Handle multipleOf overflow

Author: Zac-HD

jsonschema/_validators.py

@@ -1,4 +1,5 @@
 import re
+from fractions import Fraction
 
 from jsonschema._utils import (
     ensure_list,
@@ -166,7 +167,18 @@ def multipleOf(validator, dB, instance, schema):
 
     if isinstance(dB, float):
         quotient = instance / dB
-        failed = int(quotient) != quotient
+        try:
+            failed = int(quotient) != quotient
+        except OverflowError:
+            # When `instance` is large and `dB` is less than one, quotient can
+            # overflow to infinity; and then casting to int raises an error.
+            #
+            # In this case we fall back to Fraction logic, which is exact and
+            # cannot overflow.  The performance is also acceptable: we try the
+            # fast all-float option first, and we know that fraction(dB) can have
+            # at most a few hundred digits in each part.  The worst-case slowdown
+            # is therefore for already-slow enormous integers or Decimals.
+            failed = (Fraction(instance) / Fraction(dB)).denominator != 1
     else:
         failed = instance % dB