econet: 4 byte infoleak to the network

struct aunhdr has 4 padding bytes between 'pad' and 'handle' fields on
x86_64. These bytes are not initialized in the variable 'ah' before
sending 'ah' to the network. This leads to 4 bytes kernel stack
infoleak.

This bug was introduced before the git epoch.

Signed-off-by: Vasiliy Kulikov <[e-mail]>
Acked-by: Phil Blundell <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/econet/af_econet.c

···
 		udpdest.sin_addr.s_addr = htonl(network | addr.station);
 	}
 
+	memset(&ah, 0, sizeof(ah));
 	ah.port = port;
 	ah.cb = cb & 0x7f;
 	ah.code = 2;		/* magic */
-	ah.pad = 0;
 
 	/* tack our header on the front of the iovec */
 	size = sizeof(struct aunhdr);