[Python-checkins] [3.8] bpo-38588: Fix possible crashes in dict and list when calling P… (GH-17764)

[Pablo Galindo]

https://github.com/python/cpython/commit/2ee87913dde038436a25f1db13ee3fddd2bcc983
commit: 2ee87913dde038436a25f1db13ee3fddd2bcc983
branch: 3.8
author: Dong-hee Na <donghee.na92 at gmail.com>
committer: Pablo Galindo <Pablogsal at gmail.com>
date: 2019-12-31T04:15:36Z
summary:

[3.8] bpo-38588: Fix possible crashes in dict and list when calling P… (GH-17764)

* [3.8] bpo-38588: Fix possible crashes in dict and list when calling PyObject_RichCompareBool (GH-17734)

Take strong references before calling PyObject_RichCompareBool to protect against the case
where the object dies during the call.
(cherry picked from commit 2d5bf568eaa5059402ccce9ba5a366986ba27c8a)

Co-authored-by: Dong-hee Na <donghee.na92 at gmail.com>

* Update Objects/listobject.c

@methane's suggestion

Co-Authored-By: Inada Naoki <songofacandy at gmail.com>

Co-authored-by: Inada Naoki <songofacandy at gmail.com>

files:
A Misc/NEWS.d/next/Core and Builtins/2019-12-29-19-13-54.bpo-38588.pgXnNS.rst
M Lib/test/test_dict.py
M Lib/test/test_list.py
M Objects/dictobject.c
M Objects/listobject.c

diff --git a/Lib/test/test_dict.py b/Lib/test/test_dict.py
index 5b513765f7b08..de483ab552155 100644
--- a/Lib/test/test_dict.py
+++ b/Lib/test/test_dict.py
@@ -1221,7 +1221,7 @@ def test_free_after_iterating(self):
         support.check_free_after_iterating(self, lambda d: iter(d.items()), dict)
 
     def test_equal_operator_modifying_operand(self):
-        # test fix for seg fault reported in issue 27945 part 3.
+        # test fix for seg fault reported in bpo-27945 part 3.
         class X():
             def __del__(self):
                 dict_b.clear()
@@ -1237,6 +1237,16 @@ def __hash__(self):
         dict_b = {X(): X()}
         self.assertTrue(dict_a == dict_b)
 
+        # test fix for seg fault reported in bpo-38588 part 1.
+        class Y:
+            def __eq__(self, other):
+                dict_d.clear()
+                return True
+
+        dict_c = {0: Y()}
+        dict_d = {0: set()}
+        self.assertTrue(dict_c == dict_d)
+
     def test_fromkeys_operator_modifying_dict_operand(self):
         # test fix for seg fault reported in issue 27945 part 4a.
         class X(int):
diff --git a/Lib/test/test_list.py b/Lib/test/test_list.py
index 55c6eede527c2..f4dcced9c167f 100644
--- a/Lib/test/test_list.py
+++ b/Lib/test/test_list.py
@@ -158,6 +158,31 @@ class L(list): pass
         with self.assertRaises(TypeError):
             (3,) + L([1,2])
 
+    def test_equal_operator_modifying_operand(self):
+        # test fix for seg fault reported in bpo-38588 part 2.
+        class X:
+            def __eq__(self,other) :
+                list2.clear()
+                return NotImplemented
+
+        class Y:
+            def __eq__(self, other):
+                list1.clear()
+                return NotImplemented
+
+        class Z:
+            def __eq__(self, other):
+                list3.clear()
+                return NotImplemented
+
+        list1 = [X()]
+        list2 = [Y()]
+        self.assertTrue(list1 == list2)
+
+        list3 = [Z()]
+        list4 = [1]
+        self.assertFalse(list3 == list4)
+
     @cpython_only
     def test_preallocation(self):
         iterable = [0] * 10
diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-12-29-19-13-54.bpo-38588.pgXnNS.rst b/Misc/NEWS.d/next/Core and Builtins/2019-12-29-19-13-54.bpo-38588.pgXnNS.rst
new file mode 100644
index 0000000000000..0b81085a89d25
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-12-29-19-13-54.bpo-38588.pgXnNS.rst	
@@ -0,0 +1,2 @@
+Fix possible crashes in dict and list when calling
+:c:func:`PyObject_RichCompareBool`.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 76f4fefe0979f..3c56f4a515e8a 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -2773,9 +2773,11 @@ dict_equal(PyDictObject *a, PyDictObject *b)
                     return -1;
                 return 0;
             }
+            Py_INCREF(bval);
             cmp = PyObject_RichCompareBool(aval, bval, Py_EQ);
             Py_DECREF(key);
             Py_DECREF(aval);
+            Py_DECREF(bval);
             if (cmp <= 0)  /* error or not equal */
                 return cmp;
         }
diff --git a/Objects/listobject.c b/Objects/listobject.c
index 8b52fa5ef267a..d506c0817336b 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2664,8 +2664,18 @@ list_richcompare(PyObject *v, PyObject *w, int op)
 
     /* Search for the first index where items are different */
     for (i = 0; i < Py_SIZE(vl) && i < Py_SIZE(wl); i++) {
+        PyObject *vitem = vl->ob_item[i];
+        PyObject *witem = wl->ob_item[i];
+        if (vitem == witem) {
+            continue;
+        }
+
+        Py_INCREF(vitem);
+        Py_INCREF(witem);
         int k = PyObject_RichCompareBool(vl->ob_item[i],
                                          wl->ob_item[i], Py_EQ);
+        Py_DECREF(vitem);
+        Py_DECREF(witem);
         if (k < 0)
             return NULL;
         if (!k)