netdev - [PATCH stable 4.4 06/11] ipv6: defrag: drop non-last frags smaller than min mtu

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Message-ID: <1548209986-83527-7-git-send-email-maowenan@huawei.com>
Date:   Wed, 23 Jan 2019 10:19:41 +0800
From:   Mao Wenan <maowenan@...wei.com>
To:     <netdev@...r.kernel.org>, <gregkh@...ux-foundation.org>,
        <eric.dumazet@...il.com>, <davem@...emloft.net>,
        <stable@...r.kernel.org>, <edumazet@...gle.com>
Subject: [PATCH stable 4.4 06/11] ipv6: defrag: drop non-last frags smaller than min mtu

From: Florian Westphal <fw@...len.de>

[ Upstream commit 0ed4229b08c13c84a3c301a08defdc9e7f4467e6 ]

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>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Mao Wenan <maowenan@...wei.com>
---
 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 9cd8863..c5033a2 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -602,6 +602,10 @@ struct sk_buff *nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 use
 	hdr = ipv6_hdr(clone);
 	fhdr = (struct frag_hdr *)skb_transport_header(clone);
 
+	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 adc7512..44c7f4c 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -549,6 +549,10 @@ 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) {
-- 
1.8.3.1