[PATCH AUTOSEL 4.19 20/60] netfilter: ipv6: nf_defrag: accept duplicate fragments again

Sasha Levin
2019-06-27T00:37:20Z

From: Guillaume Nault <gnault@redhat.com>

[ Upstream commit 8a3dca632538c550930ce8bafa8c906b130d35cf ]

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: a0d56cb911ca ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/netfilter/nf_conntrack_reasm.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
index 73c29ddcfb95..35d5a76867d0 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -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);
--
2.20.1