[PATCH] bfd: Always check compressed sections with the corrupt size

[Hans-Peter Nilsson]

On Thu, 4 Nov 2021, H.J. Lu via Binutils wrote:

> Always check compressed sections with the corrupt size for non-MMO
> files.  Skip MMO files for compress_status == COMPRESS_SECTION_NONE
> since MMO has special handling for COMPRESS_SECTION_NONE.
>
> I am checking in this.

Did I miss the approval?

> H.J.
> ---
> 	PR binutils/28530
> 	* compress.c (bfd_get_full_section_contents): Always check
> 	compressed sections with the corrupt size.
> ---
>  bfd/compress.c | 50 +++++++++++++++++++++++++++-----------------------
>  1 file changed, 27 insertions(+), 23 deletions(-)
>
> diff --git a/bfd/compress.c b/bfd/compress.c
> index 4a2ada3e3eb..a3adb8d8250 100644
> --- a/bfd/compress.c
> +++ b/bfd/compress.c
> @@ -232,6 +232,7 @@ bfd_get_full_section_contents (bfd *abfd, sec_ptr sec, bfd_byte **ptr)
>    bfd_size_type save_rawsize;
>    bfd_byte *compressed_buffer;
>    unsigned int compression_header_size;
> +  ufile_ptr filesize;
>
>    if (abfd->direction != write_direction && sec->rawsize != 0)
>      sz = sec->rawsize;
> @@ -243,34 +244,37 @@ bfd_get_full_section_contents (bfd *abfd, sec_ptr sec, bfd_byte **ptr)
>        return true;
>      }
>
> +  filesize = bfd_get_file_size (abfd);
> +  if (filesize > 0
> +      && filesize < sz
> +      /* PR 24753: Linker created sections can be larger than
> +	 the file size, eg if they are being used to hold stubs.  */
> +      && (bfd_section_flags (sec) & SEC_LINKER_CREATED) == 0
> +      /* PR 24753: Sections which have no content should also be
> +	 excluded as they contain no size on disk.  */
> +      && (bfd_section_flags (sec) & SEC_HAS_CONTENTS) != 0
> +      /* PR 28530: Check compressed sections with the corrupt size.  */
> +      && (sec->compress_status != COMPRESS_SECTION_NONE
> +      /* The MMO file format supports its own special compression
> +	 technique, but it uses COMPRESS_SECTION_NONE when loading
> +	 a section's contents.  */
> +	  || bfd_get_flavour (abfd) != bfd_target_mmo_flavour))

Looking at the BFD flavor seems like the wrong thing to me.
Perhaps add a (defaulted) BFD field or hook if needed?

Also, ELF section contents in the mmo format is embedded, not
compressed.  "Coded" if you will, compared to the file contents;
not a straight blob of bytes, rather escaped sequences.  Also,
for future reference, it's "mmo", not "MMO".

brgds, H-P