Re: [edk2-platforms][PATCH v2 1/1] MinPlatformPkg/TestPointCheckLib: Fix DMAR structure length calculation

["Nate DeSimone" <nathaniel.l.desimone@intel.com>]

Pushed: https://github.com/tianocore/edk2-platforms/commit/871ce77

-----Original Message-----
From: mikuback@linux.microsoft.com <mikuback@linux.microsoft.com> 
Sent: Friday, December 10, 2021 4:22 PM
To: devel@edk2.groups.io
Cc: Chiu, Chasel <chasel.chiu@intel.com>; Desimone, Nathaniel L <nathaniel.l.desimone@intel.com>; Liming Gao <gaoliming@byosoft.com.cn>; Dong, Eric <eric.dong@intel.com>
Subject: [edk2-platforms][PATCH v2 1/1] MinPlatformPkg/TestPointCheckLib: Fix DMAR structure length calculation

From: Michael Kubacki <michael.kubacki@microsoft.com>

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3768

When processing DMAR structures of type
EFI_ACPI_DMAR_STRUCTURE_HEADER within the ACPI DMAR table, the code determines the structure length by subtracting the DMAR structure headers present from the overall DMAR ACPI table size.

The terminating condition is that the remaining total DMAR length is greater than zero. However, the current DMAR structure length is subtracted after the DMAR structure pointer has already been assigned to the next structure.

This change subtracts the current DMAR structure length before transitioning to the next structure.

The terminating condition is also updated to ensure the remaining size is at least as large as the expected structure header size.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Eric Dong <eric.dong@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
---

Notes:
    V2 Changes:
    
    - Updated the terminating condition to ensure the remaining size
      is at least as large as the expected structure size.

 Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCheckAcpiDmar.c      | 8 ++++----
 Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCheckDmaProtection.c | 4 ++--  Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/PeiCheckDmaProtection.c | 4 ++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCheckAcpiDmar.c b/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCheckAcpiDmar.c
index b2279966d8ed..e0b7aaa48527 100644
--- a/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCheckAcpiDmar.c
+++ b/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCh
+++ eckAcpiDmar.c
@@ -133,7 +133,7 @@ DumpAcpiDmar (
   //
   DmarLen  = Dmar->Header.Length - sizeof(EFI_ACPI_DMAR_HEADER);
   DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)(Dmar + 1);
-  while (DmarLen > 0) {
+  while (DmarLen >= sizeof (*DmarStructHeader)) {
     switch (DmarStructHeader->Type) {
     case EFI_ACPI_DMAR_TYPE_DRHD:
       Drhd = (EFI_ACPI_DMAR_DRHD_HEADER *)DmarStructHeader; @@ -204,8 +204,8 @@ DumpAcpiDmar (
       DEBUG ((DEBUG_INFO, "\n"));
       break;
     }
-    DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)((UINT8 *)DmarStructHeader + DmarStructHeader->Length);
     DmarLen         -= DmarStructHeader->Length;
+    DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)((UINT8 
+ *)DmarStructHeader + DmarStructHeader->Length);
   }
 }
 
@@ -220,7 +220,7 @@ CheckAcpiDmar (
     
   DmarLen  = Dmar->Header.Length - sizeof(EFI_ACPI_DMAR_HEADER);
   DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)(Dmar + 1);
-  while (DmarLen > 0) {
+  while (DmarLen >= sizeof (*DmarStructHeader)) {
     switch (DmarStructHeader->Type) {
     case EFI_ACPI_DMAR_TYPE_DRHD:
       Drhd = (EFI_ACPI_DMAR_DRHD_HEADER *)DmarStructHeader; @@ -232,8 +232,8 @@ CheckAcpiDmar (
     default:
       break;
     }
-    DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)((UINT8 *)DmarStructHeader + DmarStructHeader->Length);
     DmarLen         -= DmarStructHeader->Length;
+    DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)((UINT8 
+ *)DmarStructHeader + DmarStructHeader->Length);
   }
   return EFI_SUCCESS;
 }
\ No newline at end of file
diff --git a/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCheckDmaProtection.c b/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCheckDmaProtection.c
index 10b44fe8b9b8..aba0985956f2 100644
--- a/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCheckDmaProtection.c
+++ b/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/DxeCh
+++ eckDmaProtection.c
@@ -38,7 +38,7 @@ CheckDrhd (
   //
   DmarLen  = Dmar->Header.Length - sizeof(EFI_ACPI_DMAR_HEADER);
   DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)(Dmar + 1);
-  while (DmarLen > 0) {
+  while (DmarLen >= sizeof (*DmarStructHeader)) {
     switch (DmarStructHeader->Type) {
     case EFI_ACPI_DMAR_TYPE_DRHD:
       Drhd = (EFI_ACPI_DMAR_DRHD_HEADER *)DmarStructHeader; @@ -56,8 +56,8 @@ CheckDrhd (
     default:
       break;
     }
-    DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)((UINT8 *)DmarStructHeader + DmarStructHeader->Length);
     DmarLen         -= DmarStructHeader->Length;
+    DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)((UINT8 
+ *)DmarStructHeader + DmarStructHeader->Length);
   }
 
   return EFI_SUCCESS;
diff --git a/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/PeiCheckDmaProtection.c b/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/PeiCheckDmaProtection.c
index cb764b3633ef..5a18235eddf4 100644
--- a/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/PeiCheckDmaProtection.c
+++ b/Platform/Intel/MinPlatformPkg/Test/Library/TestPointCheckLib/PeiCh
+++ eckDmaProtection.c
@@ -36,7 +36,7 @@ CheckDrhd (
   //
   DmarLen  = Dmar->Header.Length - sizeof(EFI_ACPI_DMAR_HEADER);
   DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)(Dmar + 1);
-  while (DmarLen > 0) {
+  while (DmarLen >= sizeof (*DmarStructHeader)) {
     switch (DmarStructHeader->Type) {
     case EFI_ACPI_DMAR_TYPE_DRHD:
       Drhd = (EFI_ACPI_DMAR_DRHD_HEADER *)DmarStructHeader; @@ -61,8 +61,8 @@ CheckDrhd (
     default:
       break;
     }
-    DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)((UINT8 *)DmarStructHeader + DmarStructHeader->Length);
     DmarLen         -= DmarStructHeader->Length;
+    DmarStructHeader = (EFI_ACPI_DMAR_STRUCTURE_HEADER *)((UINT8 
+ *)DmarStructHeader + DmarStructHeader->Length);
   }
 
   return EFI_SUCCESS;
--
2.28.0.windows.1