Re: [edk2-devel] [PATCH v1 1/1] OvmfPkg/QemuVideoDxe: Zero out PixelInformation in QueryMode

["Gerd Hoffmann" <kraxel@redhat.com>]

On Tue, Jun 28, 2022 at 01:48:16PM -0500, Dimitrije Pavlov wrote:
> Ensure that the PixelInformation field of the
> EFI_GRAPHICS_OUTPUT_MODE_INFORMATION structure is zeroed out in
> EFI_GRAPHICS_OUTPUT_PROTOCOL.QueryMode() and
> EFI_GRAPHICS_OUTPUT_PROTOCOL.SetMode() when PixelFormat is
> PixelBlueGreenRedReserved8BitPerColor.
> 
> According to UEFI 2.9 Section 12.9, PixelInformation field of the
> EFI_GRAPHICS_OUTPUT_MODE_INFORMATION structure is valid only if
> PixelFormat is PixelBitMask. This means that firmware is not required
> to fill out the PixelInformation field for other PixelFormat types,
> which implies that the QemuVideoDxe implementation is technically
> correct.
> 
> However, not zeroing out those fields will leak the contents of the
> memory returned by the memory allocator, so it is better to explicitly
> set them to zero.
> 
> In addition, the SCT test suite relies on PixelInformation always
> having a consistent value, which causes failures.
> 
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Jeff Booher-Kaeding <Jeff.Booher-Kaeding@arm.com>
> Cc: Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>
> Cc: Sunny Wang <Sunny.Wang@arm.com>
> Cc: Jeremy Linton <Jeremy.Linton@arm.com>
> 
> Signed-off-by: Dimitrije Pavlov <Dimitrije.Pavlov@arm.com>

Acked-by: Gerd Hoffmann <kraxel@redhat.com>