On 9/2/22 10:52, Alexander Ivanov wrote:
> The BDRVParallelsState structure contains data_end field that
> is measured in sectors.
> In parallels_open() initially this field is set by data_off field from
> parallels image header.
>
> According to the parallels format documentation,
> data_off field contains an offset, in sectors, from the start of the file
> to the start of the data area.
> For "WithoutFreeSpace" images: if data_off is zero,
> the offset is calculated as the end of the BAT table
> plus some padding to ensure sector size alignment.
>
> The parallels_open() function has code for handling zero value
> in data_off, but in the result data_end contains the offset in bytes.
>
> Replace the alignment to sector size by division by sector size
> and fix the comparision with s->header_size.
>
> Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
> ---
> block/parallels.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/block/parallels.c b/block/parallels.c
> index e6e8b9e369..7b4e997ebd 100644
> --- a/block/parallels.c
> +++ b/block/parallels.c
> @@ -863,9 +863,9 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
> }
> s->data_end = le32_to_cpu(ph.data_off);
> if (s->data_end == 0) {
> - s->data_end = ROUND_UP(bat_entry_off(s->bat_size), BDRV_SECTOR_SIZE);
> + s->data_end = DIV_ROUND_UP(size, BDRV_SECTOR_SIZE);
> }
> - if (s->data_end < s->header_size) {
> + if (s->data_end < (s->header_size >> BDRV_SECTOR_BITS)) {
> /* there is not enough unused space to fit to block align between BAT
> and actual data. We can't avoid read-modify-write... */
> s->header_size = size;
Reviewed-by: Denis V. Lunev <den@openvz.org>
Sidenote: if the image is truncated for more than BAT size and there is
no data inside
the image, we would get memory corruption during BAT access. That should
be addressed
separately.