netfilter: nf_tables: Carry s_idx in nft_rule_dump_ctx

In order to move the context into struct netlink_callback's scratch
area, the latter must be unused first.
Signed-off-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Florian Westphal <fw@strlen.de>

net/netfilter/nf_tables_api.c

@@ -3441,6 +3441,7 @@ static void audit_log_rule_reset(const struct nft_table *table,
 }
 
 struct nft_rule_dump_ctx {
+	unsigned int s_idx;
 	char *table;
 	char *chain;
 	bool reset;
@@ -3455,7 +3456,6 @@ static int __nf_tables_dump_rules(struct sk_buff *skb,
 	struct nft_rule_dump_ctx *ctx = cb->data;
 	struct net *net = sock_net(skb->sk);
 	const struct nft_rule *rule, *prule;
-	unsigned int s_idx = cb->args[0];
 	unsigned int entries = 0;
 	int ret = 0;
 	u64 handle;
@@ -3464,7 +3464,7 @@ static int __nf_tables_dump_rules(struct sk_buff *skb,
 	list_for_each_entry_rcu(rule, &chain->rules, list) {
 		if (!nft_is_active(net, rule))
 			goto cont_skip;
-		if (*idx < s_idx)
+		if (*idx < ctx->s_idx)
 			goto cont;
 		if (prule)
 			handle = prule->handle;
@@ -3498,7 +3498,7 @@ static int nf_tables_dump_rules(struct sk_buff *skb,
 				struct netlink_callback *cb)
 {
 	const struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh);
-	const struct nft_rule_dump_ctx *ctx = cb->data;
+	struct nft_rule_dump_ctx *ctx = cb->data;
 	struct nft_table *table;
 	const struct nft_chain *chain;
 	unsigned int idx = 0;
@@ -3547,7 +3547,7 @@ static int nf_tables_dump_rules(struct sk_buff *skb,
 done:
 	rcu_read_unlock();
 
-	cb->args[0] = idx;
+	ctx->s_idx = idx;
 	return skb->len;
 }