Re: [PATCH 1/3] autofs4 - fix device ioctl mount lookup

[Al Viro <viro@ZenIV.linux.org.uk>]

On Wed, Sep 04, 2013 at 08:54:57AM +0800, Ian Kent wrote:
> +static int kern_path_top(const char *pathname,
> +			 unsigned int flags, struct path *path)
> +{
> +	struct dentry *dentry;
> +	struct qstr name;
> +	const char *tmp;
> +	unsigned int len;
> +	int err;
> +
> +	len = strlen(pathname);
> +	if (len <= 1)
> +		return -EINVAL;
> +
> +	tmp = pathname + len - 1;
> +	len = 0;
> +	if (*tmp == '/')
> +		tmp--;
> +	do {
> +		if (*tmp == '/')
> +			break;
> +		len++;
> +	} while (--tmp >= pathname);
> +	tmp++;
> +
> +	err = kern_path(pathname, flags | LOOKUP_PARENT, path);
> +	if (err)
> +		return err;
> +
> +	name.name = tmp;
> +	name.len = len;
> +	name.hash = full_name_hash(tmp, len);
> +
> +	dentry = d_lookup(path->dentry, &name);
> +	if (!dentry) {
> +		path_put(path);
> +		return -ENOENT;
> +	}
> +	dput(path->dentry);
> +	path->dentry = dentry;
> +
> +	while (follow_down_one(path))
> +		;
> +
> +	return 0;
> +}

Ewwww...   NAK in that form.  Just what will happen if the last component
given to that sucker will be . or .., for starters?  Or a symlink, with
'/' added to it to force following the damn thing?