[34-longterm 101/179] af_packet: prevent information leak

[Paul Gortmaker]

From: Eric Dumazet <eric.dumazet@xxxxxxxxx>

                   -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
                   -------------------

commit 13fcb7bd322164c67926ffe272846d4860196dc6 upstream.

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@xxxxxxxxx>
CC: Patrick McHardy <kaber@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
---
 include/linux/if_packet.h |    2 ++
 net/packet/af_packet.c    |    2 ++
 2 files changed, 4 insertions(+)

diff --git a/include/linux/if_packet.h b/include/linux/if_packet.h
index aa57a5f..9b8dc3a 100644
--- a/include/linux/if_packet.h
+++ b/include/linux/if_packet.h
@@ -60,6 +60,7 @@ struct tpacket_auxdata {
 	__u16		tp_mac;
 	__u16		tp_net;
 	__u16		tp_vlan_tci;
+	__u16		tp_padding;
 };
 
 /* Rx ring - header status */
@@ -98,6 +99,7 @@ struct tpacket2_hdr {
 	__u32		tp_sec;
 	__u32		tp_nsec;
 	__u16		tp_vlan_tci;
+	__u16		tp_padding;
 };
 
 #define TPACKET2_HDRLEN		(TPACKET_ALIGN(sizeof(struct tpacket2_hdr)) + sizeof(struct sockaddr_ll))
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index b1bc2d2..4096a66 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -751,6 +751,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
 		h.h2->tp_sec = ts.tv_sec;
 		h.h2->tp_nsec = ts.tv_nsec;
 		h.h2->tp_vlan_tci = vlan_tx_tag_get(skb);
+		h.h2->tp_padding = 0;
 		hdrlen = sizeof(*h.h2);
 		break;
 	default:
@@ -1617,6 +1618,7 @@ static int packet_recvmsg(struct kiocb *iocb, struct socket *sock,
 		aux.tp_net = skb_network_offset(skb);
 		aux.tp_vlan_tci = vlan_tx_tag_get(skb);
 
+		aux.tp_padding = 0;
 		put_cmsg(msg, SOL_PACKET, PACKET_AUXDATA, sizeof(aux), &aux);
 	}
 
-- 
1.7.9.6

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