netfilter: nf_tables: fix chain binding transaction logic

Add bound flag to rule and chain transactions as in 6a0a8d10a366
("netfilter: nf_tables: use-after-free in failing rule with bound set")
to skip them in case that the chain is already bound from the abort
path.

This patch fixes an imbalance in the chain use refcnt that triggers a
WARN_ON on the table and chain destroy path.

This patch also disallows nested chain bindings, which is not
supported from userspace.

The logic to deal with chain binding in nft_data_hold() and
nft_data_release() is not correct. The NFT_TRANS_PREPARE state needs a
special handling in case a chain is bound but next expressions in the
same rule fail to initialize as described by 1240eb93f061 ("netfilter:
nf_tables: incorrect error path handling with NFT_MSG_NEWRULE").

The chain is left bound if rule construction fails, so the objects
stored in this chain (and the chain itself) are released by the
transaction records from the abort path, follow up patch ("netfilter:
nf_tables: add NFT_TRANS_PREPARE_ERROR to deal with bound set/chain")
completes this error handling.

When deleting an existing rule, chain bound flag is set off so the
rule expression .destroy path releases the objects.

Fixes: d0e2c7de92c7 ("netfilter: nf_tables: add NFT_CHAIN_BINDING")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 78 insertions, 9 deletions

diff --git a/net/netfilter/nft_immediate.c b/net/netfilter/nft_immediate.c
index c9d2f7c29f530..0492a04064f11 100644
--- a/net/netfilter/nft_immediate.c
+++ b/net/netfilter/nft_immediate.c
@@ -76,11 +76,9 @@ static int nft_immediate_init(const struct nft_ctx *ctx,
 		switch (priv->data.verdict.code) {
 		case NFT_JUMP:
 		case NFT_GOTO:
-			if (nft_chain_is_bound(chain)) {
-				err = -EBUSY;
-				goto err1;
-			}
-			chain->bound = true;
+			err = nf_tables_bind_chain(ctx, chain);
+			if (err < 0)
+				return err;
 			break;
 		default:
 			break;
@@ -98,6 +96,31 @@ static void nft_immediate_activate(const struct nft_ctx *ctx,
 				   const struct nft_expr *expr)
 {
 	const struct nft_immediate_expr *priv = nft_expr_priv(expr);
+	const struct nft_data *data = &priv->data;
+	struct nft_ctx chain_ctx;
+	struct nft_chain *chain;
+	struct nft_rule *rule;
+
+	if (priv->dreg == NFT_REG_VERDICT) {
+		switch (data->verdict.code) {
+		case NFT_JUMP:
+		case NFT_GOTO:
+			chain = data->verdict.chain;
+			if (!nft_chain_binding(chain))
+				break;
+
+			chain_ctx = *ctx;
+			chain_ctx.chain = chain;
+
+			list_for_each_entry(rule, &chain->rules, list)
+				nft_rule_expr_activate(&chain_ctx, rule);
+
+			nft_clear(ctx->net, chain);
+			break;
+		default:
+			break;
+		}
+	}
 
 	return nft_data_hold(&priv->data, nft_dreg_to_type(priv->dreg));
 }
@@ -107,6 +130,40 @@ static void nft_immediate_deactivate(const struct nft_ctx *ctx,
 				     enum nft_trans_phase phase)
 {
 	const struct nft_immediate_expr *priv = nft_expr_priv(expr);
+	const struct nft_data *data = &priv->data;
+	struct nft_ctx chain_ctx;
+	struct nft_chain *chain;
+	struct nft_rule *rule;
+
+	if (priv->dreg == NFT_REG_VERDICT) {
+		switch (data->verdict.code) {
+		case NFT_JUMP:
+		case NFT_GOTO:
+			chain = data->verdict.chain;
+			if (!nft_chain_binding(chain))
+				break;
+
+			chain_ctx = *ctx;
+			chain_ctx.chain = chain;
+
+			list_for_each_entry(rule, &chain->rules, list)
+				nft_rule_expr_deactivate(&chain_ctx, rule, phase);
+
+			switch (phase) {
+			case NFT_TRANS_PREPARE:
+				nft_deactivate_next(ctx->net, chain);
+				break;
+			default:
+				nft_chain_del(chain);
+				chain->bound = false;
+				chain->table->use--;
+				break;
+			}
+			break;
+		default:
+			break;
+		}
+	}
 
 	if (phase == NFT_TRANS_COMMIT)
 		return;
@@ -131,15 +188,27 @@ static void nft_immediate_destroy(const struct nft_ctx *ctx,
 	case NFT_GOTO:
 		chain = data->verdict.chain;
 
-		if (!nft_chain_is_bound(chain))
+		if (!nft_chain_binding(chain))
+			break;
+
+		/* Rule construction failed, but chain is already bound:
+		 * let the transaction records release this chain and its rules.
+		 */
+		if (chain->bound) {
+			chain->use--;
 			break;
+		}
 
+		/* Rule has been deleted, release chain and its rules. */
 		chain_ctx = *ctx;
 		chain_ctx.chain = chain;
 
-		list_for_each_entry_safe(rule, n, &chain->rules, list)
-			nf_tables_rule_release(&chain_ctx, rule);
-
+		chain->use--;
+		list_for_each_entry_safe(rule, n, &chain->rules, list) {
+			chain->use--;
+			list_del(&rule->list);
+			nf_tables_rule_destroy(&chain_ctx, rule);
+		}
 		nf_tables_chain_destroy(&chain_ctx);
 		break;
 	default: