[SRU Focal] netfilter: nf_tables_offload: incorrect flow offload action array size

[Thadeu Lima de Souza Cascardo]

From: Pablo Neira Ayuso <pablo at netfilter.org>

immediate verdict expression needs to allocate one slot in the flow offload
action array, however, immediate data expression does not need to do so.

fwd and dup expression need to allocate one slot, this is missing.

Add a new offload_action interface to report if this expression needs to
allocate one slot in the flow offload action array.

Fixes: be2861dc36d7 ("netfilter: nft_{fwd,dup}_netdev: add offload support")
Reported-and-tested-by: Nick Gregory <Nick.Gregory at Sophos.com>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(backported from commit b1a5983f56e371046dcf164f90bfaf704d2b89f6 net.git)
[cascardo: there is no offload_stats at struct nft_expr_ops]
CVE-2022-25636
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
---
 include/net/netfilter/nf_tables.h         |  2 +-
 include/net/netfilter/nf_tables_offload.h |  2 --
 net/netfilter/nf_tables_offload.c         |  3 ++-
 net/netfilter/nft_dup_netdev.c            |  6 ++++++
 net/netfilter/nft_fwd_netdev.c            |  6 ++++++
 net/netfilter/nft_immediate.c             | 12 +++++++++++-
 6 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index f694f08ad635..886866bee8b2 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -805,7 +805,7 @@ struct nft_expr_ops {
 	int				(*offload)(struct nft_offload_ctx *ctx,
 						   struct nft_flow_rule *flow,
 						   const struct nft_expr *expr);
-	u32				offload_flags;
+	bool				(*offload_action)(const struct nft_expr *expr);
 	const struct nft_expr_type	*type;
 	void				*data;
 };
diff --git a/include/net/netfilter/nf_tables_offload.h b/include/net/netfilter/nf_tables_offload.h
index d0bb9e3bcec1..a9989ca6e5af 100644
--- a/include/net/netfilter/nf_tables_offload.h
+++ b/include/net/netfilter/nf_tables_offload.h
@@ -60,8 +60,6 @@ struct nft_flow_rule {
 	struct flow_rule	*rule;
 };
 
-#define NFT_OFFLOAD_F_ACTION	(1 << 0)
-
 void nft_flow_rule_set_addr_type(struct nft_flow_rule *flow,
 				 enum flow_dissector_key_id addr_type);
 
diff --git a/net/netfilter/nf_tables_offload.c b/net/netfilter/nf_tables_offload.c
index 3aa4306ca39f..2d3bc22c855c 100644
--- a/net/netfilter/nf_tables_offload.c
+++ b/net/netfilter/nf_tables_offload.c
@@ -55,7 +55,8 @@ struct nft_flow_rule *nft_flow_rule_create(struct net *net,
 
 	expr = nft_expr_first(rule);
 	while (nft_expr_more(rule, expr)) {
-		if (expr->ops->offload_flags & NFT_OFFLOAD_F_ACTION)
+		if (expr->ops->offload_action &&
+		    expr->ops->offload_action(expr))
 			num_actions++;
 
 		expr = nft_expr_next(expr);
diff --git a/net/netfilter/nft_dup_netdev.c b/net/netfilter/nft_dup_netdev.c
index c2e78c160fd7..6007089e1c2f 100644
--- a/net/netfilter/nft_dup_netdev.c
+++ b/net/netfilter/nft_dup_netdev.c
@@ -67,6 +67,11 @@ static int nft_dup_netdev_offload(struct nft_offload_ctx *ctx,
 	return nft_fwd_dup_netdev_offload(ctx, flow, FLOW_ACTION_MIRRED, oif);
 }
 
+static bool nft_dup_netdev_offload_action(const struct nft_expr *expr)
+{
+	return true;
+}
+
 static struct nft_expr_type nft_dup_netdev_type;
 static const struct nft_expr_ops nft_dup_netdev_ops = {
 	.type		= &nft_dup_netdev_type,
@@ -75,6 +80,7 @@ static const struct nft_expr_ops nft_dup_netdev_ops = {
 	.init		= nft_dup_netdev_init,
 	.dump		= nft_dup_netdev_dump,
 	.offload	= nft_dup_netdev_offload,
+	.offload_action	= nft_dup_netdev_offload_action,
 };
 
 static struct nft_expr_type nft_dup_netdev_type __read_mostly = {
diff --git a/net/netfilter/nft_fwd_netdev.c b/net/netfilter/nft_fwd_netdev.c
index b77985986b24..3b0dcd170551 100644
--- a/net/netfilter/nft_fwd_netdev.c
+++ b/net/netfilter/nft_fwd_netdev.c
@@ -77,6 +77,11 @@ static int nft_fwd_netdev_offload(struct nft_offload_ctx *ctx,
 	return nft_fwd_dup_netdev_offload(ctx, flow, FLOW_ACTION_REDIRECT, oif);
 }
 
+static bool nft_fwd_netdev_offload_action(const struct nft_expr *expr)
+{
+	return true;
+}
+
 struct nft_fwd_neigh {
 	enum nft_registers	sreg_dev:8;
 	enum nft_registers	sreg_addr:8;
@@ -219,6 +224,7 @@ static const struct nft_expr_ops nft_fwd_netdev_ops = {
 	.dump		= nft_fwd_netdev_dump,
 	.validate	= nft_fwd_validate,
 	.offload	= nft_fwd_netdev_offload,
+	.offload_action	= nft_fwd_netdev_offload_action,
 };
 
 static const struct nft_expr_ops *
diff --git a/net/netfilter/nft_immediate.c b/net/netfilter/nft_immediate.c
index c7f0ef73d939..98a8149be094 100644
--- a/net/netfilter/nft_immediate.c
+++ b/net/netfilter/nft_immediate.c
@@ -163,6 +163,16 @@ static int nft_immediate_offload(struct nft_offload_ctx *ctx,
 	return 0;
 }
 
+static bool nft_immediate_offload_action(const struct nft_expr *expr)
+{
+	const struct nft_immediate_expr *priv = nft_expr_priv(expr);
+
+	if (priv->dreg == NFT_REG_VERDICT)
+		return true;
+
+	return false;
+}
+
 static const struct nft_expr_ops nft_imm_ops = {
 	.type		= &nft_imm_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_immediate_expr)),
@@ -173,7 +183,7 @@ static const struct nft_expr_ops nft_imm_ops = {
 	.dump		= nft_immediate_dump,
 	.validate	= nft_immediate_validate,
 	.offload	= nft_immediate_offload,
-	.offload_flags	= NFT_OFFLOAD_F_ACTION,
+	.offload_action	= nft_immediate_offload_action,
 };
 
 struct nft_expr_type nft_imm_type __read_mostly = {
-- 
2.32.0