VSOCK: Fix missing msg_namelen update in vsock_stream_recvmsg()

The code misses to update the msg_namelen member to 0 and therefore
makes net/socket.c leak the local, uninitialized sockaddr_storage
variable to userland -- 128 bytes of kernel stack memory.

Cc: Andy King <acking@vmware.com>
Cc: Dmitry Torokhov <dtor@vmware.com>
Cc: George Zhang <georgezhang@vmware.com>
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static int vsock_getname(struct socket *sock,
			 struct sockaddr *addr, int *addr_len, int peer)
{
	int err;
	struct sock *sk;
	struct vsock_sock *vsk;
	struct sockaddr_vm *vm_addr;

	sk = sock->sk;
	vsk = vsock_sk(sk);
	err = 0;

	lock_sock(sk);

	if (peer) {
		if (sock->state != SS_CONNECTED) {
			err = -ENOTCONN;
			goto out;
		}
		vm_addr = &vsk->remote_addr;
	} else {
		vm_addr = &vsk->local_addr;
	}

	if (!vm_addr) {
		err = -EINVAL;
		goto out;
	}

	/* sys_getsockname() and sys_getpeername() pass us a
	 * MAX_SOCK_ADDR-sized buffer and don't set addr_len.  Unfortunately
	 * that macro is defined in socket.c instead of .h, so we hardcode its
	 * value here.
	 */
	BUILD_BUG_ON(sizeof(*vm_addr) > 128);
	memcpy(addr, vm_addr, sizeof(*vm_addr));
	*addr_len = sizeof(*vm_addr);

out:
	release_sock(sk);
	return err;
}

static int vsock_getname(struct socket *sock,
			 struct sockaddr *addr, int *addr_len, int peer)
{
	int err;
	struct sock *sk;
	struct vsock_sock *vsk;
	struct sockaddr_vm *vm_addr;

	sk = sock->sk;
	vsk = vsock_sk(sk);
	err = 0;

	lock_sock(sk);

	if (peer) {
		if (sock->state != SS_CONNECTED) {
			err = -ENOTCONN;
			goto out;
		}
		vm_addr = &vsk->remote_addr;
	} else {
		vm_addr = &vsk->local_addr;
	}

	if (!vm_addr) {
		err = -EINVAL;
		goto out;
	}

	/* sys_getsockname() and sys_getpeername() pass us a
	 * MAX_SOCK_ADDR-sized buffer and don't set addr_len.  Unfortunately
	 * that macro is defined in socket.c instead of .h, so we hardcode its
	 * value here.
	 */
	BUILD_BUG_ON(sizeof(*vm_addr) > 128);
	memcpy(addr, vm_addr, sizeof(*vm_addr));
	*addr_len = sizeof(*vm_addr);

out:
	release_sock(sk);
	return err;
}
