wifi: mac80211: Don't finalize CSA in IBSS mode if state is disconnected

commit 15bc8966 upstream.

When we are not connected to a channel, sending channel "switch"
announcement doesn't make any sense.

The BSS list is empty in that case. This causes the for loop in
cfg80211_get_bss() to be bypassed, so the function returns NULL
(check line 1424 of net/wireless/scan.c), causing the WARN_ON()
in ieee80211_ibss_csa_beacon() to get triggered (check line 500
of net/mac80211/ibss.c), which was consequently reported on the
syzkaller dashboard.

Thus, check if we have an existing connection before generating
the CSA beacon in ieee80211_ibss_finish_csa().

Cc: stable@vger.kernel.org
Fixes: cd7760e6 ("mac80211: add support for CSA in IBSS mode")
Link: https://syzkaller.appspot.com/bug?id=05603ef4ae8926761b678d2939a3b2ad28ab9ca6


Reported-by:  <syzbot+b6c9fe29aefe68e4ad34@syzkaller.appspotmail.com>
Signed-off-by: Siddh Raman Pant <code@siddh.me>
Tested-by:  <syzbot+b6c9fe29aefe68e4ad34@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/20220814151512.9985-1-code@siddh.me


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>