From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: [PATCH 4.9 64/71] ipv6: defrag: drop non-last frags smaller than min mtu Date: Tue, 16 Oct 2018 19:10:01 +0200 Message-ID: <20181016170542.593416686@linuxfoundation.org> References: <20181016170539.315587743@linuxfoundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Peter Oskolkov , Eric Dumazet , Florian Westphal , "David S. Miller" To: linux-kernel@vger.kernel.org, netdev@vger.kernel.org Return-path: In-Reply-To: <20181016170539.315587743@linuxfoundation.org> Sender: stable-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Florian Westphal 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 Cc: Eric Dumazet Signed-off-by: Florian Westphal Signed-off-by: David S. Miller (cherry picked from commit 0ed4229b08c13c84a3c301a08defdc9e7f4467e6) Signed-off-by: Greg Kroah-Hartman --- net/ipv6/netfilter/nf_conntrack_reasm.c | 4 ++++ net/ipv6/reassembly.c | 4 ++++ 2 files changed, 8 insertions(+) --- a/net/ipv6/netfilter/nf_conntrack_reasm.c +++ b/net/ipv6/netfilter/nf_conntrack_reasm.c @@ -564,6 +564,10 @@ int nf_ct_frag6_gather(struct net *net, 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); --- a/net/ipv6/reassembly.c +++ b/net/ipv6/reassembly.c @@ -516,6 +516,10 @@ static int ipv6_frag_rcv(struct sk_buff 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) {