Merge git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf

Pablo Neira Ayuso says:

====================
Netfilter fixes for net

1) Restore set counter when one of the CPU loses race to add elements
to sets.

2) After NF_STOLEN, skb might be there no more, update nftables trace
infra to avoid access to skb in this case. From Florian Westphal.

3) nftables bridge might register a prerouting hook with zero priority,
br_netfilter incorrectly skips it. Also from Florian.

* git://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf:
netfilter: br_netfilter: do not skip all hooks with 0 priority
netfilter: nf_tables: avoid skb access on nf_stolen
netfilter: nft_dynset: restore set element counter when failing to update
====================

Link: https://lore.kernel.org/r/
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/netfilter/nf_tables.h

···
 /**
  *	struct nft_traceinfo - nft tracing information and state
  *
+ *	@trace: other struct members are initialised
+ *	@nf_trace: copy of skb->nf_trace before rule evaluation
+ *	@type: event type (enum nft_trace_types)
+ *	@skbid: hash of skb to be used as trace id
+ *	@packet_dumped: packet headers sent in a previous traceinfo message
  *	@pkt: pktinfo currently processed
  *	@basechain: base chain currently processed
  *	@chain: chain currently processed
  *	@rule:  rule that was evaluated
  *	@verdict: verdict given by rule
- *	@type: event type (enum nft_trace_types)
- *	@packet_dumped: packet headers sent in a previous traceinfo message
- *	@trace: other struct members are initialised
  */
 struct nft_traceinfo {
+	bool				trace;
+	bool				nf_trace;
+	bool				packet_dumped;
+	enum nft_trace_types		type:8;
+	u32				skbid;
 	const struct nft_pktinfo	*pkt;
 	const struct nft_base_chain	*basechain;
 	const struct nft_chain		*chain;
 	const struct nft_rule_dp	*rule;
 	const struct nft_verdict	*verdict;
-	enum nft_trace_types		type;
-	bool				packet_dumped;
-	bool				trace;
 };
 
 void nft_trace_init(struct nft_traceinfo *info, const struct nft_pktinfo *pkt,

net/bridge/br_netfilter_hooks.c

···
 		return okfn(net, sk, skb);
 
 	ops = nf_hook_entries_get_hook_ops(e);
-	for (i = 0; i < e->num_hook_entries &&
-	      ops[i]->priority <= NF_BR_PRI_BRNF; i++)
-		;
+	for (i = 0; i < e->num_hook_entries; i++) {
+		/* These hooks have already been called */
+		if (ops[i]->priority < NF_BR_PRI_BRNF)
+			continue;
+
+		/* These hooks have not been called yet, run them. */
+		if (ops[i]->priority > NF_BR_PRI_BRNF)
+			break;
+
+		/* take a closer look at NF_BR_PRI_BRNF. */
+		if (ops[i]->hook == br_nf_pre_routing) {
+			/* This hook diverted the skb to this function,
+			 * hooks after this have not been run yet.
+			 */
+			i++;
+			break;
+		}
+	}
 
 	nf_hook_state_init(&state, hook, NFPROTO_BRIDGE, indev, outdev,
 			   sk, net, okfn);

net/netfilter/nf_tables_core.c

···
 					const struct nft_chain *chain,
 					enum nft_trace_types type)
 {
-	const struct nft_pktinfo *pkt = info->pkt;
-
-	if (!info->trace || !pkt->skb->nf_trace)
+	if (!info->trace || !info->nf_trace)
 		return;
 
 	info->chain = chain;
···
 				    enum nft_trace_types type)
 {
 	if (static_branch_unlikely(&nft_trace_enabled)) {
+		const struct nft_pktinfo *pkt = info->pkt;
+
+		info->nf_trace = pkt->skb->nf_trace;
 		info->rule = rule;
 		__nft_trace_packet(info, chain, type);
+	}
+}
+
+static inline void nft_trace_copy_nftrace(struct nft_traceinfo *info)
+{
+	if (static_branch_unlikely(&nft_trace_enabled)) {
+		const struct nft_pktinfo *pkt = info->pkt;
+
+		if (info->trace)
+			info->nf_trace = pkt->skb->nf_trace;
 	}
 }
 
···
 					 const struct nft_chain *chain,
 					 const struct nft_regs *regs)
 {
+	const struct nft_pktinfo *pkt = info->pkt;
 	enum nft_trace_types type;
 
 	switch (regs->verdict.code) {
···
 	case NFT_RETURN:
 		type = NFT_TRACETYPE_RETURN;
 		break;
+	case NF_STOLEN:
+		type = NFT_TRACETYPE_RULE;
+		/* can't access skb->nf_trace; use copy */
+		break;
 	default:
 		type = NFT_TRACETYPE_RULE;
+		info->nf_trace = pkt->skb->nf_trace;
 		break;
 	}
 
···
 		switch (regs.verdict.code) {
 		case NFT_BREAK:
 			regs.verdict.code = NFT_CONTINUE;
+			nft_trace_copy_nftrace(&info);
 			continue;
 		case NFT_CONTINUE:
 			nft_trace_packet(&info, chain, rule,

net/netfilter/nf_tables_trace.c

···
 #include <linux/module.h>
 #include <linux/static_key.h>
 #include <linux/hash.h>
-#include <linux/jhash.h>
+#include <linux/siphash.h>
 #include <linux/if_vlan.h>
 #include <linux/init.h>
 #include <linux/skbuff.h>
···
 
 DEFINE_STATIC_KEY_FALSE(nft_trace_enabled);
 EXPORT_SYMBOL_GPL(nft_trace_enabled);
-
-static int trace_fill_id(struct sk_buff *nlskb, struct sk_buff *skb)
-{
-	__be32 id;
-
-	/* using skb address as ID results in a limited number of
-	 * values (and quick reuse).
-	 *
-	 * So we attempt to use as many skb members that will not
-	 * change while skb is with netfilter.
-	 */
-	id = (__be32)jhash_2words(hash32_ptr(skb), skb_get_hash(skb),
-				  skb->skb_iif);
-
-	return nla_put_be32(nlskb, NFTA_TRACE_ID, id);
-}
 
 static int trace_fill_header(struct sk_buff *nlskb, u16 type,
 			     const struct sk_buff *skb,
···
 	struct nlmsghdr *nlh;
 	struct sk_buff *skb;
 	unsigned int size;
+	u32 mark = 0;
 	u16 event;
 
 	if (!nfnetlink_has_listeners(nft_net(pkt), NFNLGRP_NFTRACE))
···
 	if (nla_put_be32(skb, NFTA_TRACE_TYPE, htonl(info->type)))
 		goto nla_put_failure;
 
-	if (trace_fill_id(skb, pkt->skb))
+	if (nla_put_u32(skb, NFTA_TRACE_ID, info->skbid))
 		goto nla_put_failure;
 
 	if (nla_put_string(skb, NFTA_TRACE_CHAIN, info->chain->name))
···
 	case NFT_TRACETYPE_RULE:
 		if (nft_verdict_dump(skb, NFTA_TRACE_VERDICT, info->verdict))
 			goto nla_put_failure;
+
+		/* pkt->skb undefined iff NF_STOLEN, disable dump */
+		if (info->verdict->code == NF_STOLEN)
+			info->packet_dumped = true;
+		else
+			mark = pkt->skb->mark;
+
 		break;
 	case NFT_TRACETYPE_POLICY:
+		mark = pkt->skb->mark;
+
 		if (nla_put_be32(skb, NFTA_TRACE_POLICY,
 				 htonl(info->basechain->policy)))
 			goto nla_put_failure;
 		break;
 	}
 
-	if (pkt->skb->mark &&
-	    nla_put_be32(skb, NFTA_TRACE_MARK, htonl(pkt->skb->mark)))
+	if (mark && nla_put_be32(skb, NFTA_TRACE_MARK, htonl(mark)))
 		goto nla_put_failure;
 
 	if (!info->packet_dumped) {
···
 		    const struct nft_verdict *verdict,
 		    const struct nft_chain *chain)
 {
+	static siphash_key_t trace_key __read_mostly;
+	struct sk_buff *skb = pkt->skb;
+
 	info->basechain = nft_base_chain(chain);
 	info->trace = true;
+	info->nf_trace = pkt->skb->nf_trace;
 	info->packet_dumped = false;
 	info->pkt = pkt;
 	info->verdict = verdict;
+
+	net_get_random_once(&trace_key, sizeof(trace_key));
+
+	info->skbid = (u32)siphash_3u32(hash32_ptr(skb),
+					skb_get_hash(skb),
+					skb->skb_iif,
+					&trace_key);
 }

net/netfilter/nft_set_hash.c

···
 	/* Another cpu may race to insert the element with the same key */
 	if (prev) {
 		nft_set_elem_destroy(set, he, true);
+		atomic_dec(&set->nelems);
 		he = prev;
 	}
 
···
 
 err2:
 	nft_set_elem_destroy(set, he, true);
+	atomic_dec(&set->nelems);
 err1:
 	return false;
 }