From ea9cfcdf6e9aa50a1564851cbc083c857be6b352 Mon Sep 17 00:00:00 2001
From: Somnath <snb895@outlook.com>
Date: Wed, 4 Sep 2024 16:58:30 +0400
Subject: [PATCH] core: Check `gasBailout` before deducting balance in
 trace_call (#11813)

**Existing behaviour:**
- Add up the possible value that user must pay beforehand to buy gas
- Deduct that amount from the sender's account in `intraBlockState`,
but:
- Don't deduct the gas value amount if the user doesn't have enough, and
`gasBailout` is set

**New behaviour:**
- Don't check if sender's balance is enough to pay gas value amount, nor
deduct it, if `gasBailout` is set

**More rationale**
This would mean the sender's account would show `"balance": "="` in
`trace_call` rpc method, that is, no change, if gas is the only thing
the user pays for. This is fine because the gas price can fluctuate in a
real transaction. This also removes the inconsistency of sometimes
having to bother deducting the amount if it is less than sender's
balance, thereby causing a bug/inconsistency.
---
 core/state_transition.go | 51 +++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 29 deletions(-)

diff --git a/core/state_transition.go b/core/state_transition.go
index 9b61dda9e84..fe7621042ee 100644
--- a/core/state_transition.go
+++ b/core/state_transition.go
@@ -192,49 +192,42 @@ func (st *StateTransition) buyGas(gasBailout bool) error {
 		}
 	}
 
-	balanceCheck := gasVal
-	if st.gasFeeCap != nil {
-		balanceCheck = st.sharedBuyGasBalance.SetUint64(st.msg.Gas())
-		balanceCheck, overflow = balanceCheck.MulOverflow(balanceCheck, st.gasFeeCap)
-		if overflow {
-			return fmt.Errorf("%w: address %v", ErrInsufficientFunds, st.msg.From().Hex())
-		}
-		balanceCheck, overflow = balanceCheck.AddOverflow(balanceCheck, st.value)
-		if overflow {
-			return fmt.Errorf("%w: address %v", ErrInsufficientFunds, st.msg.From().Hex())
-		}
-		if st.evm.ChainRules().IsCancun {
-			maxBlobFee, overflow := new(uint256.Int).MulOverflow(st.msg.MaxFeePerBlobGas(), new(uint256.Int).SetUint64(st.msg.BlobGas()))
+	if !gasBailout {
+		balanceCheck := gasVal
+		if st.gasFeeCap != nil {
+			balanceCheck = st.sharedBuyGasBalance.SetUint64(st.msg.Gas())
+			balanceCheck, overflow = balanceCheck.MulOverflow(balanceCheck, st.gasFeeCap)
 			if overflow {
 				return fmt.Errorf("%w: address %v", ErrInsufficientFunds, st.msg.From().Hex())
 			}
-			balanceCheck, overflow = balanceCheck.AddOverflow(balanceCheck, maxBlobFee)
+			balanceCheck, overflow = balanceCheck.AddOverflow(balanceCheck, st.value)
 			if overflow {
 				return fmt.Errorf("%w: address %v", ErrInsufficientFunds, st.msg.From().Hex())
 			}
+			if st.evm.ChainRules().IsCancun {
+				maxBlobFee, overflow := new(uint256.Int).MulOverflow(st.msg.MaxFeePerBlobGas(), new(uint256.Int).SetUint64(st.msg.BlobGas()))
+				if overflow {
+					return fmt.Errorf("%w: address %v", ErrInsufficientFunds, st.msg.From().Hex())
+				}
+				balanceCheck, overflow = balanceCheck.AddOverflow(balanceCheck, maxBlobFee)
+				if overflow {
+					return fmt.Errorf("%w: address %v", ErrInsufficientFunds, st.msg.From().Hex())
+				}
+			}
 		}
-	}
-	var subBalance = false
-	if have, want := st.state.GetBalance(st.msg.From()), balanceCheck; have.Cmp(want) < 0 {
-		if !gasBailout {
+		if have, want := st.state.GetBalance(st.msg.From()), balanceCheck; have.Cmp(want) < 0 {
 			return fmt.Errorf("%w: address %v have %v want %v", ErrInsufficientFunds, st.msg.From().Hex(), have, want)
 		}
-	} else {
-		subBalance = true
+		st.state.SubBalance(st.msg.From(), gasVal, tracing.BalanceDecreaseGasBuy)
+		st.state.SubBalance(st.msg.From(), blobGasVal, tracing.BalanceDecreaseGasBuy)
 	}
+
 	if err := st.gp.SubGas(st.msg.Gas()); err != nil {
-		if !gasBailout {
-			return err
-		}
+		return err
 	}
 	st.gasRemaining += st.msg.Gas()
 	st.initialGas = st.msg.Gas()
 	st.evm.BlobFee = blobGasVal
-
-	if subBalance {
-		st.state.SubBalance(st.msg.From(), gasVal, tracing.BalanceDecreaseGasBuy)
-		st.state.SubBalance(st.msg.From(), blobGasVal, tracing.BalanceDecreaseGasBuy)
-	}
 	return nil
 }
 
@@ -456,7 +449,7 @@ func (st *StateTransition) TransitionDb(refunds bool, gasBailout bool) (*evmtype
 	} else {
 		ret, st.gasRemaining, vmerr = st.evm.Call(sender, st.to(), st.data, st.gasRemaining, st.value, bailout)
 	}
-	if refunds {
+	if refunds && !gasBailout {
 		if rules.IsLondon {
 			// After EIP-3529: refunds are capped to gasUsed / 5
 			st.refundGas(params.RefundQuotientEIP3529)