From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: [PATCH 01/10] netfilter: don't track fragmented packets Date: Wed, 15 Mar 2017 18:01:03 +0100 Message-ID: <1489597272-30347-2-git-send-email-pablo@netfilter.org> References: <1489597272-30347-1-git-send-email-pablo@netfilter.org> Cc: davem@davemloft.net, netdev@vger.kernel.org To: netfilter-devel@vger.kernel.org Return-path: Received: from mail.us.es ([193.147.175.20]:37452 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752119AbdCORBk (ORCPT ); Wed, 15 Mar 2017 13:01:40 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id E1E951324C3 for ; Wed, 15 Mar 2017 18:01:19 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id C96EBDA80B for ; Wed, 15 Mar 2017 18:01:19 +0100 (CET) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 69A76DA872 for ; Wed, 15 Mar 2017 18:01:17 +0100 (CET) In-Reply-To: <1489597272-30347-1-git-send-email-pablo@netfilter.org> Sender: netdev-owner@vger.kernel.org List-ID: From: Florian Westphal Andrey reports syzkaller splat caused by NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb))); in ipv4 nat. But this assertion (and the comment) are wrong, this function does see fragments when IP_NODEFRAG setsockopt is used. As conntrack doesn't track packets without complete l4 header, only the first fragment is tracked. Because applying nat to first packet but not the rest makes no sense this also turns off tracking of all fragments. Reported-by: Andrey Konovalov Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c | 4 ++++ net/ipv4/netfilter/nf_nat_l3proto_ipv4.c | 5 ----- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c index bc1486f2c064..2e14ed11a35c 100644 --- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c @@ -165,6 +165,10 @@ static unsigned int ipv4_conntrack_local(void *priv, if (skb->len < sizeof(struct iphdr) || ip_hdrlen(skb) < sizeof(struct iphdr)) return NF_ACCEPT; + + if (ip_is_fragment(ip_hdr(skb))) /* IP_NODEFRAG setsockopt set */ + return NF_ACCEPT; + return nf_conntrack_in(state->net, PF_INET, state->hook, skb); } diff --git a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c index f8aad03d674b..6f5e8d01b876 100644 --- a/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c +++ b/net/ipv4/netfilter/nf_nat_l3proto_ipv4.c @@ -255,11 +255,6 @@ nf_nat_ipv4_fn(void *priv, struct sk_buff *skb, /* maniptype == SRC for postrouting. */ enum nf_nat_manip_type maniptype = HOOK2MANIP(state->hook); - /* We never see fragments: conntrack defrags on pre-routing - * and local-out, and nf_nat_out protects post-routing. - */ - NF_CT_ASSERT(!ip_is_fragment(ip_hdr(skb))); - ct = nf_ct_get(skb, &ctinfo); /* Can't track? It's not due to stress, or conntrack would * have dropped it. Hence it's the user's responsibilty to -- 2.1.4