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netfilter: conntrack: remove unneeded nf_ct_put

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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 <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2020-08-26 00:52:45 +02:00 committed by Pablo Neira Ayuso
parent bc92470413
commit ff73e7479b
1 changed files with 3 additions and 4 deletions
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7
net/netfilter/nf_conntrack_core.c
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@ -908,6 +908,7 @@ static void __nf_conntrack_insert_prepare(struct nf_conn *ct)
tstamp->start = ktime_get_real_ns(); tstamp->start = ktime_get_real_ns();
} }
/* caller must hold locks to prevent concurrent changes */
static int __nf_ct_resolve_clash(struct sk_buff *skb, static int __nf_ct_resolve_clash(struct sk_buff *skb,
struct nf_conntrack_tuple_hash *h) 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)) if (nf_ct_is_dying(ct))
return NF_DROP; return NF_DROP;
if (!atomic_inc_not_zero(&ct->ct_general.use))
return NF_DROP;
if (((ct->status & IPS_NAT_DONE_MASK) == 0) || if (((ct->status & IPS_NAT_DONE_MASK) == 0) ||
nf_ct_match(ct, loser_ct)) { nf_ct_match(ct, loser_ct)) {
struct net *net = nf_ct_net(ct); struct net *net = nf_ct_net(ct);
nf_conntrack_get(&ct->ct_general);
nf_ct_acct_merge(ct, ctinfo, loser_ct); nf_ct_acct_merge(ct, ctinfo, loser_ct);
nf_ct_add_to_dying_list(loser_ct); nf_ct_add_to_dying_list(loser_ct);
nf_conntrack_put(&loser_ct->ct_general); nf_conntrack_put(&loser_ct->ct_general);
@ -937,7 +937,6 @@ static int __nf_ct_resolve_clash(struct sk_buff *skb,
return NF_ACCEPT; return NF_ACCEPT;
} }
nf_ct_put(ct);
return NF_DROP; return NF_DROP;
} }