[PATCH] MdeModulePkg/Core: fix feature conflict between NX and heap guard

[Jian J Wang <jian.j.wang@intel.com>]

Considering following scenario (both NX memory protection and heap guard
are enabled):

   1. Allocate 3 pages. The attributes of adjacent memory pages will be

      |NOT-PRESENT|  present  |  present  |  present  |NOT-PRESENT|

   2. Free the middle page. The attributes of adjacent memory pages should
      be

      |NOT-PRESENT|  present  |NOT-PRESENT|  present  |NOT-PRESENT|

      But the NX feature will overwrite the attributes of middle page. So
      it looks still like below, which is wrong.

      |NOT-PRESENT|  present  |  PRESENT  |  present  |NOT-PRESENT|

The solution is checking the first and/or last page of a memory block to be
marked as NX, and skipping them if they are Guard pages.

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>
---
 MdeModulePkg/Core/Dxe/Mem/HeapGuard.c         | 14 ++++++++++++++
 MdeModulePkg/Core/Dxe/Mem/HeapGuard.h         | 10 ++++++++++
 MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c | 22 ++++++++++++++++++++++
 3 files changed, 46 insertions(+)

diff --git a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
index 392aeb8a02..d7906e08c5 100644
--- a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
+++ b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
@@ -728,6 +728,20 @@ IsPageTypeToGuard (
   return IsMemoryTypeToGuard (MemoryType, AllocateType, GUARD_HEAP_TYPE_PAGE);
 }
 
+/**
+  Check to see if the heap guard is enabled for page and/or pool allocation.
+
+  @return TRUE/FALSE.
+**/
+BOOLEAN
+IsHeapGuardEnabled (
+  VOID
+  )
+{
+  return IsMemoryTypeToGuard (EfiMaxMemoryType, AllocateAnyPages,
+                              GUARD_HEAP_TYPE_POOL|GUARD_HEAP_TYPE_PAGE);
+}
+
 /**
   Set head Guard and tail Guard for the given memory range.
 
diff --git a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.h b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.h
index 30ac0e678f..7208ab1437 100644
--- a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.h
+++ b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.h
@@ -389,6 +389,16 @@ AdjustPoolHeadF (
   IN EFI_PHYSICAL_ADDRESS    Memory
   );
 
+/**
+  Check to see if the heap guard is enabled for page and/or pool allocation.
+
+  @return TRUE/FALSE.
+**/
+BOOLEAN
+IsHeapGuardEnabled (
+  VOID
+  );
+
 extern BOOLEAN mOnGuarding;
 
 #endif
diff --git a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
index 150167bf66..877e6e5025 100644
--- a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
+++ b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
@@ -48,6 +48,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 #include <Protocol/SimpleFileSystem.h>
 
 #include "DxeMain.h"
+#include "Mem/HeapGuard.h"
 
 #define CACHE_ATTRIBUTE_MASK   (EFI_MEMORY_UC | EFI_MEMORY_WC | EFI_MEMORY_WT | EFI_MEMORY_WB | EFI_MEMORY_UCE | EFI_MEMORY_WP)
 #define MEMORY_ATTRIBUTE_MASK  (EFI_MEMORY_RP | EFI_MEMORY_XP | EFI_MEMORY_RO)
@@ -1200,6 +1201,27 @@ ApplyMemoryProtectionPolicy (
     return EFI_SUCCESS;
   }
 
+  //
+  // Don't overwrite Guard pages, which should be the first and/or last page,
+  // if any.
+  //
+  if (IsHeapGuardEnabled ()) {
+    if (IsGuardPage (Memory))  {
+      Memory += EFI_PAGE_SIZE;
+      Length -= EFI_PAGE_SIZE;
+      if (Length == 0) {
+        return EFI_SUCCESS;
+      }
+    }
+
+    if (IsGuardPage (Memory + Length - EFI_PAGE_SIZE))  {
+      Length -= EFI_PAGE_SIZE;
+      if (Length == 0) {
+        return EFI_SUCCESS;
+      }
+    }
+  }
+
   //
   // Update the executable permissions according to the DXE memory
   // protection policy, but only if
-- 
2.14.1.windows.1