Due to the fact that HeapGuard needs CpuArchProtocol to update page
attributes, the feature is normally enabled after CpuArchProtocol is
installed. Since there're some drivers are loaded before CpuArchProtocl,
they cannot make use HeapGuard feature to detect potential issues.

This patch fixes above situation by updating the DXE core to skip the
NULL check against global gCpu in the IsMemoryTypeToGuard(), and adding
NULL check against gCpu in SetGuardPage() and UnsetGuardPage() to make
sure that they can be called but do nothing. This will allow HeapGuard to
record all guarded memory without setting the related Guard pages to not-
present.

Once the CpuArchProtocol is installed, a protocol notify will be called
to complete the work of setting Guard pages to not-present.

Please note that above changes will cause a #PF in GCD code during cleanup
of map entries, which is initiated by CpuDxe driver to update real mtrr
and paging attributes back to GCD. During that time, CpuDxe doesn't allow
GCD to update memory attributes and then any Guard page cannot be unset.
As a result, this will prevent Guarded memory from freeing during memory
map cleanup.

The solution is to avoid allocating guarded memory as memory map entries
in GCD code. It's done by setting global mOnGuarding to TRUE before memory
allocation and setting it back to FALSE afterwards in GCD function
CoreAllocateGcdMapEntry().

Cc: Star Zeng <star.zeng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
---
 MdeModulePkg/Core/Dxe/Gcd/Gcd.c               |  10 ++
 MdeModulePkg/Core/Dxe/Mem/HeapGuard.c         | 132 +++++++++++++++++++++++++-
 MdeModulePkg/Core/Dxe/Mem/HeapGuard.h         |   8 ++
 MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c |   5 +
 4 files changed, 154 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Core/Dxe/Gcd/Gcd.c b/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
index 8fbc3d282c..77f4adb4bc 100644
--- a/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
+++ b/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
@@ -16,6 +16,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
 
 #include "DxeMain.h"
 #include "Gcd.h"
+#include "Mem/HeapGuard.h"
 
 #define MINIMUM_INITIAL_MEMORY_SIZE 0x10000
 
@@ -391,12 +392,21 @@ CoreAllocateGcdMapEntry (
   IN OUT EFI_GCD_MAP_ENTRY  **BottomEntry
   )
 {
+  //
+  // Set to mOnGuarding to TRUE before memory allocation. This will make sure
+  // that the entry memory is not "guarded" by HeapGuard. Otherwise it might
+  // cause problem when it's freed (if HeapGuard is enabled).
+  //
+  mOnGuarding = TRUE;
   *TopEntry = AllocateZeroPool (sizeof (EFI_GCD_MAP_ENTRY));
+  mOnGuarding = FALSE;
   if (*TopEntry == NULL) {
     return EFI_OUT_OF_RESOURCES;
   }
 
+  mOnGuarding = TRUE;
   *BottomEntry = AllocateZeroPool (sizeof (EFI_GCD_MAP_ENTRY));
+  mOnGuarding = FALSE;
   if (*BottomEntry == NULL) {
     CoreFreePool (*TopEntry);
     return EFI_OUT_OF_RESOURCES;
diff --git a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
index ac043b5d9b..f6068c459c 100644
--- a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
+++ b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
@@ -576,6 +576,10 @@ SetGuardPage (
   IN  EFI_PHYSICAL_ADDRESS      BaseAddress
   )
 {
+  if (gCpu == NULL) {
+    return;
+  }
+
   //
   // Set flag to make sure allocating memory without GUARD for page table
   // operation; otherwise infinite loops could be caused.
@@ -606,6 +610,10 @@ UnsetGuardPage (
 {
   UINT64          Attributes;
 
+  if (gCpu == NULL) {
+    return;
+  }
+
   //
   // Once the Guard page is unset, it will be freed back to memory pool. NX
   // memory protection must be restored for this page if NX is enabled for free
@@ -652,7 +660,7 @@ IsMemoryTypeToGuard (
   UINT64 ConfigBit;
   BOOLEAN     InSmm;
 
-  if (gCpu == NULL || AllocateType == AllocateAddress) {
+  if (AllocateType == AllocateAddress) {
     return FALSE;
   }
 
@@ -1164,6 +1172,128 @@ CoreConvertPagesWithGuard (
   return CoreConvertPages (Start, NumberOfPages, NewType);
 }
 
+/**
+  Set all Guard pages which cannot be set before CPU Arch Protocol installed.
+**/
+VOID
+SetAllGuardPages (
+  VOID
+  )
+{
+  UINTN     Entries[GUARDED_HEAP_MAP_TABLE_DEPTH];
+  UINTN     Shifts[GUARDED_HEAP_MAP_TABLE_DEPTH];
+  UINTN     Indices[GUARDED_HEAP_MAP_TABLE_DEPTH];
+  UINT64    Tables[GUARDED_HEAP_MAP_TABLE_DEPTH];
+  UINT64    Addresses[GUARDED_HEAP_MAP_TABLE_DEPTH];
+  UINT64    TableEntry;
+  UINT64    Address;
+  UINT64    GuardPage;
+  INTN      Level;
+  UINTN     Index;
+  BOOLEAN   OnGuarding;
+
+  if (mGuardedMemoryMap == 0 ||
+      mMapLevel == 0 ||
+      mMapLevel > GUARDED_HEAP_MAP_TABLE_DEPTH) {
+    return;
+  }
+
+  CopyMem (Entries, mLevelMask, sizeof (Entries));
+  CopyMem (Shifts, mLevelShift, sizeof (Shifts));
+
+  SetMem (Tables, sizeof(Tables), 0);
+  SetMem (Addresses, sizeof(Addresses), 0);
+  SetMem (Indices, sizeof(Indices), 0);
+
+  Level         = GUARDED_HEAP_MAP_TABLE_DEPTH - mMapLevel;
+  Tables[Level] = mGuardedMemoryMap;
+  Address       = 0;
+  OnGuarding    = FALSE;
+
+  DEBUG_CODE (
+    DumpGuardedMemoryBitmap ();
+  );
+
+  while (TRUE) {
+    if (Indices[Level] > Entries[Level]) {
+      Tables[Level] = 0;
+      Level        -= 1;
+    } else {
+
+      TableEntry  = ((UINT64 *)(UINTN)(Tables[Level]))[Indices[Level]];
+      Address     = Addresses[Level];
+
+      if (TableEntry == 0) {
+
+        OnGuarding = FALSE;
+
+      } else if (Level < GUARDED_HEAP_MAP_TABLE_DEPTH - 1) {
+
+        Level            += 1;
+        Tables[Level]     = TableEntry;
+        Addresses[Level]  = Address;
+        Indices[Level]    = 0;
+
+        continue;
+
+      } else {
+
+        Index = 0;
+        while (Index < GUARDED_HEAP_MAP_ENTRY_BITS) {
+          if ((TableEntry & 1) == 1) {
+            if (OnGuarding) {
+              GuardPage = 0;
+            } else {
+              GuardPage = Address - EFI_PAGE_SIZE;
+            }
+            OnGuarding = TRUE;
+          } else {
+            if (OnGuarding) {
+              GuardPage = Address;
+            } else {
+              GuardPage = 0;
+            }
+            OnGuarding = FALSE;
+          }
+
+          if (GuardPage != 0) {
+            SetGuardPage (GuardPage);
+          }
+
+          if (TableEntry == 0) {
+            break;
+          }
+
+          TableEntry = RShiftU64 (TableEntry, 1);
+          Address   += EFI_PAGE_SIZE;
+          Index     += 1;
+        }
+      }
+    }
+
+    if (Level < (GUARDED_HEAP_MAP_TABLE_DEPTH - (INTN)mMapLevel)) {
+      break;
+    }
+
+    Indices[Level] += 1;
+    Address = (Level == 0) ? 0 : Addresses[Level - 1];
+    Addresses[Level] = Address | LShiftU64(Indices[Level], Shifts[Level]);
+
+  }
+}
+
+/**
+  Notify function used to set all Guard pages before CPU Arch Protocol installed.
+**/
+VOID
+HeapGuardCpuArchProtocolNotify (
+  VOID
+  )
+{
+  ASSERT (gCpu != NULL);
+  SetAllGuardPages ();
+}
+
 /**
   Helper function to convert a UINT64 value in binary to a string.
 
diff --git a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.h b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.h
index 7208ab1437..8c34692439 100644
--- a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.h
+++ b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.h
@@ -399,6 +399,14 @@ IsHeapGuardEnabled (
   VOID
   );
 
+/**
+  Notify function used to set all Guard pages after CPU Arch Protocol installed.
+**/
+VOID
+HeapGuardCpuArchProtocolNotify (
+  VOID
+  );
+
 extern BOOLEAN mOnGuarding;
 
 #endif
diff --git a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
index 407aece807..2f7e490af1 100644
--- a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
+++ b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
@@ -1001,6 +1001,11 @@ MemoryProtectionCpuArchProtocolNotify (
     InitializeDxeNxMemoryProtectionPolicy ();
   }
 
+  //
+  // Call notify function meant for Heap Guard.
+  //
+  HeapGuardCpuArchProtocolNotify ();
+
   if (mImageProtectionPolicy == 0) {
     return;
   }
-- 
2.16.2.windows.1

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