There are some uses of ksize in the kernel making use of the real usable size of memory allocations rather than only the requested amount. It's incorrect when mixed with alloc_size markers, since if a number like 14 is passed that's used as the upper bound, rather than a rounded size like 16 returned by ksize. It's unlikely to trigger any issues with only CONFIG_FORTIFY_SOURCE, but it becomes more likely with -fsanitize=object-size or other library-based usage of __builtin_object_size.
