Re: [PATCH] rust: firmware: return empty slice for zero-size firmware

["Gary Guo" <gary@garyguo.net>]

On Fri Jun 5, 2026 at 8:10 AM BST, Onur Özkan wrote:
> On Thu, 04 Jun 2026 21:11:34 -0700
> Yuan Tan <ytan089@ucr.edu> wrote:
>
>> Firmware::data() builds a Rust slice with core::slice::from_raw_parts().
>> Unlike many C APIs, from_raw_parts() requires its pointer argument to be
>> non-NULL even when the length is zero.
>> 
>> The firmware loader can represent an empty firmware image with size == 0
>
>
> I haven't checked in detail yet but "empty firmware image with size == 0"
> sounds like an invalid image. Can such an image actually make it all the way
> to Firmware::data()? I would be surprised if the loader accepted it.

`kernel_read_file` will return EINVAL if file is of zero size. But I think the
decompression path might produce this? The zstd code just does a

    out_buf = vzalloc(out_size);

which will trigger a WARN but still return NULL.

That said, I doubt any valid firmware will be just a compressed empty file.

Best,
Gary