cfg80211: Check if NAN service ID is of expected size

cfg80211: Check if NAN service ID is of expected size

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, cfg80211 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_NAN_FUNC_SERVICE_ID to make these NLA_UNSPEC and to make sure
minimum NL80211_NAN_FUNC_SERVICE_ID_LEN bytes are received from
userspace with NL80211_NAN_FUNC_SERVICE_ID.

Fixes: a442b761b24 ("cfg80211: add add_nan_func / del_nan_func")
Cc: [email protected]
Signed-off-by: Srinivas Dasari <[email protected]>
Signed-off-by: Jouni Malinen <[email protected]>
Signed-off-by: Johannes Berg <[email protected]>