Per spec, the maximum value for the MaxBSSID ('n') indicator is 8,
and the minimum is 1 since a multiple BSSID set with just one BSSID
doesn't make sense (the # of BSSIDs is limited by 2^n).
Limit this in the parsing in both cfg80211 and mac80211, rejecting
any elements with an invalid value.
This fixes potentially bad shifts in the processing of these inside
the cfg80211_gen_new_bssid() function later.
I found this during the investigation of CVE-2022-41674 fixed by the
previous patch.
Fixes: 0b8fb8235b ("cfg80211: Parsing of Multiple BSSID information in scanning")
Fixes: 78ac51f815 ("mac80211: support multi-bssid")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
8f033d2bec