fastparse: Fix bug in overflow detection (vitessio#13702)

Signed-off-by: Dirkjan Bussink <[email protected]>

go/mysql/fastparse/fastparse.go

@@ -65,6 +65,18 @@ next:
 			break next
 		}
 
+		var cutoff uint64
+		switch base {
+		case 10:
+			cutoff = math.MaxUint64/10 + 1
+		case 16:
+			cutoff = math.MaxUint64/16 + 1
+		default:
+			cutoff = math.MaxUint64/uint64(base) + 1
+		}
+		if d >= cutoff {
+			return math.MaxUint64, fmt.Errorf("cannot parse uint64 from %q: %w", s, ErrOverflow)
+		}
 		v := d*uint64(base) + uint64(b)
 		if v < d {
 			return math.MaxUint64, fmt.Errorf("cannot parse uint64 from %q: %w", s, ErrOverflow)
@@ -139,6 +151,22 @@ next:
 			break next
 		}
 
+		var cutoff uint64
+		switch base {
+		case 10:
+			cutoff = math.MaxInt64/10 + 1
+		case 16:
+			cutoff = math.MaxInt64/16 + 1
+		default:
+			cutoff = math.MaxInt64/uint64(base) + 1
+		}
+		if d >= cutoff {
+			if minus {
+				return math.MinInt64, fmt.Errorf("cannot parse int64 from %q: %w", s, ErrOverflow)
+			}
+			return math.MaxInt64, fmt.Errorf("cannot parse int64 from %q: %w", s, ErrOverflow)
+		}
+
 		v := d*uint64(base) + uint64(b)
 		if v < d {
 			if minus {

go/mysql/fastparse/fastparse_test.go

@@ -161,6 +161,12 @@ func TestParseInt64(t *testing.T) {
 			expected: 9223372036854775807,
 			err:      `cannot parse int64 from "18446744073709551616": overflow`,
 		},
+		{
+			input:    "31415926535897932384",
+			base:     10,
+			expected: 9223372036854775807,
+			err:      `cannot parse int64 from "31415926535897932384": overflow`,
+		},
 		{
 			input:    "1.1",
 			base:     10,
@@ -297,6 +303,12 @@ func TestParseUint64(t *testing.T) {
 			expected: 18446744073709551615,
 			err:      `cannot parse uint64 from "18446744073709551616": overflow`,
 		},
+		{
+			input:    "31415926535897932384",
+			base:     10,
+			expected: 18446744073709551615,
+			err:      `cannot parse uint64 from "31415926535897932384": overflow`,
+		},
 		{
 			input:    "1.1",
 			base:     10,