Re: UBSAN: array-index-out-of-bounds in kernel/bpf/arraymap.c:177

[Andrii Nakryiko]

On Sun, May 17, 2020 at 7:45 PM Qian Cai <cai@xxxxxx> wrote:
>
> With Clang 9.0.1,
>
> return array->value + array->elem_size * (index & array->index_mask);
>
> but array->value is,
>
> char value[0] __aligned(8);

This, and ptrs and pptrs, should be flexible arrays. But they are in a
union, and unions don't support flexible arrays. Putting each of them
into anonymous struct field also doesn't work:

/data/users/andriin/linux/include/linux/bpf.h:820:18: error: flexible
array member in a struct with no named members
   struct { void *ptrs[] __aligned(8); };

So it probably has to stay this way. Is there a way to silence UBSAN
for this particular case?