[31/35] af_packet: prevent information leak

[Greg KH]

2.6.33-longterm review patch.  If anyone has any objections, please let us know.

------------------


From: Eric Dumazet <eric.dumazet@xxxxxxxxx>

[ Upstream commit 13fcb7bd322164c67926ffe272846d4860196dc6 ]

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: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
 include/linux/if_packet.h |    2 ++
 net/packet/af_packet.c    |    2 ++
 2 files changed, 4 insertions(+)

--- a/include/linux/if_packet.h
+++ b/include/linux/if_packet.h
@@ -59,6 +59,7 @@ struct tpacket_auxdata {
 	__u16		tp_mac;
 	__u16		tp_net;
 	__u16		tp_vlan_tci;
+	__u16		tp_padding;
 };
 
 /* Rx ring - header status */
@@ -97,6 +98,7 @@ 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))
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -759,6 +759,7 @@ static int tpacket_rcv(struct sk_buff *s
 		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:
@@ -1495,6 +1496,7 @@ static int packet_recvmsg(struct kiocb *
 		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);
 	}
 


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