Re: [PATCH 1/3] pc-bios/s390-ccw: fix off-by-one error

[Thomas Huth]

On 24/09/2020 10.59, Marc Hartmayer wrote:
> This error takes effect when the magic value "zIPL" is located at the
> end of a block. For example if s2_cur_blk = 0x7fe18000 and the magic
> value "zIPL" is located at 0x7fe18ffc - 0x7fe18fff.
> 
> Fixes: ba831b25262a ("s390-ccw: read stage2 boot loader data to find menu")
> Reviewed-by: Collin Walling <walling@linux.ibm.com>
> Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
> ---
>  pc-bios/s390-ccw/bootmap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/pc-bios/s390-ccw/bootmap.c b/pc-bios/s390-ccw/bootmap.c
> index 97205674e59a..0d29dceaa3cc 100644
> --- a/pc-bios/s390-ccw/bootmap.c
> +++ b/pc-bios/s390-ccw/bootmap.c
> @@ -163,7 +163,7 @@ static bool find_zipl_boot_menu_banner(int *offset)
>      int i;
>  
>      /* Menu banner starts with "zIPL" */
> -    for (i = 0; i < virtio_get_block_size() - 4; i++) {
> +    for (i = 0; i < virtio_get_block_size() - 3; i++) {
>          if (magic_match(s2_cur_blk + i, ZIPL_MAGIC_EBCDIC)) {
>              *offset = i;
>              return true;

I agree with Philippe, i <= virtio_get_block_size() - 4 would be a
little bit nicer. Anyway:

Reviewed-by: Thomas Huth <thuth@redhat.com>