Re: [PATCH 1/3] MdeModulePkg/PciHostBridge: Enhance boundary check in Io/Mem.Read/Write

["Zeng, Star" <star.zeng@intel.com>]

Two very small comments are added below.

On 2018/9/21 15:25, Ruiyu Ni wrote:
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
> Cc: Star Zeng <star.zeng@intel.com>
> ---
>   .../Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c     | 26 +++++++++++++++++-----
>   1 file changed, 21 insertions(+), 5 deletions(-)
> 
> diff --git a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> index f8a1239ceb..0b6b56f846 100644
> --- a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> +++ b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c
> @@ -321,6 +321,7 @@ RootBridgeIoCheckParameter (
>     UINT64                                       Base;
>     UINT64                                       Limit;
>     UINT32                                       Size;
> +  UINT64                                       Length;
>   
>     //
>     // Check to see if Buffer is NULL
> @@ -337,7 +338,7 @@ RootBridgeIoCheckParameter (
>     }
>   
>     //
> -  // For FIFO type, the target address won't increase during the access,
> +  // For FIFO type, the device address won't increase during the access,
>     // so treat Count as 1
>     //
>     if (Width >= EfiPciWidthFifoUint8 && Width <= EfiPciWidthFifoUint64) {
> @@ -347,6 +348,13 @@ RootBridgeIoCheckParameter (
>     Width = (EFI_PCI_ROOT_BRIDGE_IO_PROTOCOL_WIDTH) (Width & 0x03);
>     Size  = 1 << Width;
>   
> +  //
> +  // Make sure (Count * Size) doesn't exceed MAX_UINT64
> +  //
> +  if (Count > DivU64x32 (MAX_UINT64, Size)) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +

Mark as "Code Block 1".

>     //
>     // Check to see if Address is aligned
>     //
> @@ -354,6 +362,14 @@ RootBridgeIoCheckParameter (
>       return EFI_UNSUPPORTED;
>     }
>   
> +  //
> +  // Make sure (Address + Count * Size) doesn't exceed MAX_UINT64
> +  //
> +  Length = MultU64x32 (Count, Size);
> +  if (Address > MAX_UINT64 - Length) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +

Is there some reason this code block is not put together with the "Code 
Block 1"? Both are checking integer overflow.

How about also enhancing the function description a little to add one 
line for describing the overflow invalid parameter cases?

   @retval EFI_INVALID_PARAMETER  XXX.

or just updating the line below?

   @retval EFI_UNSUPPORTED        The address range specified by 
Address, Width,
                                  and Count is not valid for this PI system.


Thanks,
Star

>     RootBridge = ROOT_BRIDGE_FROM_THIS (This);
>   
>     //
> @@ -372,7 +388,7 @@ RootBridgeIoCheckParameter (
>       //
>       // Allow Legacy IO access
>       //
> -    if (Address + MultU64x32 (Count, Size) <= 0x1000) {
> +    if (Address + Length <= 0x1000) {
>         if ((RootBridge->Attributes & (
>              EFI_PCI_ATTRIBUTE_ISA_IO | EFI_PCI_ATTRIBUTE_VGA_PALETTE_IO | EFI_PCI_ATTRIBUTE_VGA_IO |
>              EFI_PCI_ATTRIBUTE_IDE_PRIMARY_IO | EFI_PCI_ATTRIBUTE_IDE_SECONDARY_IO |
> @@ -386,7 +402,7 @@ RootBridgeIoCheckParameter (
>       //
>       // Allow Legacy MMIO access
>       //
> -    if ((Address >= 0xA0000) && (Address + MultU64x32 (Count, Size)) <= 0xC0000) {
> +    if ((Address >= 0xA0000) && (Address + Length) <= 0xC0000) {
>         if ((RootBridge->Attributes & EFI_PCI_ATTRIBUTE_VGA_MEMORY) != 0) {
>           return EFI_SUCCESS;
>         }
> @@ -395,7 +411,7 @@ RootBridgeIoCheckParameter (
>       // By comparing the Address against Limit we know which range to be used
>       // for checking
>       //
> -    if (Address + MultU64x32 (Count, Size) <= RootBridge->Mem.Limit + 1) {
> +    if (Address + Length <= RootBridge->Mem.Limit + 1) {
>         Base = RootBridge->Mem.Base;
>         Limit = RootBridge->Mem.Limit;
>       } else {
> @@ -427,7 +443,7 @@ RootBridgeIoCheckParameter (
>         return EFI_INVALID_PARAMETER;
>     }
>   
> -  if (Address + MultU64x32 (Count, Size) > Limit + 1) {
> +  if (Address + Length > Limit + 1) {
>       return EFI_INVALID_PARAMETER;
>     }
>   
>