net: sctp: sctp_v6_get_dst: fix boolean test in dst cache

We walk through the bind address list and try to get the best source
address for a given destination. However, currently, we take the
'continue' path of the loop when an entry is invalid (!laddr->valid)
*and* the entry state does not equal SCTP_ADDR_SRC (laddr->state !=
SCTP_ADDR_SRC).

Thus, still, invalid entries with SCTP_ADDR_SRC might not 'continue'
as well as valid entries with SCTP_ADDR_{NEW, SRC, DEL}, with a possible
false baddr and matchlen as a result, causing in worst case dst route
to be false or possibly NULL.

This test should actually be a '||' instead of '&&'. But lets fix it
and make this a bit easier to read by having the condition the same way
as similarly done in sctp_v4_get_dst.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/ipv6.c

@@ -326,9 +326,10 @@ static void sctp_v6_get_dst(struct sctp_transport *t, union sctp_addr *saddr,
 	 */
 	rcu_read_lock();
 	list_for_each_entry_rcu(laddr, &bp->address_list, list) {
-		if (!laddr->valid && laddr->state != SCTP_ADDR_SRC)
+		if (!laddr->valid)
 			continue;
-		if ((laddr->a.sa.sa_family == AF_INET6) &&
+		if ((laddr->state == SCTP_ADDR_SRC) &&
+		    (laddr->a.sa.sa_family == AF_INET6) &&
 		    (scope <= sctp_scope(&laddr->a))) {
 			bmatchlen = sctp_v6_addr_match_len(daddr, &laddr->a);
 			if (!baddr || (matchlen < bmatchlen)) {