f_writefile(typval_T *argvars, typval_T *rettv)
{
    int		binary = FALSE;
    int		append = FALSE;
#ifdef HAVE_FSYNC
    int		do_fsync = p_fs;
#endif
    char_u	*fname;
    FILE	*fd;
    int		ret = 0;
    listitem_T	*li;
    list_T	*list = NULL;
    blob_T	*blob = NULL;

    rettv->vval.v_number = -1;
    if (check_secure())
	return;

    if (in_vim9script()
	    && (check_for_list_or_blob_arg(argvars, 0) == FAIL
		|| check_for_string_arg(argvars, 1) == FAIL
		|| check_for_opt_string_arg(argvars, 2) == FAIL))
	return;

    if (argvars[0].v_type == VAR_LIST)
    {
	list = argvars[0].vval.v_list;
	if (list == NULL)
	    return;
	CHECK_LIST_MATERIALIZE(list);
	FOR_ALL_LIST_ITEMS(list, li)
	    if (tv_get_string_chk(&li->li_tv) == NULL)
		return;
    }
    else if (argvars[0].v_type == VAR_BLOB)
    {
	blob = argvars[0].vval.v_blob;
	if (blob == NULL)
	    return;
    }
    else
    {
	semsg(_(e_invalid_argument_str),
		_("writefile() first argument must be a List or a Blob"));
	return;
    }

    if (argvars[2].v_type != VAR_UNKNOWN)
    {
	char_u *arg2 = tv_get_string_chk(&argvars[2]);

	if (arg2 == NULL)
	    return;
	if (vim_strchr(arg2, 'b') != NULL)
	    binary = TRUE;
	if (vim_strchr(arg2, 'a') != NULL)
	    append = TRUE;
#ifdef HAVE_FSYNC
	if (vim_strchr(arg2, 's') != NULL)
	    do_fsync = TRUE;
	else if (vim_strchr(arg2, 'S') != NULL)
	    do_fsync = FALSE;
#endif
    }

    fname = tv_get_string_chk(&argvars[1]);
    if (fname == NULL)
	return;

    // Always open the file in binary mode, library functions have a mind of
    // their own about CR-LF conversion.
    if (*fname == NUL || (fd = mch_fopen((char *)fname,
				      append ? APPENDBIN : WRITEBIN)) == NULL)
    {
	semsg(_(e_cant_create_file_str), *fname == NUL ? (char_u *)_("<empty>") : fname);
	ret = -1;
    }
    else if (blob)
    {
	if (write_blob(fd, blob) == FAIL)
	    ret = -1;
#ifdef HAVE_FSYNC
	else if (do_fsync)
	    // Ignore the error, the user wouldn't know what to do about it.
	    // May happen for a device.
	    vim_ignored = vim_fsync(fileno(fd));
#endif
	fclose(fd);
    }
    else
    {
	if (write_list(fd, list, binary) == FAIL)
	    ret = -1;
#ifdef HAVE_FSYNC
	else if (do_fsync)
	    // Ignore the error, the user wouldn't know what to do about it.
	    // May happen for a device.
	    vim_ignored = vim_fsync(fileno(fd));
#endif
	fclose(fd);
    }

    rettv->vval.v_number = ret;
}


skipwhite(char_u *q)
{
    char_u	*p = q;

    while (VIM_ISWHITE(*p))
	++p;
    return p;
}

patch 8.2.4418: crash when using special multi-byte character

Problem:    Crash when using special multi-byte character.
Solution:   Don't use isalpha() for an arbitrary character.


readdirex_checkitem(void *context, void *item)
{
    dict_T	*dict = (dict_T*)item;

    return checkitem_common(context, NULL, dict);
}


checkitem_common(void *context, char_u *name, dict_T *dict)
{
    typval_T	*expr = (typval_T *)context;
    typval_T	save_val;
    typval_T	rettv;
    typval_T	argv[2];
    int		retval = 0;
    int		error = FALSE;

    prepare_vimvar(VV_VAL, &save_val);
    if (name != NULL)
    {
	set_vim_var_string(VV_VAL, name, -1);
	argv[0].v_type = VAR_STRING;
	argv[0].vval.v_string = name;
    }
    else
    {
	set_vim_var_dict(VV_VAL, dict);
	argv[0].v_type = VAR_DICT;
	argv[0].vval.v_dict = dict;
    }

    if (eval_expr_typval(expr, argv, 1, &rettv) == FAIL)
	goto theend;

    // We want to use -1, but also true/false should be allowed.
    if (rettv.v_type == VAR_SPECIAL || rettv.v_type == VAR_BOOL)
    {
	rettv.v_type = VAR_NUMBER;
	rettv.vval.v_number = rettv.vval.v_number == VVAL_TRUE;
    }
    retval = tv_get_number_chk(&rettv, &error);
    if (error)
	retval = -1;
    clear_tv(&rettv);

theend:
    if (name != NULL)
	set_vim_var_string(VV_VAL, NULL, 0);
    else
	set_vim_var_dict(VV_VAL, NULL);
    restore_vimvar(VV_VAL, &save_val);
    return retval;
}


vim_isfilec(int c)
{
    return (c >= 0x100 || (c > 0 && (g_chartab[c] & CT_FNAME_CHAR)));
}


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

Safer ABI for O_TMPFILE

[suggested by Rasmus Villemoes] make O_DIRECTORY | O_RDWR part of O_TMPFILE;
that will fail on old kernels in a lot more cases than what I came up with.
And make sure O_CREAT doesn't get there...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>


SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
		int, newdfd, const char __user *, newname, int, flags)
{
	struct dentry *new_dentry;
	struct path old_path, new_path;
	int how = 0;
	int error;

	if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
		return -EINVAL;
	/*
	 * To use null names we require CAP_DAC_READ_SEARCH
	 * This ensures that not everyone will be able to create
	 * handlink using the passed filedescriptor.
	 */
	if (flags & AT_EMPTY_PATH) {
		if (!capable(CAP_DAC_READ_SEARCH))
			return -ENOENT;
		how = LOOKUP_EMPTY;
	}

	if (flags & AT_SYMLINK_FOLLOW)
		how |= LOOKUP_FOLLOW;
retry:
	error = user_path_at(olddfd, oldname, how, &old_path);
	if (error)
		return error;

	new_dentry = user_path_create(newdfd, newname, &new_path,
					(how & LOOKUP_REVAL));
	error = PTR_ERR(new_dentry);
	if (IS_ERR(new_dentry))
		goto out;

	error = -EXDEV;
	if (old_path.mnt != new_path.mnt)
		goto out_dput;
	error = may_linkat(&old_path);
	if (unlikely(error))
		goto out_dput;
	error = security_path_link(old_path.dentry, &new_path, new_dentry);
	if (error)
		goto out_dput;
	error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
out_dput:
	done_path_create(&new_path, new_dentry);
	if (retry_estale(error, how)) {
		how |= LOOKUP_REVAL;
		goto retry;
	}
out:
	path_put(&old_path);

	return error;
}


static inline unsigned int fold_hash(unsigned long hash)
{
	hash += hash >> (8*sizeof(int));
	return hash;
}


SYSCALL_DEFINE1(chdir, const char __user *, filename)
{
	struct path path;
	int error;
	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
retry:
	error = user_path_at(AT_FDCWD, filename, lookup_flags, &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);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
out:
	return error;
}


COMPAT_SYSCALL_DEFINE2(ftruncate, unsigned int, fd, compat_ulong_t, length)
{
	return do_sys_ftruncate(fd, length, 1);
}


SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
{
	return sys_symlinkat(oldname, AT_FDCWD, newname);
}


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


unsigned int full_name_hash(const unsigned char *name, unsigned int len)
{
	unsigned long a, mask;
	unsigned long hash = 0;

	for (;;) {
		a = load_unaligned_zeropad(name);
		if (len < sizeof(unsigned long))
			break;
		hash += a;
		hash *= 9;
		name += sizeof(unsigned long);
		len -= sizeof(unsigned long);
		if (!len)
			goto done;
	}
	mask = ~(~0ul << len*8);
	hash += mask & a;
done:
	return fold_hash(hash);
}


static inline int should_follow_link(struct inode *inode, int follow)
{
	if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
		if (likely(inode->i_op->follow_link))
			return follow;

		/* This gets set once for the inode lifetime */
		spin_lock(&inode->i_lock);
		inode->i_opflags |= IOP_NOFOLLOW;
		spin_unlock(&inode->i_lock);
	}
	return 0;
}


SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
{
	if ((flag & ~AT_REMOVEDIR) != 0)
		return -EINVAL;

	if (flag & AT_REMOVEDIR)
		return do_rmdir(dfd, pathname);

	return do_unlinkat(dfd, pathname);
}


SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
		int, newdfd, const char __user *, newname)
{
	struct dentry *old_dir, *new_dir;
	struct dentry *old_dentry, *new_dentry;
	struct dentry *trap;
	struct nameidata oldnd, newnd;
	struct filename *from;
	struct filename *to;
	unsigned int lookup_flags = 0;
	bool should_retry = false;
	int error;
retry:
	from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
	if (IS_ERR(from)) {
		error = PTR_ERR(from);
		goto exit;
	}

	to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
	if (IS_ERR(to)) {
		error = PTR_ERR(to);
		goto exit1;
	}

	error = -EXDEV;
	if (oldnd.path.mnt != newnd.path.mnt)
		goto exit2;

	old_dir = oldnd.path.dentry;
	error = -EBUSY;
	if (oldnd.last_type != LAST_NORM)
		goto exit2;

	new_dir = newnd.path.dentry;
	if (newnd.last_type != LAST_NORM)
		goto exit2;

	error = mnt_want_write(oldnd.path.mnt);
	if (error)
		goto exit2;

	oldnd.flags &= ~LOOKUP_PARENT;
	newnd.flags &= ~LOOKUP_PARENT;
	newnd.flags |= LOOKUP_RENAME_TARGET;

	trap = lock_rename(new_dir, old_dir);

	old_dentry = lookup_hash(&oldnd);
	error = PTR_ERR(old_dentry);
	if (IS_ERR(old_dentry))
		goto exit3;
	/* source must exist */
	error = -ENOENT;
	if (!old_dentry->d_inode)
		goto exit4;
	/* unless the source is a directory trailing slashes give -ENOTDIR */
	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
		error = -ENOTDIR;
		if (oldnd.last.name[oldnd.last.len])
			goto exit4;
		if (newnd.last.name[newnd.last.len])
			goto exit4;
	}
	/* source should not be ancestor of target */
	error = -EINVAL;
	if (old_dentry == trap)
		goto exit4;
	new_dentry = lookup_hash(&newnd);
	error = PTR_ERR(new_dentry);
	if (IS_ERR(new_dentry))
		goto exit4;
	/* target should not be an ancestor of source */
	error = -ENOTEMPTY;
	if (new_dentry == trap)
		goto exit5;

	error = security_path_rename(&oldnd.path, old_dentry,
				     &newnd.path, new_dentry);
	if (error)
		goto exit5;
	error = vfs_rename(old_dir->d_inode, old_dentry,
				   new_dir->d_inode, new_dentry);
exit5:
	dput(new_dentry);
exit4:
	dput(old_dentry);
exit3:
	unlock_rename(new_dir, old_dir);
	mnt_drop_write(oldnd.path.mnt);
exit2:
	if (retry_estale(error, lookup_flags))
		should_retry = true;
	path_put(&newnd.path);
	putname(to);
exit1:
	path_put(&oldnd.path);
	putname(from);
	if (should_retry) {
		should_retry = false;
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
exit:
	return error;
}


static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
{
	int error = security_path_mknod(dir, dentry, mode, 0);
	if (error)
		return error;

	error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
	if (error)
		return error;

	return security_inode_create(dir->dentry->d_inode, dentry, mode);
}


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);

	f = get_empty_filp();
	if (!IS_ERR(f)) {
		f->f_flags = flags;
		f->f_path = *path;
		error = do_dentry_open(f, NULL, cred);
		if (!error) {
			/* from now on we need fput() to dispose of f */
			error = open_check_o_direct(f);
			if (error) {
				fput(f);
				f = ERR_PTR(error);
			}
		} else {
			put_filp(f);
			f = ERR_PTR(error);
		}
	}
	return f;
}


static inline bool managed_dentry_might_block(struct dentry *dentry)
{
	return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
		dentry->d_op->d_manage(dentry, true) < 0);
}


struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
{
	struct qstr this;
	unsigned int c;
	int err;

	WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));

	this.name = name;
	this.len = len;
	this.hash = full_name_hash(name, len);
	if (!len)
		return ERR_PTR(-EACCES);

	if (unlikely(name[0] == '.')) {
		if (len < 2 || (len == 2 && name[1] == '.'))
			return ERR_PTR(-EACCES);
	}

	while (len--) {
		c = *(const unsigned char *)name++;
		if (c == '/' || c == '\0')
			return ERR_PTR(-EACCES);
	}
	/*
	 * See if the low-level filesystem might want
	 * to use its own hash..
	 */
	if (base->d_flags & DCACHE_OP_HASH) {
		int err = base->d_op->d_hash(base, &this);
		if (err < 0)
			return ERR_PTR(err);
	}

	err = inode_permission(base->d_inode, MAY_EXEC);
	if (err)
		return ERR_PTR(err);

	return __lookup_hash(&this, base, 0);
}


void dentry_unhash(struct dentry *dentry)
{
	shrink_dcache_parent(dentry);
	spin_lock(&dentry->d_lock);
	if (dentry->d_count == 1)
		__d_drop(dentry);
	spin_unlock(&dentry->d_lock);
}


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


int nonseekable_open(struct inode *inode, struct file *filp)
{
	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
	return 0;
}


static struct file *path_openat(int dfd, struct filename *pathname,
		struct nameidata *nd, const struct open_flags *op, int flags)
{
	struct file *base = NULL;
	struct file *file;
	struct path path;
	int opened = 0;
	int error;

	file = get_empty_filp();
	if (IS_ERR(file))
		return file;

	file->f_flags = op->open_flag;

	if (unlikely(file->f_flags & __O_TMPFILE)) {
		error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened);
		goto out;
	}

	error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
	if (unlikely(error))
		goto out;

	current->total_link_count = 0;
	error = link_path_walk(pathname->name, nd);
	if (unlikely(error))
		goto out;

	error = do_last(nd, &path, file, op, &opened, pathname);
	while (unlikely(error > 0)) { /* trailing symlink */
		struct path link = path;
		void *cookie;
		if (!(nd->flags & LOOKUP_FOLLOW)) {
			path_put_conditional(&path, nd);
			path_put(&nd->path);
			error = -ELOOP;
			break;
		}
		error = may_follow_link(&link, nd);
		if (unlikely(error))
			break;
		nd->flags |= LOOKUP_PARENT;
		nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
		error = follow_link(&link, nd, &cookie);
		if (unlikely(error))
			break;
		error = do_last(nd, &path, file, op, &opened, pathname);
		put_link(nd, &link, cookie);
	}
out:
	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
		path_put(&nd->root);
	if (base)
		fput(base);
	if (!(opened & FILE_OPENED)) {
		BUG_ON(!error);
		put_filp(file);
	}
	if (unlikely(error)) {
		if (error == -EOPENSTALE) {
			if (flags & LOOKUP_RCU)
				error = -ECHILD;
			else
				error = -ESTALE;
		}
		file = ERR_PTR(error);
	}
	return file;
}


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;
}


struct dentry *user_path_create(int dfd, const char __user *pathname,
				struct path *path, unsigned int lookup_flags)
{
	struct filename *tmp = getname(pathname);
	struct dentry *res;
	if (IS_ERR(tmp))
		return ERR_CAST(tmp);
	res = kern_path_create(dfd, tmp->name, path, lookup_flags);
	putname(tmp);
	return res;
}


SYSCALL_DEFINE2(ftruncate, unsigned int, fd, unsigned long, length)
{
	return do_sys_ftruncate(fd, length, 1);
}


static long do_rmdir(int dfd, const char __user *pathname)
{
	int error = 0;
	struct filename *name;
	struct dentry *dentry;
	struct nameidata nd;
	unsigned int lookup_flags = 0;
retry:
	name = user_path_parent(dfd, pathname, &nd, lookup_flags);
	if (IS_ERR(name))
		return PTR_ERR(name);

	switch(nd.last_type) {
	case LAST_DOTDOT:
		error = -ENOTEMPTY;
		goto exit1;
	case LAST_DOT:
		error = -EINVAL;
		goto exit1;
	case LAST_ROOT:
		error = -EBUSY;
		goto exit1;
	}

	nd.flags &= ~LOOKUP_PARENT;
	error = mnt_want_write(nd.path.mnt);
	if (error)
		goto exit1;

	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
	dentry = lookup_hash(&nd);
	error = PTR_ERR(dentry);
	if (IS_ERR(dentry))
		goto exit2;
	if (!dentry->d_inode) {
		error = -ENOENT;
		goto exit3;
	}
	error = security_path_rmdir(&nd.path, dentry);
	if (error)
		goto exit3;
	error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
exit3:
	dput(dentry);
exit2:
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
	mnt_drop_write(nd.path.mnt);
exit1:
	path_put(&nd.path);
	putname(name);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}


int vfs_follow_link(struct nameidata *nd, const char *link)
{
	return __vfs_follow_link(nd, link);
}


static long do_sys_truncate(const char __user *pathname, loff_t length)
{
	unsigned int lookup_flags = LOOKUP_FOLLOW;
	struct path path;
	int error;

	if (length < 0)	/* sorry, but loff_t says... */
		return -EINVAL;

retry:
	error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
	if (!error) {
		error = vfs_truncate(&path, length);
		path_put(&path);
	}
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}


static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
{
	struct fs_struct *fs = current->fs;
	struct dentry *parent = nd->path.dentry;
	int want_root = 0;

	BUG_ON(!(nd->flags & LOOKUP_RCU));
	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
		want_root = 1;
		spin_lock(&fs->lock);
		if (nd->root.mnt != fs->root.mnt ||
				nd->root.dentry != fs->root.dentry)
			goto err_root;
	}
	spin_lock(&parent->d_lock);
	if (!dentry) {
		if (!__d_rcu_to_refcount(parent, nd->seq))
			goto err_parent;
		BUG_ON(nd->inode != parent->d_inode);
	} else {
		if (dentry->d_parent != parent)
			goto err_parent;
		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
		if (!__d_rcu_to_refcount(dentry, nd->seq))
			goto err_child;
		/*
		 * If the sequence check on the child dentry passed, then
		 * the child has not been removed from its parent. This
		 * means the parent dentry must be valid and able to take
		 * a reference at this point.
		 */
		BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
		BUG_ON(!parent->d_count);
		parent->d_count++;
		spin_unlock(&dentry->d_lock);
	}
	spin_unlock(&parent->d_lock);
	if (want_root) {
		path_get(&nd->root);
		spin_unlock(&fs->lock);
	}
	mntget(nd->path.mnt);

	unlock_rcu_walk();
	nd->flags &= ~LOOKUP_RCU;
	return 0;

err_child:
	spin_unlock(&dentry->d_lock);
err_parent:
	spin_unlock(&parent->d_lock);
err_root:
	if (want_root)
		spin_unlock(&fs->lock);
	return -ECHILD;
}


SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
		unsigned, dev)
{
	struct dentry *dentry;
	struct path path;
	int error;
	unsigned int lookup_flags = 0;

	error = may_mknod(mode);
	if (error)
		return error;
retry:
	dentry = user_path_create(dfd, filename, &path, lookup_flags);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	if (!IS_POSIXACL(path.dentry->d_inode))
		mode &= ~current_umask();
	error = security_path_mknod(&path, dentry, mode, dev);
	if (error)
		goto out;
	switch (mode & S_IFMT) {
		case 0: case S_IFREG:
			error = vfs_create(path.dentry->d_inode,dentry,mode,true);
			break;
		case S_IFCHR: case S_IFBLK:
			error = vfs_mknod(path.dentry->d_inode,dentry,mode,
					new_decode_dev(dev));
			break;
		case S_IFIFO: case S_IFSOCK:
			error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
			break;
	}
out:
	done_path_create(&path, dentry);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
	return error;
}


static inline void unlock_rcu_walk(void)
{
	rcu_read_unlock();
	br_read_unlock(&vfsmount_lock);
}


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;
}


static int lookup_open(struct nameidata *nd, struct path *path,
			struct file *file,
			const struct open_flags *op,
			bool got_write, int *opened)
{
	struct dentry *dir = nd->path.dentry;
	struct inode *dir_inode = dir->d_inode;
	struct dentry *dentry;
	int error;
	bool need_lookup;

	*opened &= ~FILE_CREATED;
	dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	/* Cached positive dentry: will open in f_op->open */
	if (!need_lookup && dentry->d_inode)
		goto out_no_open;

	if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
		return atomic_open(nd, dentry, path, file, op, got_write,
				   need_lookup, opened);
	}

	if (need_lookup) {
		BUG_ON(dentry->d_inode);

		dentry = lookup_real(dir_inode, dentry, nd->flags);
		if (IS_ERR(dentry))
			return PTR_ERR(dentry);
	}

	/* Negative dentry, just create the file */
	if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
		umode_t mode = op->mode;
		if (!IS_POSIXACL(dir->d_inode))
			mode &= ~current_umask();
		/*
		 * This write is needed to ensure that a
		 * rw->ro transition does not occur between
		 * the time when the file is created and when
		 * a permanent write count is taken through
		 * the 'struct file' in finish_open().
		 */
		if (!got_write) {
			error = -EROFS;
			goto out_dput;
		}
		*opened |= FILE_CREATED;
		error = security_path_mknod(&nd->path, dentry, mode, 0);
		if (error)
			goto out_dput;
		error = vfs_create(dir->d_inode, dentry, mode,
				   nd->flags & LOOKUP_EXCL);
		if (error)
			goto out_dput;
	}
out_no_open:
	path->dentry = dentry;
	path->mnt = nd->path.mnt;
	return 1;

out_dput:
	dput(dentry);
	return error;
}


int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
	struct inode *inode = file_inode(file);
	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;
}


int user_path_at(int dfd, const char __user *name, unsigned flags,
		 struct path *path)
{
	return user_path_at_empty(dfd, name, flags, path, NULL);
}


SYSCALL_DEFINE2(ftruncate64, unsigned int, fd, loff_t, length)
{
	return do_sys_ftruncate(fd, length, 0);
}


static inline int may_create(struct inode *dir, struct dentry *child)
{
	if (child->d_inode)
		return -EEXIST;
	if (IS_DEADDIR(dir))
		return -ENOENT;
	return inode_permission(dir, MAY_WRITE | MAY_EXEC);
}


static struct dentry *lookup_hash(struct nameidata *nd)
{
	return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
}


int __inode_permission(struct inode *inode, int mask)
{
	int retval;

	if (unlikely(mask & MAY_WRITE)) {
		/*
		 * Nobody gets write access to an immutable file.
		 */
		if (IS_IMMUTABLE(inode))
			return -EACCES;
	}

	retval = do_inode_permission(inode, mask);
	if (retval)
		return retval;

	retval = devcgroup_inode_permission(inode, mask);
	if (retval)
		return retval;

	return security_inode_permission(inode, mask);
}


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


static int do_last(struct nameidata *nd, struct path *path,
		   struct file *file, const struct open_flags *op,
		   int *opened, struct filename *name)
{
	struct dentry *dir = nd->path.dentry;
	int open_flag = op->open_flag;
	bool will_truncate = (open_flag & O_TRUNC) != 0;
	bool got_write = false;
	int acc_mode = op->acc_mode;
	struct inode *inode;
	bool symlink_ok = false;
	struct path save_parent = { .dentry = NULL, .mnt = NULL };
	bool retried = false;
	int error;

	nd->flags &= ~LOOKUP_PARENT;
	nd->flags |= op->intent;

	if (nd->last_type != LAST_NORM) {
		error = handle_dots(nd, nd->last_type);
		if (error)
			return error;
		goto finish_open;
	}

	if (!(open_flag & O_CREAT)) {
		if (nd->last.name[nd->last.len])
			nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
		if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
			symlink_ok = true;
		/* we _can_ be in RCU mode here */
		error = lookup_fast(nd, path, &inode);
		if (likely(!error))
			goto finish_lookup;

		if (error < 0)
			goto out;

		BUG_ON(nd->inode != dir->d_inode);
	} else {
		/* create side of things */
		/*
		 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
		 * has been cleared when we got to the last component we are
		 * about to look up
		 */
		error = complete_walk(nd);
		if (error)
			return error;

		audit_inode(name, dir, LOOKUP_PARENT);
		error = -EISDIR;
		/* trailing slashes? */
		if (nd->last.name[nd->last.len])
			goto out;
	}

retry_lookup:
	if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
		error = mnt_want_write(nd->path.mnt);
		if (!error)
			got_write = true;
		/*
		 * do _not_ fail yet - we might not need that or fail with
		 * a different error; let lookup_open() decide; we'll be
		 * dropping this one anyway.
		 */
	}
	mutex_lock(&dir->d_inode->i_mutex);
	error = lookup_open(nd, path, file, op, got_write, opened);
	mutex_unlock(&dir->d_inode->i_mutex);

	if (error <= 0) {
		if (error)
			goto out;

		if ((*opened & FILE_CREATED) ||
		    !S_ISREG(file_inode(file)->i_mode))
			will_truncate = false;

		audit_inode(name, file->f_path.dentry, 0);
		goto opened;
	}

	if (*opened & FILE_CREATED) {
		/* Don't check for write permission, don't truncate */
		open_flag &= ~O_TRUNC;
		will_truncate = false;
		acc_mode = MAY_OPEN;
		path_to_nameidata(path, nd);
		goto finish_open_created;
	}

	/*
	 * create/update audit record if it already exists.
	 */
	if (path->dentry->d_inode)
		audit_inode(name, path->dentry, 0);

	/*
	 * If atomic_open() acquired write access it is dropped now due to
	 * possible mount and symlink following (this might be optimized away if
	 * necessary...)
	 */
	if (got_write) {
		mnt_drop_write(nd->path.mnt);
		got_write = false;
	}

	error = -EEXIST;
	if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
		goto exit_dput;

	error = follow_managed(path, nd->flags);
	if (error < 0)
		goto exit_dput;

	if (error)
		nd->flags |= LOOKUP_JUMPED;

	BUG_ON(nd->flags & LOOKUP_RCU);
	inode = path->dentry->d_inode;
finish_lookup:
	/* we _can_ be in RCU mode here */
	error = -ENOENT;
	if (!inode) {
		path_to_nameidata(path, nd);
		goto out;
	}

	if (should_follow_link(inode, !symlink_ok)) {
		if (nd->flags & LOOKUP_RCU) {
			if (unlikely(unlazy_walk(nd, path->dentry))) {
				error = -ECHILD;
				goto out;
			}
		}
		BUG_ON(inode != path->dentry->d_inode);
		return 1;
	}

	if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
		path_to_nameidata(path, nd);
	} else {
		save_parent.dentry = nd->path.dentry;
		save_parent.mnt = mntget(path->mnt);
		nd->path.dentry = path->dentry;

	}
	nd->inode = inode;
	/* Why this, you ask?  _Now_ we might have grown LOOKUP_JUMPED... */
finish_open:
	error = complete_walk(nd);
	if (error) {
		path_put(&save_parent);
		return error;
	}
	audit_inode(name, nd->path.dentry, 0);
	error = -EISDIR;
	if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode))
		goto out;
	error = -ENOTDIR;
	if ((nd->flags & LOOKUP_DIRECTORY) && !can_lookup(nd->inode))
		goto out;
	if (!S_ISREG(nd->inode->i_mode))
		will_truncate = false;

	if (will_truncate) {
		error = mnt_want_write(nd->path.mnt);
		if (error)
			goto out;
		got_write = true;
	}
finish_open_created:
	error = may_open(&nd->path, acc_mode, open_flag);
	if (error)
		goto out;
	file->f_path.mnt = nd->path.mnt;
	error = finish_open(file, nd->path.dentry, NULL, opened);
	if (error) {
		if (error == -EOPENSTALE)
			goto stale_open;
		goto out;
	}
opened:
	error = open_check_o_direct(file);
	if (error)
		goto exit_fput;
	error = ima_file_check(file, op->acc_mode);
	if (error)
		goto exit_fput;

	if (will_truncate) {
		error = handle_truncate(file);
		if (error)
			goto exit_fput;
	}
out:
	if (got_write)
		mnt_drop_write(nd->path.mnt);
	path_put(&save_parent);
	terminate_walk(nd);
	return error;

exit_dput:
	path_put_conditional(path, nd);
	goto out;
exit_fput:
	fput(file);
	goto out;

stale_open:
	/* If no saved parent or already retried then can't retry */
	if (!save_parent.dentry || retried)
		goto out;

	BUG_ON(save_parent.dentry != dir);
	path_put(&nd->path);
	nd->path = save_parent;
	nd->inode = dir->d_inode;
	save_parent.mnt = NULL;
	save_parent.dentry = NULL;
	if (got_write) {
		mnt_drop_write(nd->path.mnt);
		got_write = false;
	}
	retried = true;
	goto retry_lookup;
}


follow_link(struct path *link, struct nameidata *nd, void **p)
{
	struct dentry *dentry = link->dentry;
	int error;
	char *s;

	BUG_ON(nd->flags & LOOKUP_RCU);

	if (link->mnt == nd->path.mnt)
		mntget(link->mnt);

	error = -ELOOP;
	if (unlikely(current->total_link_count >= 40))
		goto out_put_nd_path;

	cond_resched();
	current->total_link_count++;

	touch_atime(link);
	nd_set_link(nd, NULL);

	error = security_inode_follow_link(link->dentry, nd);
	if (error)
		goto out_put_nd_path;

	nd->last_type = LAST_BIND;
	*p = dentry->d_inode->i_op->follow_link(dentry, nd);
	error = PTR_ERR(*p);
	if (IS_ERR(*p))
		goto out_put_nd_path;

	error = 0;
	s = nd_get_link(nd);
	if (s) {
		error = __vfs_follow_link(nd, s);
		if (unlikely(error))
			put_link(nd, link, *p);
	}

	return error;

out_put_nd_path:
	*p = NULL;
	path_put(&nd->path);
	path_put(link);
	return error;
}


SYSCALL_DEFINE1(chroot, const char __user *, filename)
{
	struct path path;
	int error;
	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
retry:
	error = user_path_at(AT_FDCWD, filename, lookup_flags, &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 (!nsown_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);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
out:
	return error;
}


void unlock_rename(struct dentry *p1, struct dentry *p2)
{
	mutex_unlock(&p1->d_inode->i_mutex);
	if (p1 != p2) {
		mutex_unlock(&p2->d_inode->i_mutex);
		mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
	}
}


void nd_jump_link(struct nameidata *nd, struct path *path)
{
	path_put(&nd->path);

	nd->path = *path;
	nd->inode = nd->path.dentry->d_inode;
	nd->flags |= LOOKUP_JUMPED;
}


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;
}


int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
		 struct path *path, int *empty)
{
	struct nameidata nd;
	struct filename *tmp = getname_flags(name, flags, empty);
	int err = PTR_ERR(tmp);
	if (!IS_ERR(tmp)) {

		BUG_ON(flags & LOOKUP_PARENT);

		err = filename_lookup(dfd, tmp, flags, &nd);
		putname(tmp);
		if (!err)
			*path = nd.path;
	}
	return err;
}


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;
}


int kern_path(const char *name, unsigned int flags, struct path *path)
{
	struct nameidata nd;
	int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
	if (!res)
		*path = nd.path;
	return res;
}


static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
{
	if (unlikely(mask & MAY_WRITE)) {
		umode_t mode = inode->i_mode;

		/* Nobody gets write access to a read-only fs. */
		if ((sb->s_flags & MS_RDONLY) &&
		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
			return -EROFS;
	}
	return 0;
}


struct dentry *kern_path_locked(const char *name, struct path *path)
{
	struct nameidata nd;
	struct dentry *d;
	int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd);
	if (err)
		return ERR_PTR(err);
	if (nd.last_type != LAST_NORM) {
		path_put(&nd.path);
		return ERR_PTR(-EINVAL);
	}
	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
	d = __lookup_hash(&nd.last, nd.path.dentry, 0);
	if (IS_ERR(d)) {
		mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
		path_put(&nd.path);
		return d;
	}
	*path = nd.path;
	return d;
}


SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename, umode_t, mode)
{
	struct path path;
	int error;
	unsigned int lookup_flags = LOOKUP_FOLLOW;
retry:
	error = user_path_at(dfd, filename, lookup_flags, &path);
	if (!error) {
		error = chmod_common(&path, mode);
		path_put(&path);
		if (retry_estale(error, lookup_flags)) {
			lookup_flags |= LOOKUP_REVAL;
			goto retry;
		}
	}
	return error;
}


static struct dentry *__lookup_hash(struct qstr *name,
		struct dentry *base, unsigned int flags)
{
	bool need_lookup;
	struct dentry *dentry;

	dentry = lookup_dcache(name, base, flags, &need_lookup);
	if (!need_lookup)
		return dentry;

	return lookup_real(base->d_inode, dentry, flags);
}


COMPAT_SYSCALL_DEFINE2(truncate, const char __user *, path, compat_off_t, length)
{
	return do_sys_truncate(path, length);
}


int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
	struct page *page = NULL;
	char *s = page_getlink(dentry, &page);
	int res = vfs_readlink(dentry,buffer,buflen,s);
	if (page) {
		kunmap(page);
		page_cache_release(page);
	}
	return res;
}


user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
		 unsigned int flags)
{
	struct filename *s = getname(path);
	int error;

	/* only LOOKUP_REVAL is allowed in extra flags */
	flags &= LOOKUP_REVAL;

	if (IS_ERR(s))
		return s;

	error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd);
	if (error) {
		putname(s);
		return ERR_PTR(error);
	}

	return s;
}


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;
}


static inline int may_follow_link(struct path *link, struct nameidata *nd)
{
	const struct inode *inode;
	const struct inode *parent;

	if (!sysctl_protected_symlinks)
		return 0;

	/* Allowed if owner and follower match. */
	inode = link->dentry->d_inode;
	if (uid_eq(current_cred()->fsuid, inode->i_uid))
		return 0;

	/* Allowed if parent directory not sticky and world-writable. */
	parent = nd->path.dentry->d_inode;
	if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
		return 0;

	/* Allowed if parent directory and link owner match. */
	if (uid_eq(parent->i_uid, inode->i_uid))
		return 0;

	audit_log_link_denied("follow_link", link);
	path_put_conditional(link, nd);
	path_put(&nd->path);
	return -EACCES;
}


static int follow_managed(struct path *path, unsigned flags)
{
	struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
	unsigned managed;
	bool need_mntput = false;
	int ret = 0;

	/* Given that we're not holding a lock here, we retain the value in a
	 * local variable for each dentry as we look at it so that we don't see
	 * the components of that value change under us */
	while (managed = ACCESS_ONCE(path->dentry->d_flags),
	       managed &= DCACHE_MANAGED_DENTRY,
	       unlikely(managed != 0)) {
		/* Allow the filesystem to manage the transit without i_mutex
		 * being held. */
		if (managed & DCACHE_MANAGE_TRANSIT) {
			BUG_ON(!path->dentry->d_op);
			BUG_ON(!path->dentry->d_op->d_manage);
			ret = path->dentry->d_op->d_manage(path->dentry, false);
			if (ret < 0)
				break;
		}

		/* Transit to a mounted filesystem. */
		if (managed & DCACHE_MOUNTED) {
			struct vfsmount *mounted = lookup_mnt(path);
			if (mounted) {
				dput(path->dentry);
				if (need_mntput)
					mntput(path->mnt);
				path->mnt = mounted;
				path->dentry = dget(mounted->mnt_root);
				need_mntput = true;
				continue;
			}

			/* Something is mounted on this dentry in another
			 * namespace and/or whatever was mounted there in this
			 * namespace got unmounted before we managed to get the
			 * vfsmount_lock */
		}

		/* Handle an automount point */
		if (managed & DCACHE_NEED_AUTOMOUNT) {
			ret = follow_automount(path, flags, &need_mntput);
			if (ret < 0)
				break;
			continue;
		}

		/* We didn't change the current path point */
		break;
	}

	if (need_mntput && path->mnt == mnt)
		mntput(path->mnt);
	if (ret == -EISDIR)
		ret = 0;
	return ret < 0 ? ret : need_mntput;
}


int inode_permission(struct inode *inode, int mask)
{
	int retval;

	retval = sb_permission(inode->i_sb, inode, mask);
	if (retval)
		return retval;
	return __inode_permission(inode, mask);
}


int generic_permission(struct inode *inode, int mask)
{
	int ret;

	/*
	 * Do the basic permission checks.
	 */
	ret = acl_permission_check(inode, mask);
	if (ret != -EACCES)
		return ret;

	if (S_ISDIR(inode->i_mode)) {
		/* DACs are overridable for directories */
		if (inode_capable(inode, CAP_DAC_OVERRIDE))
			return 0;
		if (!(mask & MAY_WRITE))
			if (inode_capable(inode, CAP_DAC_READ_SEARCH))
				return 0;
		return -EACCES;
	}
	/*
	 * Read/write DACs are always overridable.
	 * Executable DACs are overridable when there is
	 * at least one exec bit set.
	 */
	if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
		if (inode_capable(inode, CAP_DAC_OVERRIDE))
			return 0;

	/*
	 * Searching includes executable on directories, else just read.
	 */
	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
	if (mask == MAY_READ)
		if (inode_capable(inode, CAP_DAC_READ_SEARCH))
			return 0;

	return -EACCES;
}


static inline int handle_dots(struct nameidata *nd, int type)
{
	if (type == LAST_DOTDOT) {
		if (nd->flags & LOOKUP_RCU) {
			if (follow_dotdot_rcu(nd))
				return -ECHILD;
		} else
			follow_dotdot(nd);
	}
	return 0;
}


void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
{
	struct page *page = NULL;
	nd_set_link(nd, page_getlink(dentry, &page));
	return page;
}


static int lookup_fast(struct nameidata *nd,
		       struct path *path, struct inode **inode)
{
	struct vfsmount *mnt = nd->path.mnt;
	struct dentry *dentry, *parent = nd->path.dentry;
	int need_reval = 1;
	int status = 1;
	int err;

	/*
	 * Rename seqlock is not required here because in the off chance
	 * of a false negative due to a concurrent rename, we're going to
	 * do the non-racy lookup, below.
	 */
	if (nd->flags & LOOKUP_RCU) {
		unsigned seq;
		dentry = __d_lookup_rcu(parent, &nd->last, &seq);
		if (!dentry)
			goto unlazy;

		/*
		 * This sequence count validates that the inode matches
		 * the dentry name information from lookup.
		 */
		*inode = dentry->d_inode;
		if (read_seqcount_retry(&dentry->d_seq, seq))
			return -ECHILD;

		/*
		 * This sequence count validates that the parent had no
		 * changes while we did the lookup of the dentry above.
		 *
		 * The memory barrier in read_seqcount_begin of child is
		 *  enough, we can use __read_seqcount_retry here.
		 */
		if (__read_seqcount_retry(&parent->d_seq, nd->seq))
			return -ECHILD;
		nd->seq = seq;

		if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
			status = d_revalidate(dentry, nd->flags);
			if (unlikely(status <= 0)) {
				if (status != -ECHILD)
					need_reval = 0;
				goto unlazy;
			}
		}
		path->mnt = mnt;
		path->dentry = dentry;
		if (unlikely(!__follow_mount_rcu(nd, path, inode)))
			goto unlazy;
		if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
			goto unlazy;
		return 0;
unlazy:
		if (unlazy_walk(nd, dentry))
			return -ECHILD;
	} else {
		dentry = __d_lookup(parent, &nd->last);
	}

	if (unlikely(!dentry))
		goto need_lookup;

	if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
		status = d_revalidate(dentry, nd->flags);
	if (unlikely(status <= 0)) {
		if (status < 0) {
			dput(dentry);
			return status;
		}
		if (!d_invalidate(dentry)) {
			dput(dentry);
			goto need_lookup;
		}
	}

	path->mnt = mnt;
	path->dentry = dentry;
	err = follow_managed(path, nd->flags);
	if (unlikely(err < 0)) {
		path_put_conditional(path, nd);
		return err;
	}
	if (err)
		nd->flags |= LOOKUP_JUMPED;
	*inode = path->dentry->d_inode;
	return 0;

need_lookup:
	return 1;
}


int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
		    const char *name, unsigned int flags,
		    struct path *path)
{
	struct nameidata nd;
	int err;
	nd.root.dentry = dentry;
	nd.root.mnt = mnt;
	BUG_ON(flags & LOOKUP_PARENT);
	/* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
	err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
	if (!err)
		*path = nd.path;
	return err;
}


static int lookup_slow(struct nameidata *nd, struct path *path)
{
	struct dentry *dentry, *parent;
	int err;

	parent = nd->path.dentry;
	BUG_ON(nd->inode != parent->d_inode);

	mutex_lock(&parent->d_inode->i_mutex);
	dentry = __lookup_hash(&nd->last, parent, nd->flags);
	mutex_unlock(&parent->d_inode->i_mutex);
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);
	path->mnt = nd->path.mnt;
	path->dentry = dentry;
	err = follow_managed(path, nd->flags);
	if (unlikely(err < 0)) {
		path_put_conditional(path, nd);
		return err;
	}
	if (err)
		nd->flags |= LOOKUP_JUMPED;
	return 0;
}


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;
}


static void terminate_walk(struct nameidata *nd)
{
	if (!(nd->flags & LOOKUP_RCU)) {
		path_put(&nd->path);
	} else {
		nd->flags &= ~LOOKUP_RCU;
		if (!(nd->flags & LOOKUP_ROOT))
			nd->root.mnt = NULL;
		unlock_rcu_walk();
	}
}


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;
retry:
	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);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
out:
	return error;
}


static int filename_lookup(int dfd, struct filename *name,
				unsigned int flags, struct nameidata *nd)
{
	int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
	if (unlikely(retval == -ECHILD))
		retval = path_lookupat(dfd, name->name, flags, nd);
	if (unlikely(retval == -ESTALE))
		retval = path_lookupat(dfd, name->name,
						flags | LOOKUP_REVAL, nd);

	if (likely(!retval))
		audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
	return retval;
}


static int complete_walk(struct nameidata *nd)
{
	struct dentry *dentry = nd->path.dentry;
	int status;

	if (nd->flags & LOOKUP_RCU) {
		nd->flags &= ~LOOKUP_RCU;
		if (!(nd->flags & LOOKUP_ROOT))
			nd->root.mnt = NULL;
		spin_lock(&dentry->d_lock);
		if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
			spin_unlock(&dentry->d_lock);
			unlock_rcu_walk();
			return -ECHILD;
		}
		BUG_ON(nd->inode != dentry->d_inode);
		spin_unlock(&dentry->d_lock);
		mntget(nd->path.mnt);
		unlock_rcu_walk();
	}

	if (likely(!(nd->flags & LOOKUP_JUMPED)))
		return 0;

	if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
		return 0;

	status = dentry->d_op->d_weak_revalidate(dentry, nd->flags);
	if (status > 0)
		return 0;

	if (!status)
		status = -ESTALE;

	path_put(&nd->path);
	return status;
}


static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
			    struct inode *new_dir, struct dentry *new_dentry)
{
	struct inode *target = new_dentry->d_inode;
	int error;

	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
	if (error)
		return error;

	dget(new_dentry);
	if (target)
		mutex_lock(&target->i_mutex);

	error = -EBUSY;
	if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
		goto out;

	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
	if (error)
		goto out;

	if (target)
		dont_mount(new_dentry);
	if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
		d_move(old_dentry, new_dentry);
out:
	if (target)
		mutex_unlock(&target->i_mutex);
	dput(new_dentry);
	return error;
}


static inline unsigned long hash_name(const char *name, unsigned int *hashp)
{
	unsigned long hash = init_name_hash();
	unsigned long len = 0, c;

	c = (unsigned char)*name;
	do {
		len++;
		hash = partial_name_hash(c, hash);
		c = (unsigned char)name[len];
	} while (c && c != '/');
	*hashp = end_name_hash(hash);
	return len;
}


struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
		const char *name, const struct open_flags *op)
{
	struct nameidata nd;
	struct file *file;
	struct filename filename = { .name = name };
	int flags = op->lookup_flags | LOOKUP_ROOT;

	nd.root.mnt = mnt;
	nd.root.dentry = dentry;

	if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
		return ERR_PTR(-ELOOP);

	file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
	if (unlikely(file == ERR_PTR(-ECHILD)))
		file = path_openat(-1, &filename, &nd, op, flags);
	if (unlikely(file == ERR_PTR(-ESTALE)))
		file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL);
	return file;
}


SYSCALL_DEFINE0(vhangup)
{
	if (capable(CAP_SYS_TTY_CONFIG)) {
		tty_vhangup_self();
		return 0;
	}
	return -EPERM;
}


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 (flags & __O_TMPFILE) {
		if ((flags & O_TMPFILE_MASK) != O_TMPFILE)
			return -EINVAL;
		acc_mode = MAY_OPEN | ACC_MODE(flags);
	} else if (flags & O_PATH) {
		/*
		 * If we have O_PATH in the open flag. Then we
		 * cannot have anything other than the below set of flags
		 */
		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;
	op->lookup_flags = lookup_flags;
	return 0;
}


static __always_inline void set_root_rcu(struct nameidata *nd)
{
	if (!nd->root.mnt) {
		struct fs_struct *fs = current->fs;
		unsigned seq;

		do {
			seq = read_seqcount_begin(&fs->seq);
			nd->root = fs->root;
			nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
		} while (read_seqcount_retry(&fs->seq, seq));
	}
}


static inline int lookup_last(struct nameidata *nd, struct path *path)
{
	if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
		nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;

	nd->flags &= ~LOOKUP_PARENT;
	return walk_component(nd, path, nd->flags & LOOKUP_FOLLOW);
}


static long do_unlinkat(int dfd, const char __user *pathname)
{
	int error;
	struct filename *name;
	struct dentry *dentry;
	struct nameidata nd;
	struct inode *inode = NULL;
	unsigned int lookup_flags = 0;
retry:
	name = user_path_parent(dfd, pathname, &nd, lookup_flags);
	if (IS_ERR(name))
		return PTR_ERR(name);

	error = -EISDIR;
	if (nd.last_type != LAST_NORM)
		goto exit1;

	nd.flags &= ~LOOKUP_PARENT;
	error = mnt_want_write(nd.path.mnt);
	if (error)
		goto exit1;

	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
	dentry = lookup_hash(&nd);
	error = PTR_ERR(dentry);
	if (!IS_ERR(dentry)) {
		/* Why not before? Because we want correct error value */
		if (nd.last.name[nd.last.len])
			goto slashes;
		inode = dentry->d_inode;
		if (!inode)
			goto slashes;
		ihold(inode);
		error = security_path_unlink(&nd.path, dentry);
		if (error)
			goto exit2;
		error = vfs_unlink(nd.path.dentry->d_inode, dentry);
exit2:
		dput(dentry);
	}
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
	if (inode)
		iput(inode);	/* truncate the inode here */
	mnt_drop_write(nd.path.mnt);
exit1:
	path_put(&nd.path);
	putname(name);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		inode = NULL;
		goto retry;
	}
	return error;

slashes:
	error = !dentry->d_inode ? -ENOENT :
		S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
	goto exit2;
}


static inline int may_lookup(struct nameidata *nd)
{
	if (nd->flags & LOOKUP_RCU) {
		int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
		if (err != -ECHILD)
			return err;
		if (unlazy_walk(nd, NULL))
			return -ECHILD;
	}
	return inode_permission(nd->inode, MAY_EXEC);
}


static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
{
	int error;

	if (!victim->d_inode)
		return -ENOENT;

	BUG_ON(victim->d_parent->d_inode != dir);
	audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);

	error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
	if (error)
		return error;
	if (IS_APPEND(dir))
		return -EPERM;
	if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
	    IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
		return -EPERM;
	if (isdir) {
		if (!S_ISDIR(victim->d_inode->i_mode))
			return -ENOTDIR;
		if (IS_ROOT(victim))
			return -EBUSY;
	} else if (S_ISDIR(victim->d_inode->i_mode))
		return -EISDIR;
	if (IS_DEADDIR(dir))
		return -ENOENT;
	if (victim->d_flags & DCACHE_NFSFS_RENAMED)
		return -EBUSY;
	return 0;
}


SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
{
	return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
}


static int may_linkat(struct path *link)
{
	const struct cred *cred;
	struct inode *inode;

	if (!sysctl_protected_hardlinks)
		return 0;

	cred = current_cred();
	inode = link->dentry->d_inode;

	/* Source inode owner (or CAP_FOWNER) can hardlink all they like,
	 * otherwise, it must be a safe source.
	 */
	if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
	    capable(CAP_FOWNER))
		return 0;

	audit_log_link_denied("linkat", link);
	return -EPERM;
}


static inline int walk_component(struct nameidata *nd, struct path *path,
		int follow)
{
	struct inode *inode;
	int err;
	/*
	 * "." and ".." are special - ".." especially so because it has
	 * to be able to know about the current root directory and
	 * parent relationships.
	 */
	if (unlikely(nd->last_type != LAST_NORM))
		return handle_dots(nd, nd->last_type);
	err = lookup_fast(nd, path, &inode);
	if (unlikely(err)) {
		if (err < 0)
			goto out_err;

		err = lookup_slow(nd, path);
		if (err < 0)
			goto out_err;

		inode = path->dentry->d_inode;
	}
	err = -ENOENT;
	if (!inode)
		goto out_path_put;

	if (should_follow_link(inode, follow)) {
		if (nd->flags & LOOKUP_RCU) {
			if (unlikely(unlazy_walk(nd, path->dentry))) {
				err = -ECHILD;
				goto out_err;
			}
		}
		BUG_ON(inode != path->dentry->d_inode);
		return 1;
	}
	path_to_nameidata(path, nd);
	nd->inode = inode;
	return 0;

out_path_put:
	path_to_nameidata(path, nd);
out_err:
	terminate_walk(nd);
	return err;
}


static int do_path_lookup(int dfd, const char *name,
				unsigned int flags, struct nameidata *nd)
{
	struct filename filename = { .name = name };

	return filename_lookup(dfd, &filename, flags, nd);
}


static inline void lock_rcu_walk(void)
{
	br_read_lock(&vfsmount_lock);
	rcu_read_lock();
}


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


static int check_acl(struct inode *inode, int mask)
{
#ifdef CONFIG_FS_POSIX_ACL
	struct posix_acl *acl;

	if (mask & MAY_NOT_BLOCK) {
		acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
	        if (!acl)
	                return -EAGAIN;
		/* no ->get_acl() calls in RCU mode... */
		if (acl == ACL_NOT_CACHED)
			return -ECHILD;
	        return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
	}

	acl = get_cached_acl(inode, ACL_TYPE_ACCESS);

	/*
	 * A filesystem can force a ACL callback by just never filling the
	 * ACL cache. But normally you'd fill the cache either at inode
	 * instantiation time, or on the first ->get_acl call.
	 *
	 * If the filesystem doesn't have a get_acl() function at all, we'll
	 * just create the negative cache entry.
	 */
	if (acl == ACL_NOT_CACHED) {
	        if (inode->i_op->get_acl) {
			acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
			if (IS_ERR(acl))
				return PTR_ERR(acl);
		} else {
		        set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
		        return -EAGAIN;
		}
	}

	if (acl) {
	        int error = posix_acl_permission(inode, acl, mask);
	        posix_acl_release(acl);
	        return error;
	}
#endif

	return -EAGAIN;
}


SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
{
	return sys_mknodat(AT_FDCWD, filename, mode, dev);
}


int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
{
	struct address_space *mapping = inode->i_mapping;
	struct page *page;
	void *fsdata;
	int err;
	char *kaddr;
	unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
	if (nofs)
		flags |= AOP_FLAG_NOFS;

retry:
	err = pagecache_write_begin(NULL, mapping, 0, len-1,
				flags, &page, &fsdata);
	if (err)
		goto fail;

	kaddr = kmap_atomic(page);
	memcpy(kaddr, symname, len-1);
	kunmap_atomic(kaddr);

	err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
							page, fsdata);
	if (err < 0)
		goto fail;
	if (err < len-1)
		goto retry;

	mark_inode_dirty(inode);
	return 0;
fail:
	return err;
}


static int path_lookupat(int dfd, const char *name,
				unsigned int flags, struct nameidata *nd)
{
	struct file *base = NULL;
	struct path path;
	int err;

	/*
	 * Path walking is largely split up into 2 different synchronisation
	 * schemes, rcu-walk and ref-walk (explained in
	 * Documentation/filesystems/path-lookup.txt). These share much of the
	 * path walk code, but some things particularly setup, cleanup, and
	 * following mounts are sufficiently divergent that functions are
	 * duplicated. Typically there is a function foo(), and its RCU
	 * analogue, foo_rcu().
	 *
	 * -ECHILD is the error number of choice (just to avoid clashes) that
	 * is returned if some aspect of an rcu-walk fails. Such an error must
	 * be handled by restarting a traditional ref-walk (which will always
	 * be able to complete).
	 */
	err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);

	if (unlikely(err))
		return err;

	current->total_link_count = 0;
	err = link_path_walk(name, nd);

	if (!err && !(flags & LOOKUP_PARENT)) {
		err = lookup_last(nd, &path);
		while (err > 0) {
			void *cookie;
			struct path link = path;
			err = may_follow_link(&link, nd);
			if (unlikely(err))
				break;
			nd->flags |= LOOKUP_PARENT;
			err = follow_link(&link, nd, &cookie);
			if (err)
				break;
			err = lookup_last(nd, &path);
			put_link(nd, &link, cookie);
		}
	}

	if (!err)
		err = complete_walk(nd);

	if (!err && nd->flags & LOOKUP_DIRECTORY) {
		if (!can_lookup(nd->inode)) {
			path_put(&nd->path);
			err = -ENOTDIR;
		}
	}

	if (base)
		fput(base);

	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
		path_put(&nd->root);
		nd->root.mnt = NULL;
	}
	return err;
}


int page_symlink(struct inode *inode, const char *symname, int len)
{
	return __page_symlink(inode, symname, len,
			!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
}


SYSCALL_DEFINE4(openat, int, dfd, const char __user *, filename, int, flags,
		umode_t, mode)
{
	if (force_o_largefile())
		flags |= O_LARGEFILE;

	return do_sys_open(dfd, filename, flags, mode);
}


static int handle_truncate(struct file *filp)
{
	struct path *path = &filp->f_path;
	struct inode *inode = path->dentry->d_inode;
	int error = get_write_access(inode);
	if (error)
		return error;
	/*
	 * Refuse to truncate files with mandatory locks held on them.
	 */
	error = locks_verify_locked(inode);
	if (!error)
		error = security_path_truncate(path);
	if (!error) {
		error = do_truncate(path->dentry, 0,
				    ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
				    filp);
	}
	put_write_access(inode);
	return error;
}


SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
{
	return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
}


struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
{
	struct dentry *p;

	if (p1 == p2) {
		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
		return NULL;
	}

	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);

	p = d_ancestor(p2, p1);
	if (p) {
		mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
		return p;
	}

	p = d_ancestor(p1, p2);
	if (p) {
		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
		mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
		return p;
	}

	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
	return NULL;
}


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;
}


void putname(struct filename *name)
{
	if (unlikely(!audit_dummy_context()))
		return audit_putname(name);
	final_putname(name);
}


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;
	unsigned int lookup_flags = LOOKUP_FOLLOW;

	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);
retry:
	res = user_path_at(dfd, filename, lookup_flags, &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);
	if (retry_estale(res, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
out:
	revert_creds(old_cred);
	put_cred(override_cred);
	return res;
}


static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
{
	struct inode *inode = link->dentry->d_inode;
	if (inode->i_op->put_link)
		inode->i_op->put_link(link->dentry, nd, cookie);
	path_put(link);
}


static void follow_dotdot(struct nameidata *nd)
{
	set_root(nd);

	while(1) {
		struct dentry *old = nd->path.dentry;

		if (nd->path.dentry == nd->root.dentry &&
		    nd->path.mnt == nd->root.mnt) {
			break;
		}
		if (nd->path.dentry != nd->path.mnt->mnt_root) {
			/* rare case of legitimate dget_parent()... */
			nd->path.dentry = dget_parent(nd->path.dentry);
			dput(old);
			break;
		}
		if (!follow_up(&nd->path))
			break;
	}
	follow_mount(&nd->path);
	nd->inode = nd->path.dentry->d_inode;
}


void final_putname(struct filename *name)
{
	if (name->separate) {
		__putname(name->name);
		kfree(name);
	} else {
		__putname(name);
	}
}


SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
{
	return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
}


static inline unsigned long hash_name(const char *name, unsigned int *hashp)
{
	unsigned long a, b, adata, bdata, mask, hash, len;
	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;

	hash = a = 0;
	len = -sizeof(unsigned long);
	do {
		hash = (hash + a) * 9;
		len += sizeof(unsigned long);
		a = load_unaligned_zeropad(name+len);
		b = a ^ REPEAT_BYTE('/');
	} while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));

	adata = prep_zero_mask(a, adata, &constants);
	bdata = prep_zero_mask(b, bdata, &constants);

	mask = create_zero_mask(adata | bdata);

	hash += a & zero_bytemask(mask);
	*hashp = fold_hash(hash);

	return len + find_zero(mask);
}


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;
}


static int follow_up_rcu(struct path *path)
{
	struct mount *mnt = real_mount(path->mnt);
	struct mount *parent;
	struct dentry *mountpoint;

	parent = mnt->mnt_parent;
	if (&parent->mnt == path->mnt)
		return 0;
	mountpoint = mnt->mnt_mountpoint;
	path->dentry = mountpoint;
	path->mnt = &parent->mnt;
	return 1;
}


void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
	struct page *page = cookie;

	if (page) {
		kunmap(page);
		page_cache_release(page);
	}
}


static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
{
	return dentry->d_op->d_revalidate(dentry, flags);
}


SYSCALL_DEFINE3(open, const char __user *, filename, int, flags, umode_t, mode)
{
	if (force_o_largefile())
		flags |= O_LARGEFILE;

	return do_sys_open(AT_FDCWD, filename, flags, mode);
}


static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
{
	int ret;

	if (IS_ERR(link))
		goto fail;

	if (*link == '/') {
		set_root(nd);
		path_put(&nd->path);
		nd->path = nd->root;
		path_get(&nd->root);
		nd->flags |= LOOKUP_JUMPED;
	}
	nd->inode = nd->path.dentry->d_inode;

	ret = link_path_walk(link, nd);
	return ret;
fail:
	path_put(&nd->path);
	return PTR_ERR(link);
}


SYSCALL_DEFINE1(unlink, const char __user *, pathname)
{
	return do_unlinkat(AT_FDCWD, pathname);
}


int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
	       struct inode *new_dir, struct dentry *new_dentry)
{
	int error;
	int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
	const unsigned char *old_name;

	if (old_dentry->d_inode == new_dentry->d_inode)
 		return 0;

	error = may_delete(old_dir, old_dentry, is_dir);
	if (error)
		return error;

	if (!new_dentry->d_inode)
		error = may_create(new_dir, new_dentry);
	else
		error = may_delete(new_dir, new_dentry, is_dir);
	if (error)
		return error;

	if (!old_dir->i_op->rename)
		return -EPERM;

	old_name = fsnotify_oldname_init(old_dentry->d_name.name);

	if (is_dir)
		error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
	else
		error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
	if (!error)
		fsnotify_move(old_dir, new_dir, old_name, is_dir,
			      new_dentry->d_inode, old_dentry);
	fsnotify_oldname_free(old_name);

	return error;
}


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;
}


struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
			    const char *filename, int flags)
{
	struct open_flags op;
	int err = build_open_flags(flags, 0, &op);
	if (err)
		return ERR_PTR(err);
	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);
}


getname_flags(const char __user *filename, int flags, int *empty)
{
	struct filename *result, *err;
	int len;
	long max;
	char *kname;

	result = audit_reusename(filename);
	if (result)
		return result;

	result = __getname();
	if (unlikely(!result))
		return ERR_PTR(-ENOMEM);

	/*
	 * First, try to embed the struct filename inside the names_cache
	 * allocation
	 */
	kname = (char *)result + sizeof(*result);
	result->name = kname;
	result->separate = false;
	max = EMBEDDED_NAME_MAX;

recopy:
	len = strncpy_from_user(kname, filename, max);
	if (unlikely(len < 0)) {
		err = ERR_PTR(len);
		goto error;
	}

	/*
	 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
	 * separate struct filename so we can dedicate the entire
	 * names_cache allocation for the pathname, and re-do the copy from
	 * userland.
	 */
	if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
		kname = (char *)result;

		result = kzalloc(sizeof(*result), GFP_KERNEL);
		if (!result) {
			err = ERR_PTR(-ENOMEM);
			result = (struct filename *)kname;
			goto error;
		}
		result->name = kname;
		result->separate = true;
		max = PATH_MAX;
		goto recopy;
	}

	/* The empty path is special. */
	if (unlikely(!len)) {
		if (empty)
			*empty = 1;
		err = ERR_PTR(-ENOENT);
		if (!(flags & LOOKUP_EMPTY))
			goto error;
	}

	err = ERR_PTR(-ENAMETOOLONG);
	if (unlikely(len >= PATH_MAX))
		goto error;

	result->uptr = filename;
	audit_getname(result);
	return result;

error:
	final_putname(result);
	return err;
}


static int follow_dotdot_rcu(struct nameidata *nd)
{
	set_root_rcu(nd);

	while (1) {
		if (nd->path.dentry == nd->root.dentry &&
		    nd->path.mnt == nd->root.mnt) {
			break;
		}
		if (nd->path.dentry != nd->path.mnt->mnt_root) {
			struct dentry *old = nd->path.dentry;
			struct dentry *parent = old->d_parent;
			unsigned seq;

			seq = read_seqcount_begin(&parent->d_seq);
			if (read_seqcount_retry(&old->d_seq, nd->seq))
				goto failed;
			nd->path.dentry = parent;
			nd->seq = seq;
			break;
		}
		if (!follow_up_rcu(&nd->path))
			break;
		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
	}
	follow_mount_rcu(nd);
	nd->inode = nd->path.dentry->d_inode;
	return 0;

failed:
	nd->flags &= ~LOOKUP_RCU;
	if (!(nd->flags & LOOKUP_ROOT))
		nd->root.mnt = NULL;
	unlock_rcu_walk();
	return -ECHILD;
}


int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
{
	struct inode *inode = old_dentry->d_inode;
	unsigned max_links = dir->i_sb->s_max_links;
	int error;

	if (!inode)
		return -ENOENT;

	error = may_create(dir, new_dentry);
	if (error)
		return error;

	if (dir->i_sb != inode->i_sb)
		return -EXDEV;

	/*
	 * A link to an append-only or immutable file cannot be created.
	 */
	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
		return -EPERM;
	if (!dir->i_op->link)
		return -EPERM;
	if (S_ISDIR(inode->i_mode))
		return -EPERM;

	error = security_inode_link(old_dentry, dir, new_dentry);
	if (error)
		return error;

	mutex_lock(&inode->i_mutex);
	/* Make sure we don't allow creating hardlink to an unlinked file */
	if (inode->i_nlink == 0 && !(inode->i_state & I_LINKABLE))
		error =  -ENOENT;
	else if (max_links && inode->i_nlink >= max_links)
		error = -EMLINK;
	else
		error = dir->i_op->link(old_dentry, dir, new_dentry);

	if (!error && (inode->i_state & I_LINKABLE)) {
		spin_lock(&inode->i_lock);
		inode->i_state &= ~I_LINKABLE;
		spin_unlock(&inode->i_lock);
	}
	mutex_unlock(&inode->i_mutex);
	if (!error)
		fsnotify_link(dir, inode, new_dentry);
	return error;
}


int follow_down(struct path *path)
{
	unsigned managed;
	int ret;

	while (managed = ACCESS_ONCE(path->dentry->d_flags),
	       unlikely(managed & DCACHE_MANAGED_DENTRY)) {
		/* Allow the filesystem to manage the transit without i_mutex
		 * being held.
		 *
		 * We indicate to the filesystem if someone is trying to mount
		 * something here.  This gives autofs the chance to deny anyone
		 * other than its daemon the right to mount on its
		 * superstructure.
		 *
		 * The filesystem may sleep at this point.
		 */
		if (managed & DCACHE_MANAGE_TRANSIT) {
			BUG_ON(!path->dentry->d_op);
			BUG_ON(!path->dentry->d_op->d_manage);
			ret = path->dentry->d_op->d_manage(
				path->dentry, false);
			if (ret < 0)
				return ret == -EISDIR ? 0 : ret;
		}

		/* Transit to a mounted filesystem. */
		if (managed & DCACHE_MOUNTED) {
			struct vfsmount *mounted = lookup_mnt(path);
			if (!mounted)
				break;
			dput(path->dentry);
			mntput(path->mnt);
			path->mnt = mounted;
			path->dentry = dget(mounted->mnt_root);
			continue;
		}

		/* Don't handle automount points here */
		break;
	}
	return 0;
}


static inline int nested_symlink(struct path *path, struct nameidata *nd)
{
	int res;

	if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
		path_put_conditional(path, nd);
		path_put(&nd->path);
		return -ELOOP;
	}
	BUG_ON(nd->depth >= MAX_NESTED_LINKS);

	nd->depth++;
	current->link_count++;

	do {
		struct path link = *path;
		void *cookie;

		res = follow_link(&link, nd, &cookie);
		if (res)
			break;
		res = walk_component(nd, path, LOOKUP_FOLLOW);
		put_link(nd, &link, cookie);
	} while (res > 0);

	current->link_count--;
	nd->depth--;
	return res;
}


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 = file_inode(f.file);

	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;
}


struct dentry *kern_path_create(int dfd, const char *pathname,
				struct path *path, unsigned int lookup_flags)
{
	struct dentry *dentry = ERR_PTR(-EEXIST);
	struct nameidata nd;
	int err2;
	int error;
	bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);

	/*
	 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
	 * other flags passed in are ignored!
	 */
	lookup_flags &= LOOKUP_REVAL;

	error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd);
	if (error)
		return ERR_PTR(error);

	/*
	 * Yucky last component or no last component at all?
	 * (foo/., foo/.., /////)
	 */
	if (nd.last_type != LAST_NORM)
		goto out;
	nd.flags &= ~LOOKUP_PARENT;
	nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;

	/* don't fail immediately if it's r/o, at least try to report other errors */
	err2 = mnt_want_write(nd.path.mnt);
	/*
	 * Do the final lookup.
	 */
	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
	dentry = lookup_hash(&nd);
	if (IS_ERR(dentry))
		goto unlock;

	error = -EEXIST;
	if (dentry->d_inode)
		goto fail;
	/*
	 * Special case - lookup gave negative, but... we had foo/bar/
	 * From the vfs_mknod() POV we just have a negative dentry -
	 * all is fine. Let's be bastards - you had / on the end, you've
	 * been asking for (non-existent) directory. -ENOENT for you.
	 */
	if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
		error = -ENOENT;
		goto fail;
	}
	if (unlikely(err2)) {
		error = err2;
		goto fail;
	}
	*path = nd.path;
	return dentry;
fail:
	dput(dentry);
	dentry = ERR_PTR(error);
unlock:
	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
	if (!err2)
		mnt_drop_write(nd.path.mnt);
out:
	path_put(&nd.path);
	return dentry;
}


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(mkdir, const char __user *, pathname, umode_t, mode)
{
	return sys_mkdirat(AT_FDCWD, pathname, mode);
}


int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
	struct nameidata nd;
	void *cookie;
	int res;

	nd.depth = 0;
	cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
	if (IS_ERR(cookie))
		return PTR_ERR(cookie);

	res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
	if (dentry->d_inode->i_op->put_link)
		dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
	return res;
}


static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
			  struct inode *new_dir, struct dentry *new_dentry)
{
	int error = 0;
	struct inode *target = new_dentry->d_inode;
	unsigned max_links = new_dir->i_sb->s_max_links;

	/*
	 * If we are going to change the parent - check write permissions,
	 * we'll need to flip '..'.
	 */
	if (new_dir != old_dir) {
		error = inode_permission(old_dentry->d_inode, MAY_WRITE);
		if (error)
			return error;
	}

	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
	if (error)
		return error;

	dget(new_dentry);
	if (target)
		mutex_lock(&target->i_mutex);

	error = -EBUSY;
	if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
		goto out;

	error = -EMLINK;
	if (max_links && !target && new_dir != old_dir &&
	    new_dir->i_nlink >= max_links)
		goto out;

	if (target)
		shrink_dcache_parent(new_dentry);
	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
	if (error)
		goto out;

	if (target) {
		target->i_flags |= S_DEAD;
		dont_mount(new_dentry);
	}
out:
	if (target)
		mutex_unlock(&target->i_mutex);
	dput(new_dentry);
	if (!error)
		if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
			d_move(old_dentry,new_dentry);
	return error;
}


int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
{
	int len;

	len = PTR_ERR(link);
	if (IS_ERR(link))
		goto out;

	len = strlen(link);
	if (len > (unsigned) buflen)
		len = buflen;
	if (copy_to_user(buffer, link, len))
		len = -EFAULT;
out:
	return len;
}


SYSCALL_DEFINE4(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;
}


static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
				    unsigned int flags, bool *need_lookup)
{
	struct dentry *dentry;
	int error;

	*need_lookup = false;
	dentry = d_lookup(dir, name);
	if (dentry) {
		if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
			error = d_revalidate(dentry, flags);
			if (unlikely(error <= 0)) {
				if (error < 0) {
					dput(dentry);
					return ERR_PTR(error);
				} else if (!d_invalidate(dentry)) {
					dput(dentry);
					dentry = NULL;
				}
			}
		}
	}

	if (!dentry) {
		dentry = d_alloc(dir, name);
		if (unlikely(!dentry))
			return ERR_PTR(-ENOMEM);

		*need_lookup = true;
	}
	return dentry;
}


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_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;
	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;
	f->f_inode = NULL;
	return error;
}


int vfs_unlink(struct inode *dir, struct dentry *dentry)
{
	int error = may_delete(dir, dentry, 0);

	if (error)
		return error;

	if (!dir->i_op->unlink)
		return -EPERM;

	mutex_lock(&dentry->d_inode->i_mutex);
	if (d_mountpoint(dentry))
		error = -EBUSY;
	else {
		error = security_inode_unlink(dir, dentry);
		if (!error) {
			error = dir->i_op->unlink(dir, dentry);
			if (!error)
				dont_mount(dentry);
		}
	}
	mutex_unlock(&dentry->d_inode->i_mutex);

	/* We don't d_delete() NFS sillyrenamed files--they still exist. */
	if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
		fsnotify_link_count(dentry->d_inode);
		d_delete(dentry);
	}

	return error;
}


static int do_tmpfile(int dfd, struct filename *pathname,
		struct nameidata *nd, int flags,
		const struct open_flags *op,
		struct file *file, int *opened)
{
	static const struct qstr name = QSTR_INIT("/", 1);
	struct dentry *dentry, *child;
	struct inode *dir;
	int error = path_lookupat(dfd, pathname->name,
				  flags | LOOKUP_DIRECTORY, nd);
	if (unlikely(error))
		return error;
	error = mnt_want_write(nd->path.mnt);
	if (unlikely(error))
		goto out;
	/* we want directory to be writable */
	error = inode_permission(nd->inode, MAY_WRITE | MAY_EXEC);
	if (error)
		goto out2;
	dentry = nd->path.dentry;
	dir = dentry->d_inode;
	if (!dir->i_op->tmpfile) {
		error = -EOPNOTSUPP;
		goto out2;
	}
	child = d_alloc(dentry, &name);
	if (unlikely(!child)) {
		error = -ENOMEM;
		goto out2;
	}
	nd->flags &= ~LOOKUP_DIRECTORY;
	nd->flags |= op->intent;
	dput(nd->path.dentry);
	nd->path.dentry = child;
	error = dir->i_op->tmpfile(dir, nd->path.dentry, op->mode);
	if (error)
		goto out2;
	audit_inode(pathname, nd->path.dentry, 0);
	error = may_open(&nd->path, op->acc_mode, op->open_flag);
	if (error)
		goto out2;
	file->f_path.mnt = nd->path.mnt;
	error = finish_open(file, nd->path.dentry, NULL, opened);
	if (error)
		goto out2;
	error = open_check_o_direct(file);
	if (error) {
		fput(file);
	} else if (!(op->open_flag & O_EXCL)) {
		struct inode *inode = file_inode(file);
		spin_lock(&inode->i_lock);
		inode->i_state |= I_LINKABLE;
		spin_unlock(&inode->i_lock);
	}
out2:
	mnt_drop_write(nd->path.mnt);
out:
	path_put(&nd->path);
	return error;
}


static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
				  unsigned int flags)
{
	struct dentry *old;

	/* Don't create child dentry for a dead directory. */
	if (unlikely(IS_DEADDIR(dir))) {
		dput(dentry);
		return ERR_PTR(-ENOENT);
	}

	old = dir->i_op->lookup(dir, dentry, flags);
	if (unlikely(old)) {
		dput(dentry);
		dentry = old;
	}
	return dentry;
}


int follow_up(struct path *path)
{
	struct mount *mnt = real_mount(path->mnt);
	struct mount *parent;
	struct dentry *mountpoint;

	br_read_lock(&vfsmount_lock);
	parent = mnt->mnt_parent;
	if (parent == mnt) {
		br_read_unlock(&vfsmount_lock);
		return 0;
	}
	mntget(&parent->mnt);
	mountpoint = dget(mnt->mnt_mountpoint);
	br_read_unlock(&vfsmount_lock);
	dput(path->dentry);
	path->dentry = mountpoint;
	mntput(path->mnt);
	path->mnt = &parent->mnt;
	return 1;
}


static void follow_mount_rcu(struct nameidata *nd)
{
	while (d_mountpoint(nd->path.dentry)) {
		struct mount *mounted;
		mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
		if (!mounted)
			break;
		nd->path.mnt = &mounted->mnt;
		nd->path.dentry = mounted->mnt.mnt_root;
		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
	}
}


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


SYSCALL_DEFINE2(truncate64, const char __user *, path, loff_t, length)
{
	return do_sys_truncate(path, length);
}


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


struct file *do_filp_open(int dfd, struct filename *pathname,
		const struct open_flags *op)
{
	struct nameidata nd;
	int flags = op->lookup_flags;
	struct file *filp;

	filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
	if (unlikely(filp == ERR_PTR(-ECHILD)))
		filp = path_openat(dfd, pathname, &nd, op, flags);
	if (unlikely(filp == ERR_PTR(-ESTALE)))
		filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
	return filp;
}


void done_path_create(struct path *path, struct dentry *dentry)
{
	dput(dentry);
	mutex_unlock(&path->dentry->d_inode->i_mutex);
	mnt_drop_write(path->mnt);
	path_put(path);
}


SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
		int, newdfd, const char __user *, newname)
{
	int error;
	struct filename *from;
	struct dentry *dentry;
	struct path path;
	unsigned int lookup_flags = 0;

	from = getname(oldname);
	if (IS_ERR(from))
		return PTR_ERR(from);
retry:
	dentry = user_path_create(newdfd, newname, &path, lookup_flags);
	error = PTR_ERR(dentry);
	if (IS_ERR(dentry))
		goto out_putname;

	error = security_path_symlink(&path, dentry, from->name);
	if (!error)
		error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
	done_path_create(&path, dentry);
	if (retry_estale(error, lookup_flags)) {
		lookup_flags |= LOOKUP_REVAL;
		goto retry;
	}
out_putname:
	putname(from);
	return error;
}


static inline int check_sticky(struct inode *dir, struct inode *inode)
{
	kuid_t fsuid = current_fsuid();

	if (!(dir->i_mode & S_ISVTX))
		return 0;
	if (uid_eq(inode->i_uid, fsuid))
		return 0;
	if (uid_eq(dir->i_uid, fsuid))
		return 0;
	return !inode_capable(inode, CAP_FOWNER);
}


int vfs_rmdir(struct inode *dir, struct dentry *dentry)
{
	int error = may_delete(dir, dentry, 1);

	if (error)
		return error;

	if (!dir->i_op->rmdir)
		return -EPERM;

	dget(dentry);
	mutex_lock(&dentry->d_inode->i_mutex);

	error = -EBUSY;
	if (d_mountpoint(dentry))
		goto out;

	error = security_inode_rmdir(dir, dentry);
	if (error)
		goto out;

	shrink_dcache_parent(dentry);
	error = dir->i_op->rmdir(dir, dentry);
	if (error)
		goto out;

	dentry->d_inode->i_flags |= S_DEAD;
	dont_mount(dentry);

out:
	mutex_unlock(&dentry->d_inode->i_mutex);
	dput(dentry);
	if (!error)
		d_delete(dentry);
	return error;
}


static __always_inline void set_root(struct nameidata *nd)
{
	if (!nd->root.mnt)
		get_fs_root(current->fs, &nd->root);
}


long vfs_truncate(struct path *path, loff_t length)
{
	struct inode *inode;
	long error;

	inode = path->dentry->d_inode;

	/* For directories it's -EISDIR, for other non-regulars - -EINVAL */
	if (S_ISDIR(inode->i_mode))
		return -EISDIR;
	if (!S_ISREG(inode->i_mode))
		return -EINVAL;

	error = mnt_want_write(path->mnt);
	if (error)
		goto 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);
out:
	return error;
}


static int path_init(int dfd, const char *name, unsigned int flags,
		     struct nameidata *nd, struct file **fp)
{
	int retval = 0;

	nd->last_type = LAST_ROOT; /* if there are only slashes... */
	nd->flags = flags | LOOKUP_JUMPED;
	nd->depth = 0;
	if (flags & LOOKUP_ROOT) {
		struct inode *inode = nd->root.dentry->d_inode;
		if (*name) {
			if (!can_lookup(inode))
				return -ENOTDIR;
			retval = inode_permission(inode, MAY_EXEC);
			if (retval)
				return retval;
		}
		nd->path = nd->root;
		nd->inode = inode;
		if (flags & LOOKUP_RCU) {
			lock_rcu_walk();
			nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
		} else {
			path_get(&nd->path);
		}
		return 0;
	}

	nd->root.mnt = NULL;

	if (*name=='/') {
		if (flags & LOOKUP_RCU) {
			lock_rcu_walk();
			set_root_rcu(nd);
		} else {
			set_root(nd);
			path_get(&nd->root);
		}
		nd->path = nd->root;
	} else if (dfd == AT_FDCWD) {
		if (flags & LOOKUP_RCU) {
			struct fs_struct *fs = current->fs;
			unsigned seq;

			lock_rcu_walk();

			do {
				seq = read_seqcount_begin(&fs->seq);
				nd->path = fs->pwd;
				nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
			} while (read_seqcount_retry(&fs->seq, seq));
		} else {
			get_fs_pwd(current->fs, &nd->path);
		}
	} else {
		/* Caller must check execute permissions on the starting path component */
		struct fd f = fdget_raw(dfd);
		struct dentry *dentry;

		if (!f.file)
			return -EBADF;

		dentry = f.file->f_path.dentry;

		if (*name) {
			if (!can_lookup(dentry->d_inode)) {
				fdput(f);
				return -ENOTDIR;
			}
		}

		nd->path = f.file->f_path;
		if (flags & LOOKUP_RCU) {
			if (f.need_put)
				*fp = f.file;
			nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
			lock_rcu_walk();
		} else {
			path_get(&nd->path);
			fdput(f);
		}
	}

	nd->inode = nd->path.dentry->d_inode;
	return 0;
}


static char *page_getlink(struct dentry * dentry, struct page **ppage)
{
	char *kaddr;
	struct page *page;
	struct address_space *mapping = dentry->d_inode->i_mapping;
	page = read_mapping_page(mapping, 0, NULL);
	if (IS_ERR(page))
		return (char*)page;
	*ppage = page;
	kaddr = kmap(page);
	nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
	return kaddr;
}


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;
}


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;
}


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


static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
			       struct inode **inode)
{
	for (;;) {
		struct mount *mounted;
		/*
		 * Don't forget we might have a non-mountpoint managed dentry
		 * that wants to block transit.
		 */
		if (unlikely(managed_dentry_might_block(path->dentry)))
			return false;

		if (!d_mountpoint(path->dentry))
			break;

		mounted = __lookup_mnt(path->mnt, path->dentry, 1);
		if (!mounted)
			break;
		path->mnt = &mounted->mnt;
		path->dentry = mounted->mnt.mnt_root;
		nd->flags |= LOOKUP_JUMPED;
		nd->seq = read_seqcount_begin(&path->dentry->d_seq);
		/*
		 * Update the inode too. We don't need to re-check the
		 * dentry sequence number here after this d_inode read,
		 * because a mount-point is always pinned.
		 */
		*inode = path->dentry->d_inode;
	}
	return true;
}


unsigned int full_name_hash(const unsigned char *name, unsigned int len)
{
	unsigned long hash = init_name_hash();
	while (len--)
		hash = partial_name_hash(*name++, hash);
	return end_name_hash(hash);
}


static int link_path_walk(const char *name, struct nameidata *nd)
{
	struct path next;
	int err;

	while (*name=='/')
		name++;
	if (!*name)
		return 0;

	/* At this point we know we have a real path component. */
	for(;;) {
		struct qstr this;
		long len;
		int type;

		err = may_lookup(nd);
 		if (err)
			break;

		len = hash_name(name, &this.hash);
		this.name = name;
		this.len = len;

		type = LAST_NORM;
		if (name[0] == '.') switch (len) {
			case 2:
				if (name[1] == '.') {
					type = LAST_DOTDOT;
					nd->flags |= LOOKUP_JUMPED;
				}
				break;
			case 1:
				type = LAST_DOT;
		}
		if (likely(type == LAST_NORM)) {
			struct dentry *parent = nd->path.dentry;
			nd->flags &= ~LOOKUP_JUMPED;
			if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
				err = parent->d_op->d_hash(parent, &this);
				if (err < 0)
					break;
			}
		}

		nd->last = this;
		nd->last_type = type;

		if (!name[len])
			return 0;
		/*
		 * If it wasn't NUL, we know it was '/'. Skip that
		 * slash, and continue until no more slashes.
		 */
		do {
			len++;
		} while (unlikely(name[len] == '/'));
		if (!name[len])
			return 0;

		name += len;

		err = walk_component(nd, &next, LOOKUP_FOLLOW);
		if (err < 0)
			return err;

		if (err) {
			err = nested_symlink(&next, nd);
			if (err)
				return err;
		}
		if (!can_lookup(nd->inode)) {
			err = -ENOTDIR;
			break;
		}
	}
	terminate_walk(nd);
	return err;
}


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

	if (fd)
		return fd;

	tmp = getname(filename);
	if (IS_ERR(tmp))
		return PTR_ERR(tmp);

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


static int may_open(struct path *path, int acc_mode, int flag)
{
	struct dentry *dentry = path->dentry;
	struct inode *inode = dentry->d_inode;
	int error;

	/* O_PATH? */
	if (!acc_mode)
		return 0;

	if (!inode)
		return -ENOENT;

	switch (inode->i_mode & S_IFMT) {
	case S_IFLNK:
		return -ELOOP;
	case S_IFDIR:
		if (acc_mode & MAY_WRITE)
			return -EISDIR;
		break;
	case S_IFBLK:
	case S_IFCHR:
		if (path->mnt->mnt_flags & MNT_NODEV)
			return -EACCES;
		/*FALLTHRU*/
	case S_IFIFO:
	case S_IFSOCK:
		flag &= ~O_TRUNC;
		break;
	}

	error = inode_permission(inode, acc_mode);
	if (error)
		return error;

	/*
	 * An append-only file must be opened in append mode for writing.
	 */
	if (IS_APPEND(inode)) {
		if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
			return -EPERM;
		if (flag & O_TRUNC)
			return -EPERM;
	}

	/* O_NOATIME can only be set by the owner or superuser */
	if (flag & O_NOATIME && !inode_owner_or_capable(inode))
		return -EPERM;

	return 0;
}


static inline int can_lookup(struct inode *inode)
{
	if (likely(inode->i_opflags & IOP_LOOKUP))
		return 1;
	if (likely(!inode->i_op->lookup))
		return 0;

	/* We do this once for the lifetime of the inode */
	spin_lock(&inode->i_lock);
	inode->i_opflags |= IOP_LOOKUP;
	spin_unlock(&inode->i_lock);
	return 1;
}


static int atomic_open(struct nameidata *nd, struct dentry *dentry,
			struct path *path, struct file *file,
			const struct open_flags *op,
			bool got_write, bool need_lookup,
			int *opened)
{
	struct inode *dir =  nd->path.dentry->d_inode;
	unsigned open_flag = open_to_namei_flags(op->open_flag);
	umode_t mode;
	int error;
	int acc_mode;
	int create_error = 0;
	struct dentry *const DENTRY_NOT_SET = (void *) -1UL;

	BUG_ON(dentry->d_inode);

	/* Don't create child dentry for a dead directory. */
	if (unlikely(IS_DEADDIR(dir))) {
		error = -ENOENT;
		goto out;
	}

	mode = op->mode;
	if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
		mode &= ~current_umask();

	if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) {
		open_flag &= ~O_TRUNC;
		*opened |= FILE_CREATED;
	}

	/*
	 * Checking write permission is tricky, bacuse we don't know if we are
	 * going to actually need it: O_CREAT opens should work as long as the
	 * file exists.  But checking existence breaks atomicity.  The trick is
	 * to check access and if not granted clear O_CREAT from the flags.
	 *
	 * Another problem is returing the "right" error value (e.g. for an
	 * O_EXCL open we want to return EEXIST not EROFS).
	 */
	if (((open_flag & (O_CREAT | O_TRUNC)) ||
	    (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
		if (!(open_flag & O_CREAT)) {
			/*
			 * No O_CREATE -> atomicity not a requirement -> fall
			 * back to lookup + open
			 */
			goto no_open;
		} else if (open_flag & (O_EXCL | O_TRUNC)) {
			/* Fall back and fail with the right error */
			create_error = -EROFS;
			goto no_open;
		} else {
			/* No side effects, safe to clear O_CREAT */
			create_error = -EROFS;
			open_flag &= ~O_CREAT;
		}
	}

	if (open_flag & O_CREAT) {
		error = may_o_create(&nd->path, dentry, mode);
		if (error) {
			create_error = error;
			if (open_flag & O_EXCL)
				goto no_open;
			open_flag &= ~O_CREAT;
		}
	}

	if (nd->flags & LOOKUP_DIRECTORY)
		open_flag |= O_DIRECTORY;

	file->f_path.dentry = DENTRY_NOT_SET;
	file->f_path.mnt = nd->path.mnt;
	error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
				      opened);
	if (error < 0) {
		if (create_error && error == -ENOENT)
			error = create_error;
		goto out;
	}

	acc_mode = op->acc_mode;
	if (*opened & FILE_CREATED) {
		fsnotify_create(dir, dentry);
		acc_mode = MAY_OPEN;
	}

	if (error) {	/* returned 1, that is */
		if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
			error = -EIO;
			goto out;
		}
		if (file->f_path.dentry) {
			dput(dentry);
			dentry = file->f_path.dentry;
		}
		if (create_error && dentry->d_inode == NULL) {
			error = create_error;
			goto out;
		}
		goto looked_up;
	}

	/*
	 * We didn't have the inode before the open, so check open permission
	 * here.
	 */
	error = may_open(&file->f_path, acc_mode, open_flag);
	if (error)
		fput(file);

out:
	dput(dentry);
	return error;

no_open:
	if (need_lookup) {
		dentry = lookup_real(dir, dentry, nd->flags);
		if (IS_ERR(dentry))
			return PTR_ERR(dentry);

		if (create_error) {
			int open_flag = op->open_flag;

			error = create_error;
			if ((open_flag & O_EXCL)) {
				if (!dentry->d_inode)
					goto out;
			} else if (!dentry->d_inode) {
				goto out;
			} else if ((open_flag & O_TRUNC) &&
				   S_ISREG(dentry->d_inode->i_mode)) {
				goto out;
			}
			/* will fail later, go on to get the right error */
		}
	}
looked_up:
	path->dentry = dentry;
	path->mnt = nd->path.mnt;
	return 1;
}