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MdeModulePkg/Core: fix feature conflict between NX and NULL detection 

If enabled, NX memory protection feature will mark all free memory as
NX (non-executable), including page 0. This will overwrite the attributes
of page 0 if NULL pointer detection feature is also enabled and then
compromise the functionality of it. The solution is skipping the NX
attributes setting to page 0 if NULL pointer detection feature is enabled.

Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
This commit is contained in:
Jian J Wang 2018-01-29 19:07:29 +08:00 committed by Star Zeng
parent 1263ecf2ff
commit 9b17c6511d
1 changed files with 18 additions and 4 deletions
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14
MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
View File

@ -845,11 +845,25 @@ InitializeDxeNxMemoryProtectionPolicy (
Attributes = GetPermissionAttributeForMemoryType (MemoryMapEntry->Type);
if (Attributes != 0) {
if (MemoryMapEntry->PhysicalStart == 0 &&
PcdGet8 (PcdNullPointerDetectionPropertyMask) != 0) {
ASSERT (MemoryMapEntry->NumberOfPages > 0);
//
// Skip page 0 if NULL pointer detection is enabled to avoid attributes
// overwritten.
//
SetUefiImageMemoryAttributes (
MemoryMapEntry->PhysicalStart + EFI_PAGE_SIZE,
LShiftU64 (MemoryMapEntry->NumberOfPages - 1, EFI_PAGE_SHIFT),
Attributes);
} else {
SetUefiImageMemoryAttributes (
MemoryMapEntry->PhysicalStart,
LShiftU64 (MemoryMapEntry->NumberOfPages, EFI_PAGE_SHIFT),
Attributes);
}
}
MemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);
}
FreePool (MemoryMap);