Re: [edk2-platforms] [PATCH] KabylakeSiliconPkg: Possible out-of-bounds memory writes

["Chaganty, Rangasai V" <rangasai.v.chaganty@intel.com>]

Looks good. 
Can we assign a local variable for "EndPtr" and use that in the For loop, instead of the expression and keep the implementation cleaner?

EndPtr = CurrPtr + ((EFI_ACPI_COMMON_HEADER *) CurrPtr)->Length;

for (DsdtPointer = CurrPtr; DsdtPointer < EndPtr; DsdtPointer++) {



-----Original Message-----
From: Desimone, Nathaniel L 
Sent: Monday, July 15, 2019 1:40 PM
To: devel@edk2.groups.io
Cc: Chiu, Chasel <chasel.chiu@intel.com>; Kubacki, Michael A <michael.a.kubacki@intel.com>; Chaganty, Rangasai V <rangasai.v.chaganty@intel.com>
Subject: [edk2-platforms] [PATCH] KabylakeSiliconPkg: Possible out-of-bounds memory writes

- Add check for the DSDT not existing.
- Fixed logic errors in loop boundary check.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Michael A Kubacki <michael.a.kubacki@intel.com>
Cc: Sai Chaganty <rangasai.v.chaganty@intel.com>

Co-authored-by: John Mathews <john.mathews@intel.com>
Signed-off-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
---
 .../Library/DxeAslUpdateLib/DxeAslUpdateLib.c               | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Silicon/Intel/KabylakeSiliconPkg/Library/DxeAslUpdateLib/DxeAslUpdateLib.c b/Silicon/Intel/KabylakeSiliconPkg/Library/DxeAslUpdateLib/DxeAslUpdateLib.c
index e6ab43db6d..a9611f750f 100644
--- a/Silicon/Intel/KabylakeSiliconPkg/Library/DxeAslUpdateLib/DxeAslUpdateLib.c
+++ b/Silicon/Intel/KabylakeSiliconPkg/Library/DxeAslUpdateLib/DxeAslUpdateLib.c
@@ -59,6 +59,7 @@ InitializeAslUpdateLib (
   @param[in] Length            - length of data to be overwritten
 
   @retval EFI_SUCCESS          - The function completed successfully.
+  @retval EFI_NOT_FOUND        - Failed to locate AcpiTable.
 **/
 EFI_STATUS
 UpdateNameAslCode (
@@ -99,11 +100,14 @@ UpdateNameAslCode (
   /// Point to the beginning of the DSDT table
   ///
   CurrPtr = (UINT8 *) Table;
+  if (CurrPtr == NULL) {
+    return EFI_NOT_FOUND;
+  }
 
   ///
   /// Loop through the ASL looking for values that we must fix up.
   ///
-  for (DsdtPointer = CurrPtr; DsdtPointer <= (CurrPtr + ((EFI_ACPI_COMMON_HEADER *) CurrPtr)->Length); DsdtPointer++) {
+  for (DsdtPointer = CurrPtr; DsdtPointer < (CurrPtr + ((EFI_ACPI_COMMON_HEADER *) CurrPtr)->Length); DsdtPointer++) {
     ///
     /// Get a pointer to compare for signature
     ///
-- 
2.17.1.windows.2