Re: [PATCH V3 1/3] MdeModulePkg/PartitionDxe: Correct the MBR last block value

["Ni, Ray" <ray.ni@intel.com>]

Reviewed-by: Ray Ni <ray.ni@intel.com>

> -----Original Message-----
> From: Gao, Zhichao <zhichao.gao@intel.com>
> Sent: Tuesday, July 14, 2020 9:23 AM
> To: devel@edk2.groups.io
> Cc: Wu, Hao A <hao.a.wu@intel.com>; Ni, Ray <ray.ni@intel.com>
> Subject: [PATCH V3 1/3] MdeModulePkg/PartitionDxe: Correct the MBR last
> block value
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2823
> 
> PartitionValidMbr function's second parameter should be the
> last sector of the device. For MBR partition, the block size is
> sector size, i.e. 512 bytes. The original value is media block
> last LBA which is counted by the media block size. And media
> block size is not always 512 bytes, it may be larger which would
> cause the MBR boundary check incorrect. The boundary check is
> based on the partition entry start LBA and size of LBA which
> are both counted by the sector number (512 bytes).
> 
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Signed-off-by: Zhichao Gao <zhichao.gao@intel.com>
> ---
>  MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c
> b/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c
> index dac451a144..f0c92aa09a 100644
> --- a/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c
> +++ b/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c
> @@ -135,14 +135,17 @@ PartitionInstallMbrChildHandles (
>    EFI_DEVICE_PATH_PROTOCOL     *LastDevicePathNode;
>    UINT32                       BlockSize;
>    UINT32                       MediaId;
> -  EFI_LBA                      LastBlock;
> +  EFI_LBA                      LastSector;
>    EFI_PARTITION_INFO_PROTOCOL  PartitionInfo;
> 
>    Found           = EFI_NOT_FOUND;
> 
> -  BlockSize = BlockIo->Media->BlockSize;
> -  MediaId   = BlockIo->Media->MediaId;
> -  LastBlock = BlockIo->Media->LastBlock;
> +  BlockSize   = BlockIo->Media->BlockSize;
> +  MediaId     = BlockIo->Media->MediaId;
> +  LastSector  = DivU64x32 (
> +                  MultU64x32 (BlockIo->Media->LastBlock + 1, BlockSize),
> +                  MBR_SIZE
> +                  ) - 1;
> 
>    //
>    // Ensure the block size can hold the MBR
> @@ -167,7 +170,7 @@ PartitionInstallMbrChildHandles (
>      Found = Status;
>      goto Done;
>    }
> -  if (!PartitionValidMbr (Mbr, LastBlock)) {
> +  if (!PartitionValidMbr (Mbr, LastSector)) {
>      goto Done;
>    }
>    //
> --
> 2.21.0.windows.1