net: packet: fix information leak to userland

commit 67286640 upstream.

packet_getname_spkt() doesn't initialize all members of sa_data field of
sockaddr struct if strlen(dev->name) < 13.  This structure is then copied
to userland.  It leads to leaking of contents of kernel stack memory.
We have to fully fill sa_data with strncpy() instead of strlcpy().

The same with packet_getname(): it doesn't initialize sll_pkttype field of
sockaddr_ll.  Set it to zero.
Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Moritz Muehlenhoff <jmm@debian.org>
[jmm: Backported to 2.6.32]
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

net/packet/af_packet.c

@@ -1526,7 +1526,7 @@ static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr,
 	uaddr->sa_family = AF_PACKET;
 	dev = dev_get_by_index(sock_net(sk), pkt_sk(sk)->ifindex);
 	if (dev) {
-		strlcpy(uaddr->sa_data, dev->name, 15);
+		strncpy(uaddr->sa_data, dev->name, 14);
 		dev_put(dev);
 	} else
 		memset(uaddr->sa_data, 0, 14);
@@ -1549,6 +1549,7 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr,
 	sll->sll_family = AF_PACKET;
 	sll->sll_ifindex = po->ifindex;
 	sll->sll_protocol = po->num;
+	sll->sll_pkttype = 0;
 	dev = dev_get_by_index(sock_net(sk), po->ifindex);
 	if (dev) {
 		sll->sll_hatype = dev->type;