Re: [edk2-devel] [PATCH edk2 v2 3/3] StandaloneMmPkg: Fix check buffer address failed issue from TF-A

["Marvin Häuser" <mhaeuser@posteo.de>]

Hey Ming,

Please check 
https://edk2.groups.io/g/devel/message/84973?p=%2C%2C%2C20%2C0%2C0%2C0%3A%3Arecentpostdate%2Fsticky%2C%2CMarvin%2C20%2C2%2C0%2C86334815
While a few comments were cosmetical, there is an invalid memory access 
outlined too, which persists in this patch.

For the future, this should also check buffer alignment before casting 
(lets hope my corresponding patch passes review within this decade...).

Best regards,
Marvin

On 21.12.21 16:06, Ming Huang wrote:
> There are two scene communicate with StandaloneMm(MM):
> 1 edk2 -> TF-A -> MM, communicate MM use non-secure buffer which
>    specify by EFI_SECURE_PARTITION_BOOT_INFO.SpNsCommBufBase;
> 2 RAS scene: fiq -> TF-A -> MM, use secure buffer which
>    specify by EFI_SECURE_PARTITION_BOOT_INFO.SpShareBufBase;
>
> For now, the second scene will failed because check buffer address.
> This patch add CheckBufferAddr() to support check address for secure
> buffer.
>
> Signed-off-by: Ming Huang <huangming@linux.alibaba.com>
> ---
>   StandaloneMmPkg/Drivers/StandaloneMmCpu/EventHandle.c     | 59 +++++++++++++++-----
>   StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.c | 21 +++++++
>   StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.h |  1 +
>   3 files changed, 68 insertions(+), 13 deletions(-)
>
> diff --git a/StandaloneMmPkg/Drivers/StandaloneMmCpu/EventHandle.c b/StandaloneMmPkg/Drivers/StandaloneMmCpu/EventHandle.c
> index 5dfaf9d751..ba8639a26a 100644
> --- a/StandaloneMmPkg/Drivers/StandaloneMmCpu/EventHandle.c
> +++ b/StandaloneMmPkg/Drivers/StandaloneMmCpu/EventHandle.c
> @@ -50,6 +50,7 @@ EFI_MM_COMMUNICATE_HEADER **PerCpuGuidedEventContext = NULL;
>   
>   // Descriptor with whereabouts of memory used for communication with the normal world
>   EFI_MMRAM_DESCRIPTOR  mNsCommBuffer;
> +EFI_MMRAM_DESCRIPTOR  mSCommBuffer;
>   
>   MP_INFORMATION_HOB_DATA *mMpInformationHobData;
>   
> @@ -60,6 +61,47 @@ EFI_MM_CONFIGURATION_PROTOCOL mMmConfig = {
>   
>   STATIC EFI_MM_ENTRY_POINT     mMmEntryPoint = NULL;
>   
> +STATIC
> +EFI_STATUS
> +CheckBufferAddr (
> +  IN UINTN CommBufferAddr
> +  )
> +{
> +  UINTN      CommBufferSize;
> +  EFI_STATUS Status;
> +  UINT64     NsCommBufferEnd;
> +  UINT64     SCommBufferEnd;
> +  UINT64     CommBufferEnd;
> +
> +  Status = EFI_SUCCESS;
> +  NsCommBufferEnd = mNsCommBuffer.PhysicalStart + mNsCommBuffer.PhysicalSize;
> +  SCommBufferEnd = mSCommBuffer.PhysicalStart + mSCommBuffer.PhysicalSize;
> +
> +  if ((CommBufferAddr >= mNsCommBuffer.PhysicalStart) &&
> +      (CommBufferAddr < NsCommBufferEnd)) {
> +    CommBufferEnd = NsCommBufferEnd;
> +  } else if ((CommBufferAddr >= mSCommBuffer.PhysicalStart) &&
> +             (CommBufferAddr <= SCommBufferEnd)) {
> +    CommBufferEnd = SCommBufferEnd;
> +  } else {
> +    return EFI_ACCESS_DENIED;
> +  }
> +
> +  if ((CommBufferAddr + sizeof (EFI_MM_COMMUNICATE_HEADER)) >= CommBufferEnd) {
> +    Status = EFI_INVALID_PARAMETER;
> +  }
> +
> +  // Find out the size of the buffer passed
> +  CommBufferSize = ((EFI_MM_COMMUNICATE_HEADER *) CommBufferAddr)->MessageLength +
> +    sizeof (EFI_MM_COMMUNICATE_HEADER);
> +  // perform bounds check.
> +  if (CommBufferAddr + CommBufferSize >= CommBufferEnd) {
> +    Status = EFI_ACCESS_DENIED;
> +  }
> +
> +  return Status;
> +}
> +
>   /**
>     The PI Standalone MM entry point for the TF-A CPU driver.
>   
> @@ -104,25 +146,16 @@ PiMmStandaloneArmTfCpuDriverEntry (
>       return EFI_INVALID_PARAMETER;
>     }
>   
> -  if (NsCommBufferAddr < mNsCommBuffer.PhysicalStart) {
> -    return EFI_ACCESS_DENIED;
> -  }
> -
> -  if ((NsCommBufferAddr + sizeof (EFI_MM_COMMUNICATE_HEADER)) >=
> -      (mNsCommBuffer.PhysicalStart + mNsCommBuffer.PhysicalSize)) {
> -    return EFI_INVALID_PARAMETER;
> +  Status = CheckBufferAddr (NsCommBufferAddr);
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "Check Buffer failed: %r\n", Status));
> +    return Status;
>     }
>   
>     // Find out the size of the buffer passed
>     NsCommBufferSize = ((EFI_MM_COMMUNICATE_HEADER *) NsCommBufferAddr)->MessageLength +
>       sizeof (EFI_MM_COMMUNICATE_HEADER);
>   
> -  // perform bounds check.
> -  if (NsCommBufferAddr + NsCommBufferSize >=
> -      mNsCommBuffer.PhysicalStart + mNsCommBuffer.PhysicalSize) {
> -    return EFI_ACCESS_DENIED;
> -  }
> -
>     GuidedEventContext = NULL;
>     // Now that the secure world can see the normal world buffer, allocate
>     // memory to copy the communication buffer to the secure world.
> diff --git a/StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.c b/StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.c
> index fd9c59b4da..96dad20dd1 100644
> --- a/StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.c
> +++ b/StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.c
> @@ -107,6 +107,7 @@ StandaloneMmCpuInitialize (
>     UINTN                            Index;
>     UINTN                            ArraySize;
>     VOID                            *HobStart;
> +  EFI_MMRAM_HOB_DESCRIPTOR_BLOCK  *MmramRangesHob;
>   
>     ASSERT (SystemTable != NULL);
>     mMmst = SystemTable;
> @@ -186,6 +187,26 @@ StandaloneMmCpuInitialize (
>     CopyMem (&mNsCommBuffer, NsCommBufMmramRange, sizeof(EFI_MMRAM_DESCRIPTOR));
>     DEBUG ((DEBUG_INFO, "mNsCommBuffer: 0x%016lx - 0x%lx\n", mNsCommBuffer.CpuStart, mNsCommBuffer.PhysicalSize));
>   
> +  Status = GetGuidedHobData (
> +             HobStart,
> +             &gEfiMmPeiMmramMemoryReserveGuid,
> +             (VOID **) &MmramRangesHob
> +             );
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_ERROR, "MmramRangesHob data extraction failed - 0x%x\n", Status));
> +    return Status;
> +  }
> +
> +  //
> +  // As CreateHobListFromBootInfo(), the base and size of buffer shared with
> +  // privileged Secure world software is in second one.
> +  //
> +  CopyMem (
> +    &mSCommBuffer,
> +    &MmramRangesHob->Descriptor[0] + 1,
> +    sizeof(EFI_MMRAM_DESCRIPTOR)
> +  );
> +
>     //
>     // Extract the MP information from the Hoblist
>     //
> diff --git a/StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.h b/StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.h
> index 2c96439c15..2e03b20d85 100644
> --- a/StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.h
> +++ b/StandaloneMmPkg/Drivers/StandaloneMmCpu/StandaloneMmCpu.h
> @@ -30,6 +30,7 @@ extern EFI_MM_CPU_PROTOCOL mMmCpuState;
>   //
>   extern EFI_MM_COMMUNICATE_HEADER    **PerCpuGuidedEventContext;
>   extern EFI_MMRAM_DESCRIPTOR          mNsCommBuffer;
> +extern EFI_MMRAM_DESCRIPTOR          mSCommBuffer;
>   extern MP_INFORMATION_HOB_DATA       *mMpInformationHobData;
>   extern EFI_MM_CONFIGURATION_PROTOCOL mMmConfig;
>