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netfilter: ipv6: nf_defrag: accept duplicate fragments again 

When fixing the skb leak introduced by the conversion to rbtree, I
forgot about the special case of duplicate fragments. The condition
under the 'insert_error' label isn't effective anymore as
nf_ct_frg6_gather() doesn't override the returned value anymore. So
duplicate fragments now get NF_DROP verdict.

To accept duplicate fragments again, handle them specially as soon as
inet_frag_queue_insert() reports them. Return -EINPROGRESS which will
translate to NF_STOLEN verdict, like any accepted fragment. However,
such packets don't carry any new information and aren't queued, so we
just drop them immediately.

Fixes: a0d56cb911 ("netfilter: ipv6: nf_defrag: fix leakage of unqueued fragments")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Guillaume Nault 2019-06-06 18:04:00 +02:00 committed by Pablo Neira Ayuso
parent a0d56cb911
commit 8a3dca6325
1 changed files with 7 additions and 3 deletions
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10
net/ipv6/netfilter/nf_conntrack_reasm.c
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@ -265,8 +265,14 @@ static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
prev = fq->q.fragments_tail;
err = inet_frag_queue_insert(&fq->q, skb, offset, end);
if (err)
if (err) {
if (err == IPFRAG_DUP) {
/* No error for duplicates, pretend they got queued. */
kfree_skb(skb);
return -EINPROGRESS;
}
goto insert_error;
}
if (dev)
fq->iif = dev->ifindex;
@ -304,8 +310,6 @@ static int nf_ct_frag6_queue(struct frag_queue *fq, struct sk_buff *skb,
return -EINPROGRESS;
insert_error:
if (err == IPFRAG_DUP)
goto err;
inet_frag_kill(&fq->q);
err:
skb_dst_drop(skb);