length of the information elements (int left) could end up being
negative. This would result in reading significantly past the stack
buffer while parsing the IEs in ieee802_11_parse_elems() and while doing
so, resulting in segmentation fault.
This can result in an invalid frame being used for a denial of service
attack (hostapd process killed) against an AP with a driver that uses
hostapd for management frame processing (e.g., all mac80211-based
drivers).
Thanks to Kostya Kortchinsky of Google security team for discovering and
reporting this issue.
XXX: pullup-7
c23d0f7f66