From c5d36e749672a7aa999fe9a4b4020c15a5f47e45 Mon Sep 17 00:00:00 2001
From: Gary Rong <garyrong0905@gmail.com>
Date: Mon, 6 Jul 2026 11:03:20 +0800
Subject: [PATCH] core/vm: implement access cost check in SSTORE

---
 core/vm/eip8038_test.go | 46 +++++++++++++++++++++++++++++++++++++++++
 core/vm/gas_table.go    | 24 ++++++++++++++++-----
 2 files changed, 65 insertions(+), 5 deletions(-)

diff --git a/core/vm/eip8038_test.go b/core/vm/eip8038_test.go
index c08c54fb2c..3d0383942b 100644
--- a/core/vm/eip8038_test.go
+++ b/core/vm/eip8038_test.go
@@ -235,3 +235,49 @@ func TestEIP8038SelfdestructAccountWrite(t *testing.T) {
 		t.Fatalf("state gas = %d, want %d", res.UsedStateGas, want)
 	}
 }
+
+// EIP-7928: SSTORE must cover the slot's access cost before its implicit read
+// of the current value, so that a failing SSTORE does not leak the slot into
+// the block access list. The stipend sentry alone cannot guard the read, as
+// COLD_STORAGE_ACCESS (3000) exceeds GAS_CALL_STIPEND (2300).
+func TestSStoreBALAccessCostCheck(t *testing.T) {
+	self := common.BytesToAddress([]byte("self"))
+	slot := common.BytesToHash([]byte{0})
+
+	// run executes a noop write (1 -> 1) on a cold slot with block access list
+	// recording enabled and returns the recorded storage reads of the contract.
+	run := func(regular uint64) (map[common.Hash]struct{}, error) {
+		statedb, _ := state.New(types.EmptyRootHash, state.NewDatabaseForTesting())
+		statedb.CreateAccount(self)
+		statedb.SetCode(self, sstore(0, 1), tracing.CodeChangeUnspecified)
+		statedb.SetState(self, slot, common.BytesToHash([]byte{1}))
+		statedb.Finalise(true)
+
+		evm := amsterdam8037EVM(statedb)
+		statedb.Prepare(evm.chainRules, common.Address{}, common.Address{}, &self, nil, nil)
+		_, _, err := evm.Call(common.Address{}, self, nil, NewGasBudget(regular, 0), new(uint256.Int))
+		acct := statedb.Finalise(true).Accounts[self]
+		if acct == nil {
+			return nil, err
+		}
+		return acct.StorageReads, err
+	}
+
+	// gas_left at the SSTORE clears the stipend sentry but falls one short of
+	// the cold access cost: the op must fail without touching the slot.
+	reads, err := run(6 + params.ColdStorageAccessAmsterdam - 1)
+	if err == nil {
+		t.Fatal("expected OOG below the cold access cost")
+	}
+	if _, ok := reads[slot]; ok {
+		t.Fatal("failing SSTORE leaked the slot into the block access list")
+	}
+	// Exactly the cold access cost succeeds and records the read.
+	reads, err = run(6 + params.ColdStorageAccessAmsterdam)
+	if err != nil {
+		t.Fatalf("unexpected failure at the cold access cost: %v", err)
+	}
+	if _, ok := reads[slot]; !ok {
+		t.Fatal("successful SSTORE missing from the block access list")
+	}
+}
diff --git a/core/vm/gas_table.go b/core/vm/gas_table.go
index 8cc63cb236..fbef287270 100644
--- a/core/vm/gas_table.go
+++ b/core/vm/gas_table.go
@@ -696,17 +696,31 @@ func gasSStore8037And8038(evm *EVM, contract *Contract, stack *Stack, mem *Memor
 		return GasCosts{}, errors.New("not enough gas for reentrancy sentry")
 	}
 	var (
-		y, x              = stack.back(1), stack.peek()
-		slot              = common.Hash(x.Bytes32())
-		current, original = evm.StateDB.GetStateAndCommittedState(contract.Address(), slot)
-		value             = common.Hash(y.Bytes32())
+		y, x = stack.back(1), stack.peek()
+		slot = common.Hash(x.Bytes32())
 	)
 	// Check slot presence in the access list
 	access := params.WarmStorageReadCostEIP2929
-	if _, slotPresent := evm.StateDB.SlotInAccessList(contract.Address(), slot); !slotPresent {
+	_, slotPresent := evm.StateDB.SlotInAccessList(contract.Address(), slot)
+	if !slotPresent {
 		access = params.ColdStorageAccessAmsterdam
+	}
+	// SSTORE performs an implicit read of the current storage value for the gas
+	// calculation below. Since the cold access cost exceeds GAS_CALL_STIPEND
+	// after the Amsterdam repricing, the reentrancy sentry alone no longer
+	// guards this read: the frame must also cover the slot's access cost
+	// beforehand, otherwise the slot must not be recorded in the block access
+	// list (EIP-7928).
+	if contract.Gas.RegularGas < access {
+		return GasCosts{}, ErrOutOfGas
+	}
+	if !slotPresent {
 		evm.StateDB.AddSlotToAccessList(contract.Address(), slot)
 	}
+	var (
+		current, original = evm.StateDB.GetStateAndCommittedState(contract.Address(), slot)
+		value             = common.Hash(y.Bytes32())
+	)
 	stateSet := params.StorageCreationSize * evm.Context.CostPerStateByte
 
 	if current == value { // noop (1)