batman-adv: verify tt len does not exceed packet len

batman-adv: verify tt len does not exceed packet len

[ Upstream commit b47506d91259c29b9c75c404737eb6525556f9b4 ]

batadv_iv_ogm_process() accesses the packet using the tt_num_changes
attribute regardless of the real packet len (assuming the length check
was done before). Therefore a length check is needed to avoid reading
random memory.

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>