netdev - [PATCH v2 net-next 02/11] net_sched: act_connmark: use RCU in tcf_connmark

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Message-ID: <20250709090204.797558-3-edumazet@google.com>
Date: Wed,  9 Jul 2025 09:01:54 +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 02/11] net_sched: act_connmark: use RCU in tcf_connmark_dump()

Also storing tcf_action into struct tcf_connmark_parms
makes sure there is no discrepancy in tcf_connmark_act().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tc_act/tc_connmark.h |  1 +
 net/sched/act_connmark.c         | 18 ++++++++++--------
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/net/tc_act/tc_connmark.h b/include/net/tc_act/tc_connmark.h
index e8dd77a967480352f398f654f331016e2733a371..a5ce83f3eea4bfd5ab2b20071738c08f64d1cdf7 100644
--- a/include/net/tc_act/tc_connmark.h
+++ b/include/net/tc_act/tc_connmark.h
@@ -7,6 +7,7 @@
 struct tcf_connmark_parms {
 	struct net *net;
 	u16 zone;
+	int action;
 	struct rcu_head rcu;
 };
 
diff --git a/net/sched/act_connmark.c b/net/sched/act_connmark.c
index 0fce631e7c91113e5559d12ddc4d0ebeef1237e4..3e89927d711647d75f31c8d80a3ddd102e3d2e36 100644
--- a/net/sched/act_connmark.c
+++ b/net/sched/act_connmark.c
@@ -88,7 +88,7 @@ TC_INDIRECT_SCOPE int tcf_connmark_act(struct sk_buff *skb,
 	/* using overlimits stats to count how many packets marked */
 	tcf_action_inc_overlimit_qstats(&ca->common);
 out:
-	return READ_ONCE(ca->tcf_action);
+	return parms->action;
 }
 
 static const struct nla_policy connmark_policy[TCA_CONNMARK_MAX + 1] = {
@@ -167,6 +167,8 @@ static int tcf_connmark_init(struct net *net, struct nlattr *nla,
 	if (err < 0)
 		goto release_idr;
 
+	nparms->action = parm->action;
+
 	spin_lock_bh(&ci->tcf_lock);
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 	oparms = rcu_replace_pointer(ci->parms, nparms, lockdep_is_held(&ci->tcf_lock));
@@ -190,20 +192,20 @@ static int tcf_connmark_init(struct net *net, struct nlattr *nla,
 static inline int tcf_connmark_dump(struct sk_buff *skb, struct tc_action *a,
 				    int bind, int ref)
 {
+	const struct tcf_connmark_info *ci = to_connmark(a);
 	unsigned char *b = skb_tail_pointer(skb);
-	struct tcf_connmark_info *ci = to_connmark(a);
+	const struct tcf_connmark_parms *parms;
 	struct tc_connmark opt = {
 		.index   = ci->tcf_index,
 		.refcnt  = refcount_read(&ci->tcf_refcnt) - ref,
 		.bindcnt = atomic_read(&ci->tcf_bindcnt) - bind,
 	};
-	struct tcf_connmark_parms *parms;
 	struct tcf_t t;
 
-	spin_lock_bh(&ci->tcf_lock);
-	parms = rcu_dereference_protected(ci->parms, lockdep_is_held(&ci->tcf_lock));
+	rcu_read_lock();
+	parms = rcu_dereference(ci->parms);
 
-	opt.action = ci->tcf_action;
+	opt.action = parms->action;
 	opt.zone = parms->zone;
 	if (nla_put(skb, TCA_CONNMARK_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
@@ -212,12 +214,12 @@ static inline int tcf_connmark_dump(struct sk_buff *skb, struct tc_action *a,
 	if (nla_put_64bit(skb, TCA_CONNMARK_TM, sizeof(t), &t,
 			  TCA_CONNMARK_PAD))
 		goto nla_put_failure;
-	spin_unlock_bh(&ci->tcf_lock);
+	rcu_read_unlock();
 
 	return skb->len;
 
 nla_put_failure:
-	spin_unlock_bh(&ci->tcf_lock);
+	rcu_read_unlock();
 	nlmsg_trim(skb, b);
 	return -1;
 }
-- 
2.50.0.727.gbf7dc18ff4-goog