Merge pull request #2011 from OffchainLabs/fix-float-to-big-overflow

Fix FloatToBig overflowing on values greater than an int64

arbnode/dataposter/data_poster.go

@@ -11,6 +11,7 @@ import (
 	"crypto/x509"
 	"errors"
 	"fmt"
+	"math"
 	"math/big"
 	"net/http"
 	"os"
@@ -379,13 +380,27 @@ func (p *DataPoster) evalMaxFeeCapExpr(backlogOfBatches uint64, elapsed time.Dur
 		"ElapsedTimeBase":       float64(config.ElapsedTimeBase),
 		"ElapsedTimeImportance": config.ElapsedTimeImportance,
 		"TargetPriceGWei":       config.TargetPriceGwei,
-		"GWei":                  params.GWei,
 	}
 	result, err := p.maxFeeCapExpression.Evaluate(parameters)
 	if err != nil {
 		return nil, fmt.Errorf("error evaluating maxFeeCapExpression: %w", err)
 	}
-	return arbmath.FloatToBig(result.(float64)), nil
+	resultFloat, ok := result.(float64)
+	if !ok {
+		// This shouldn't be possible because we only pass in float64s as arguments
+		return nil, fmt.Errorf("maxFeeCapExpression evaluated to non-float64: %v", result)
+	}
+	// 1e9 gwei gas price is practically speaking an infinite gas price, so we cap it there.
+	// This also allows the formula to return positive infinity safely.
+	resultFloat = math.Min(resultFloat, 1e9)
+	resultBig := arbmath.FloatToBig(resultFloat * params.GWei)
+	if resultBig == nil {
+		return nil, fmt.Errorf("maxFeeCapExpression evaluated to float64 not convertible to integer: %v", resultFloat)
+	}
+	if resultBig.Sign() < 0 {
+		return nil, fmt.Errorf("maxFeeCapExpression evaluated < 0: %v", resultFloat)
+	}
+	return resultBig, nil
 }
 
 func (p *DataPoster) feeAndTipCaps(ctx context.Context, nonce uint64, gasLimit uint64, lastFeeCap *big.Int, lastTipCap *big.Int, dataCreatedAt time.Time, backlogOfBatches uint64) (*big.Int, *big.Int, error) {
@@ -854,9 +869,9 @@ func DataPosterConfigAddOptions(prefix string, f *pflag.FlagSet, defaultDataPost
 	f.Bool(prefix+".use-db-storage", defaultDataPosterConfig.UseDBStorage, "uses database storage when enabled")
 	f.Bool(prefix+".use-noop-storage", defaultDataPosterConfig.UseNoOpStorage, "uses noop storage, it doesn't store anything")
 	f.Bool(prefix+".legacy-storage-encoding", defaultDataPosterConfig.LegacyStorageEncoding, "encodes items in a legacy way (as it was before dropping generics)")
-	f.String(prefix+".max-fee-cap-formula", defaultDataPosterConfig.MaxFeeCapFormula, "mathematical formula to calculate maximum fee cap the result of which would be float64.\n"+
+	f.String(prefix+".max-fee-cap-formula", defaultDataPosterConfig.MaxFeeCapFormula, "mathematical formula to calculate maximum fee cap gwei the result of which would be float64.\n"+
 		"This expression is expected to be evaluated please refer https://github.com/Knetic/govaluate/blob/master/MANUAL.md to find all available mathematical operators.\n"+
-		"Currently available variables to construct the formula are BacklogOfBatches, UrgencyGWei, ElapsedTime, ElapsedTimeBase, ElapsedTimeImportance, TargetPriceGWei and GWei")
+		"Currently available variables to construct the formula are BacklogOfBatches, UrgencyGWei, ElapsedTime, ElapsedTimeBase, ElapsedTimeImportance, and TargetPriceGWei")
 	f.Duration(prefix+".elapsed-time-base", defaultDataPosterConfig.ElapsedTimeBase, "unit to measure the time elapsed since creation of transaction used for maximum fee cap calculation")
 	f.Float64(prefix+".elapsed-time-importance", defaultDataPosterConfig.ElapsedTimeImportance, "weight given to the units of time elapsed used for maximum fee cap calculation")
 
@@ -893,7 +908,7 @@ var DefaultDataPosterConfig = DataPosterConfig{
 	LegacyStorageEncoding:  false,
 	Dangerous:              DangerousConfig{ClearDBStorage: false},
 	ExternalSigner:         ExternalSignerCfg{Method: "eth_signTransaction"},
-	MaxFeeCapFormula:       "(((BacklogOfBatches * UrgencyGWei) ** 2) + ((ElapsedTime/ElapsedTimeBase) ** 2) * ElapsedTimeImportance + TargetPriceGWei) * GWei",
+	MaxFeeCapFormula:       "((BacklogOfBatches * UrgencyGWei) ** 2) + ((ElapsedTime/ElapsedTimeBase) ** 2) * ElapsedTimeImportance + TargetPriceGWei",
 	ElapsedTimeBase:        10 * time.Minute,
 	ElapsedTimeImportance:  10,
 }
@@ -919,7 +934,7 @@ var TestDataPosterConfig = DataPosterConfig{
 	UseNoOpStorage:         false,
 	LegacyStorageEncoding:  false,
 	ExternalSigner:         ExternalSignerCfg{Method: "eth_signTransaction"},
-	MaxFeeCapFormula:       "(((BacklogOfBatches * UrgencyGWei) ** 2) + ((ElapsedTime/ElapsedTimeBase) ** 2) * ElapsedTimeImportance + TargetPriceGWei) * GWei",
+	MaxFeeCapFormula:       "((BacklogOfBatches * UrgencyGWei) ** 2) + ((ElapsedTime/ElapsedTimeBase) ** 2) * ElapsedTimeImportance + TargetPriceGWei",
 	ElapsedTimeBase:        10 * time.Minute,
 	ElapsedTimeImportance:  10,
 }

arbnode/dataposter/dataposter_test.go

@@ -19,6 +19,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/signer/core/apitypes"
 	"github.com/google/go-cmp/cmp"
@@ -262,6 +263,14 @@ func TestMaxFeeCapFormulaCalculation(t *testing.T) {
 		t.Fatalf("Error evaluating MaxFeeCap expression: %v", err)
 	}
 	if result.Cmp(common.Big0) != 0 {
-		t.Fatalf("Unexpected result. Got: %d, want: 0", result.Uint64())
+		t.Fatalf("Unexpected result. Got: %d, want: 0", result)
+	}
+
+	result, err = p.evalMaxFeeCapExpr(0, time.Since(time.Time{}))
+	if err != nil {
+		t.Fatalf("Error evaluating MaxFeeCap expression: %v", err)
+	}
+	if result.Cmp(big.NewInt(params.GWei)) <= 0 {
+		t.Fatalf("Unexpected result. Got: %d, want: >0", result)
 	}
 }

util/arbmath/math.go

@@ -75,8 +75,13 @@ func UintToBig(value uint64) *big.Int {
 }
 
 // FloatToBig casts a float to a huge
+// Returns nil when passed NaN or Infinity
 func FloatToBig(value float64) *big.Int {
-	return new(big.Int).SetInt64(int64(value))
+	if math.IsNaN(value) {
+		return nil
+	}
+	result, _ := new(big.Float).SetFloat64(value).Int(nil)
+	return result
 }
 
 // UintToBigFloat casts a uint to a big float