It is apparently possible to somehow trigger the driver to report a
channel switch event during ACS operation when the interface information
is not yet complete. hapd->iface->current_mode could be NULL in that
case and that would result in process termination due to NULL pointer
dereference.
It should not really be possible to trigger a channel switch during ACS
is running (i.e., before the AP mode operation has been started), but
since that has been seen in an arbitrary test sequence with interface
start/stop operations with various parameters (both valid and invalid),
better prevent a crash here by ignoring the unexpected event instead of
trying to process it.
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
c3805fb623