netdev - [PATCH v2 net-next 07/11] net_sched: act_mpls: use RCU in tcf_mpls

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Message-ID: <20250709090204.797558-8-edumazet@google.com>
Date: Wed,  9 Jul 2025 09:01:59 +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 07/11] net_sched: act_mpls: use RCU in tcf_mpls_dump()

Also storing tcf_action into struct tcf_mpls_params
makes sure there is no discrepancy in tcf_mpls_act().

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tc_act/tc_mpls.h |  1 +
 net/sched/act_mpls.c         | 21 ++++++++++-----------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/include/net/tc_act/tc_mpls.h b/include/net/tc_act/tc_mpls.h
index d452e5e94fd0f6dfaf9510d8722f79b62c6d69bb..dd067bd4018d4bb70ca024f7997d22c7b993782a 100644
--- a/include/net/tc_act/tc_mpls.h
+++ b/include/net/tc_act/tc_mpls.h
@@ -10,6 +10,7 @@
 struct tcf_mpls_params {
 	int tcfm_action;
 	u32 tcfm_label;
+	int action; /* tcf_action */
 	u8 tcfm_tc;
 	u8 tcfm_ttl;
 	u8 tcfm_bos;
diff --git a/net/sched/act_mpls.c b/net/sched/act_mpls.c
index 9f86f4e666d3363b83cfc883136b2c4a231479a4..6654011dcd2ba30769b2f52078373a834e259f88 100644
--- a/net/sched/act_mpls.c
+++ b/net/sched/act_mpls.c
@@ -57,7 +57,7 @@ TC_INDIRECT_SCOPE int tcf_mpls_act(struct sk_buff *skb,
 	struct tcf_mpls *m = to_mpls(a);
 	struct tcf_mpls_params *p;
 	__be32 new_lse;
-	int ret, mac_len;
+	int mac_len;
 
 	tcf_lastuse_update(&m->tcf_tm);
 	bstats_update(this_cpu_ptr(m->common.cpu_bstats), skb);
@@ -72,8 +72,6 @@ TC_INDIRECT_SCOPE int tcf_mpls_act(struct sk_buff *skb,
 		mac_len = skb_network_offset(skb);
 	}
 
-	ret = READ_ONCE(m->tcf_action);
-
 	p = rcu_dereference_bh(m->mpls_p);
 
 	switch (p->tcfm_action) {
@@ -122,7 +120,7 @@ TC_INDIRECT_SCOPE int tcf_mpls_act(struct sk_buff *skb,
 	if (skb_at_tc_ingress(skb))
 		skb_pull_rcsum(skb, skb->mac_len);
 
-	return ret;
+	return p->action;
 
 drop:
 	qstats_drop_inc(this_cpu_ptr(m->common.cpu_qstats));
@@ -296,6 +294,7 @@ static int tcf_mpls_init(struct net *net, struct nlattr *nla,
 					 ACT_MPLS_BOS_NOT_SET);
 	p->tcfm_proto = nla_get_be16_default(tb[TCA_MPLS_PROTO],
 					     htons(ETH_P_MPLS_UC));
+	p->action = parm->action;
 
 	spin_lock_bh(&m->tcf_lock);
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
@@ -330,8 +329,8 @@ static int tcf_mpls_dump(struct sk_buff *skb, struct tc_action *a,
 			 int bind, int ref)
 {
 	unsigned char *b = skb_tail_pointer(skb);
-	struct tcf_mpls *m = to_mpls(a);
-	struct tcf_mpls_params *p;
+	const struct tcf_mpls *m = to_mpls(a);
+	const struct tcf_mpls_params *p;
 	struct tc_mpls opt = {
 		.index    = m->tcf_index,
 		.refcnt   = refcount_read(&m->tcf_refcnt) - ref,
@@ -339,10 +338,10 @@ static int tcf_mpls_dump(struct sk_buff *skb, struct tc_action *a,
 	};
 	struct tcf_t t;
 
-	spin_lock_bh(&m->tcf_lock);
-	opt.action = m->tcf_action;
-	p = rcu_dereference_protected(m->mpls_p, lockdep_is_held(&m->tcf_lock));
+	rcu_read_lock();
+	p = rcu_dereference(m->mpls_p);
 	opt.m_action = p->tcfm_action;
+	opt.action = p->action;
 
 	if (nla_put(skb, TCA_MPLS_PARMS, sizeof(opt), &opt))
 		goto nla_put_failure;
@@ -370,12 +369,12 @@ static int tcf_mpls_dump(struct sk_buff *skb, struct tc_action *a,
 	if (nla_put_64bit(skb, TCA_MPLS_TM, sizeof(t), &t, TCA_MPLS_PAD))
 		goto nla_put_failure;
 
-	spin_unlock_bh(&m->tcf_lock);
+	rcu_read_unlock();
 
 	return skb->len;
 
 nla_put_failure:
-	spin_unlock_bh(&m->tcf_lock);
+	rcu_read_unlock();
 	nlmsg_trim(skb, b);
 	return -EMSGSIZE;
 }
-- 
2.50.0.727.gbf7dc18ff4-goog