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MdeModulePkg: Fix buffer overflow in MergeMemoryMap

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Check that the next map entry is valid before dereferencing to merge the
guard pages. If the final entry is at the end of a page with no valid page
following it, then this can cause an access violation.

Signed-off-by: Kenneth Lautner <kenlautner3@gmail.com>
This commit is contained in:
Ken Lautner 2024-08-28 10:55:09 -07:00 committed by mergify[bot]
parent a9b38305b6
commit 964c22b8ea
1 changed files with 5 additions and 2 deletions
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7
MdeModulePkg/Core/Dxe/Misc/MemoryAttributesTable.c
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@ -395,11 +395,14 @@ MergeMemoryMap (
NewMemoryMapEntry = MemoryMap;
MemoryMapEnd = (EFI_MEMORY_DESCRIPTOR *)((UINT8 *)MemoryMap + *MemoryMapSize);
while ((UINTN)MemoryMapEntry < (UINTN)MemoryMapEnd) {
CopyMem (NewMemoryMapEntry, MemoryMapEntry, sizeof (EFI_MEMORY_DESCRIPTOR));
CopyMem (NewMemoryMapEntry, MemoryMapEntry, DescriptorSize);
NextMemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry, DescriptorSize);
do {
MergeGuardPages (NewMemoryMapEntry, NextMemoryMapEntry->PhysicalStart);
if ((UINTN)NextMemoryMapEntry < (UINTN)MemoryMapEnd) {
MergeGuardPages (NewMemoryMapEntry, NextMemoryMapEntry->PhysicalStart);
}
MemoryBlockLength = LShiftU64 (NewMemoryMapEntry->NumberOfPages, EFI_PAGE_SHIFT);
if (((UINTN)NextMemoryMapEntry < (UINTN)MemoryMapEnd) &&
(NewMemoryMapEntry->Type == NextMemoryMapEntry->Type) &&