econet: Fix econet_getname() leak

commit 80922bbb upstream.

econet_getname() can leak kernel memory to user.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>