netlink: policy: correct validation type check

In the policy export for binary attributes I erroneously used
a != NLA_VALIDATE_NONE comparison instead of checking for the
two possible values, which meant that if a validation function
pointer ended up aliasing the min/max as negatives, we'd hit
a warning in nla_get_range_unsigned().

Fix this to correctly check for only the two types that should
be handled here, i.e. range with or without warn-too-long.

Reported-by: syzbot+353df1490da781637624@syzkaller.appspotmail.com
Fixes: 8aa26c57 ("netlink: make NLA_BINARY validation more flexible")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/policy.c

@@ -264,7 +264,8 @@ int netlink_policy_dump_write(struct sk_buff *skb, unsigned long _state)
 		else
 			type = NL_ATTR_TYPE_BINARY;
 
-		if (pt->validation_type != NLA_VALIDATE_NONE) {
+		if (pt->validation_type == NLA_VALIDATE_RANGE ||
+		    pt->validation_type == NLA_VALIDATE_RANGE_WARN_TOO_LONG) {
 			struct netlink_range_validation range;
 
 			nla_get_range_unsigned(pt, &range);