If we pick a high value for "offset" then it could lead to an integer
overflow and we would get past the check for:
	if (offset + len > buflen) { ...
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NJussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>