atm: fix info leak in getsockopt(SO_ATMPVC)

commit e862f1a9 upstream.

The ATM code fails to initialize the two padding bytes of struct
sockaddr_atmpvc inserted for alignment. Add an explicit memset(0)
before filling the structure to avoid the info leak.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 2.6.32: adjust context, indentation]
Signed-off-by: Willy Tarreau <w@1wt.eu>

net/atm/common.c

@@ -751,6 +751,7 @@ int vcc_getsockopt(struct socket *sock, int level, int optname,
 				if (!vcc->dev ||
 				    !test_bit(ATM_VF_ADDR,&vcc->flags))
 					return -ENOTCONN;
+				memset(&pvc, 0, sizeof(pvc));
 				pvc.sap_family = AF_ATMPVC;
 				pvc.sap_addr.itf = vcc->dev->number;
 				pvc.sap_addr.vpi = vcc->vpi;