fix mempool logic to restrict gas limit for oracle txs

custom/auth/ante/spamming_prevention.go

@@ -30,8 +30,12 @@ func NewSpammingPreventionDecorator(oracleKeeper OracleKeeper) SpammingPreventio
 
 // AnteHandle handles msg tax fee checking
 func (spd SpammingPreventionDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool, next sdk.AnteHandler) (newCtx sdk.Context, err error) {
-	if ctx.IsCheckTx() {
-		if !simulate && !ctx.IsReCheckTx() {
+	if ctx.IsReCheckTx() {
+		return next(ctx, tx, simulate)
+	}
+
+	if !simulate {
+		if ctx.IsCheckTx() {
 			err := spd.CheckOracleSpamming(ctx, tx.GetMsgs())
 			if err != nil {
 				return ctx, err

custom/auth/ante/tax.go

@@ -10,9 +10,13 @@ import (
 	core "github.com/terra-project/core/types"
 	marketexported "github.com/terra-project/core/x/market/exported"
 	msgauthexported "github.com/terra-project/core/x/msgauth/exported"
+	oracleexported "github.com/terra-project/core/x/oracle/exported"
 	wasmexported "github.com/terra-project/core/x/wasm/exported"
 )
 
+// MaxOracleMsgGasUsage is constant expected oracle msg gas cost
+const MaxOracleMsgGasUsage = uint64(100_000)
+
 // TaxFeeDecorator will check if the transaction's fee is at least as large
 // as tax + the local validator's minimum gasFee (defined in validator config)
 // and record tax proceeds to treasury module to track tax proceeds.
@@ -40,13 +44,16 @@ func (tfd TaxFeeDecorator) AnteHandle(ctx sdk.Context, tx sdk.Tx, simulate bool,
 
 	feeCoins := feeTx.GetFee()
 	gas := feeTx.GetGas()
+	msgs := feeTx.GetMsgs()
 
 	if !simulate {
 		// Compute taxes
-		taxes := FilterMsgAndComputeTax(ctx, tfd.treasuryKeeper, feeTx.GetMsgs()...)
+		taxes := FilterMsgAndComputeTax(ctx, tfd.treasuryKeeper, msgs...)
 
 		// Mempool fee validation
-		if ctx.IsCheckTx() {
+		// No fee validation for oracle txs
+		if ctx.IsCheckTx() &&
+			!(isOracleTx(ctx, msgs) && gas <= uint64(len(msgs))*MaxOracleMsgGasUsage) {
 			if err := EnsureSufficientMempoolFees(ctx, gas, feeCoins, taxes); err != nil {
 				return ctx, sdkerrors.Wrapf(sdkerrors.ErrInsufficientFee, err.Error())
 			}
@@ -160,3 +167,18 @@ func computeTax(ctx sdk.Context, tk TreasuryKeeper, principal sdk.Coins) sdk.Coi
 
 	return taxes
 }
+
+func isOracleTx(ctx sdk.Context, msgs []sdk.Msg) bool {
+	for _, msg := range msgs {
+		switch msg.(type) {
+		case *oracleexported.MsgAggregateExchangeRatePrevote:
+			continue
+		case *oracleexported.MsgAggregateExchangeRateVote:
+			continue
+		default:
+			return false
+		}
+	}
+
+	return true
+}