gh-97728: Argument Clinic: Fix uninitialized variable in the Py_UNICODE converter (GH-97729)

It affects function os.system() on Windows and Windows-specific modules
winreg, _winapi, _overlapped, and _msi.

8 files changed, 46 insertions, 42 deletions

diff --git a/Lib/test/clinic.test b/Lib/test/clinic.test
index c73a75b..47e3e02 100644
--- a/Lib/test/clinic.test
+++ b/Lib/test/clinic.test
@@ -1803,12 +1803,12 @@ static PyObject *
 test_Py_UNICODE_converter(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    const Py_UNICODE *a;
-    const Py_UNICODE *b;
-    const Py_UNICODE *c;
-    const Py_UNICODE *d;
+    const Py_UNICODE *a = NULL;
+    const Py_UNICODE *b = NULL;
+    const Py_UNICODE *c = NULL;
+    const Py_UNICODE *d = NULL;
     Py_ssize_t d_length;
-    const Py_UNICODE *e;
+    const Py_UNICODE *e = NULL;
     Py_ssize_t e_length;
 
     if (!_PyArg_ParseStack(args, nargs, "O&O&O&u#Z#:test_Py_UNICODE_converter",
@@ -1833,7 +1833,7 @@ test_Py_UNICODE_converter_impl(PyObject *module, const Py_UNICODE *a,
                                const Py_UNICODE *b, const Py_UNICODE *c,
                                const Py_UNICODE *d, Py_ssize_t d_length,
                                const Py_UNICODE *e, Py_ssize_t e_length)
-/*[clinic end generated code: output=4d426808cdbb3ea3 input=064a3b68ad7f04b0]*/
+/*[clinic end generated code: output=9f34a249b3071fdd input=064a3b68ad7f04b0]*/
 
 
 /*[clinic input]
diff --git a/Misc/NEWS.d/next/Windows/2022-10-02-11-59-23.gh-issue-97728.dIdlPE.rst b/Misc/NEWS.d/next/Windows/2022-10-02-11-59-23.gh-issue-97728.dIdlPE.rst
new file mode 100644
index 0000000..2a6a253
--- /dev/null
+++ b/Misc/NEWS.d/next/Windows/2022-10-02-11-59-23.gh-issue-97728.dIdlPE.rst
@@ -0,0 +1,3 @@
+Fix possible crashes caused by the use of uninitialized variables when pass
+invalid arguments in :func:`os.system` on Windows and in Windows-specific
+modules (like ``winreg``).
diff --git a/Modules/clinic/_winapi.c.h b/Modules/clinic/_winapi.c.h
index 53d5ccc..cc1a588 100644
--- a/Modules/clinic/_winapi.c.h
+++ b/Modules/clinic/_winapi.c.h
@@ -221,7 +221,7 @@ _winapi_CreateFileMapping(PyObject *module, PyObject *const *args, Py_ssize_t na
     DWORD protect;
     DWORD max_size_high;
     DWORD max_size_low;
-    LPCWSTR name;
+    LPCWSTR name = NULL;
     HANDLE _return_value;
 
     if (!_PyArg_ParseStack(args, nargs, "" F_HANDLE "" F_POINTER "kkkO&:CreateFileMapping",
@@ -260,8 +260,8 @@ static PyObject *
 _winapi_CreateJunction(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    LPCWSTR src_path;
-    LPCWSTR dst_path;
+    LPCWSTR src_path = NULL;
+    LPCWSTR dst_path = NULL;
 
     if (!_PyArg_CheckPositional("CreateJunction", nargs, 2, 2)) {
         goto exit;
@@ -409,14 +409,14 @@ static PyObject *
 _winapi_CreateProcess(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    const Py_UNICODE *application_name;
+    const Py_UNICODE *application_name = NULL;
     PyObject *command_line;
     PyObject *proc_attrs;
     PyObject *thread_attrs;
     BOOL inherit_handles;
     DWORD creation_flags;
     PyObject *env_mapping;
-    const Py_UNICODE *current_directory;
+    const Py_UNICODE *current_directory = NULL;
     PyObject *startup_info;
 
     if (!_PyArg_ParseStack(args, nargs, "O&OOOikOO&O:CreateProcess",
@@ -760,7 +760,7 @@ _winapi_OpenFileMapping(PyObject *module, PyObject *const *args, Py_ssize_t narg
     PyObject *return_value = NULL;
     DWORD desired_access;
     BOOL inherit_handle;
-    LPCWSTR name;
+    LPCWSTR name = NULL;
     HANDLE _return_value;
 
     if (!_PyArg_ParseStack(args, nargs, "kiO&:OpenFileMapping",
@@ -890,9 +890,9 @@ _winapi_LCMapStringEx(PyObject *module, PyObject *const *args, Py_ssize_t nargs,
         .kwtuple = KWTUPLE,
     };
     #undef KWTUPLE
-    LPCWSTR locale;
+    LPCWSTR locale = NULL;
     DWORD flags;
-    LPCWSTR src;
+    LPCWSTR src = NULL;
 
     if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser,
         _PyUnicode_WideCharString_Converter, &locale, &flags, _PyUnicode_WideCharString_Converter, &src)) {
@@ -1345,4 +1345,4 @@ _winapi__mimetypes_read_windows_registry(PyObject *module, PyObject *const *args
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=3e51e0b2ea3fea5a input=a9049054013a1b77]*/
+/*[clinic end generated code: output=83c4a3f0e70e7775 input=a9049054013a1b77]*/
diff --git a/Modules/clinic/overlapped.c.h b/Modules/clinic/overlapped.c.h
index cc0c74c..e8c2fe5 100644
--- a/Modules/clinic/overlapped.c.h
+++ b/Modules/clinic/overlapped.c.h
@@ -282,7 +282,7 @@ _overlapped_CreateEvent(PyObject *module, PyObject *const *args, Py_ssize_t narg
     PyObject *EventAttributes;
     BOOL ManualReset;
     BOOL InitialState;
-    const Py_UNICODE *Name;
+    const Py_UNICODE *Name = NULL;
 
     if (!_PyArg_CheckPositional("CreateEvent", nargs, 4, 4)) {
         goto exit;
@@ -1047,7 +1047,7 @@ static PyObject *
 _overlapped_Overlapped_ConnectPipe(OverlappedObject *self, PyObject *arg)
 {
     PyObject *return_value = NULL;
-    const Py_UNICODE *Address;
+    const Py_UNICODE *Address = NULL;
 
     if (!PyUnicode_Check(arg)) {
         _PyArg_BadArgument("ConnectPipe", "argument", "str", arg);
@@ -1254,4 +1254,4 @@ exit:
 
     return return_value;
 }
-/*[clinic end generated code: output=ed7ca699b5cf6260 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=e0f866222bd5873b input=a9049054013a1b77]*/
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index a26cb82..7fac078 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -2399,7 +2399,7 @@ os_system(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *k
     };
     #undef KWTUPLE
     PyObject *argsbuf[1];
-    const Py_UNICODE *command;
+    const Py_UNICODE *command = NULL;
     long _return_value;
 
     args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser, 1, 1, 0, argsbuf);
@@ -11367,4 +11367,4 @@ exit:
 #ifndef OS_WAITSTATUS_TO_EXITCODE_METHODDEF
     #define OS_WAITSTATUS_TO_EXITCODE_METHODDEF
 #endif /* !defined(OS_WAITSTATUS_TO_EXITCODE_METHODDEF) */
-/*[clinic end generated code: output=dc71eece3fc988a7 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=dd43d388b442c96d input=a9049054013a1b77]*/
diff --git a/PC/clinic/_msi.c.h b/PC/clinic/_msi.c.h
index 1b7234a..c77f070 100644
--- a/PC/clinic/_msi.c.h
+++ b/PC/clinic/_msi.c.h
@@ -201,7 +201,7 @@ _msi_Record_SetString(msiobj *self, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     int field;
-    const Py_UNICODE *value;
+    const Py_UNICODE *value = NULL;
 
     if (!_PyArg_CheckPositional("SetString", nargs, 2, 2)) {
         goto exit;
@@ -244,7 +244,7 @@ _msi_Record_SetStream(msiobj *self, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     int field;
-    const Py_UNICODE *value;
+    const Py_UNICODE *value = NULL;
 
     if (!_PyArg_CheckPositional("SetStream", nargs, 2, 2)) {
         goto exit;
@@ -549,7 +549,7 @@ static PyObject *
 _msi_Database_OpenView(msiobj *self, PyObject *arg)
 {
     PyObject *return_value = NULL;
-    const Py_UNICODE *sql;
+    const Py_UNICODE *sql = NULL;
 
     if (!PyUnicode_Check(arg)) {
         _PyArg_BadArgument("OpenView", "argument", "str", arg);
@@ -638,7 +638,7 @@ static PyObject *
 _msi_OpenDatabase(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    const Py_UNICODE *path;
+    const Py_UNICODE *path = NULL;
     int persist;
 
     if (!_PyArg_CheckPositional("OpenDatabase", nargs, 2, 2)) {
@@ -695,4 +695,4 @@ _msi_CreateRecord(PyObject *module, PyObject *arg)
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=583505220fadb52b input=a9049054013a1b77]*/
+/*[clinic end generated code: output=7d083c61679eed83 input=a9049054013a1b77]*/
diff --git a/PC/clinic/winreg.c.h b/PC/clinic/winreg.c.h
index dc78274..2834d99 100644
--- a/PC/clinic/winreg.c.h
+++ b/PC/clinic/winreg.c.h
@@ -177,7 +177,7 @@ static PyObject *
 winreg_ConnectRegistry(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
-    const Py_UNICODE *computer_name;
+    const Py_UNICODE *computer_name = NULL;
     HKEY key;
     HKEY _return_value;
 
@@ -243,7 +243,7 @@ winreg_CreateKey(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *sub_key;
+    const Py_UNICODE *sub_key = NULL;
     HKEY _return_value;
 
     if (!_PyArg_CheckPositional("CreateKey", nargs, 2, 2)) {
@@ -343,7 +343,7 @@ winreg_CreateKeyEx(PyObject *module, PyObject *const *args, Py_ssize_t nargs, Py
     PyObject *argsbuf[4];
     Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 2;
     HKEY key;
-    const Py_UNICODE *sub_key;
+    const Py_UNICODE *sub_key = NULL;
     int reserved = 0;
     REGSAM access = KEY_WRITE;
     HKEY _return_value;
@@ -427,7 +427,7 @@ winreg_DeleteKey(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *sub_key;
+    const Py_UNICODE *sub_key = NULL;
 
     if (!_PyArg_CheckPositional("DeleteKey", nargs, 2, 2)) {
         goto exit;
@@ -520,7 +520,7 @@ winreg_DeleteKeyEx(PyObject *module, PyObject *const *args, Py_ssize_t nargs, Py
     PyObject *argsbuf[4];
     Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 2;
     HKEY key;
-    const Py_UNICODE *sub_key;
+    const Py_UNICODE *sub_key = NULL;
     REGSAM access = KEY_WOW64_64KEY;
     int reserved = 0;
 
@@ -587,7 +587,7 @@ winreg_DeleteValue(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *value;
+    const Py_UNICODE *value = NULL;
 
     if (!_PyArg_CheckPositional("DeleteValue", nargs, 2, 2)) {
         goto exit;
@@ -731,7 +731,7 @@ static PyObject *
 winreg_ExpandEnvironmentStrings(PyObject *module, PyObject *arg)
 {
     PyObject *return_value = NULL;
-    const Py_UNICODE *string;
+    const Py_UNICODE *string = NULL;
 
     if (!PyUnicode_Check(arg)) {
         _PyArg_BadArgument("ExpandEnvironmentStrings", "argument", "str", arg);
@@ -830,8 +830,8 @@ winreg_LoadKey(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *sub_key;
-    const Py_UNICODE *file_name;
+    const Py_UNICODE *sub_key = NULL;
+    const Py_UNICODE *file_name = NULL;
 
     if (!_PyArg_CheckPositional("LoadKey", nargs, 3, 3)) {
         goto exit;
@@ -924,7 +924,7 @@ winreg_OpenKey(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObje
     PyObject *argsbuf[4];
     Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 2;
     HKEY key;
-    const Py_UNICODE *sub_key;
+    const Py_UNICODE *sub_key = NULL;
     int reserved = 0;
     REGSAM access = KEY_READ;
     HKEY _return_value;
@@ -1037,7 +1037,7 @@ winreg_OpenKeyEx(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyOb
     PyObject *argsbuf[4];
     Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 2;
     HKEY key;
-    const Py_UNICODE *sub_key;
+    const Py_UNICODE *sub_key = NULL;
     int reserved = 0;
     REGSAM access = KEY_READ;
     HKEY _return_value;
@@ -1159,7 +1159,7 @@ winreg_QueryValue(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *sub_key;
+    const Py_UNICODE *sub_key = NULL;
 
     if (!_PyArg_CheckPositional("QueryValue", nargs, 2, 2)) {
         goto exit;
@@ -1216,7 +1216,7 @@ winreg_QueryValueEx(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *name;
+    const Py_UNICODE *name = NULL;
 
     if (!_PyArg_CheckPositional("QueryValueEx", nargs, 2, 2)) {
         goto exit;
@@ -1278,7 +1278,7 @@ winreg_SaveKey(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *file_name;
+    const Py_UNICODE *file_name = NULL;
 
     if (!_PyArg_CheckPositional("SaveKey", nargs, 2, 2)) {
         goto exit;
@@ -1341,7 +1341,7 @@ winreg_SetValue(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *sub_key;
+    const Py_UNICODE *sub_key = NULL;
     DWORD type;
     PyObject *value_obj;
 
@@ -1440,7 +1440,7 @@ winreg_SetValueEx(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     HKEY key;
-    const Py_UNICODE *value_name;
+    const Py_UNICODE *value_name = NULL;
     PyObject *reserved;
     DWORD type;
     PyObject *value;
@@ -1579,4 +1579,4 @@ winreg_QueryReflectionKey(PyObject *module, PyObject *arg)
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=5dfd7dbce8ccb392 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=7e817dc5edc914d3 input=a9049054013a1b77]*/
diff --git a/Tools/clinic/clinic.py b/Tools/clinic/clinic.py
index 805bdcb..30a6763 100755
--- a/Tools/clinic/clinic.py
+++ b/Tools/clinic/clinic.py
@@ -3586,6 +3586,7 @@ class Py_UNICODE_converter(CConverter):
                 self.converter = '_PyUnicode_WideCharString_Opt_Converter'
             else:
                 fail("Py_UNICODE_converter: illegal 'accept' argument " + repr(accept))
+        self.c_default = "NULL"
 
     def cleanup(self):
         if not self.length: