rtnetlink: Mask the rta_type when range checking

Range/validity checks on rta_type in rtnetlink_rcv_msg() do
not account for flags that may be set.  This causes the function
to return -EINVAL when flags are set on the type (for example
NLA_F_NESTED).
Signed-off-by: NVlad Yasevich <vyasevic@redhat.com>
Acked-by: NThomas Graf <tgraf@suug.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

@@ -2621,7 +2621,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 		struct rtattr *attr = (void *)nlh + NLMSG_ALIGN(min_len);
 
 		while (RTA_OK(attr, attrlen)) {
-			unsigned int flavor = attr->rta_type;
+			unsigned int flavor = attr->rta_type & NLA_TYPE_MASK;
 			if (flavor) {
 				if (flavor > rta_max[sz_idx])
 					return -EINVAL;