[PATCH nf,v2] netfilter: nf_tables: cancel register tracking if .reduce is not defined

[Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>]

Cancel all register tracking if the the reduce function is not defined.
Add missing reduce function to cmp and compat since these are a
read-only operations.

This patch unbreaks selftests/netfilter/nft_nat_zones.sh.

Fixes: 12e4ecfa244b ("netfilter: nf_tables: add register tracking infrastructure")
Suggested-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
v2: add nft_match_reduce() and nft_target_reduce() so iptables-nft still
    benefits from the register tracking infrastructure.

 net/netfilter/nf_tables_api.c |  2 ++
 net/netfilter/nft_cmp.c       |  8 ++++++++
 net/netfilter/nft_compat.c    | 14 ++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index c86748b3873b..861a3a36024a 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -8311,6 +8311,8 @@ static int nf_tables_commit_chain_prepare(struct net *net, struct nft_chain *cha
 			    expr->ops->reduce(&track, expr)) {
 				expr = track.cur;
 				continue;
+			} else if (expr->ops->reduce == NULL) {
+				memset(track.regs, 0, sizeof(track.regs));
 			}
 
 			if (WARN_ON_ONCE(data + expr->ops->size > data_boundary))
diff --git a/net/netfilter/nft_cmp.c b/net/netfilter/nft_cmp.c
index 47b6d05f1ae6..23bef7df48f1 100644
--- a/net/netfilter/nft_cmp.c
+++ b/net/netfilter/nft_cmp.c
@@ -187,12 +187,19 @@ static int nft_cmp_offload(struct nft_offload_ctx *ctx,
 	return __nft_cmp_offload(ctx, flow, priv);
 }
 
+static bool nft_cmp_reduce(struct nft_regs_track *track,
+			   const struct nft_expr *expr)
+{
+	return false;
+}
+
 static const struct nft_expr_ops nft_cmp_ops = {
 	.type		= &nft_cmp_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_cmp_expr)),
 	.eval		= nft_cmp_eval,
 	.init		= nft_cmp_init,
 	.dump		= nft_cmp_dump,
+	.reduce		= nft_cmp_reduce,
 	.offload	= nft_cmp_offload,
 };
 
@@ -269,6 +276,7 @@ const struct nft_expr_ops nft_cmp_fast_ops = {
 	.eval		= NULL,	/* inlined */
 	.init		= nft_cmp_fast_init,
 	.dump		= nft_cmp_fast_dump,
+	.reduce		= nft_cmp_reduce,
 	.offload	= nft_cmp_fast_offload,
 };
 
diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c
index f69cc73c5813..404cc806d12b 100644
--- a/net/netfilter/nft_compat.c
+++ b/net/netfilter/nft_compat.c
@@ -731,6 +731,12 @@ static const struct nfnetlink_subsystem nfnl_compat_subsys = {
 
 static struct nft_expr_type nft_match_type;
 
+static bool nft_match_reduce(struct nft_regs_track *track,
+			     const struct nft_expr *expr)
+{
+	return false;
+}
+
 static const struct nft_expr_ops *
 nft_match_select_ops(const struct nft_ctx *ctx,
 		     const struct nlattr * const tb[])
@@ -773,6 +779,7 @@ nft_match_select_ops(const struct nft_ctx *ctx,
 	ops->dump = nft_match_dump;
 	ops->validate = nft_match_validate;
 	ops->data = match;
+	ops->reduce = nft_match_reduce;
 
 	matchsize = NFT_EXPR_SIZE(XT_ALIGN(match->matchsize));
 	if (matchsize > NFT_MATCH_LARGE_THRESH) {
@@ -811,6 +818,12 @@ static struct nft_expr_type nft_match_type __read_mostly = {
 
 static struct nft_expr_type nft_target_type;
 
+static bool nft_target_reduce(struct nft_regs_track *track,
+			      const struct nft_expr *expr)
+{
+	return false;
+}
+
 static const struct nft_expr_ops *
 nft_target_select_ops(const struct nft_ctx *ctx,
 		      const struct nlattr * const tb[])
@@ -862,6 +875,7 @@ nft_target_select_ops(const struct nft_ctx *ctx,
 	ops->dump = nft_target_dump;
 	ops->validate = nft_target_validate;
 	ops->data = target;
+	ops->reduce = nft_target_reduce;
 
 	if (family == NFPROTO_BRIDGE)
 		ops->eval = nft_target_eval_bridge;
-- 
2.30.2