Even if you obtain your company's agreement to a particular leave period. It has been known on the past for this permission to be withdrawn if the situation (operational requirements) changes closer to the date of your leave.
I know at least two people in the past who had their leave cancelled even though they had an exit permit. One was pulled out of the departure lounge by the authorities when waiting to board a flight with his family.
In case of emegencies (family bereavement)in which a permit is required urgently, many of the larger companies hold approved permits for use in such instances. It is at times like this that working for a well organised outfit pays dividends.