Re: [PATCH 1/2] MdeModulePkg/Core: Fix heap guard issues

["Yao, Jiewen" <jiewen.yao@intel.com>]

It is pity to add this alignment requirement, because the some special case tail overflow might not be caught.

If any other driver has such assumption, we may add ASSERT() to make sure the memory allocated is 8-byte aligned. As such we can catch this problem earlier, such as the Variable driver. It can be done in a separate patch.

Reviewed-by: Jiewen.yao@intel.com

Thank you
Yao Jiewen

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Jian J
> Wang
> Sent: Monday, December 25, 2017 10:23 AM
> To: edk2-devel@lists.01.org
> Cc: Yao, Jiewen <jiewen.yao@intel.com>; Dong, Eric <eric.dong@intel.com>;
> Zeng, Star <star.zeng@intel.com>
> Subject: [edk2] [PATCH 1/2] MdeModulePkg/Core: Fix heap guard issues
> 
> Two 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.
> 
> 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/Mem/HeapGuard.c         | 31
> ++++++++++++++++++++++-----
>  MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c |  3 ---
>  MdeModulePkg/Core/PiSmmCore/HeapGuard.c       | 14 ++++++++++--
>  3 files changed, 38 insertions(+), 10 deletions(-)
> 
> diff --git a/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
> b/MdeModulePkg/Core/Dxe/Mem/HeapGuard.c
> index bee229f4c8..0f035043e1 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 a74cfc137a..862593f562 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 04fa1747a1..063a330b18 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
>      //
> --
> 2.15.1.windows.2
> 
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