Re: [syzbot] [zstd] UBSAN: array-index-out-of-bounds in FSE_decompress_wksp_body_bmi2

[Eric Biggers]

Hi Nick,

On Wed, Aug 30, 2023 at 12:49:53AM -0700, syzbot wrote:
> UBSAN: array-index-out-of-bounds in lib/zstd/common/fse_decompress.c:345:30
> index 33 is out of range for type 'FSE_DTable[1]' (aka 'unsigned int[1]')

Zstandard needs to be converted to use C99 flex-arrays instead of length-1
arrays.  https://github.com/facebook/zstd/pull/3785 would fix this in upstream
Zstandard, though it doesn't work well with the fact that upstream Zstandard
supports C90.  Not sure how you want to handle this.

- Eric