DECnet: don't leak uninitialized stack byte

A single uninitialized padding byte is leaked to userspace.
Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
CC: stable <stable@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/decnet/af_decnet.c

@@ -1556,6 +1556,8 @@ static int __dn_getsockopt(struct socket *sock, int level,int optname, char __us
 			if (r_len > sizeof(struct linkinfo_dn))
 				r_len = sizeof(struct linkinfo_dn);
 
+			memset(&link, 0, sizeof(link));
+
 			switch(sock->state) {
 				case SS_CONNECTING:
 					link.idn_linkstate = LL_CONNECTING;