Commit 07153c6e authored by Jozsef Kadlecsik's avatar Jozsef Kadlecsik Committed by Pablo Neira Ayuso

netfilter: nf_ct_ipv4: packets with wrong ihl are invalid

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: default avatarJozsef Kadlecsik <kadlec@blackhole.kfki.hu>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 8430eac2
...@@ -84,6 +84,14 @@ static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff, ...@@ -84,6 +84,14 @@ static int ipv4_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
*dataoff = nhoff + (iph->ihl << 2); *dataoff = nhoff + (iph->ihl << 2);
*protonum = iph->protocol; *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; return NF_ACCEPT;
} }
......
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