From 29809a36314f43b6ad93a79fcd32576353747fc9 Mon Sep 17 00:00:00 2001
From: leekyungun <leekyungun91@gmail.com>
Date: Fri, 21 Aug 2026 16:13:18 +0900
Subject: [PATCH] fix(statedb): guard SubBalance against underflow; make
 ParseAmount denom-aware

Backports cosmos/evm#1176. Adds an underflow guard to stateObject.SubBalance so
a subtraction larger than the current balance panics (reverting the tx) instead
of wrapping the uint256 balance to a near-max value. Also makes precompile
bank-event amount parsing account for both the base and extended EVM-coin denoms.

This closes the class of issue used to drain MANTRA (delegate() with a tiny
amount triggering a balance underflow). Full fix is upstream cosmos/evm v0.6.2;
recommend rebasing this fork onto v0.6.2 for the complete set of changes.

Ref: https://github.com/cosmos/evm/pull/1176
---
 precompiles/common/utils.go  |  9 +++++++--
 x/vm/statedb/state_object.go | 12 +++++++++++-
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/precompiles/common/utils.go b/precompiles/common/utils.go
index 520dc5e0..0db1efc7 100644
--- a/precompiles/common/utils.go
+++ b/precompiles/common/utils.go
@@ -42,8 +42,13 @@ func ParseAmount(event sdk.Event) (*uint256.Int, error) {
 		return nil, fmt.Errorf("failed to parse coins from %q: %w", amountAttr.Value, err)
 	}
 
-	amountBigInt := amountCoins.AmountOf(evmtypes.GetEVMCoinDenom()).BigInt()
-	amount, err := utils.Uint256FromBigInt(evmtypes.ConvertAmountTo18DecimalsBigInt(amountBigInt))
+	baseAmount := amountCoins.AmountOf(evmtypes.GetEVMCoinDenom()).BigInt()
+	amountBigInt := evmtypes.ConvertAmountTo18DecimalsBigInt(baseAmount)
+	if evmtypes.GetEVMCoinExtendedDenom() != evmtypes.GetEVMCoinDenom() {
+		extendedAmount := amountCoins.AmountOf(evmtypes.GetEVMCoinExtendedDenom()).BigInt()
+		amountBigInt = new(big.Int).Add(amountBigInt, extendedAmount)
+	}
+	amount, err := utils.Uint256FromBigInt(amountBigInt)
 	if err != nil {
 		return nil, fmt.Errorf("failed to convert coin amount to Uint256: %w", err)
 	}
diff --git a/x/vm/statedb/state_object.go b/x/vm/statedb/state_object.go
index 0b06e64e..a93f3dcd 100644
--- a/x/vm/statedb/state_object.go
+++ b/x/vm/statedb/state_object.go
@@ -2,6 +2,7 @@ package statedb
 
 import (
 	"bytes"
+	"fmt"
 	"math/big"
 	"sort"
 
@@ -147,7 +148,16 @@ func (s *stateObject) SubBalance(amount *uint256.Int) uint256.Int {
 	if amount.IsZero() {
 		return *(s.Balance())
 	}
-	return s.SetBalance(new(uint256.Int).Sub(s.Balance(), amount))
+	balance := s.Balance()
+	if balance.Lt(amount) {
+		panic(fmt.Sprintf(
+			"state balance underflow for %s: have=%s sub=%s",
+			s.address.Hex(),
+			balance.String(),
+			amount.String(),
+		))
+	}
+	return s.SetBalance(new(uint256.Int).Sub(balance, amount))
 }
 
 // SetBalance updates account balance.