gh-116738: Consolidate group function calls under one mutex

Author: yoney

Modules/grpmodule.c

@@ -55,6 +55,11 @@ get_grp_state(PyObject *module)
 
 static struct PyModuleDef grpmodule;
 
+/* Mutex to protect calls to getgrgid(), getgrnam(), and getgrent().
+ * These functions return pointer to static data structure, which
+ * may be overwritten by any subsequent calls. */
+static PyMutex group_db_mutex = {0};
+
 #define DEFAULT_BUFFER_SIZE 1024
 
 static PyObject *
@@ -168,15 +173,14 @@ grp_getgrgid_impl(PyObject *module, PyObject *id)
 
     Py_END_ALLOW_THREADS
 #else
-    static PyMutex getgrgid_mutex = {0};
-    PyMutex_Lock(&getgrgid_mutex);
+    PyMutex_Lock(&group_db_mutex);
     // The getgrgid() function need not be thread-safe.
     // https://pubs.opengroup.org/onlinepubs/9699919799/functions/getgrgid.html
     p = getgrgid(gid);
 #endif
     if (p == NULL) {
 #ifndef HAVE_GETGRGID_R
-        PyMutex_Unlock(&getgrgid_mutex);
+        PyMutex_Unlock(&group_db_mutex);
 #endif
         PyMem_RawFree(buf);
         if (nomem == 1) {
@@ -193,7 +197,7 @@ grp_getgrgid_impl(PyObject *module, PyObject *id)
 #ifdef HAVE_GETGRGID_R
     PyMem_RawFree(buf);
 #else
-    PyMutex_Unlock(&getgrgid_mutex);
+    PyMutex_Unlock(&group_db_mutex);
 #endif
     return retval;
 }
@@ -258,15 +262,14 @@ grp_getgrnam_impl(PyObject *module, PyObject *name)
 
     Py_END_ALLOW_THREADS
 #else
-    static PyMutex getgrnam_mutex = {0};
-    PyMutex_Lock(&getgrnam_mutex);
+    PyMutex_Lock(&group_db_mutex);
     // The getgrnam() function need not be thread-safe.
     // https://pubs.opengroup.org/onlinepubs/9699919799/functions/getgrnam.html
     p = getgrnam(name_chars);
 #endif
     if (p == NULL) {
 #ifndef HAVE_GETGRNAM_R
-        PyMutex_Unlock(&getgrnam_mutex);
+        PyMutex_Unlock(&group_db_mutex);
 #endif
         if (nomem == 1) {
             PyErr_NoMemory();
@@ -278,7 +281,7 @@ grp_getgrnam_impl(PyObject *module, PyObject *name)
     }
     retval = mkgrent(module, p);
 #ifndef HAVE_GETGRNAM_R
-    PyMutex_Unlock(&getgrnam_mutex);
+    PyMutex_Unlock(&group_db_mutex);
 #endif
 out:
     PyMem_RawFree(buf);
@@ -304,8 +307,7 @@ grp_getgrall_impl(PyObject *module)
         return NULL;
     }
 
-    static PyMutex getgrall_mutex = {0};
-    PyMutex_Lock(&getgrall_mutex);
+    PyMutex_Lock(&group_db_mutex);
     setgrent();
 
     struct group *p;
@@ -325,7 +327,7 @@ grp_getgrall_impl(PyObject *module)
 
 done:
     endgrent();
-    PyMutex_Unlock(&getgrall_mutex);
+    PyMutex_Unlock(&group_db_mutex);
     return d;
 }