[ 169/184] netfilter: nf_ct_ipv4: packets with wrong ihl are

[Willy Tarreau]

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------
 invalid

From: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>

commit 07153c6ec074257ade76a461429b567cff2b3a1e upstream.

It was reported that the Linux kernel sometimes logs:

klogd: [2629147.402413] kernel BUG at net / netfilter /
nf_conntrack_proto_tcp.c: 447!
klogd: [1072212.887368] kernel BUG at net / netfilter /
nf_conntrack_proto_tcp.c: 392

ipv4_get_l4proto() in nf_conntrack_l3proto_ipv4.c and tcp_error() in
nf_conntrack_proto_tcp.c should catch malformed packets, so the errors
at the indicated lines - TCP options parsing - should not happen.
However, tcp_error() relies on the "dataoff" offset to the TCP header,
calculated by ipv4_get_l4proto().  But ipv4_get_l4proto() does not check
bogus ihl values in IPv4 packets, which then can slip through tcp_error()
and get caught at the TCP options parsing routines.

The patch fixes ipv4_get_l4proto() by invalidating packets with bogus
ihl value.

The patch closes netfilter bugzilla id 771.

Signed-off-by: Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Acked-by: David Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
 net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
index 1032a15..c6437d5 100644
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
@@ -83,6 +83,14 @@ static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
 	*dataoff = nhoff + (iph->ihl << 2);
 	*protonum = iph->protocol;
 
+	/* Check bogus IP headers */
+	if (*dataoff > skb->len) {
+		pr_debug("nf_conntrack_ipv4: bogus IPv4 packet: "
+			 "nhoff %u, ihl %u, skblen %u\n",
+			 nhoff, iph->ihl << 2, skb->len);
+		return -NF_ACCEPT;
+	}
+
 	return NF_ACCEPT;
 }
 
-- 
1.7.12.2.21.g234cd45.dirty



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/