netdev - [PATCH v2 net-next 08/11] net_sched: act_nat: use RCU in tcf_nat

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Message-ID: <20250709090204.797558-9-edumazet@google.com>
Date: Wed,  9 Jul 2025 09:02:00 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, Jamal Hadi Salim <jhs@...atatu.com>, 
	Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 net-next 08/11] net_sched: act_nat: use RCU in tcf_nat_dump()

Also storing tcf_action into struct tcf_nat_params
makes sure there is no discrepancy in tcf_nat_act().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tc_act/tc_nat.h |  1 +
 net/sched/act_nat.c         | 25 ++++++++++++-------------
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/include/net/tc_act/tc_nat.h b/include/net/tc_act/tc_nat.h
index c869274ac529b2667a5d9ebcc4a35dbd34da71bb..ae35f4009445560401b78584d165fbcc635c4ae5 100644
--- a/include/net/tc_act/tc_nat.h
+++ b/include/net/tc_act/tc_nat.h
@@ -6,6 +6,7 @@
 #include <net/act_api.h>
 
 struct tcf_nat_parms {
+	int action;
 	__be32 old_addr;
 	__be32 new_addr;
 	__be32 mask;
diff --git a/net/sched/act_nat.c b/net/sched/act_nat.c
index d541f553805face5a0d444659c17e0b720aeb843..26241d80ebe03e74a92e951fb5ae065493b93277 100644
--- a/net/sched/act_nat.c
+++ b/net/sched/act_nat.c
@@ -91,6 +91,7 @@ static int tcf_nat_init(struct net *net, struct nlattr *nla, struct nlattr *est,
 	nparm->new_addr = parm->new_addr;
 	nparm->mask = parm->mask;
 	nparm->flags = parm->flags;
+	nparm->action = parm->action;
 
 	p = to_tcf_nat(*a);
 
@@ -130,17 +131,16 @@ TC_INDIRECT_SCOPE int tcf_nat_act(struct sk_buff *skb,
 	tcf_lastuse_update(&p->tcf_tm);
 	tcf_action_update_bstats(&p->common, skb);
 
-	action = READ_ONCE(p->tcf_action);
-
 	parms = rcu_dereference_bh(p->parms);
+	action = parms->action;
+	if (unlikely(action == TC_ACT_SHOT))
+		goto drop;
+
 	old_addr = parms->old_addr;
 	new_addr = parms->new_addr;
 	mask = parms->mask;
 	egress = parms->flags & TCA_NAT_FLAG_EGRESS;
 
-	if (unlikely(action == TC_ACT_SHOT))
-		goto drop;
-
 	noff = skb_network_offset(skb);
 	if (!pskb_may_pull(skb, sizeof(*iph) + noff))
 		goto drop;
@@ -268,21 +268,20 @@ static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 			int bind, int ref)
 {
 	unsigned char *b = skb_tail_pointer(skb);
-	struct tcf_nat *p = to_tcf_nat(a);
+	const struct tcf_nat *p = to_tcf_nat(a);
+	const struct tcf_nat_parms *parms;
 	struct tc_nat opt = {
 		.index    = p->tcf_index,
 		.refcnt   = refcount_read(&p->tcf_refcnt) - ref,
 		.bindcnt  = atomic_read(&p->tcf_bindcnt) - bind,
 	};
-	struct tcf_nat_parms *parms;
 	struct tcf_t t;
 
-	spin_lock_bh(&p->tcf_lock);
-
-	opt.action = p->tcf_action;
+	rcu_read_lock();
 
-	parms = rcu_dereference_protected(p->parms, lockdep_is_held(&p->tcf_lock));
+	parms = rcu_dereference(p->parms);
 
+	opt.action = parms->action;
 	opt.old_addr = parms->old_addr;
 	opt.new_addr = parms->new_addr;
 	opt.mask = parms->mask;
@@ -294,12 +293,12 @@ static int tcf_nat_dump(struct sk_buff *skb, struct tc_action *a,
 	tcf_tm_dump(&t, &p->tcf_tm);
 	if (nla_put_64bit(skb, TCA_NAT_TM, sizeof(t), &t, TCA_NAT_PAD))
 		goto nla_put_failure;
-	spin_unlock_bh(&p->tcf_lock);
+	rcu_read_unlock();
 
 	return skb->len;
 
 nla_put_failure:
-	spin_unlock_bh(&p->tcf_lock);
+	rcu_read_unlock();
 	nlmsg_trim(skb, b);
 	return -1;
 }
-- 
2.50.0.727.gbf7dc18ff4-goog