From: Florian Westphal <fw@strlen.de>
Date: Fri, 3 Aug 2018 02:22:20 +0200
Subject: ipv6: defrag: drop non-last frags smaller than min mtu
Patch-mainline: v4.19-rc1
Git-commit: 0ed4229b08c13c84a3c301a08defdc9e7f4467e6
References: CVE-2018-5391 bsc#1103097
don't bother with pathological cases, they only waste cycles.
IPv6 requires a minimum MTU of 1280 so we should never see fragments
smaller than this (except last frag).
v3: don't use awkward "-offset + len"
v2: drop IPv4 part, which added same check w. IPV4_MIN_MTU (68).
There were concerns that there could be even smaller frags
generated by intermediate nodes, e.g. on radio networks.
Cc: Peter Oskolkov <posk@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Kubecek <mkubecek@suse.cz>
---
net/ipv6/netfilter/nf_conntrack_reasm.c | 4 ++++
net/ipv6/reassembly.c | 4 ++++
2 files changed, 8 insertions(+)
diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
index b263bf3a19f7..3c3fd3f19a95 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -589,6 +589,10 @@ int nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
hdr = ipv6_hdr(skb);
fhdr = (struct frag_hdr *)skb_transport_header(skb);
+ if (skb->len - skb_network_offset(skb) < IPV6_MIN_MTU &&
+ fhdr->frag_off & htons(IP6_MF))
+ return -EINVAL;
+
skb_orphan(skb);
fq = fq_find(net, fhdr->identification, user, &hdr->saddr, &hdr->daddr,
skb->dev ? skb->dev->ifindex : 0, ip6_frag_ecn(hdr));
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 846012eae526..9fe5caa7b032 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -558,6 +558,10 @@ static int ipv6_frag_rcv(struct sk_buff *skb)
return 1;
}
+ if (skb->len - skb_network_offset(skb) < IPV6_MIN_MTU &&
+ fhdr->frag_off & htons(IP6_MF))
+ goto fail_hdr;
+
fq = fq_find(net, fhdr->identification, &hdr->saddr, &hdr->daddr,
skb->dev ? skb->dev->ifindex : 0, ip6_frag_ecn(hdr));
if (fq) {
--
2.18.0