From cd945a64775a4c78bab47299c72cc35e871bcea2 Mon Sep 17 00:00:00 2001
From: Marius van der Wijden <m.vanderwijden@live.de>
Date: Tue, 10 Mar 2026 16:21:01 +0100
Subject: [PATCH] core: verify BAL gas limit

---
 core/blockchain.go             |  5 +++++
 core/types/bal/bal_encoding.go | 25 +++++++++++++++++++++++++
 params/protocol_params.go      |  2 ++
 3 files changed, 32 insertions(+)

diff --git a/core/blockchain.go b/core/blockchain.go
index d88687c245..6345e05609 100644
--- a/core/blockchain.go
+++ b/core/blockchain.go
@@ -2418,6 +2418,11 @@ func (bc *BlockChain) ProcessBlock(ctx context.Context, parentRoot common.Hash,
 			bc.reportBadBlock(block, res, err)
 			return nil, err
 		}
+		// EIP-7928: Validate BAL items do not exceed block gas limit
+		if err := computedAccessList.ValidateGasLimit(block.Header().GasLimit); err != nil {
+			bc.reportBadBlock(block, res, err)
+			return nil, err
+		}
 		if block.AccessList() == nil {
 			// attach the computed access list to the block so it gets persisted
 			// when the block is written to disk
diff --git a/core/types/bal/bal_encoding.go b/core/types/bal/bal_encoding.go
index 124b7712c9..25d8bedc01 100644
--- a/core/types/bal/bal_encoding.go
+++ b/core/types/bal/bal_encoding.go
@@ -131,6 +131,31 @@ func (e BlockAccessList) Validate(blockTxCount int) error {
 	return nil
 }
 
+// ValidateGasLimit checks that the total number of BAL items (addresses +
+// unique storage keys) does not exceed block_gas_limit / GasBlockAccessListItem.
+// See EIP-7928 validate_block_access_list_gas_limit.
+func (e BlockAccessList) ValidateGasLimit(blockGasLimit uint64) error {
+	var balItems uint64
+	for _, account := range e {
+		// Count each address as one item
+		balItems++
+		// Count unique storage keys across both reads and writes
+		uniqueSlots := make(map[common.Hash]struct{})
+		for _, sc := range account.StorageChanges {
+			uniqueSlots[sc.Slot.ToHash()] = struct{}{}
+		}
+		for _, sr := range account.StorageReads {
+			uniqueSlots[sr.ToHash()] = struct{}{}
+		}
+		balItems += uint64(len(uniqueSlots))
+	}
+	limit := blockGasLimit / params.GasBlockAccessListItem
+	if balItems > limit {
+		return fmt.Errorf("block access list exceeds gas limit: %d items exceeds limit of %d", balItems, limit)
+	}
+	return nil
+}
+
 // Hash computes the keccak256 hash of the access list
 func (e *BlockAccessList) Hash() common.Hash {
 	var enc bytes.Buffer
diff --git a/params/protocol_params.go b/params/protocol_params.go
index a729b938f5..f2c6b5f1c9 100644
--- a/params/protocol_params.go
+++ b/params/protocol_params.go
@@ -192,6 +192,8 @@ const (
 	AccountCreationSize       = 112
 	StorageCreationSize       = 32
 	AuthorizationCreationSize = 23
+
+	GasBlockAccessListItem = 2000 // EIP-7928: gas cost per BAL item for gas limit check
 )
 
 // Bls12381G1MultiExpDiscountTable is the gas discount table for BLS12-381 G1 multi exponentiation operation