This is a note to let you know that I've just added the patch titled

netfilter: don't track fragmented packets

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: netfilter-don-t-track-fragmented-packets.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Tue Dec 12 13:26:17 CET 2017

From: Florian Westphal fw@strlen.de Date: Fri, 3 Mar 2017 21:44:00 +0100 Subject: netfilter: don't track fragmented packets

From: Florian Westphal fw@strlen.de

[ Upstream commit 7b4fdf77a450ec0fdcb2f677b080ddbf2c186544 ]

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 andreyknvl@google.com Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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(-)

--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c +++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c @@ -158,6 +158,10 @@ static unsigned int ipv4_conntrack_local 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); }

--- 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_buf /* 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

Patches currently in stable-queue which might be from fw@strlen.de are

queue-4.9/netfilter-don-t-track-fragmented-packets.patch