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Date: Fri, 3 Aug 2018 02:22:20 +0200 From: Florian Westphal <fw@...len.de> To: <netdev@...r.kernel.org> Cc: Florian Westphal <fw@...len.de>, Peter Oskolkov <posk@...gle.com>, Eric Dumazet <edumazet@...gle.com> Subject: [PATCH net-next v3] ipv6: defrag: drop non-last frags smaller than min mtu 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@...gle.com> Cc: Eric Dumazet <edumazet@...gle.com> Signed-off-by: Florian Westphal <fw@...len.de> --- 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 0610bdab721c..aed9766559c9 100644 --- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -557,6 +557,10 @@ 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, skb->dev ? skb->dev->ifindex : 0); diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c index 6edd2ac8ae4b..a976b143463b 100644 --- a/net/ipv6/reassembly.c +++ b/net/ipv6/reassembly.c @@ -455,6 +455,10 @@ 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; + iif = skb->dev ? skb->dev->ifindex : 0; fq = fq_find(net, fhdr->identification, hdr, iif); if (fq) { -- 2.16.4
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