Take care not to dereference BlockEntry if it may be pointing past
the end of the page table we are manipulating. It is only a read,
and thus harmless, but HeapGuard triggers on it so let's fix it.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
---
 ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c 
b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
index e41044142ef4..d66df3e17a02 100644
--- a/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
+++ b/ArmPkg/Library/ArmMmuLib/AArch64/ArmMmuLibCore.c
@@ -382,7 +382,7 @@ UpdateRegionMapping (
 
       // Break the inner loop when next block is a table
       // Rerun GetBlockEntryListFromAddress to avoid page table memory leak
-      if (TableLevel != 3 &&
+      if (TableLevel != 3 && BlockEntry <= LastBlockEntry &&
           (*BlockEntry & TT_TYPE_MASK) == TT_TYPE_TABLE_ENTRY) {
             break;
       }
-- 
2.20.1

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