# HG changeset patch
# Parent 1edff7001f589dffaf8de4aebcb65a1f1d7deb5c

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -7936,12 +7936,32 @@ posix_confstr(PyObject *self, PyObject *
     PyObject *result = NULL;
     int name;
     char buffer[256];
+    char *recvbuf = buffer;
+    char *allocated = NULL;
+    size_t buflen = sizeof(buffer);
+    size_t len;
+    const int max_attempts = 20;
+    int attempts_remaining = max_attempts;
 
     if (PyArg_ParseTuple(args, "O&:confstr", conv_confstr_confname, &name)) {
-    int len;
-
-    errno = 0;
-    len = confstr(name, buffer, sizeof(buffer));
+
+    /* Reset errno before each call as we may need to check it afterwards */
+    while (errno = 0, (len = confstr(name, recvbuf, buflen)) > buflen) {
+        if (--attempts_remaining <= 0) {
+            PyErr_Format(PyExc_RuntimeError,
+                         "confstr() made %d consecutive requests for a larger "
+                         "buffer; giving up", max_attempts);
+            goto finally;
+        }
+        recvbuf = PyMem_Realloc(allocated, len);
+        if (recvbuf == NULL) {
+            PyErr_NoMemory();
+            goto finally;
+        }
+        allocated = recvbuf;
+        buflen = len;
+    }
+
     if (len == 0) {
         if (errno) {
         posix_error();
@@ -7952,15 +7972,11 @@ posix_confstr(PyObject *self, PyObject *
         }
     }
     else {
-        if ((unsigned int)len >= sizeof(buffer)) {
-        result = PyString_FromStringAndSize(NULL, len-1);
-        if (result != NULL)
-            confstr(name, PyString_AS_STRING(result), len);
-        }
-        else
-        result = PyString_FromStringAndSize(buffer, len-1);
-    }
-    }
+        result = PyString_FromStringAndSize(recvbuf, len-1);
+    }
+    }
+finally:
+    PyMem_Free(allocated);
     return result;
 }
 #endif