net_sched: act_ct: use RCU in tcf_ct_dump()

Also storing tcf_action into struct tcf_ct_params
makes sure there is no discrepancy in tcf_ct_act().

Signed-off-by: Eric Dumazet <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/tc_act/tc_ct.h

···
 	struct nf_conntrack_helper *helper;
 	struct nf_conn *tmpl;
 	u16 zone;
-
+	int action;
 	u32 mark;
 	u32 mark_mask;
 

net/sched/act_ct.c

···
 
 	p = rcu_dereference_bh(c->params);
 
-	retval = READ_ONCE(c->tcf_action);
+	retval = p->action;
 	commit = p->ct_action & TCA_CT_ACT_COMMIT;
 	clear = p->ct_action & TCA_CT_ACT_CLEAR;
 	tmpl = p->tmpl;
···
 	if (err)
 		goto cleanup;
 
+	params->action = parm->action;
 	spin_lock_bh(&c->tcf_lock);
 	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
 	params = rcu_replace_pointer(c->params, params,
···
 }
 
 static int tcf_ct_dump_key_val(struct sk_buff *skb,
-			       void *val, int val_type,
-			       void *mask, int mask_type,
+			       const void *val, int val_type,
+			       const void *mask, int mask_type,
 			       int len)
 {
 	int err;
···
 	return 0;
 }
 
-static int tcf_ct_dump_nat(struct sk_buff *skb, struct tcf_ct_params *p)
+static int tcf_ct_dump_nat(struct sk_buff *skb, const struct tcf_ct_params *p)
 {
-	struct nf_nat_range2 *range = &p->range;
+	const struct nf_nat_range2 *range = &p->range;
 
 	if (!(p->ct_action & TCA_CT_ACT_NAT))
 		return 0;
···
 	return 0;
 }
 
-static int tcf_ct_dump_helper(struct sk_buff *skb, struct nf_conntrack_helper *helper)
+static int tcf_ct_dump_helper(struct sk_buff *skb,
+			      const struct nf_conntrack_helper *helper)
 {
 	if (!helper)
 		return 0;
···
 			      int bind, int ref)
 {
 	unsigned char *b = skb_tail_pointer(skb);
-	struct tcf_ct *c = to_ct(a);
-	struct tcf_ct_params *p;
-
+	const struct tcf_ct *c = to_ct(a);
+	const struct tcf_ct_params *p;
 	struct tc_ct opt = {
 		.index   = c->tcf_index,
 		.refcnt  = refcount_read(&c->tcf_refcnt) - ref,
···
 	};
 	struct tcf_t t;
 
-	spin_lock_bh(&c->tcf_lock);
-	p = rcu_dereference_protected(c->params,
-				      lockdep_is_held(&c->tcf_lock));
-	opt.action = c->tcf_action;
+	rcu_read_lock();
+	p = rcu_dereference(c->params);
+	opt.action = p->action;
 
 	if (tcf_ct_dump_key_val(skb,
 				&p->ct_action, TCA_CT_ACTION,
···
 	tcf_tm_dump(&t, &c->tcf_tm);
 	if (nla_put_64bit(skb, TCA_CT_TM, sizeof(t), &t, TCA_CT_PAD))
 		goto nla_put_failure;
-	spin_unlock_bh(&c->tcf_lock);
+	rcu_read_unlock();
 
 	return skb->len;
 nla_put_failure:
-	spin_unlock_bh(&c->tcf_lock);
+	rcu_read_unlock();
 	nlmsg_trim(skb, b);
 	return -1;
 }