gh-99127: Allow some features of syslog to the main interpreter only

Lib/test/test_syslog.py

@@ -5,6 +5,7 @@
 import threading
 import time
 import unittest
+from textwrap import dedent
 
 # XXX(nnorwitz): This test sucks.  I don't know of a platform independent way
 # to verify that the messages were really logged.
@@ -78,6 +79,69 @@ def logger():
         finally:
             sys.setswitchinterval(orig_si)
 
+    def test_subinterpreter_syslog(self):
+        # syslog.syslog() is not allowed in subinterpreters, but only if
+        # syslog.openlog() hasn't been called in the main interpreter yet.
+        with self.subTest('before openlog()'):
+            code = dedent('''
+                import syslog
+                caught_error = False
+                try:
+                    syslog.syslog('foo')
+                except RuntimeError:
+                    caught_error = True
+                assert(caught_error)
+            ''')
+            res = support.run_in_subinterp(code)
+            self.assertEqual(res, 0)
+
+        syslog.openlog()
+        try:
+            with self.subTest('after openlog()'):
+                code = dedent('''
+                    import syslog
+                    syslog.syslog('foo')
+                ''')
+                res = support.run_in_subinterp(code)
+                self.assertEqual(res, 0)
+        finally:
+            syslog.closelog()
+
+    def test_subinterpreter_openlog(self):
+        try:
+            code = dedent('''
+                import syslog
+                caught_error = False
+                try:
+                    syslog.openlog()
+                except RuntimeError:
+                    caught_error = True
+
+                assert(caught_error)
+            ''')
+            res = support.run_in_subinterp(code)
+            self.assertEqual(res, 0)
+        finally:
+            syslog.closelog()
+
+    def test_subinterpreter_closelog(self):
+        syslog.openlog('python')
+        try:
+            code = dedent('''
+                import syslog
+                caught_error = False
+                try:
+                    syslog.closelog()
+                except RuntimeError:
+                    caught_error = True
+
+                assert(caught_error)
+            ''')
+            res = support.run_in_subinterp(code)
+            self.assertEqual(res, 0)
+        finally:
+            syslog.closelog()
+
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Core and Builtins/2022-11-05-22-26-35.gh-issue-99127.Btk7ih.rst

@@ -0,0 +1 @@
+Allow some features of :mod:`syslog` to the main interpreter only. Patch by Dong-hee Na.

Modules/syslogmodule.c

@@ -61,10 +61,22 @@ module syslog
 
 #include "clinic/syslogmodule.c.h"
 
-/*  only one instance, only one syslog, so globals should be ok  */
-static PyObject *S_ident_o = NULL;                      /*  identifier, held by openlog()  */
+/*  only one instance, only one syslog, so globals should be ok,
+ *  these fields are writable from the main interpreter only. */
+static PyObject *S_ident_o = NULL;  // identifier, held by openlog()
 static char S_log_open = 0;
 
+static inline int
+is_main_interpreter(void)
+{
+    PyInterpreterState *main_interp = PyInterpreterState_Main();
+    PyThreadState *tstate = PyThreadState_GET();
+    PyInterpreterState *current_interp = PyThreadState_GetInterpreter(tstate);
+    if (current_interp == main_interp) {
+        return 1;
+    }
+    return 0;
+}
 
 static PyObject *
 syslog_get_argv(void)
@@ -135,6 +147,13 @@ syslog_openlog_impl(PyObject *module, PyObject *ident, long logopt,
                     long facility)
 /*[clinic end generated code: output=5476c12829b6eb75 input=8a987a96a586eee7]*/
 {
+    // Since the sys.openlog changes the process level state of syslog library,
+    // this operation is only allowed for the main interpreter.
+    if (!is_main_interpreter()) {
+        PyErr_SetString(PyExc_RuntimeError, "subinterpreter can not use syslog.openlog");
+        return NULL;
+    }
+
     const char *ident_str = NULL;
 
     if (ident) {
@@ -195,6 +214,11 @@ syslog_syslog_impl(PyObject *module, int group_left_1, int priority,
 
     /*  if log is not opened, open it now  */
     if (!S_log_open) {
+        if (!is_main_interpreter()) {
+            PyErr_SetString(PyExc_RuntimeError, "subinterpreter can't use syslog.syslog "
+                                                "until the syslog is opened by the main interpreter");
+            return NULL;
+        }
         PyObject *openlog_ret = syslog_openlog_impl(module, NULL, 0, LOG_USER);
         if (openlog_ret == NULL) {
             return NULL;
@@ -230,6 +254,13 @@ static PyObject *
 syslog_closelog_impl(PyObject *module)
 /*[clinic end generated code: output=97890a80a24b1b84 input=fb77a54d447acf07]*/
 {
+    // Since the sys.closelog changes the process level state of syslog library,
+    // this operation is only allowed for the main interpreter.
+    if (!is_main_interpreter()) {
+        PyErr_SetString(PyExc_RuntimeError, "sunbinterpreter can not use syslog.closelog");
+        return NULL;
+    }
+
     if (PySys_Audit("syslog.closelog", NULL) < 0) {
         return NULL;
     }