MdeModulePkg/Core: Fix heap guard issues

Three issues addressed here:

a. Make NX memory protection and heap guard to be compatible
The solution is to check PcdDxeNxMemoryProtectionPolicy in Heap Guard to
see if the free memory should be set to NX, and set the Guard page to NX
before it's freed back to memory pool. This can solve the issue which NX
setting would be overwritten by Heap Guard feature in certain
configuration.

b. Returned pool address was not 8-byte aligned sometimes
This happened only when BIT7 is not set in PcdHeapGuardPropertyMask. Since
8-byte alignment is UEFI spec required, letting allocated pool adjacent to
tail guard page cannot be guaranteed.

c. NULL address handling due to allocation failure
When allocation failure, normally a NULL will be returned. But Heap Guard
code will still try to adjust the starting address of it, which will cause
a non-NULL pointer returned.

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>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

3 files changed, 38 insertions, 10 deletions

diff --git a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
index bee229f..0f03504 100644
--- a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
+++ b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
@@ -583,8 +583,7 @@ SetGuardPage (
   mOnGuarding = TRUE;

   //

   // Note: This might overwrite other attributes needed by other features,

-  // such as memory protection (NX). Please make sure they are not enabled

-  // at the same time.

+  // such as NX memory protection.

   //

   gCpu->SetMemoryAttributes (gCpu, BaseAddress, EFI_PAGE_SIZE, EFI_MEMORY_RP);

   mOnGuarding = FALSE;

@@ -605,6 +604,18 @@ UnsetGuardPage (
   IN  EFI_PHYSICAL_ADDRESS      BaseAddress

   )

 {

+  UINT64          Attributes;

+

+  //

+  // 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

+  // memory.

+  //

+  Attributes = 0;

+  if ((PcdGet64 (PcdDxeNxMemoryProtectionPolicy) & (1 << EfiConventionalMemory)) != 0) {

+    Attributes |= EFI_MEMORY_XP;

+  }

+

   //

   // Set flag to make sure allocating memory without GUARD for page table

   // operation; otherwise infinite loops could be caused.

@@ -615,7 +626,7 @@ UnsetGuardPage (
   // such as memory protection (NX). Please make sure they are not enabled

   // at the same time.

   //

-  gCpu->SetMemoryAttributes (gCpu, BaseAddress, EFI_PAGE_SIZE, 0);

+  gCpu->SetMemoryAttributes (gCpu, BaseAddress, EFI_PAGE_SIZE, Attributes);

   mOnGuarding = FALSE;

 }

 

@@ -869,6 +880,15 @@ AdjustMemoryS (
 {

   UINT64  Target;

 

+  //

+  // UEFI spec requires that allocated pool must be 8-byte aligned. If it's

+  // indicated to put the pool near the Tail Guard, we need extra bytes to

+  // make sure alignment of the returned pool address.

+  //

+  if ((PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) == 0) {

+    SizeRequested = ALIGN_VALUE(SizeRequested, 8);

+  }

+

   Target = Start + Size - SizeRequested;

 

   //

@@ -1052,7 +1072,7 @@ AdjustPoolHeadA (
   IN UINTN                   Size

   )

 {

-  if ((PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) != 0) {

+  if (Memory == 0 || (PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) != 0) {

     //

     // Pool head is put near the head Guard

     //

@@ -1062,6 +1082,7 @@ AdjustPoolHeadA (
   //

   // Pool head is put near the tail Guard

   //

+  Size = ALIGN_VALUE (Size, 8);

   return (VOID *)(UINTN)(Memory + EFI_PAGES_TO_SIZE (NoPages) - Size);

 }

 

@@ -1077,7 +1098,7 @@ AdjustPoolHeadF (
   IN EFI_PHYSICAL_ADDRESS    Memory

   )

 {

-  if ((PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) != 0) {

+  if (Memory == 0 || (PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) != 0) {

     //

     // Pool head is put near the head Guard

     //

diff --git a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
index a74cfc1..862593f 100644
--- a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
+++ b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
@@ -1070,15 +1070,12 @@ CoreInitializeMemoryProtection (
   // - code regions should have no EFI_MEMORY_XP attribute

   // - EfiConventionalMemory and EfiBootServicesData should use the

   //   same attribute

-  // - heap guard should not be enabled for the same type of memory

   //

   ASSERT ((GetPermissionAttributeForMemoryType (EfiBootServicesCode) & EFI_MEMORY_XP) == 0);

   ASSERT ((GetPermissionAttributeForMemoryType (EfiRuntimeServicesCode) & EFI_MEMORY_XP) == 0);

   ASSERT ((GetPermissionAttributeForMemoryType (EfiLoaderCode) & EFI_MEMORY_XP) == 0);

   ASSERT (GetPermissionAttributeForMemoryType (EfiBootServicesData) ==

           GetPermissionAttributeForMemoryType (EfiConventionalMemory));

-  ASSERT ((PcdGet64 (PcdDxeNxMemoryProtectionPolicy) & PcdGet64 (PcdHeapGuardPoolType)) == 0);

-  ASSERT ((PcdGet64 (PcdDxeNxMemoryProtectionPolicy) & PcdGet64 (PcdHeapGuardPageType)) == 0);

 

   if (mImageProtectionPolicy != 0 || PcdGet64 (PcdDxeNxMemoryProtectionPolicy) != 0) {

     Status = CoreCreateEvent (

diff --git a/MdeModulePkg/Core/PiSmmCore/HeapGuard.c b/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
index 04fa174..063a330 100644
--- a/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
+++ b/MdeModulePkg/Core/PiSmmCore/HeapGuard.c
@@ -877,6 +877,15 @@ AdjustMemoryS (
 {

   UINT64  Target;

 

+  //

+  // UEFI spec requires that allocated pool must be 8-byte aligned. If it's

+  // indicated to put the pool near the Tail Guard, we need extra bytes to

+  // make sure alignment of the returned pool address.

+  //

+  if ((PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) == 0) {

+    SizeRequested = ALIGN_VALUE(SizeRequested, 8);

+  }

+

   Target = Start + Size - SizeRequested;

 

   //

@@ -1060,7 +1069,7 @@ AdjustPoolHeadA (
   IN UINTN                   Size

   )

 {

-  if ((PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) != 0) {

+  if (Memory == 0 || (PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) != 0) {

     //

     // Pool head is put near the head Guard

     //

@@ -1070,6 +1079,7 @@ AdjustPoolHeadA (
   //

   // Pool head is put near the tail Guard

   //

+  Size = ALIGN_VALUE (Size, 8);

   return (VOID *)(UINTN)(Memory + EFI_PAGES_TO_SIZE (NoPages) - Size);

 }

 

@@ -1085,7 +1095,7 @@ AdjustPoolHeadF (
   IN EFI_PHYSICAL_ADDRESS    Memory

   )

 {

-  if ((PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) != 0) {

+  if (Memory == 0 || (PcdGet8 (PcdHeapGuardPropertyMask) & BIT7) != 0) {

     //

     // Pool head is put near the head Guard

     //