cfg80211: nl80211_update_ft_ies() to validate NL80211_ATTR_IE

nl80211_update_ft_ies() tried to validate NL80211_ATTR_IE with
is_valid_ie_attr() before dereferencing it, but that helper function
returns true in case of NULL pointer (i.e., attribute not included).
This can result to dereferencing a NULL pointer. Fix that by explicitly
checking that NL80211_ATTR_IE is included.

Fixes: 355199e0 ("cfg80211: Extend support for IEEE 802.11r Fast BSS Transition")
Signed-off-by: Arunk Khandavalli <akhandav@codeaurora.org>
Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/nl80211.c

@@ -12099,6 +12099,7 @@ static int nl80211_update_ft_ies(struct sk_buff *skb, struct genl_info *info)
 		return -EOPNOTSUPP;
 
 	if (!info->attrs[NL80211_ATTR_MDID] ||
+	    !info->attrs[NL80211_ATTR_IE] ||
 	    !is_valid_ie_attr(info->attrs[NL80211_ATTR_IE]))
 		return -EINVAL;