Fix crash when passing -1 as fd in os.pathconf

Author: aisk

Lib/test/test_os/test_os.py

@@ -2778,6 +2778,16 @@ def test_fpathconf_bad_fd(self):
         self.check(os.pathconf, "PC_NAME_MAX")
         self.check(os.fpathconf, "PC_NAME_MAX")
 
+    @unittest.skipUnless(hasattr(os, 'pathconf'), 'test needs os.pathconf()')
+    @unittest.skipIf(
+        support.linked_to_musl(),
+        'musl pathconf ignores the file descriptor and returns a constant',
+        )
+    def test_pathconf_negative_fd_uses_fd_semantics(self):
+        with self.assertRaises(OSError) as ctx:
+            os.pathconf(-1, 1)
+        self.assertEqual(ctx.exception.errno, errno.EBADF)
+
     @unittest.skipUnless(hasattr(os, 'ftruncate'), 'test needs os.ftruncate()')
     def test_ftruncate(self):
         self.check(os.truncate, 0)

Modules/posixmodule.c

@@ -1609,6 +1609,12 @@ follow_symlinks_specified(const char *function_name, int follow_symlinks)
     return 1;
 }
 
+static bool
+path_is_fd(const path_t *path)
+{
+    return path->allow_fd && path->object != NULL && PyIndex_Check(path->object);
+}
+
 static int
 path_and_dir_fd_invalid(const char *function_name, path_t *path, int dir_fd)
 {
@@ -14328,8 +14334,9 @@ os_pathconf_impl(PyObject *module, path_t *path, int name)
 
     errno = 0;
 #ifdef HAVE_FPATHCONF
-    if (path->fd != -1)
+    if (path_is_fd(path)) {
         limit = fpathconf(path->fd, name);
+    }
     else
 #endif
         limit = pathconf(path->narrow, name);