[PATCH nf,v2] netfilter: nf_tables: fix chain dependency validation

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The following ruleset:

 add table ip filter
 add chain ip filter input { type filter hook input priority 4; }
 add chain ip filter ap
 add rule ip filter input jump ap
 add rule ip filter ap masquerade

results in a panic, because the masquerade extension should be rejected
from the filter chain. The existing validation is missing a chain
dependency check when the rule is added to the non-base chain.

This patch fixes the problem by walking down the rules from the
basechains, searching for either immediate or lookup expressions, then
jumping to non-base chains and again walking down the rules to perform
the expression validation, so we make sure the full ruleset graph is
validated.

As a result of this patch, nf_tables_check_loops() doesn't use
->validate to check for loops, instead it just checks for immediate
expressions.

Reported-by: Taehee Yoo <ap420073@xxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
v2: restore check_loop routine that broke in v1.

 include/net/netfilter/nf_tables.h      |  2 +
 include/net/netfilter/nf_tables_core.h |  8 ++++
 net/netfilter/nf_tables_api.c          | 82 ++++++++++++++++++++++++----------
 net/netfilter/nft_immediate.c          | 27 +++++++----
 net/netfilter/nft_lookup.c             | 47 +++++++++++++++++++
 5 files changed, 134 insertions(+), 32 deletions(-)

diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h
index a1e28dd5d0bf..7cb4c197b0d8 100644
--- a/include/net/netfilter/nf_tables.h
+++ b/include/net/netfilter/nf_tables.h
@@ -873,6 +873,8 @@ struct nft_chain {
 	char				*name;
 };
 
+int nft_chain_validate(const struct nft_ctx *ctx, const struct nft_chain *chain);
+
 enum nft_chain_types {
 	NFT_CHAIN_T_DEFAULT = 0,
 	NFT_CHAIN_T_ROUTE,
diff --git a/include/net/netfilter/nf_tables_core.h b/include/net/netfilter/nf_tables_core.h
index ea5aab568be8..302913dfd0a2 100644
--- a/include/net/netfilter/nf_tables_core.h
+++ b/include/net/netfilter/nf_tables_core.h
@@ -2,6 +2,8 @@
 #ifndef _NET_NF_TABLES_CORE_H
 #define _NET_NF_TABLES_CORE_H
 
+#include <net/netfilter/nf_tables.h>
+
 extern struct nft_expr_type nft_imm_type;
 extern struct nft_expr_type nft_cmp_type;
 extern struct nft_expr_type nft_lookup_type;
@@ -20,6 +22,12 @@ struct nft_cmp_fast_expr {
 	u8			len;
 };
 
+struct nft_immediate_expr {
+	struct nft_data		data;
+	enum nft_registers	dreg:8;
+	u8			dlen;
+};
+
 /* Calculate the mask for the nft_cmp_fast expression. On big endian the
  * mask needs to include the *upper* bytes when interpreting that data as
  * something smaller than the full u32, therefore a cpu_to_le32 is done.
diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 91e80aa852d6..deb42fe18d5c 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -1903,19 +1903,7 @@ static int nf_tables_newexpr(const struct nft_ctx *ctx,
 			goto err1;
 	}
 
-	if (ops->validate) {
-		const struct nft_data *data = NULL;
-
-		err = ops->validate(ctx, expr, &data);
-		if (err < 0)
-			goto err2;
-	}
-
 	return 0;
-
-err2:
-	if (ops->destroy)
-		ops->destroy(ctx, expr);
 err1:
 	expr->ops = NULL;
 	return err;
@@ -2274,6 +2262,53 @@ static void nf_tables_rule_release(const struct nft_ctx *ctx,
 	nf_tables_rule_destroy(ctx, rule);
 }
 
+int nft_chain_validate(const struct nft_ctx *ctx, const struct nft_chain *chain)
+{
+	struct nft_expr *expr, *last;
+	const struct nft_data *data;
+	struct nft_rule *rule;
+	int err;
+
+	list_for_each_entry(rule, &chain->rules, list) {
+		if (!nft_is_active_next(ctx->net, rule))
+			continue;
+
+		nft_rule_for_each_expr(expr, last, rule) {
+			if (!expr->ops->validate)
+				continue;
+
+			err = expr->ops->validate(ctx, expr, &data);
+			if (err < 0)
+				return err;
+		}
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nft_chain_validate);
+
+static int nf_tables_validate(struct net *net, const struct nft_table *table)
+{
+	struct nft_chain *chain;
+	struct nft_ctx ctx = {
+		.net	= net,
+		.family	= table->family,
+	};
+	int err;
+
+	list_for_each_entry(chain, &table->chains, list) {
+		if (!nft_is_base_chain(chain))
+			continue;
+
+		ctx.chain = chain;
+		err = nft_chain_validate(&ctx, chain);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+
 #define NFT_RULE_MAXEXPRS	128
 
 static struct nft_expr_info *info;
@@ -2435,7 +2470,8 @@ static int nf_tables_newrule(struct net *net, struct sock *nlsk,
 		}
 	}
 	chain->use++;
-	return 0;
+
+	return nf_tables_validate(net, table);
 
 err2:
 	nf_tables_rule_release(&ctx, rule);
@@ -4132,7 +4168,7 @@ static int nf_tables_newsetelem(struct net *net, struct sock *nlsk,
 	const struct nlattr *attr;
 	struct nft_set *set;
 	struct nft_ctx ctx;
-	int rem, err = 0;
+	int rem, err;
 
 	if (nla[NFTA_SET_ELEM_LIST_ELEMENTS] == NULL)
 		return -EINVAL;
@@ -4152,9 +4188,10 @@ static int nf_tables_newsetelem(struct net *net, struct sock *nlsk,
 	nla_for_each_nested(attr, nla[NFTA_SET_ELEM_LIST_ELEMENTS], rem) {
 		err = nft_add_set_elem(&ctx, set, attr, nlh->nlmsg_flags);
 		if (err < 0)
-			break;
+			return err;
 	}
-	return err;
+
+	return nf_tables_validate(net, ctx.table);
 }
 
 /**
@@ -6214,19 +6251,18 @@ static int nf_tables_check_loops(const struct nft_ctx *ctx,
 
 	list_for_each_entry(rule, &chain->rules, list) {
 		nft_rule_for_each_expr(expr, last, rule) {
-			const struct nft_data *data = NULL;
+			struct nft_immediate_expr *priv;
+			const struct nft_data *data;
 			int err;
 
-			if (!expr->ops->validate)
+			if (strcmp(expr->ops->type->name, "immediate"))
 				continue;
 
-			err = expr->ops->validate(ctx, expr, &data);
-			if (err < 0)
-				return err;
-
-			if (data == NULL)
+			priv = nft_expr_priv(expr);
+			if (priv->dreg != NFT_REG_VERDICT)
 				continue;
 
+			data = &priv->data;
 			switch (data->verdict.code) {
 			case NFT_JUMP:
 			case NFT_GOTO:
diff --git a/net/netfilter/nft_immediate.c b/net/netfilter/nft_immediate.c
index aa87ff8beae8..15adf8ca82c3 100644
--- a/net/netfilter/nft_immediate.c
+++ b/net/netfilter/nft_immediate.c
@@ -17,12 +17,6 @@
 #include <net/netfilter/nf_tables_core.h>
 #include <net/netfilter/nf_tables.h>
 
-struct nft_immediate_expr {
-	struct nft_data		data;
-	enum nft_registers	dreg:8;
-	u8			dlen;
-};
-
 static void nft_immediate_eval(const struct nft_expr *expr,
 			       struct nft_regs *regs,
 			       const struct nft_pktinfo *pkt)
@@ -101,12 +95,27 @@ static int nft_immediate_dump(struct sk_buff *skb, const struct nft_expr *expr)
 
 static int nft_immediate_validate(const struct nft_ctx *ctx,
 				  const struct nft_expr *expr,
-				  const struct nft_data **data)
+				  const struct nft_data **d)
 {
 	const struct nft_immediate_expr *priv = nft_expr_priv(expr);
+	const struct nft_data *data;
+	int err;
 
-	if (priv->dreg == NFT_REG_VERDICT)
-		*data = &priv->data;
+	if (priv->dreg != NFT_REG_VERDICT)
+		return 0;
+
+	data = &priv->data;
+
+	switch (data->verdict.code) {
+	case NFT_JUMP:
+	case NFT_GOTO:
+		err = nft_chain_validate(ctx, data->verdict.chain);
+		if (err < 0)
+			return err;
+		break;
+	default:
+		break;
+	}
 
 	return 0;
 }
diff --git a/net/netfilter/nft_lookup.c b/net/netfilter/nft_lookup.c
index f52da5e2199f..42e6fadf1417 100644
--- a/net/netfilter/nft_lookup.c
+++ b/net/netfilter/nft_lookup.c
@@ -149,6 +149,52 @@ static int nft_lookup_dump(struct sk_buff *skb, const struct nft_expr *expr)
 	return -1;
 }
 
+static int nft_lookup_validate_setelem(const struct nft_ctx *ctx,
+				       struct nft_set *set,
+				       const struct nft_set_iter *iter,
+				       struct nft_set_elem *elem)
+{
+	const struct nft_set_ext *ext = nft_set_elem_ext(set, elem->priv);
+	const struct nft_data *data;
+
+	if (nft_set_ext_exists(ext, NFT_SET_EXT_FLAGS) &&
+	    *nft_set_ext_flags(ext) & NFT_SET_ELEM_INTERVAL_END)
+		return 0;
+
+	data = nft_set_ext_data(ext);
+	switch (data->verdict.code) {
+	case NFT_JUMP:
+	case NFT_GOTO:
+		return nft_chain_validate(ctx, data->verdict.chain);
+	default:
+		return 0;
+	}
+}
+
+static int nft_lookup_validate(const struct nft_ctx *ctx,
+			       const struct nft_expr *expr,
+			       const struct nft_data **d)
+{
+	const struct nft_lookup *priv = nft_expr_priv(expr);
+	struct nft_set_iter iter;
+
+	if (!(priv->set->flags & NFT_SET_MAP) ||
+	    priv->set->dtype != NFT_DATA_VERDICT)
+		return 0;
+
+	iter.genmask	= nft_genmask_next(ctx->net);
+	iter.skip	= 0;
+	iter.count	= 0;
+	iter.err	= 0;
+	iter.fn		= nft_lookup_validate_setelem;
+
+	priv->set->ops->walk(ctx, priv->set, &iter);
+	if (iter.err < 0)
+		return iter.err;
+
+	return 0;
+}
+
 static const struct nft_expr_ops nft_lookup_ops = {
 	.type		= &nft_lookup_type,
 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_lookup)),
@@ -156,6 +202,7 @@ static const struct nft_expr_ops nft_lookup_ops = {
 	.init		= nft_lookup_init,
 	.destroy	= nft_lookup_destroy,
 	.dump		= nft_lookup_dump,
+	.validate	= nft_lookup_validate,
 };
 
 struct nft_expr_type nft_lookup_type __read_mostly = {
-- 
2.11.0

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