bpo-29802: Fix reference counting in module-level struct functions (#1213)

serhiy-storchaka · web-flow · commit 40db90c1ce1a · 2017-04-20T21:19:31.000+03:00
when pass arguments of wrong type.
diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py
@@ -599,6 +599,16 @@ def test_boundary_error_message_with_negative_offset(self):
                 'offset -11 out of range for 10-byte buffer'):
             struct.pack_into('<B', byte_list, -11, 123)
 
+    def test_issue29802(self):
+        # When the second argument of struct.unpack() was of wrong type
+        # the Struct object was decrefed twice and the reference to
+        # deallocated object was left in a cache.
+        with self.assertRaises(TypeError):
+            struct.unpack(b'b', 0)
+        # Shouldn't crash.
+        self.assertEqual(struct.unpack(b'b', b'a'), (b'a'[0],))
+
+
 class UnpackIteratorTest(unittest.TestCase):
     """
     Tests for iterative unpacking (struct.Struct.iter_unpack).
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -317,6 +317,9 @@ Extension Modules
 Library
 -------
 
+- bpo-29802: Fixed reference counting in module-level struct functions when
+  pass arguments of wrong type.
+
 - bpo-30070: Fixed leaks and crashes in errors handling in the parser module.
 
 - bpo-22352: Column widths in the output of dis.dis() are now adjusted for
diff --git a/Modules/_struct.c b/Modules/_struct.c
@@ -2083,6 +2083,7 @@ cache_struct_converter(PyObject *fmt, PyObject **ptr)
 
     if (fmt == NULL) {
         Py_DECREF(*ptr);
+        *ptr = NULL;
         return 1;
     }
 
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
@@ -3907,6 +3907,7 @@ PyUnicode_FSDecoder(PyObject* arg, void* addr)
     PyObject *output = NULL;
     if (arg == NULL) {
         Py_DECREF(*(PyObject**)addr);
+        *(PyObject**)addr = NULL;
         return 1;
     }
 

Original file line number	Diff line number	Diff line change
`@@ -2083,6 +2083,7 @@ cache_struct_converter(PyObject fmt, PyObject *ptr)`
`2083`	`2083`
`2084`	`2084`	`if (fmt == NULL) {`
`2085`	`2085`	`Py_DECREF(*ptr);`
	`2086`	`+ *ptr = NULL;`
`2086`	`2087`	`return 1;`
`2087`	`2088`	`}`
`2088`	`2089`
Original file line number	Diff line number	Diff line change
`@@ -3907,6 +3907,7 @@ PyUnicode_FSDecoder(PyObject* arg, void* addr)`
`3907`	`3907`	`PyObject *output = NULL;`
`3908`	`3908`	`if (arg == NULL) {`
`3909`	`3909`	`Py_DECREF((PyObject*)addr);`
	`3910`	`+ (PyObject*)addr = NULL;`
`3910`	`3911`	`return 1;`
`3911`	`3912`	`}`
`3912`	`3913`