cfg80211: Fix busy loop regression in ieee80211_ie_split_ric()

cfg80211: Fix busy loop regression in ieee80211_ie_split_ric()

This function was modified to support the information element extension
case (WLAN_EID_EXTENSION) in a manner that would result in an infinite
loop when going through set of IEs that include WLAN_EID_RIC_DATA and
contain an IE that is in the after_ric array. The only place where this
can currently happen is in mac80211 ieee80211_send_assoc() where
ieee80211_ie_split_ric() is called with after_ric[].

This can be triggered by valid data from user space nl80211
association/connect request (i.e., requiring GENL_UNS_ADMIN_PERM). The
only known application having an option to include WLAN_EID_RIC_DATA in
these requests is wpa_supplicant and it had a bug that prevented this
specific contents from being used (and because of that, not triggering
this kernel bug in an automated test case ap_ft_ric) and now that this
bug is fixed, it has a workaround to avoid this kernel issue.
WLAN_EID_RIC_DATA is currently used only for testing purposes, so this
does not cause significant harm for production use cases.

Fixes: 2512b1b18d07 ("mac80211: extend ieee80211_ie_split to support EXTENSION")
Cc: stable@vger.kernel.org
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>