randomize_layout: Fix potential auto-selection bug

- Fix auto-selection bug in is_pure_ops_struct (Joonwon Kang)
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 Comment: Kees Cook <kees@outflux.net>
 
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Merge tag 'gcc-plugins-v5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull gcc-plugins fix from Kees Cook:
 "Fix a potential problem in randomize_layout structure auto-selection
  (that was not triggered by any existing kernel structures)"

* tag 'gcc-plugins-v5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  randstruct: Check member structs in is_pure_ops_struct()

scripts/gcc-plugins/randomize_layout_plugin.c

@@ -443,13 +443,13 @@ static int is_pure_ops_struct(const_tree node)
 		if (node == fieldtype)
 			continue;
 
-		if (!is_fptr(fieldtype))
-			return 0;
-
-		if (code != RECORD_TYPE && code != UNION_TYPE)
+		if (code == RECORD_TYPE || code == UNION_TYPE) {
+			if (!is_pure_ops_struct(fieldtype))
+				return 0;
 			continue;
+		}
 
-		if (!is_pure_ops_struct(fieldtype))
+		if (!is_fptr(fieldtype))
 			return 0;
 	}