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Re: [PATCH 1/3] pc-bios/s390-ccw: fix off-by-one error
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From: |
Philippe Mathieu-Daudé |
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Subject: |
Re: [PATCH 1/3] pc-bios/s390-ccw: fix off-by-one error |
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Date: |
Thu, 24 Sep 2020 12:02:37 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 |
Hi Marc,
On 9/24/20 10:59 AM, 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++) {
Easier to review as:
for (i = 0; i <= virtio_get_block_size() - 4; i++) {
Even easier defining ZIPL_MAGIC_SIZE instead of the magic '4'.
> if (magic_match(s2_cur_blk + i, ZIPL_MAGIC_EBCDIC)) {
> *offset = i;
> return true;
>