bpo-36946: Fix possible signed integer overflow when handling slices. (GH-13375)

The final addition (cur += step) may overflow, so use size_t for "cur".
"cur" is always positive (even for negative steps), so it is safe to use
size_t here.

Co-Authored-By: Martin Panter <vadmium+py@gmail.com>

diff --git a/Lib/ctypes/test/test_arrays.py b/Lib/ctypes/test/test_arrays.py
index 0fc5d7ebf84106b861a42dc81db8ee8b0370674a..87ecbf04e7edbb6f3ff74f1d7442b01569ebcaa4 100644 (file)
--- a/Lib/ctypes/test/test_arrays.py
+++ b/Lib/ctypes/test/test_arrays.py
@@ -69,6 +69,17 @@ class ArrayTestCase(unittest.TestCase):
         from operator import delitem
         self.assertRaises(TypeError, delitem, ca, 0)
 
+    def test_step_overflow(self):
+        a = (c_int * 5)()
+        a[3::sys.maxsize] = (1,)
+        self.assertListEqual(a[3::sys.maxsize], [1])
+        a = (c_char * 5)()
+        a[3::sys.maxsize] = b"A"
+        self.assertEqual(a[3::sys.maxsize], b"A")
+        a = (c_wchar * 5)()
+        a[3::sys.maxsize] = u"X"
+        self.assertEqual(a[3::sys.maxsize], u"X")
+
     def test_numeric_arrays(self):
 
         alen = 5

diff --git a/Lib/test/seq_tests.py b/Lib/test/seq_tests.py
index 6aedd2be94dba307bec044b4bd2e27a16ace6105..65b110ef7818dac652ad6414628b94fd941269ea 100644 (file)
--- a/Lib/test/seq_tests.py
+++ b/Lib/test/seq_tests.py
@@ -209,6 +209,7 @@ class CommonTest(unittest.TestCase):
         a = self.type2test([0,1,2,3,4])
         self.assertEqual(a[ -pow(2,128): 3 ], self.type2test([0,1,2]))
         self.assertEqual(a[ 3: pow(2,145) ], self.type2test([3,4]))
+        self.assertEqual(a[3::sys.maxsize], self.type2test([3]))
 
     def test_contains(self):
         u = self.type2test([0, 1, 2])

diff --git a/Lib/test/string_tests.py b/Lib/test/string_tests.py
index 836a43b81dd6f0da7ba163daee3ddc5fb099fdc1..38da941f7f50e19f4e2e33f83553a8a37d4d6f49 100644 (file)
--- a/Lib/test/string_tests.py
+++ b/Lib/test/string_tests.py
@@ -1135,7 +1135,7 @@ class MixinStrUnicodeUserStringTest:
     def test_extended_getslice(self):
         # Test extended slicing by comparing with list slicing.
         s = string.ascii_letters + string.digits
-        indices = (0, None, 1, 3, 41, -1, -2, -37)
+        indices = (0, None, 1, 3, 41, sys.maxsize, -1, -2, -37)
         for start in indices:
             for stop in indices:
                 # Skip step 0 (invalid)

diff --git a/Lib/test/test_array.py b/Lib/test/test_array.py
index 57c396d610b75c11b2dafe4957139df815d1b69c..c2439579e8ee5b456cd13b628e330b2d56749a90 100644 (file)
--- a/Lib/test/test_array.py
+++ b/Lib/test/test_array.py
@@ -746,7 +746,7 @@ class BaseTest:
         # Test extended slicing by comparing with list slicing
         # (Assumes list conversion works correctly, too)
         a = array.array(self.typecode, self.example)
-        indices = (0, None, 1, 3, 19, 100, -1, -2, -31, -100)
+        indices = (0, None, 1, 3, 19, 100, sys.maxsize, -1, -2, -31, -100)
         for start in indices:
             for stop in indices:
                 # Everything except the initial 0 (invalid step)
@@ -844,7 +844,7 @@ class BaseTest:
         self.assertRaises(TypeError, a.__setitem__, slice(0, 1), b)
 
     def test_extended_set_del_slice(self):
-        indices = (0, None, 1, 3, 19, 100, -1, -2, -31, -100)
+        indices = (0, None, 1, 3, 19, 100, sys.maxsize, -1, -2, -31, -100)
         for start in indices:
             for stop in indices:
                 # Everything except the initial 0 (invalid step)

diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index a0913603e73707174169109780a85f5dc4091760..9502a8f974bd3704aaf428192d4b99722f0cf383 100644 (file)
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -285,7 +285,7 @@ class BaseBytesTest:
         # Test extended slicing by comparing with list slicing.
         L = list(range(255))
         b = self.type2test(L)
-        indices = (0, None, 1, 3, 19, 100, -1, -2, -31, -100)
+        indices = (0, None, 1, 3, 19, 100, sys.maxsize, -1, -2, -31, -100)
         for start in indices:
             for stop in indices:
                 # Skip step 0 (invalid)
@@ -1242,7 +1242,8 @@ class ByteArrayTest(BaseBytesTest, unittest.TestCase):
         self.assertLessEqual(sys.getsizeof(b), size)
 
     def test_extended_set_del_slice(self):
-        indices = (0, None, 1, 3, 19, 300, 1<<333, -1, -2, -31, -300)
+        indices = (0, None, 1, 3, 19, 300, 1<<333, sys.maxsize,
+            -1, -2, -31, -300)
         for start in indices:
             for stop in indices:
                 # Skip invalid step 0

diff --git a/Lib/test/test_mmap.py b/Lib/test/test_mmap.py
index dd857a0632aeef475b8273109d7c185316017866..495d24ad80773003f8b373a74fb5dd10c8f780cc 100644 (file)
--- a/Lib/test/test_mmap.py
+++ b/Lib/test/test_mmap.py
@@ -439,7 +439,7 @@ class MmapTests(unittest.TestCase):
         m = mmap.mmap(-1, len(s))
         m[:] = s
         self.assertEqual(m[:], s)
-        indices = (0, None, 1, 3, 19, 300, -1, -2, -31, -300)
+        indices = (0, None, 1, 3, 19, 300, sys.maxsize, -1, -2, -31, -300)
         for start in indices:
             for stop in indices:
                 # Skip step 0 (invalid)
@@ -451,7 +451,7 @@ class MmapTests(unittest.TestCase):
         # Test extended slicing by comparing with list slicing.
         s = bytes(reversed(range(256)))
         m = mmap.mmap(-1, len(s))
-        indices = (0, None, 1, 3, 19, 300, -1, -2, -31, -300)
+        indices = (0, None, 1, 3, 19, 300, sys.maxsize, -1, -2, -31, -300)
         for start in indices:
             for stop in indices:
                 # Skip invalid step 0

diff --git a/Misc/NEWS.d/next/Core and Builtins/2019-05-16-23-53-45.bpo-36946.qjxr0Y.rst b/Misc/NEWS.d/next/Core and Builtins/2019-05-16-23-53-45.bpo-36946.qjxr0Y.rst
new file mode 100644 (file)
index 0000000..aa5de80
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2019-05-16-23-53-45.bpo-36946.qjxr0Y.rst
@@ -0,0 +1 @@
+Fix possible signed integer overflow when handling slices.

diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index 13cf76a16d768a12178a238487401de1d1a0c23b..7b5115359ed7e8a72b0b47bb0809daf55b6aa01f 100644 (file)
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -4487,7 +4487,8 @@ Array_subscript(PyObject *myself, PyObject *item)
         StgDictObject *stgdict, *itemdict;
         PyObject *proto;
         PyObject *np;
-        Py_ssize_t start, stop, step, slicelen, cur, i;
+        Py_ssize_t start, stop, step, slicelen, i;
+        size_t cur;
 
         if (PySlice_Unpack(item, &start, &stop, &step) < 0) {
             return NULL;
@@ -4627,7 +4628,8 @@ Array_ass_subscript(PyObject *myself, PyObject *item, PyObject *value)
         return Array_ass_item(myself, i, value);
     }
     else if (PySlice_Check(item)) {
-        Py_ssize_t start, stop, step, slicelen, otherlen, i, cur;
+        Py_ssize_t start, stop, step, slicelen, otherlen, i;
+        size_t cur;
 
         if (PySlice_Unpack(item, &start, &stop, &step) < 0) {
             return -1;

diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index f5fc4437deb554b71703393122f3309365f2fd2e..b1fb3eeffb110f360ca2912e4d05f1a811fbd803 100644 (file)
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -1809,7 +1809,8 @@ element_subscr(PyObject* self_, PyObject* item)
         return element_getitem(self_, i);
     }
     else if (PySlice_Check(item)) {
-        Py_ssize_t start, stop, step, slicelen, cur, i;
+        Py_ssize_t start, stop, step, slicelen, i;
+        size_t cur;
         PyObject* list;
 
         if (!self->extra)
@@ -1861,7 +1862,8 @@ element_ass_subscr(PyObject* self_, PyObject* item, PyObject* value)
         return element_setitem(self_, i, value);
     }
     else if (PySlice_Check(item)) {
-        Py_ssize_t start, stop, step, slicelen, newlen, cur, i;
+        Py_ssize_t start, stop, step, slicelen, newlen, i;
+        size_t cur;
 
         PyObject* recycle = NULL;
         PyObject* seq;

diff --git a/Modules/arraymodule.c b/Modules/arraymodule.c
index 4be3beb29ccbae933faaf34f493fa4fedd14bdf2..523afb99e8ae6eb718d72ea56e2e1cb172eb5fad 100644 (file)
--- a/Modules/arraymodule.c
+++ b/Modules/arraymodule.c
@@ -2343,7 +2343,8 @@ array_subscr(arrayobject* self, PyObject* item)
         return array_item(self, i);
     }
     else if (PySlice_Check(item)) {
-        Py_ssize_t start, stop, step, slicelength, cur, i;
+        Py_ssize_t start, stop, step, slicelength, i;
+        size_t cur;
         PyObject* result;
         arrayobject* ar;
         int itemsize = self->ob_descr->itemsize;
@@ -2527,7 +2528,8 @@ array_ass_subscr(arrayobject* self, PyObject* item, PyObject* value)
         return 0;
     }
     else {
-        Py_ssize_t cur, i;
+        size_t cur;
+        Py_ssize_t i;
 
         if (needed != slicelength) {
             PyErr_Format(PyExc_ValueError,

diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index 6ddbf70d9a9789eafe8c584773a6fcf038ed5d83..33366b2d933194a13930410e4d41f50077c08120 100644 (file)
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -806,7 +806,8 @@ mmap_subscript(mmap_object *self, PyObject *item)
                                               slicelen);
         else {
             char *result_buf = (char *)PyMem_Malloc(slicelen);
-            Py_ssize_t cur, i;
+            size_t cur;
+            Py_ssize_t i;
             PyObject *result;
 
             if (result_buf == NULL)
@@ -926,7 +927,8 @@ mmap_ass_subscript(mmap_object *self, PyObject *item, PyObject *value)
             memcpy(self->data + start, vbuf.buf, slicelen);
         }
         else {
-            Py_ssize_t cur, i;
+            size_t cur;
+            Py_ssize_t i;
 
             for (cur = start, i = 0;
                  i < slicelen;

diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index eaf5dceb03a4caa68604ea439ec5d9122e2309a5..8d5ba540120f4bc6655c9e233d51b95bd9184554 100644 (file)
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -410,7 +410,8 @@ bytearray_subscript(PyByteArrayObject *self, PyObject *index)
         return PyLong_FromLong((unsigned char)(PyByteArray_AS_STRING(self)[i]));
     }
     else if (PySlice_Check(index)) {
-        Py_ssize_t start, stop, step, slicelength, cur, i;
+        Py_ssize_t start, stop, step, slicelength, i;
+        size_t cur;
         if (PySlice_Unpack(index, &start, &stop, &step) < 0) {
             return NULL;
         }

diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index b7c5b75283ee2774f9d1ebb75a1c356bfbcc1a3e..ebbdb7c3c1642886fa958b7cdd7aac2dc576e246 100644 (file)
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -1677,7 +1677,8 @@ bytes_subscript(PyBytesObject* self, PyObject* item)
         return PyLong_FromLong((unsigned char)self->ob_sval[i]);
     }
     else if (PySlice_Check(item)) {
-        Py_ssize_t start, stop, step, slicelength, cur, i;
+        Py_ssize_t start, stop, step, slicelength, i;
+        size_t cur;
         char* source_buf;
         char* result_buf;
         PyObject* result;

diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 9f0fc1cc2c3fd4b32617a003b90beec098ee1945..dc1d0e5ad0d4585427a2c6df75183803beb4f9f2 100644 (file)
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -753,7 +753,8 @@ tuplesubscript(PyTupleObject* self, PyObject* item)
         return tupleitem(self, i);
     }
     else if (PySlice_Check(item)) {
-        Py_ssize_t start, stop, step, slicelength, cur, i;
+        Py_ssize_t start, stop, step, slicelength, i;
+        size_t cur;
         PyObject* result;
         PyObject* it;
         PyObject **src, **dest;

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index eaba5836cb1c71474bd7b3cc7b8648a774d7ec58..0aa5e4ad18dd219c8096cc6f390b6fbb2797de6e 100644 (file)
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -13991,7 +13991,8 @@ unicode_subscript(PyObject* self, PyObject* item)
             i += PyUnicode_GET_LENGTH(self);
         return unicode_getitem(self, i);
     } else if (PySlice_Check(item)) {
-        Py_ssize_t start, stop, step, slicelength, cur, i;
+        Py_ssize_t start, stop, step, slicelength, i;
+        size_t cur;
         PyObject *result;
         void *src_data, *dest_data;
         int src_kind, dest_kind;