nl80211: fix HT capability attribute validation

Since the NL80211_ATTR_HT_CAPABILITY attribute is
used as a struct, it needs a minimum, not maximum
length. Enforce that properly. Not doing so could
potentially lead to reading after the buffer.

Cc: stable@vger.kernel.org
Signed-off-by: NJohannes Berg <johannes.berg@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/wireless/nl80211.c

@@ -132,8 +132,7 @@ static const struct nla_policy nl80211_policy[NL80211_ATTR_MAX+1] = {
 	[NL80211_ATTR_MESH_CONFIG] = { .type = NLA_NESTED },
 	[NL80211_ATTR_SUPPORT_MESH_AUTH] = { .type = NLA_FLAG },
 
-	[NL80211_ATTR_HT_CAPABILITY] = { .type = NLA_BINARY,
-					 .len = NL80211_HT_CAPABILITY_LEN },
+	[NL80211_ATTR_HT_CAPABILITY] = { .len = NL80211_HT_CAPABILITY_LEN },
 
 	[NL80211_ATTR_MGMT_SUBTYPE] = { .type = NLA_U8 },
 	[NL80211_ATTR_IE] = { .type = NLA_BINARY,