netdev - [PATCH v2 net-next 03/11] net_sched: act_csum: use RCU in tcf_csum

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Message-ID: <20250709090204.797558-4-edumazet@google.com>
Date: Wed,  9 Jul 2025 09:01:55 +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 03/11] net_sched: act_csum: use RCU in tcf_csum_dump()

Also storing tcf_action into struct tcf_csum_params
makes sure there is no discrepancy in tcf_csum_act().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tc_act/tc_csum.h |  1 +
 net/sched/act_csum.c         | 18 +++++++++---------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/include/net/tc_act/tc_csum.h b/include/net/tc_act/tc_csum.h
index 2515da0142a671be82f873183077a12b5c8600b2..8d0c7a9f934525cc5fa5fd2d5ea9808629b4a550 100644
--- a/include/net/tc_act/tc_csum.h
+++ b/include/net/tc_act/tc_csum.h
@@ -8,6 +8,7 @@
 
 struct tcf_csum_params {
 	u32 update_flags;
+	int action;
 	struct rcu_head rcu;
 };
 
diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index 5cc8e407e7911c6c9f252d58b458728174913317..0939e6b2ba4d1947df0f3dcfc09bfaa339a6ace2 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -99,6 +99,7 @@ static int tcf_csum_init(struct net *net, struct nlattr *nla,
 		goto put_chain;
 	}
 	params_new->update_flags = parm->update_flags;
+	params_new->action = parm->action;
 
 	spin_lock_bh(&p->tcf_lock);
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
@@ -580,7 +581,7 @@ TC_INDIRECT_SCOPE int tcf_csum_act(struct sk_buff *skb,
 	tcf_lastuse_update(&p->tcf_tm);
 	tcf_action_update_bstats(&p->common, skb);
 
-	action = READ_ONCE(p->tcf_action);
+	action = params->action;
 	if (unlikely(action == TC_ACT_SHOT))
 		goto drop;
 
@@ -631,9 +632,9 @@ TC_INDIRECT_SCOPE int tcf_csum_act(struct sk_buff *skb,
 static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
 			 int ref)
 {
+	const struct tcf_csum *p = to_tcf_csum(a);
 	unsigned char *b = skb_tail_pointer(skb);
-	struct tcf_csum *p = to_tcf_csum(a);
-	struct tcf_csum_params *params;
+	const struct tcf_csum_params *params;
 	struct tc_csum opt = {
 		.index   = p->tcf_index,
 		.refcnt  = refcount_read(&p->tcf_refcnt) - ref,
@@ -641,10 +642,9 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
 	};
 	struct tcf_t t;
 
-	spin_lock_bh(&p->tcf_lock);
-	params = rcu_dereference_protected(p->params,
-					   lockdep_is_held(&p->tcf_lock));
-	opt.action = p->tcf_action;
+	rcu_read_lock();
+	params = rcu_dereference(p->params);
+	opt.action = params->action;
 	opt.update_flags = params->update_flags;
 
 	if (nla_put(skb, TCA_CSUM_PARMS, sizeof(opt), &opt))
@@ -653,12 +653,12 @@ static int tcf_csum_dump(struct sk_buff *skb, struct tc_action *a, int bind,
 	tcf_tm_dump(&t, &p->tcf_tm);
 	if (nla_put_64bit(skb, TCA_CSUM_TM, sizeof(t), &t, TCA_CSUM_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