Bluetooth: HCI - Fix info leak in getsockopt(HCI_FILTER)

The HCI code fails to initialize the two padding bytes of struct
hci_ufilter before copying it to userland -- that for leaking two
bytes kernel stack. Add an explicit memset(0) before filling the
structure to avoid the info leak.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bluetooth/hci_sock.c

@@ -1009,6 +1009,7 @@ static int hci_sock_getsockopt(struct socket *sock, int level, int optname,
 		{
 			struct hci_filter *f = &hci_pi(sk)->filter;
 
+			memset(&uf, 0, sizeof(uf));
 			uf.type_mask = f->type_mask;
 			uf.opcode    = f->opcode;
 			uf.event_mask[0] = *((u32 *) f->event_mask + 0);