[parted-devel] [PATCH] Do not discard bootcode from extended partition

[James Courtier-Dutton]

Petr Uzel wrote:
> Hi,
> attached patch seems to fix the problem for me. I'd appreciate any
> feedback.
> 
> Thanks!
> 
> ---
>  libparted/labels/dos.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/libparted/labels/dos.c b/libparted/labels/dos.c
> index cb7e45e..a300a87 100644
> --- a/libparted/labels/dos.c
> +++ b/libparted/labels/dos.c
> @@ -1059,7 +1059,8 @@ write_ext_table (const PedDisk* disk,
>  
>  	lba_offset = ped_disk_extended_partition (disk)->geom.start;
>  
> -	memset (&table, 0, sizeof (DosRawTable));
> +	ped_device_read (disk->dev, &table, sector, 1);
> +	memset (&(table.partitions), 0, 4 * sizeof(DosRawPartition));
>  	table.magic = PED_CPU_TO_LE16 (MSDOS_MAGIC);
>  
>  	if (!fill_raw_part (&table.partitions[0], logical, sector))
> @@ -1093,7 +1094,8 @@ write_empty_table (const PedDisk* disk, PedSector sector)
>  
>  	PED_ASSERT (disk != NULL, return 0);
>  
> -	memset (&table, 0, sizeof (DosRawTable));
> +	ped_device_read (disk->dev, &table, sector, 1);
> +	memset (&(table.partitions), 0, 4 * sizeof(DosRawPartition));
>  	table.magic = PED_CPU_TO_LE16 (MSDOS_MAGIC);
>  
>  	return ped_device_write (disk->dev, (void*) &table, sector, 1);

I thought that valid boot sectors have a checksum or some kind of
signature bytes. It might be worth verifying that it is a valid boot
sector before blindly using it. If it is not a valid boot sector, one
might as well fill it with zeros.