This fixes an issue reported by Marvin, where NX memory protections are
applied in a rather unreliable manner, resulting in the possibility that
memory mappings may exist that are using different attributes than
intended.

The reason for this approach was that applying memory protections
eagerly (i.e., after every alloc/free even if the memory attributes are
not expected to change as a result) may result in unbounded recursion in
the page table code, due to the fact that the page tables it allocates
need to be remapped with the correct attributes as well.

This has not been reported as being an issue on x86, but on ARM, this
needs a couple of fixes so that converting between EfiConventionalMemory
and EfiBootServicesData will never trigger a block entry split. With
that fixed, we can just remove the shortcut from DXE core and always
call SetMemoryAttributes.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3316

Cc: Michael Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Michael Kubacki <michael.kubacki@microsoft.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Cc: Rebecca Cran <quic_rcran@quicinc.com>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Taylor Beebe <t@taylorbeebe.com>
Cc: Marvin Häuser <mhaeuser@posteo.de>

Ard Biesheuvel (3):
  ArmPkg/ArmMmuLib: Avoid splitting block entries if possible
  ArmPkg/CpuDxe: Perform preliminary NX remap of free memory
  MdeModulePkg/DxeCore: Unconditionally set memory protections

 ArmPkg/Drivers/CpuDxe/CpuDxe.c                   | 77 ++++++++++++++++++++
 ArmPkg/Drivers/CpuDxe/CpuDxe.inf                 |  2 +
 ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c |  9 +++
 MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c    | 29 --------
 4 files changed, 88 insertions(+), 29 deletions(-)

-- 
2.39.1



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#99801): https://edk2.groups.io/g/devel/message/99801
Mute This Topic: https://groups.io/mt/96835912/1787277
Group Owner: devel+owner@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [importer@patchew.org]
-=-=-=-=-=-=-=-=-=-=-=-