cfg80211: Check if PMKID attribute is of expected size

commit 9361df14d1cbf966409d5d6f48bb334384fbe138 upstream.

nla policy checks for only maximum length of the attribute data
when the attribute type is NLA_BINARY. If userspace sends less
data than specified, the wireless drivers may access illegal
memory. When type is NLA_UNSPEC, nla policy check ensures that
userspace sends minimum specified length number of bytes.

Remove type assignment to NLA_BINARY from nla_policy of
NL80211_ATTR_PMKID to make this NLA_UNSPEC and to make sure minimum
WLAN_PMKID_LEN bytes are received from userspace with
NL80211_ATTR_PMKID.

Fixes: 67fbb16 ("nl80211: PMKSA caching support")
Change-Id: Idfccd1cd27e550986bcfbfe250bd6948592dc692
Signed-off-by: Srinivas Dasari <[email protected]>
Signed-off-by: Jouni Malinen <[email protected]>
Signed-off-by: Johannes Berg <[email protected]>
Signed-off-by: Ben Hutchings <[email protected]>
Signed-off-by: Francisco Franco <[email protected]>

net/wireless/nl80211.c

@@ -162,8 +162,7 @@ static const struct nla_policy nl80211_policy[NL80211_ATTR_MAX+1] = {
 	[NL80211_ATTR_WPA_VERSIONS] = { .type = NLA_U32 },
 	[NL80211_ATTR_PID] = { .type = NLA_U32 },
 	[NL80211_ATTR_4ADDR] = { .type = NLA_U8 },
-	[NL80211_ATTR_PMKID] = { .type = NLA_BINARY,
-				 .len = WLAN_PMKID_LEN },
+	[NL80211_ATTR_PMKID] = { .len = WLAN_PMKID_LEN },
 	[NL80211_ATTR_DURATION] = { .type = NLA_U32 },
 	[NL80211_ATTR_COOKIE] = { .type = NLA_U64 },
 	[NL80211_ATTR_TX_RATES] = { .type = NLA_NESTED },