+--- a/include/linux/union.h
++++ b/include/linux/union.h
+@@ -77,7 +77,7 @@
+ #define __union_copyup(x, y, z) ({ BUG(); (0); })
+ #define union_copyup(x, y) ({ (0); })
+ #define union_copyup_dir(x) ({ BUG(); (0); })
+-#define union_permission(x, y) inode_permission(x->dentry->d_inode, y)
++#define union_permission(x, y) inode_permission((x)->dentry->d_inode, y)
+
+ #endif /* CONFIG_UNION_MOUNT */
+ #endif /* __KERNEL__ */