Re: [PATCH] MdeModulePkg PiSmmCore: Enhance SMM FreePool to catch buffer overflow

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

Reviewed-by: jiewen.yao@intel.com

> -----Original Message-----
> From: Zeng, Star
> Sent: Wednesday, April 19, 2017 2:07 PM
> To: edk2-devel@lists.01.org
> Cc: Zeng, Star <star.zeng@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>; Wu,
> Hao <hao.wu@intel.com>
> Subject: [PATCH] MdeModulePkg PiSmmCore: Enhance SMM FreePool to catch
> buffer overflow
> 
> This solution is equivalent to DXE core.
> 
> AllocatePool() allocates POOL_TAIL after the buffer.
> This POOL_TAIL is checked at FreePool().
> If the there is buffer overflow, the issue can be caught at FreePool().
> 
> This patch could also handle the eight-byte aligned allocation
> requirement. The discussion related to the eight-byte aligned
> allocation requirement is at
> https://lists.01.org/pipermail/edk2-devel/2017-April/009995.html.
> 
> According to the PI spec (Vol 4, Section 3.2 SmmAllocatePool()):
> The SmmAllocatePool() function ... All allocations are eight-byte aligned.
> 
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Hao Wu <hao.wu@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Star Zeng <star.zeng@intel.com>
> ---
>  MdeModulePkg/Core/PiSmmCore/PiSmmCore.h | 22 ++++++++++++++---
>  MdeModulePkg/Core/PiSmmCore/Pool.c      | 44
> +++++++++++++++++++++++++++++++--
>  2 files changed, 61 insertions(+), 5 deletions(-)
> 
> diff --git a/MdeModulePkg/Core/PiSmmCore/PiSmmCore.h
> b/MdeModulePkg/Core/PiSmmCore/PiSmmCore.h
> index c12805a2dd96..b6f815c68da0 100644
> --- a/MdeModulePkg/Core/PiSmmCore/PiSmmCore.h
> +++ b/MdeModulePkg/Core/PiSmmCore/PiSmmCore.h
> @@ -1196,12 +1196,28 @@ extern LIST_ENTRY  mSmmMemoryMap;
>  //
>  #define MAX_POOL_INDEX  (MAX_POOL_SHIFT - MIN_POOL_SHIFT + 1)
> 
> +#define POOL_HEAD_SIGNATURE   SIGNATURE_32('p','h','d','0')
> +
>  typedef struct {
> -  UINTN           Size;
> -  BOOLEAN         Available;
> -  EFI_MEMORY_TYPE Type;
> +  UINT32            Signature;
> +  BOOLEAN           Available;
> +  EFI_MEMORY_TYPE   Type;
> +  UINTN             Size;
>  } POOL_HEADER;
> 
> +#define POOL_TAIL_SIGNATURE   SIGNATURE_32('p','t','a','l')
> +
> +typedef struct {
> +  UINT32            Signature;
> +  UINT32            Reserved;
> +  UINTN             Size;
> +} POOL_TAIL;
> +
> +#define POOL_OVERHEAD (sizeof(POOL_HEADER) + sizeof(POOL_TAIL))
> +
> +#define HEAD_TO_TAIL(a)   \
> +  ((POOL_TAIL *) (((CHAR8 *) (a)) + (a)->Size - sizeof(POOL_TAIL)));
> +
>  typedef struct {
>    POOL_HEADER  Header;
>    LIST_ENTRY   Link;
> diff --git a/MdeModulePkg/Core/PiSmmCore/Pool.c
> b/MdeModulePkg/Core/PiSmmCore/Pool.c
> index 43ce869d1e1a..ebb9f8c49ee9 100644
> --- a/MdeModulePkg/Core/PiSmmCore/Pool.c
> +++ b/MdeModulePkg/Core/PiSmmCore/Pool.c
> @@ -133,6 +133,7 @@ InternalAllocPoolByIndex (
>  {
>    EFI_STATUS            Status;
>    FREE_POOL_HEADER      *Hdr;
> +  POOL_TAIL             *Tail;
>    EFI_PHYSICAL_ADDRESS  Address;
>    SMM_POOL_TYPE         SmmPoolType;
> 
> @@ -154,18 +155,26 @@ InternalAllocPoolByIndex (
>    } else {
>      Status = InternalAllocPoolByIndex (PoolType, PoolIndex + 1, &Hdr);
>      if (!EFI_ERROR (Status)) {
> +      Hdr->Header.Signature = 0;
>        Hdr->Header.Size >>= 1;
>        Hdr->Header.Available = TRUE;
> -      Hdr->Header.Type = PoolType;
> +      Hdr->Header.Type = 0;
> +      Tail = HEAD_TO_TAIL(&Hdr->Header);
> +      Tail->Signature = 0;
> +      Tail->Size = 0;
>        InsertHeadList (&mSmmPoolLists[SmmPoolType][PoolIndex],
> &Hdr->Link);
>        Hdr = (FREE_POOL_HEADER*)((UINT8*)Hdr + Hdr->Header.Size);
>      }
>    }
> 
>    if (!EFI_ERROR (Status)) {
> +    Hdr->Header.Signature = POOL_HEAD_SIGNATURE;
>      Hdr->Header.Size = MIN_POOL_SIZE << PoolIndex;
>      Hdr->Header.Available = FALSE;
>      Hdr->Header.Type = PoolType;
> +    Tail = HEAD_TO_TAIL(&Hdr->Header);
> +    Tail->Signature = POOL_TAIL_SIGNATURE;
> +    Tail->Size = Hdr->Header.Size;
>    }
> 
>    *FreePoolHdr = Hdr;
> @@ -187,6 +196,7 @@ InternalFreePoolByIndex (
>  {
>    UINTN                 PoolIndex;
>    SMM_POOL_TYPE         SmmPoolType;
> +  POOL_TAIL             *PoolTail;
> 
>    ASSERT ((FreePoolHdr->Header.Size & (FreePoolHdr->Header.Size - 1)) == 0);
>    ASSERT (((UINTN)FreePoolHdr & (FreePoolHdr->Header.Size - 1)) == 0);
> @@ -195,7 +205,12 @@ InternalFreePoolByIndex (
>    SmmPoolType =
> UefiMemoryTypeToSmmPoolType(FreePoolHdr->Header.Type);
> 
>    PoolIndex = (UINTN) (HighBitSet32 ((UINT32)FreePoolHdr->Header.Size) -
> MIN_POOL_SHIFT);
> +  FreePoolHdr->Header.Signature = 0;
>    FreePoolHdr->Header.Available = TRUE;
> +  FreePoolHdr->Header.Type = 0;
> +  PoolTail = HEAD_TO_TAIL(&FreePoolHdr->Header);
> +  PoolTail->Signature = 0;
> +  PoolTail->Size = 0;
>    ASSERT (PoolIndex < MAX_POOL_INDEX);
>    InsertHeadList (&mSmmPoolLists[SmmPoolType][PoolIndex],
> &FreePoolHdr->Link);
>    return EFI_SUCCESS;
> @@ -223,6 +238,7 @@ SmmInternalAllocatePool (
>    )
>  {
>    POOL_HEADER           *PoolHdr;
> +  POOL_TAIL             *PoolTail;
>    FREE_POOL_HEADER      *FreePoolHdr;
>    EFI_STATUS            Status;
>    EFI_PHYSICAL_ADDRESS  Address;
> @@ -235,7 +251,10 @@ SmmInternalAllocatePool (
>      return EFI_INVALID_PARAMETER;
>    }
> 
> -  Size += sizeof (*PoolHdr);
> +  //
> +  // Adjust the size by the pool header & tail overhead
> +  //
> +  Size += POOL_OVERHEAD;
>    if (Size > MAX_POOL_SIZE) {
>      Size = EFI_SIZE_TO_PAGES (Size);
>      Status = SmmInternalAllocatePages (AllocateAnyPages, PoolType, Size,
> &Address);
> @@ -244,9 +263,13 @@ SmmInternalAllocatePool (
>      }
> 
>      PoolHdr = (POOL_HEADER*)(UINTN)Address;
> +    PoolHdr->Signature = POOL_HEAD_SIGNATURE;
>      PoolHdr->Size = EFI_PAGES_TO_SIZE (Size);
>      PoolHdr->Available = FALSE;
>      PoolHdr->Type = PoolType;
> +    PoolTail = HEAD_TO_TAIL(PoolHdr);
> +    PoolTail->Signature = POOL_TAIL_SIGNATURE;
> +    PoolTail->Size = PoolHdr->Size;
>      *Buffer = PoolHdr + 1;
>      return Status;
>    }
> @@ -317,13 +340,30 @@ SmmInternalFreePool (
>    )
>  {
>    FREE_POOL_HEADER  *FreePoolHdr;
> +  POOL_TAIL         *PoolTail;
> 
>    if (Buffer == NULL) {
>      return EFI_INVALID_PARAMETER;
>    }
> 
>    FreePoolHdr = (FREE_POOL_HEADER*)((POOL_HEADER*)Buffer - 1);
> +  ASSERT (FreePoolHdr->Header.Signature == POOL_HEAD_SIGNATURE);
>    ASSERT (!FreePoolHdr->Header.Available);
> +  PoolTail = HEAD_TO_TAIL(&FreePoolHdr->Header);
> +  ASSERT (PoolTail->Signature == POOL_TAIL_SIGNATURE);
> +  ASSERT (FreePoolHdr->Header.Size == PoolTail->Size);
> +
> +  if (FreePoolHdr->Header.Signature != POOL_HEAD_SIGNATURE) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  if (PoolTail->Signature != POOL_TAIL_SIGNATURE) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  if (FreePoolHdr->Header.Size != PoolTail->Size) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> 
>    if (FreePoolHdr->Header.Size > MAX_POOL_SIZE) {
>      ASSERT (((UINTN)FreePoolHdr & EFI_PAGE_MASK) == 0);
> --
> 2.7.0.windows.1