atm: fix info leak in getsockopt(SO_ATMPVC)

[ Upstream commit e862f1a9 ]

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

net/atm/common.c

@@ -784,6 +784,7 @@ 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;