vty: fix 'codec-list' command: check all given arguments first

Allocating a new list of supported codecs *before* checking the
command arguments is a bad idea.  The operator may simply mistype
one of the codecs and will end up with a list of NULL pointers.

The functions calling audio_support_to_gsm88() assume that this
list always does contain valid pointers, so if a new subscriber
connection gets established, or the operator simply invokes
'show running-config', osmo-bsc would crash due to NULL pointer
dereference.

Steps to reproduce:

  1. In the VTY, do: 'en' -> 'configure terminal' -> 'msc';
  2. Configure any invalid codec list, e.g. 'codec-list Boom!';
  3. Invoke 'show running-config', boom!

Let's check the input before changing the internal structures.

Change-Id: I35b740a39c9cf3716d286e717486ef505bc61522
Fixes: OS#4946
1 file changed