nl80211: fix MAC address validation

MAC addresses have a fixed length. The current
policy allows passing < ETH_ALEN bytes, which
might result in reading beyond the buffer.

Cc: stable@vger.kernel.org
Signed-off-by: NEliad Peller <eliad@wizery.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/wireless/nl80211.c

@@ -89,8 +89,8 @@ static const struct nla_policy nl80211_policy[NL80211_ATTR_MAX+1] = {
 	[NL80211_ATTR_IFINDEX] = { .type = NLA_U32 },
 	[NL80211_ATTR_IFNAME] = { .type = NLA_NUL_STRING, .len = IFNAMSIZ-1 },
 
-	[NL80211_ATTR_MAC] = { .type = NLA_BINARY, .len = ETH_ALEN },
-	[NL80211_ATTR_PREV_BSSID] = { .type = NLA_BINARY, .len = ETH_ALEN },
+	[NL80211_ATTR_MAC] = { .len = ETH_ALEN },
+	[NL80211_ATTR_PREV_BSSID] = { .len = ETH_ALEN },
 
 	[NL80211_ATTR_KEY] = { .type = NLA_NESTED, },
 	[NL80211_ATTR_KEY_DATA] = { .type = NLA_BINARY,