -EINVAL;

    override_cred = prepare_creds();
    if (!override_cred)
        return -ENOMEM;

    override_cred->fsuid = override_cred->uid;
    override_cred->fsgid = override_cred->gid;

    if (!issecure(SECURE_NO_SETUID_FIXUP)) {
        /* Clear the capabilities if we switch to a non-root user */
        kuid_t root_uid = make_kuid(override_cred->user_ns, 0);
        if (!uid_eq(override_cred->uid, root_uid))
            cap_clear(override_cred->cap_effective);
        else
            override_cred->cap_effective =
                override_cred->cap_permitted;
    }

    old_cred = override_creds(override_cred);

    res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
    if (res)
        goto out;

    inode = path.dentry->d_inode;

    if ((mode & MAY_EXEC) && S_ISREG(inode->i_mode)) {
        /*
         * MAY_EXEC on regular files is denied if the fs is mounted
         * with the "noexec" flag.
         */
        res = -EACCES;
        if (path.mnt->mnt_flags & MNT_NOEXEC)
            goto out_path_release;
    }

    res = inode_permission(inode, mode | MAY_ACCESS);
    /* SuS v2 requires we report a read only fs too */
    if (res || !(mode & S_IWOTH) || special_file(inode->i_mode))
        goto out_path_release;
    /*
     * This is a rare case where using __mnt_is_readonly()
     * is OK without a mnt_want/drop_write() pair.  Since
     * no actual write to the fs is performed here, we do
     * not need to telegraph to that to anyone.
     *
     * By doing this, we accept that this access is
     * inherently racy and know that the fs may change
     * state before we even see this result.
     */
    if (__mnt_is_readonly(path.mnt))
        res = -EROFS;

out_path_release:
    path_put(&path);
out:
    revert_creds(old_cred);
    put_cred(override_cred);
    return res;
}

SYSCALL_DEFINE2(access, const char __user *, filename, int, mode)
{
    return sys_faccessat(AT_FDCWD, filename, mode);
}

SYSCALL_DEFINE1(chdir, const char __user *, filename)
{
    struct path path;
    int error;

    error = user_path_dir(filename, &path);
    if (error)
        goto out;

    error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
    if (error)
        goto dput_and_out;

    set_fs_pwd(current->fs, &path);

dput_and_out:
    path_put(&path);
out:
    return error;
}

SYSCALL_DEFINE1(fchdir, unsigned int, fd)
{
    struct fd f = fdget_raw(fd);
    struct inode *inode;
    int error = -EBADF;

    error = -EBADF;
    if (!f.file)
        goto out;

    inode = f.file->f_path.dentry->d_inode;

    error = -ENOTDIR;
    if (!S_ISDIR(inode->i_mode))
        goto out_putf;

    error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
    if (!error)
        set_fs_pwd(current->fs, &f.file->f_path);
out_putf:
    fdput(f);
out:
    return error;
}

SYSCALL_DEFINE1(chroot, const char __user *, filename)
{
    struct path path;
    int error;

    error = user_path_dir(filename, &path);
    if (error)
        goto out;

    error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
    if (error)
        goto dput_and_out;

    error = -EPERM;
    if (!capable(CAP_SYS_CHROOT))
        goto dput_and_out;
    error = security_path_chroot(&path);
    if (error)
        goto dput_and_out;

    set_fs_root(current->fs, &path);
    error = 0;
dput_and_out:
    path_put(&path);
out:
    return error;
}

static int chmod_common(struct path *path, umode_t mode)
{
    struct inode *inode = path->dentry->d_inode;
    struct iattr newattrs;
    int error;

    error = mnt_want_write(path->mnt);
    if (error)
        return error;
    mutex_lock(&inode->i_mutex);
    error = security_path_chmod(path, mode);
    if (error)
        goto out_unlock;
    newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
    newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
    error = notify_change(path->dentry, &newattrs);
out_unlock:
    mutex_unlock(&inode->i_mutex);
    mnt_drop_write(path->mnt);
    return error;
}

SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
{
    struct file * file;
    int err = -EBADF;

    file = fget(fd);
    if (file) {
        audit_inode(NULL, file->f_path.dentry, 0);
        err = chmod_common(&file->f_path, mode);
        fput(file);
    }
    return err;
}

SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
{
    struct path path;
    int error;

    error = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
    if (!error) {
        error = chmod_common(&path, mode);
        path_put(&path);
    }
    return error;
}

SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
{
    return sys_fchmodat(AT_FDCWD, filename, mode);
}

static int chown_common(struct path *path, uid_t user, gid_t group)
{
    struct inode *inode = path->dentry->d_inode;
    int error;
    struct iattr newattrs;
    kuid_t uid;
    kgid_t gid;

    uid = make_kuid(current_user_ns(), user);
    gid = make_kgid(current_user_ns(), group);

    newattrs.ia_valid =  ATTR_CTIME;
    if (user != (uid_t) -1) {
        if (!uid_valid(uid))
            return -EINVAL;
        newattrs.ia_valid |= ATTR_UID;
        newattrs.ia_uid = uid;
    }
    if (group != (gid_t) -1) {
        if (!gid_valid(gid))
            return -EINVAL;
        newattrs.ia_valid |= ATTR_GID;
        newattrs.ia_gid = gid;
    }
    if (!S_ISDIR(inode->i_mode))
        newattrs.ia_valid |=
            ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
    mutex_lock(&inode->i_mutex);
    error = security_path_chown(path, uid, gid);
    if (!error)
        error = notify_change(path->dentry, &newattrs);
    mutex_unlock(&inode->i_mutex);

    return error;
}

SYSCALL_DEFINE5(fchownat, int, dfd, const char __user *, filename, uid_t, user,
        gid_t, group, int, flag)
{
    struct path path;
    int error = -EINVAL;
    int lookup_flags;

    if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)) != 0)
        goto out;

    lookup_flags = (flag & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
    if (flag & AT_EMPTY_PATH)
        lookup_flags |= LOOKUP_EMPTY;
    error = user_path_at(dfd, filename, lookup_flags, &path);
    if (error)
        goto out;
    error = mnt_want_write(path.mnt);
    if (error)
        goto out_release;
    error = chown_common(&path, user, group);
    mnt_drop_write(path.mnt);
out_release:
    path_put(&path);
out:
    return error;
}

SYSCALL_DEFINE3(chown, const char __user *, filename, uid_t, user, gid_t, group)
{
    return sys_fchownat(AT_FDCWD, filename, user, group, 0);
}

SYSCALL_DEFINE3(lchown, const char __user *, filename, uid_t, user, gid_t, group)
{
    return sys_fchownat(AT_FDCWD, filename, user, group,
                AT_SYMLINK_NOFOLLOW);
}

SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
{
    struct fd f = fdget(fd);
    int error = -EBADF;

    if (!f.file)
        goto out;

    error = mnt_want_write_file(f.file);
    if (error)
        goto out_fput;
    audit_inode(NULL, f.file->f_path.dentry, 0);
    error = chown_common(&f.file->f_path, user, group);
    mnt_drop_write_file(f.file);
out_fput:
    fdput(f);
out:
    return error;
}

/*
 * You have to be very careful that these write
 * counts get cleaned up in error cases and
 * upon __fput().  This should probably never
 * be called outside of __dentry_open().
 */
static inline int __get_file_write_access(struct inode *inode,
                      struct vfsmount *mnt)
{
    int error;
    error = get_write_access(inode);
    if (error)
        return error;
    /*
     * Do not take mount writer counts on
     * special files since no writes to
     * the mount itself will occur.
     */
    if (!special_file(inode->i_mode)) {
        /*
         * Balanced in __fput()
         */
        error = __mnt_want_write(mnt);
        if (error)
            put_write_access(inode);
    }
    return error;
}

int open_check_o_direct(struct file *f)
{
    /* NB: we're sure to have correct a_ops only after f_op->open */
    if (f->f_flags & O_DIRECT) {
        if (!f->f_mapping->a_ops ||
            ((!f->f_mapping->a_ops->direct_IO) &&
            (!f->f_mapping->a_ops->get_xip_mem))) {
            return -EINVAL;
        }
    }
    return 0;
}

static int do_dentry_open(struct file *f,
              int (*open)(struct inode *, struct file *),
              const struct cred *cred)
{
    static const struct file_operations empty_fops = {};
    struct inode *inode;
    int error;

    f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK |
                FMODE_PREAD | FMODE_PWRITE;

    if (unlikely(f->f_flags & O_PATH))
        f->f_mode = FMODE_PATH;

    path_get(&f->f_path);
    inode = f->f_path.dentry->d_inode;
    if (f->f_mode & FMODE_WRITE) {
        error = __get_file_write_access(inode, f->f_path.mnt);
        if (error)
            goto cleanup_file;
        if (!special_file(inode->i_mode))
            file_take_write(f);
    }

    f->f_mapping = inode->i_mapping;
    f->f_pos = 0;
    file_sb_list_add(f, inode->i_sb);

    if (unlikely(f->f_mode & FMODE_PATH)) {
        f->f_op = &empty_fops;
        return 0;
    }

    f->f_op = fops_get(inode->i_fop);

    error = security_file_open(f, cred);
    if (error)
        goto cleanup_all;

    error = break_lease(inode, f->f_flags);
    if (error)
        goto cleanup_all;

    if (!open && f->f_op)
        open = f->f_op->open;
    if (open) {
        error = open(inode, f);
        if (error)
            goto cleanup_all;
    }
    if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
        i_readcount_inc(inode);

    f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);

    file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);

    return 0;

cleanup_all:
    fops_put(f->f_op);
    file_sb_list_del(f);
    if (f->f_mode & FMODE_WRITE) {
        put_write_access(inode);
        if (!special_file(inode->i_mode)) {
            /*
             * We don't consider this a real
             * mnt_want/drop_write() pair
             * because it all happenend right
             * here, so just reset the state.
             */
            file_reset_write(f);
            __mnt_drop_write(f->f_path.mnt);
        }
    }
cleanup_file:
    path_put(&f->f_path);
    f->f_path.mnt = NULL;
    f->f_path.dentry = NULL;
    return error;
}

int finish_open(struct file *file, struct dentry *dentry,
        int (*open)(struct inode *, struct file *),
        int *opened)
{
    int error;
    BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */

    file->f_path.dentry = dentry;
    error = do_dentry_open(file, open, current_cred());
    if (!error)
        *opened |= FILE_OPENED;

    return error;
}
EXPORT_SYMBOL(finish_open);

int finish_no_open(struct file *file, struct dentry *dentry)
{
    file->f_path.dentry = dentry;
    return 1;
}
EXPORT_SYMBOL(finish_no_open);

struct file *dentry_open(const struct path *path, int flags,
             const struct cred *cred)
{
    int error;
    struct file *f;

    validate_creds(cred);

    /* We must always pass in a valid mount pointer. */
    BUG_ON(!path->mnt);

    error = -ENFILE;
    f = get_empty_filp();
    if (f == NULL)
        return ERR_PTR(error);

    f->f_flags = flags;
    f->f_path = *path;
    error = do_dentry_open(f, NULL, cred);
    if (!error) {
        error = open_check_o_direct(f);
        if (error) {
            fput(f);
            f = ERR_PTR(error);
        }
    } else { 
        put_filp(f);
        f = ERR_PTR(error);
    }
    return f;
}
EXPORT_SYMBOL(dentry_open);

static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op)
{
    int lookup_flags = 0;
    int acc_mode;

    if (flags & O_CREAT)
        op->mode = (mode & S_IALLUGO) | S_IFREG;
    else
        op->mode = 0;

    /* Must never be set by userspace */
    flags &= ~FMODE_NONOTIFY & ~O_CLOEXEC;

    /*
     * O_SYNC is implemented as __O_SYNC|O_DSYNC.  As many places only
     * check for O_DSYNC if the need any syncing at all we enforce it's
     * always set instead of having to deal with possibly weird behaviour
     * for malicious applications setting only __O_SYNC.
     */
    if (flags & __O_SYNC)
        flags |= O_DSYNC;

    /*
     * If we have O_PATH in the open flag. Then we
     * cannot have anything other than the below set of flags
     */
    if (flags & O_PATH) {
        flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH;
        acc_mode = 0;
    } else {
        acc_mode = MAY_OPEN | ACC_MODE(flags);
    }

    op->open_flag = flags;

    /* O_TRUNC implies we need access checks for write permissions */
    if (flags & O_TRUNC)
        acc_mode |= MAY_WRITE;

    /* Allow the LSM permission hook to distinguish append
       access from general write access. */
    if (flags & O_APPEND)
        acc_mode |= MAY_APPEND;

    op->acc_mode = acc_mode;

    op->intent = flags & O_PATH ? 0 : LOOKUP_OPEN;

    if (flags & O_CREAT) {
        op->intent |= LOOKUP_CREATE;
        if (flags & O_EXCL)
            op->intent |= LOOKUP_EXCL;
    }

    if (flags & O_DIRECTORY)
        lookup_flags |= LOOKUP_DIRECTORY;
    if (!(flags & O_NOFOLLOW))
        lookup_flags |= LOOKUP_FOLLOW;
    return lookup_flags;
}

struct file *file_open_name(struct filename *name, int flags, umode_t mode)
{
    struct open_flags op;
    int lookup = build_open_flags(flags, mode, &op);
    return do_filp_open(AT_FDCWD, name, &op, lookup);
}

struct file *filp_open(const char *filename, int flags, umode_t mode)
{
    struct filename name = {.name = filename};
    return file_open_name(&name, flags, mode);
}
EXPORT_SYMBOL(filp_open);

struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
                const char *filename, int flags)
{
    struct open_flags op;
    int lookup = build_open_flags(flags, 0, &op);
    if (flags & O_CREAT)
        return ERR_PTR(-EINVAL);
    if (!filename && (flags & O_DIRECTORY))
        if (!dentry->d_inode->i_op->lookup)
            return ERR_PTR(-ENOTDIR);
    return do_file_open_root(dentry, mnt, filename, &op, lookup);
}
EXPORT_SYMBOL(file_open_root);

long do_sys_open(int dfd, const char __user *filename, int flags, umode_t mode)
{
    struct open_flags op;
    int lookup = build_open_flags(flags, mode, &op);
    struct filename *tmp = getname(filename);
    int fd = PTR_ERR(tmp);

    if (!IS_ERR(tmp)) {
        fd = get_unused_fd_flags(flags);
        if (fd >= 0) {
            struct file *f = do_filp_open(dfd, tmp, &op, lookup);
            if (IS_ERR(f)) {
                put_unused_fd(fd);
                fd = PTR_ERR(f);
            } else {
                fsnotify_open(f);
                fd_install(fd, f);
            }
        }
        putname(tmp);
    }
    return fd;
}

SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
    long ret;

    if (force_o_largefile())
        flags |= O_LARGEFILE;

    ret = do_sys_open(AT_FDCWD, filename, flags, mode);
    /* avoid REGPARM breakage on x86: */
    asmlinkage_protect(3, ret, filename, flags, mode);
    return ret;
}

SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
        umode_t, mode)
{
    long ret;

    if (force_o_largefile())
        flags |= O_LARGEFILE;

    ret = do_sys_open(dfd, filename, flags, mode);
    /* avoid REGPARM breakage on x86: */
    asmlinkage_protect(4, ret, dfd, filename, flags, mode);
    return ret;
}

#ifndef __alpha__

/*
 * For backward compatibility?  Maybe this should be moved
 * into arch/i386 instead?
 */
SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
{
    return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
}

#endif

/*
 * "id" is the POSIX thread ID. We use the
 * files pointer for this..
 */
int filp_close(struct file *filp, fl_owner_t id)
{
    int retval = 0;

    if (!file_count(filp)) {
        printk(KERN_ERR "VFS: Close: file count is 0\n");
        return 0;
    }

    if (filp->f_op && filp->f_op->flush)
        retval = filp->f_op->flush(filp, id);

    if (likely(!(filp->f_mode & FMODE_PATH))) {
        dnotify_flush(filp, id);
        locks_remove_posix(filp, id);
    }
    fput(filp);
    return retval;
}

EXPORT_SYMBOL(filp_close);

/*
 * Careful here! We test whether the file pointer is NULL before
 * releasing the fd. This ensures that one clone task can't release
 * an fd while another clone is opening it.
 */
SYSCALL_DEFINE1(close, unsigned int, fd)
{
    int retval = __close_fd(current->files, fd);

    /* can't restart close syscall because file table entry was cleared */
    if (unlikely(retval == -ERESTARTSYS ||
             retval == -ERESTARTNOINTR ||
             retval == -ERESTARTNOHAND ||
             retval == -ERESTART_RESTARTBLOCK))
        retval = -EINTR;

    return retval;
}
EXPORT_SYMBOL(sys_close);

/*
 * This routine simulates a hangup on the tty, to arrange that users
 * are given clean terminals at login time.
 */
SYSCALL_DEFINE0(vhangup)
{
    if (capable(CAP_SYS_TTY_CONFIG)) {
        tty_vhangup_self();
        return 0;
    }
    return -EPERM;
}

/*
 * Called when an inode is about to be open.
 * We use this to disallow opening large files on 32bit systems if
 * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
 * on this flag in sys_open.
 */
int generic_file_open(struct inode * inode, struct file * filp)
{
    if (!(filp->f_flags & O_LARGEFILE) && i_size_read(inode) > MAX_NON_LFS)
        return -EOVERFLOW;
    return 0;
}

EXPORT_SYMBOL(generic_file_open);

/*
 * This is used by subsystems that don't want seekable
 * file descriptors. The function is not supposed to ever fail, the only
 * reason it returns an 'int' and not 'void' is so that it can be plugged
 * directly into file_operations structure.
 */
int nonseekable_open(struct inode *inode, struct file *filp)
{
    filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
    return 0;
}

EXPORT_SYMBOL(nonseekable_open);