gh-130163: Fix crashes related to PySys_GetObject() (GH-130503)

The use of PySys_GetObject() and _PySys_GetAttr(), which return a borrowed reference, has been replaced by using one of the following functions, which return a strong reference and distinguish a missing attribute from an error: _PySys_GetOptionalAttr(), _PySys_GetOptionalAttrString(), _PySys_GetRequiredAttr(), and _PySys_GetRequiredAttrString().
python · Feb 25, 2025 · 0ef4ffe · 0ef4ffe
1 parent 2dad1e0
commit 0ef4ffe
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Showing 23 changed files with 509 additions and 209 deletions.
diff --git a/Include/internal/pycore_sysmodule.h b/Include/internal/pycore_sysmodule.h
@@ -8,8 +8,10 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
-// Export for '_pickle' shared extension
-PyAPI_FUNC(PyObject*) _PySys_GetAttr(PyThreadState *tstate, PyObject *name);
+PyAPI_FUNC(int) _PySys_GetOptionalAttr(PyObject *, PyObject **);
+PyAPI_FUNC(int) _PySys_GetOptionalAttrString(const char *, PyObject **);
+PyAPI_FUNC(PyObject *) _PySys_GetRequiredAttr(PyObject *);
+PyAPI_FUNC(PyObject *) _PySys_GetRequiredAttrString(const char *);
 
 // Export for '_pickle' shared extension
 PyAPI_FUNC(size_t) _PySys_GetSizeOf(PyObject *);

diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
@@ -1710,6 +1710,29 @@ def test_input(self):
             sys.stdout = savestdout
             fp.close()
 
+    def test_input_gh130163(self):
+        class X(io.StringIO):
+            def __getattribute__(self, name):
+                nonlocal patch
+                if patch:
+                    patch = False
+                    sys.stdout = X()
+                    sys.stderr = X()
+                    sys.stdin = X('input\n')
+                    support.gc_collect()
+                return io.StringIO.__getattribute__(self, name)
+
+        with (support.swap_attr(sys, 'stdout', None),
+              support.swap_attr(sys, 'stderr', None),
+              support.swap_attr(sys, 'stdin', None)):
+            patch = False
+            # the only references:
+            sys.stdout = X()
+            sys.stderr = X()
+            sys.stdin = X('input\n')
+            patch = True
+            input()  # should not crash
+
     # test_int(): see test_int.py for tests of built-in function int().
 
     def test_repr(self):

diff --git a/Lib/test/test_print.py b/Lib/test/test_print.py
@@ -129,6 +129,17 @@ def flush(self):
                 raise RuntimeError
         self.assertRaises(RuntimeError, print, 1, file=noflush(), flush=True)
 
+    def test_gh130163(self):
+        class X:
+            def __str__(self):
+                sys.stdout = StringIO()
+                support.gc_collect()
+                return 'foo'
+
+        with support.swap_attr(sys, 'stdout', None):
+            sys.stdout = StringIO()  # the only reference
+            print(X())  # should not crash
+
 
 class TestPy2MigrationHint(unittest.TestCase):
     """Test that correct hint is produced analogous to Python3 syntax,

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
@@ -2,6 +2,7 @@
 import codecs
 import _datetime
 import gc
+import io
 import locale
 import operator
 import os
@@ -80,6 +81,18 @@ def baddisplayhook(obj):
             code = compile("42", "<string>", "single")
             self.assertRaises(ValueError, eval, code)
 
+    def test_gh130163(self):
+        class X:
+            def __repr__(self):
+                sys.stdout = io.StringIO()
+                support.gc_collect()
+                return 'foo'
+
+        with support.swap_attr(sys, 'stdout', None):
+            sys.stdout = io.StringIO()  # the only reference
+            sys.displayhook(X())  # should not crash
+
+
 class ActiveExceptionTests(unittest.TestCase):
     def test_exc_info_no_exception(self):
         self.assertEqual(sys.exc_info(), (None, None, None))

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-02-24-14-25-36.gh-issue-130163.rGpc9v.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-24-14-25-36.gh-issue-130163.rGpc9v.rst
@@ -0,0 +1,2 @@
+Fix possible crashes related to concurrent
+change and use of the :mod:`sys` module attributes.
diff --git a/Modules/_cursesmodule.c b/Modules/_cursesmodule.c
@@ -108,6 +108,7 @@ static const char PyCursesVersion[] = "2.2";
 #include "pycore_capsule.h"     // _PyCapsule_SetTraverse()
 #include "pycore_long.h"        // _PyLong_GetZero()
 #include "pycore_structseq.h"   // _PyStructSequence_NewType()
+#include "pycore_sysmodule.h"   // _PySys_GetOptionalAttrString()
 
 #ifdef __hpux
 #define STRICT_SYSV_CURSES
@@ -3542,16 +3543,19 @@ _curses_setupterm_impl(PyObject *module, const char *term, int fd)
     if (fd == -1) {
         PyObject* sys_stdout;
 
-        sys_stdout = PySys_GetObject("stdout");
+        if (_PySys_GetOptionalAttrString("stdout", &sys_stdout) < 0) {
+            return NULL;
+        }
 
         if (sys_stdout == NULL || sys_stdout == Py_None) {
             cursesmodule_state *state = get_cursesmodule_state(module);
             PyErr_SetString(state->error, "lost sys.stdout");
+            Py_XDECREF(sys_stdout);
             return NULL;
         }
 
         fd = PyObject_AsFileDescriptor(sys_stdout);
-
+        Py_DECREF(sys_stdout);
         if (fd == -1) {
             return NULL;
         }

diff --git a/Modules/_pickle.c b/Modules/_pickle.c
@@ -19,7 +19,7 @@
 #include "pycore_pystate.h"           // _PyThreadState_GET()
 #include "pycore_runtime.h"           // _Py_ID()
 #include "pycore_setobject.h"         // _PySet_NextEntry()
-#include "pycore_sysmodule.h"         // _PySys_GetAttr()
+#include "pycore_sysmodule.h"         // _PySys_GetSizeOf()
 
 #include <stdlib.h>               // strtol()
 
@@ -1910,10 +1910,8 @@ whichmodule(PickleState *st, PyObject *global, PyObject *global_name, PyObject *
            __module__ can be None. If it is so, then search sys.modules for
            the module of global. */
         Py_CLEAR(module_name);
-        PyThreadState *tstate = _PyThreadState_GET();
-        modules = _PySys_GetAttr(tstate, &_Py_ID(modules));
+        modules = _PySys_GetRequiredAttr(&_Py_ID(modules));
         if (modules == NULL) {
-            PyErr_SetString(PyExc_RuntimeError, "unable to get sys.modules");
             return NULL;
         }
         if (PyDict_CheckExact(modules)) {
@@ -1923,41 +1921,48 @@ whichmodule(PickleState *st, PyObject *global, PyObject *global_name, PyObject *
                 Py_INCREF(module);
                 if (_checkmodule(module_name, module, global, dotted_path) == 0) {
                     Py_DECREF(module);
+                    Py_DECREF(modules);
                     return module_name;
                 }
                 Py_DECREF(module);
                 Py_DECREF(module_name);
                 if (PyErr_Occurred()) {
+                    Py_DECREF(modules);
                     return NULL;
                 }
             }
         }
         else {
             PyObject *iterator = PyObject_GetIter(modules);
             if (iterator == NULL) {
+                Py_DECREF(modules);
                 return NULL;
             }
             while ((module_name = PyIter_Next(iterator))) {
                 module = PyObject_GetItem(modules, module_name);
                 if (module == NULL) {
                     Py_DECREF(module_name);
                     Py_DECREF(iterator);
+                    Py_DECREF(modules);
                     return NULL;
                 }
                 if (_checkmodule(module_name, module, global, dotted_path) == 0) {
                     Py_DECREF(module);
                     Py_DECREF(iterator);
+                    Py_DECREF(modules);
                     return module_name;
                 }
                 Py_DECREF(module);
                 Py_DECREF(module_name);
                 if (PyErr_Occurred()) {
                     Py_DECREF(iterator);
+                    Py_DECREF(modules);
                     return NULL;
                 }
             }
             Py_DECREF(iterator);
         }
+        Py_DECREF(modules);
         if (PyErr_Occurred()) {
             return NULL;
         }

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
@@ -8,7 +8,7 @@
 #include "pycore_modsupport.h"    // _PyArg_NoKeywords()
 #include "pycore_pylifecycle.h"
 #include "pycore_pystate.h"       // _PyThreadState_SetCurrent()
-#include "pycore_sysmodule.h"     // _PySys_GetAttr()
+#include "pycore_sysmodule.h"     // _PySys_GetOptionalAttr()
 #include "pycore_time.h"          // _PyTime_FromSeconds()
 #include "pycore_weakref.h"       // _PyWeakref_GET_REF()
 
@@ -2249,9 +2249,12 @@ thread_excepthook(PyObject *module, PyObject *args)
     PyObject *exc_tb = PyStructSequence_GET_ITEM(args, 2);
     PyObject *thread = PyStructSequence_GET_ITEM(args, 3);
 
-    PyThreadState *tstate = _PyThreadState_GET();
-    PyObject *file = _PySys_GetAttr(tstate, &_Py_ID(stderr));
+    PyObject *file;
+    if (_PySys_GetOptionalAttr( &_Py_ID(stderr), &file) < 0) {
+        return NULL;
+    }
     if (file == NULL || file == Py_None) {
+        Py_XDECREF(file);
         if (thread == Py_None) {
             /* do nothing if sys.stderr is None and thread is None */
             Py_RETURN_NONE;
@@ -2268,9 +2271,6 @@ thread_excepthook(PyObject *module, PyObject *args)
             Py_RETURN_NONE;
         }
     }
-    else {
-        Py_INCREF(file);
-    }
 
     int res = thread_excepthook_file(file, exc_type, exc_value, exc_tb,
                                      thread);

diff --git a/Modules/_tkinter.c b/Modules/_tkinter.c
@@ -31,6 +31,7 @@ Copyright (C) 1994 Steen Lumholt.
 #endif
 
 #include "pycore_long.h"          // _PyLong_IsNegative()
+#include "pycore_sysmodule.h"     // _PySys_GetOptionalAttrString()
 
 #ifdef MS_WINDOWS
 #  include <windows.h>
@@ -142,18 +143,21 @@ _get_tcl_lib_path(void)
     if (already_checked == 0) {
         struct stat stat_buf;
         int stat_return_value;
+        PyObject *prefix;
 
-        PyObject *prefix = PySys_GetObject("base_prefix");  // borrowed reference
+        (void) _PySys_GetOptionalAttrString("base_prefix", &prefix);
         if (prefix == NULL) {
             return NULL;
         }
 
         /* Check expected location for an installed Python first */
         tcl_library_path = PyUnicode_FromString("\\tcl\\tcl" TCL_VERSION);
         if (tcl_library_path == NULL) {
+            Py_DECREF(prefix);
             return NULL;
         }
         tcl_library_path = PyUnicode_Concat(prefix, tcl_library_path);
+        Py_DECREF(prefix);
         if (tcl_library_path == NULL) {
             return NULL;
         }
@@ -3516,9 +3520,10 @@ PyInit__tkinter(void)
 
     /* This helps the dynamic loader; in Unicode aware Tcl versions
        it also helps Tcl find its encodings. */
-    uexe = PySys_GetObject("executable");  // borrowed reference
+    (void) _PySys_GetOptionalAttrString("executable", &uexe);
     if (uexe && PyUnicode_Check(uexe)) {   // sys.executable can be None
         cexe = PyUnicode_EncodeFSDefault(uexe);
+        Py_DECREF(uexe);
         if (cexe) {
 #ifdef MS_WINDOWS
             int set_var = 0;
@@ -3531,12 +3536,14 @@ PyInit__tkinter(void)
             if (!ret && GetLastError() == ERROR_ENVVAR_NOT_FOUND) {
                 str_path = _get_tcl_lib_path();
                 if (str_path == NULL && PyErr_Occurred()) {
+                    Py_DECREF(cexe);
                     Py_DECREF(m);
                     return NULL;
                 }
                 if (str_path != NULL) {
                     wcs_path = PyUnicode_AsWideCharString(str_path, NULL);
                     if (wcs_path == NULL) {
+                        Py_DECREF(cexe);
                         Py_DECREF(m);
                         return NULL;
                     }
@@ -3557,6 +3564,9 @@ PyInit__tkinter(void)
         }
         Py_XDECREF(cexe);
     }
+    else {
+        Py_XDECREF(uexe);
+    }
 
     if (PyErr_Occurred()) {
         Py_DECREF(m);
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Fix possible crashes related to concurrent
		change and use of the :mod:`sys` module attributes.