[PATCH 5.15 067/167] netfilter: nf_log: incorrect offset to network header

Greg Kroah-Hartman
2022-07-19T12:37:20Z

From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit 7a847c00eeba9744353ecdfad253143b9115678a ]

NFPROTO_ARP is expecting to find the ARP header at the network offset.

In the particular case of ARP, HTYPE= field shows the initial bytes of
the ethernet header destination MAC address.

netdev out: IN= OUT=bridge0 MACSRC=c2:76:e5:71:e1:de MACDST=36:b0:4a:e2:72:ea MACPROTO=0806 ARP HTYPE=14000 PTYPE=0x4ae2 OPCODE=49782

NFPROTO_NETDEV egress hook is also expecting to find the IP headers at
the network offset.

Fixes: 35b9395104d5 ("netfilter: add generic ARP packet logger")
Reported-by: Tom Yan <tom.ty89@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_log_syslog.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_log_syslog.c b/net/netfilter/nf_log_syslog.c
index 13234641cdb3..7000e069bc07 100644
--- a/net/netfilter/nf_log_syslog.c
+++ b/net/netfilter/nf_log_syslog.c
@@ -61,7 +61,7 @@ dump_arp_packet(struct nf_log_buf *m,
unsigned int logflags;
struct arphdr _arph;

- ah = skb_header_pointer(skb, 0, sizeof(_arph), &_arph);
+ ah = skb_header_pointer(skb, nhoff, sizeof(_arph), &_arph);
if (!ah) {
nf_log_buf_add(m, "TRUNCATED");
return;
@@ -90,7 +90,7 @@ dump_arp_packet(struct nf_log_buf *m,
ah->ar_pln != sizeof(__be32))
return;

- ap = skb_header_pointer(skb, sizeof(_arph), sizeof(_arpp), &_arpp);
+ ap = skb_header_pointer(skb, nhoff + sizeof(_arph), sizeof(_arpp), &_arpp);
if (!ap) {
nf_log_buf_add(m, " INCOMPLETE [%zu bytes]",
skb->len - sizeof(_arph));
@@ -144,7 +144,7 @@ static void nf_log_arp_packet(struct net *net, u_int8_t pf,

nf_log_dump_packet_common(m, pf, hooknum, skb, in, out, loginfo,
prefix);
- dump_arp_packet(m, loginfo, skb, 0);
+ dump_arp_packet(m, loginfo, skb, skb_network_offset(skb));

nf_log_buf_close(m);
}
@@ -829,7 +829,7 @@ static void nf_log_ip_packet(struct net *net, u_int8_t pf,
if (in)
dump_ipv4_mac_header(m, loginfo, skb);

- dump_ipv4_packet(net, m, loginfo, skb, 0);
+ dump_ipv4_packet(net, m, loginfo, skb, skb_network_offset(skb));

nf_log_buf_close(m);
}
--
2.35.1