[2.7] bpo-31752: Fix possible crash in timedelta constructor called with custom integers. (GH-3947) (#4088)

Bad remainder in divmod() in intermediate calculations caused an assertion failure..
(cherry picked from commit 4ffd465)

Author: serhiy-storchaka

Lib/test/test_datetime.py

@@ -492,6 +492,46 @@ def as_hours(self):
         self.assertEqual(str(t3), str(t4))
         self.assertEqual(t4.as_hours(), -1)
 
+    def test_issue31752(self):
+        # The interpreter shouldn't crash because divmod() returns negative
+        # remainder.
+        class BadInt(int):
+            def __mul__(self, other):
+                return Prod()
+
+        class BadLong(long):
+            def __mul__(self, other):
+                return Prod()
+
+        class Prod:
+            def __radd__(self, other):
+                return Sum()
+
+        class Sum(int):
+            def __divmod__(self, other):
+                # negative remainder
+                return (0, -1)
+
+        timedelta(microseconds=BadInt(1))
+        timedelta(hours=BadInt(1))
+        timedelta(weeks=BadInt(1))
+        timedelta(microseconds=BadLong(1))
+        timedelta(hours=BadLong(1))
+        timedelta(weeks=BadLong(1))
+
+        class Sum(long):
+            def __divmod__(self, other):
+                # negative remainder
+                return (0, -1)
+
+        timedelta(microseconds=BadInt(1))
+        timedelta(hours=BadInt(1))
+        timedelta(weeks=BadInt(1))
+        timedelta(microseconds=BadLong(1))
+        timedelta(hours=BadLong(1))
+        timedelta(weeks=BadLong(1))
+
+
 #############################################################################
 # date tests
 

Misc/NEWS.d/next/Library/2017-10-11-00-45-01.bpo-31752.DhWevN.rst

@@ -0,0 +1 @@
+Fix possible crash in timedelta constructor called with custom integers.

Modules/datetimemodule.c

@@ -1537,6 +1537,7 @@ delta_to_microseconds(PyDateTime_Delta *self)
     if (x2 == NULL)
         goto Done;
     result = PyNumber_Add(x1, x2);
+    assert(result == NULL || PyInt_CheckExact(result) || PyLong_CheckExact(result));
 
 Done:
     Py_XDECREF(x1);
@@ -1559,6 +1560,7 @@ microseconds_to_delta_ex(PyObject *pyus, PyTypeObject *type)
     PyObject *num = NULL;
     PyObject *result = NULL;
 
+    assert(PyInt_CheckExact(pyus) || PyLong_CheckExact(pyus));
     tuple = PyNumber_Divmod(pyus, us_per_second);
     if (tuple == NULL)
         goto Done;
@@ -1851,11 +1853,13 @@ accum(const char* tag, PyObject *sofar, PyObject *num, PyObject *factor,
     assert(num != NULL);
 
     if (PyInt_Check(num) || PyLong_Check(num)) {
-        prod = PyNumber_Multiply(num, factor);
+        prod = PyNumber_Multiply(factor, num);
         if (prod == NULL)
             return NULL;
+        assert(PyInt_CheckExact(prod) || PyLong_CheckExact(prod));
         sum = PyNumber_Add(sofar, prod);
         Py_DECREF(prod);
+        assert(sum == NULL || PyInt_CheckExact(sum) || PyLong_CheckExact(sum));
         return sum;
     }
 
@@ -1898,7 +1902,7 @@ accum(const char* tag, PyObject *sofar, PyObject *num, PyObject *factor,
          * fractional part requires float arithmetic, and may
          * lose a little info.
          */
-        assert(PyInt_Check(factor) || PyLong_Check(factor));
+        assert(PyInt_CheckExact(factor) || PyLong_CheckExact(factor));
         if (PyInt_Check(factor))
             dnum = (double)PyInt_AsLong(factor);
         else
@@ -1916,6 +1920,7 @@ accum(const char* tag, PyObject *sofar, PyObject *num, PyObject *factor,
         Py_DECREF(sum);
         Py_DECREF(x);
         *leftover += fracpart;
+        assert(y == NULL || PyInt_CheckExact(y) || PyLong_CheckExact(y));
         return y;
     }