af_packet: prevent information leak

In 2.6.27, commit 393e52e33c6c2 (packet: deliver VLAN TCI to userspace)
added a small information leak.

Add padding field and make sure its zeroed before copy to user.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index ba248d93399a..c0c3cda19712 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -804,6 +804,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
                 } else {
                         h.h2->tp_vlan_tci = 0;
                 }
+                h.h2->tp_padding = 0;
                 hdrlen = sizeof(*h.h2);
                 break;
         default:
@@ -1736,6 +1737,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
                 } else {
                         aux.tp_vlan_tci = 0;
                 }
+                aux.tp_padding = 0;
                 put_cmsg(msg, SOL_PACKET, PACKET_AUXDATA, sizeof(aux), &aux);
         }