path: root/net
diff options
authorJozsef Kadlecsik <kadlec@blackhole.kfki.hu>2012-04-03 22:02:01 +0200
committerPablo Neira Ayuso <pablo@netfilter.org>2012-04-10 12:50:49 +0200
commit07153c6ec074257ade76a461429b567cff2b3a1e (patch)
treeca918b6b18835b650ad4a9fed8bc08b1e6c6d273 /net
parent8430eac2f6a3c2adce22d490e2ab8bb50d59077a (diff)
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: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Diffstat (limited to 'net')
1 files changed, 8 insertions, 0 deletions
diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
index 750b06afd20e..cf73cc70ed2d 100644
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
@@ -84,6 +84,14 @@ 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;