[PATCH] Reject compressed sections exceding 4 GiB on LLP64 machines

[Rui Ueyama]

On second thought, it’s probably better to teach the linkers to emit
multiple zlib streams into compressed sections if the total length
exceeds 4 GiB, rather than rejecting compressed sections
unconditionally on the consumer side when their size exceeds 4 GiB?

On Tue, Jun 3, 2025 at 11:16 AM Rui Ueyama <ruiu@cs.stanford.edu> wrote:
>
> According to the zlib FAQ (*1), zlib does not support compressed data
> larger than 4 GiB when the compiler's long type is 32 bits. Therefore,
> we need to report an error if a zlib-compressed debug section exceeds
> 4 GiB on LLP64 machines.
>
> (*1) https://zlib.net/zlib_faq.html#faq32
>
> Signed-off-by: Rui Ueyama <rui314@gmail.com>
> ---
>  bfd/compress.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/bfd/compress.c b/bfd/compress.c
> index 4f92455dbd6..99b24f7368e 100644
> --- a/bfd/compress.c
> +++ b/bfd/compress.c
> @@ -521,10 +521,8 @@ decompress_contents (bool is_zstd, bfd_byte *compressed_buffer,
>       buffers concatenated together, so we uncompress in a loop.  */
>    do
>      {
> -      uLongf dst_len = (uncompressed_size > ULONG_MAX ? ULONG_MAX
> -                       : uncompressed_size);
> -      uLong src_len = (compressed_size > ULONG_MAX ? ULONG_MAX
> -                      : compressed_size);
> +      uLongf dst_len = uncompressed_size;
> +      uLong src_len = compressed_size;
>        int rc = uncompress2 ((Bytef *) uncompressed_buffer, &dst_len,
>                             (Bytef *) compressed_buffer, &src_len);
>        if (rc != Z_OK)
> @@ -1009,6 +1007,15 @@ bfd_init_section_decompress_status (bfd *abfd, sec_ptr sec)
>        return false;
>      }
>
> +  /* PR28530, reject sizes unsupported by decompress_contents. zlib
> +     supports only up to 4 GiB input on machines whose long is 32 bits. */
> +  if (ch_type != ch_compress_zstd
> +      && (sec->size >= ULONG_MAX || uncompressed_size >= ULONG_MAX))
> +    {
> +      bfd_set_error (bfd_error_nonrepresentable_section);
> +      return false;
> +    }
> +
>    sec->compressed_size = sec->size;
>    sec->size = uncompressed_size;
>    bfd_set_section_alignment (sec, uncompressed_alignment_power);
> --
> 2.43.0
>