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ipv6: defrag: drop non-last frags smaller than min mtu

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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>
This commit is contained in:
Florian Westphal 2018-08-03 02:22:20 +02:00 committed by David S. Miller
parent c30f1fc041
commit 0ed4229b08
2 changed files with 8 additions and 0 deletions
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4
net/ipv6/netfilter/nf_conntrack_reasm.c
View file

@ -558,6 +558,10 @@ 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);

4
net/ipv6/reassembly.c
View file

@ -456,6 +456,10 @@ 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) {