Re: [PATCH] fix attempt to seek outside of the file error when parsing xen ELF notes

[Andrei Borzenkov]

03.03.2016 10:33, Michael Chang пишет:
> The kernel bzImage payload length appears to be incorrectly minus by 4 when
> trying to grub_file_offset_open for the uncompressed vmlinux image. If gzip
> used as compressor it will lead to the file->size read from offset of crc32
> instead of the uncompressed image size.
> 
> [1]
> http://www.onicos.com/staff/iz/formats/gzip.html
> ---
>  grub-core/loader/i386/xen_file.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/grub-core/loader/i386/xen_file.c 
> b/grub-core/loader/i386/xen_file.c
> index 5836218..37f9ad8 100644
> --- a/grub-core/loader/i386/xen_file.c
> +++ b/grub-core/loader/i386/xen_file.c
> @@ -55,11 +55,11 @@ grub_xen_file (grub_file_t file)
>    grub_dprintf ("xen", "found bzimage payload 0x%llx-0x%llx\n",
>               (unsigned long long) (lh.setup_sects + 1) * 512
>               + lh.payload_offset,
> -             (unsigned long long) lh.payload_length - 4);
> +             (unsigned long long) lh.payload_length);
>  
>    off_file = grub_file_offset_open (file, (lh.setup_sects + 1) * 512
>                                   + lh.payload_offset,
> -                                 lh.payload_length - 4);
> +                                 lh.payload_length);
>    if (!off_file)
>      goto fail;
>  
> 
Looks strange indeed. I wonder what was original intention, code looked
this way from the very beginning. May be it is required with some other
format?