netdev - [PATCH v2 net-next 06/11] net_sched: act_ctinfo: use RCU in tcf_ctinfo

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Message-ID: <20250709090204.797558-7-edumazet@google.com>
Date: Wed,  9 Jul 2025 09:01:58 +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 06/11] net_sched: act_ctinfo: use RCU in tcf_ctinfo_dump()

Also storing tcf_action into struct tcf_ctinfo_params
makes sure there is no discrepancy in tcf_ctinfo_act().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tc_act/tc_ctinfo.h |  1 +
 net/sched/act_ctinfo.c         | 23 +++++++++++------------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/include/net/tc_act/tc_ctinfo.h b/include/net/tc_act/tc_ctinfo.h
index a04bcac7adf4b61b73181d5dbd2ff9eee3cf5e97..7fe01ab236da4eaa0624db08d0a9599e36820bee 100644
--- a/include/net/tc_act/tc_ctinfo.h
+++ b/include/net/tc_act/tc_ctinfo.h
@@ -7,6 +7,7 @@
 struct tcf_ctinfo_params {
 	struct rcu_head rcu;
 	struct net *net;
+	int action;
 	u32 dscpmask;
 	u32 dscpstatemask;
 	u32 cpmarkmask;
diff --git a/net/sched/act_ctinfo.c b/net/sched/act_ctinfo.c
index 93ab3bcd6d3106a1561f043e078d0be5997ea277..71efe04d00b5c6195e43f1ea6dab1548f6f97293 100644
--- a/net/sched/act_ctinfo.c
+++ b/net/sched/act_ctinfo.c
@@ -88,13 +88,11 @@ TC_INDIRECT_SCOPE int tcf_ctinfo_act(struct sk_buff *skb,
 	struct tcf_ctinfo_params *cp;
 	struct nf_conn *ct;
 	int proto, wlen;
-	int action;
 
 	cp = rcu_dereference_bh(ca->params);
 
 	tcf_lastuse_update(&ca->tcf_tm);
 	tcf_action_update_bstats(&ca->common, skb);
-	action = READ_ONCE(ca->tcf_action);
 
 	wlen = skb_network_offset(skb);
 	switch (skb_protocol(skb, true)) {
@@ -141,7 +139,7 @@ TC_INDIRECT_SCOPE int tcf_ctinfo_act(struct sk_buff *skb,
 	if (thash)
 		nf_ct_put(ct);
 out:
-	return action;
+	return cp->action;
 }
 
 static const struct nla_policy ctinfo_policy[TCA_CTINFO_MAX + 1] = {
@@ -258,6 +256,8 @@ static int tcf_ctinfo_init(struct net *net, struct nlattr *nla,
 		cp_new->mode |= CTINFO_MODE_CPMARK;
 	}
 
+	cp_new->action = actparm->action;
+
 	spin_lock_bh(&ci->tcf_lock);
 	goto_ch = tcf_action_set_ctrlact(*a, actparm->action, goto_ch);
 	cp_new = rcu_replace_pointer(ci->params, cp_new,
@@ -282,25 +282,24 @@ static int tcf_ctinfo_init(struct net *net, struct nlattr *nla,
 static int tcf_ctinfo_dump(struct sk_buff *skb, struct tc_action *a,
 			   int bind, int ref)
 {
-	struct tcf_ctinfo *ci = to_ctinfo(a);
+	const struct tcf_ctinfo *ci = to_ctinfo(a);
+	unsigned char *b = skb_tail_pointer(skb);
+	const struct tcf_ctinfo_params *cp;
 	struct tc_ctinfo opt = {
 		.index   = ci->tcf_index,
 		.refcnt  = refcount_read(&ci->tcf_refcnt) - ref,
 		.bindcnt = atomic_read(&ci->tcf_bindcnt) - bind,
 	};
-	unsigned char *b = skb_tail_pointer(skb);
-	struct tcf_ctinfo_params *cp;
 	struct tcf_t t;
 
-	spin_lock_bh(&ci->tcf_lock);
-	cp = rcu_dereference_protected(ci->params,
-				       lockdep_is_held(&ci->tcf_lock));
+	rcu_read_lock();
+	cp = rcu_dereference(ci->params);
 
 	tcf_tm_dump(&t, &ci->tcf_tm);
 	if (nla_put_64bit(skb, TCA_CTINFO_TM, sizeof(t), &t, TCA_CTINFO_PAD))
 		goto nla_put_failure;
 
-	opt.action = ci->tcf_action;
+	opt.action = cp->action;
 	if (nla_put(skb, TCA_CTINFO_ACT, sizeof(opt), &opt))
 		goto nla_put_failure;
 
@@ -337,11 +336,11 @@ static int tcf_ctinfo_dump(struct sk_buff *skb, struct tc_action *a,
 			      TCA_CTINFO_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