Re: [PATCH 09/20] midx: check size of object offset chunk

[Taylor Blau <me@ttaylorr.com>]

On Mon, Oct 09, 2023 at 05:05:27PM -0400, Jeff King wrote:
> @@ -88,6 +88,19 @@ static int midx_read_oid_lookup(const unsigned char *chunk_start,
>  	return 0;
>  }
>
> +static int midx_read_object_offsets(const unsigned char *chunk_start,
> +				    size_t chunk_size, void *data)
> +{
> +	struct multi_pack_index *m = data;
> +	m->chunk_object_offsets = chunk_start;
> +
> +	if (chunk_size != st_mult(m->num_objects, MIDX_CHUNK_OFFSET_WIDTH)) {
> +		error(_("multi-pack-index object offset chunk is the wrong size"));
> +		return 1;
> +	}
> +	return 0;
> +}

Makes sense, and the (elided) test below looks good, too. I think that
this is another case that would benefit from having the chunk-format API
take in an "expected size" and validate that the requested chunk is
actually that size before assigning its address to some pointer.

Thanks,
Taylor