[PATCH 07/13] netfilter: conntrack: remove unneeded nf_ct_put

[Pablo Neira Ayuso]

From: Florian Westphal <f...@strlen.de>

We can delay refcount increment until we reassign the existing entry to
the current skb.

A 0 refcount can't happen while the nf_conn object is still in the
hash table and parallel mutations are impossible because we hold the
bucket lock.

Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
---
 net/netfilter/nf_conntrack_core.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nf_conntrack_core.c 
b/net/netfilter/nf_conntrack_core.c
index 93e77ca0efad..234b7cab37c3 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -908,6 +908,7 @@ static void __nf_conntrack_insert_prepare(struct nf_conn 
*ct)
                tstamp->start = ktime_get_real_ns();
 }
 
+/* caller must hold locks to prevent concurrent changes */
 static int __nf_ct_resolve_clash(struct sk_buff *skb,
                                 struct nf_conntrack_tuple_hash *h)
 {
@@ -921,13 +922,12 @@ static int __nf_ct_resolve_clash(struct sk_buff *skb,
        if (nf_ct_is_dying(ct))
                return NF_DROP;
 
-       if (!atomic_inc_not_zero(&ct->ct_general.use))
-               return NF_DROP;
-
        if (((ct->status & IPS_NAT_DONE_MASK) == 0) ||
            nf_ct_match(ct, loser_ct)) {
                struct net *net = nf_ct_net(ct);
 
+               nf_conntrack_get(&ct->ct_general);
+
                nf_ct_acct_merge(ct, ctinfo, loser_ct);
                nf_ct_add_to_dying_list(loser_ct);
                nf_conntrack_put(&loser_ct->ct_general);
@@ -937,7 +937,6 @@ static int __nf_ct_resolve_clash(struct sk_buff *skb,
                return NF_ACCEPT;
        }
 
-       nf_ct_put(ct);
        return NF_DROP;
 }
 
-- 
2.20.1