Re: [PATCH v2 4/6] BaseTools/DevicePath: use MAX_UINT16 as default device path max size

["Gao, Liming" <liming.gao@intel.com>]

Yes. The change is necessary. 

> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> Sent: Wednesday, December 5, 2018 3:42 PM
> To: Gao, Liming <liming.gao@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>; edk2-devel@lists.01.org; Zhu, Yonghong <yonghong.zhu@intel.com>; Feng, Bob C
> <bob.c.feng@intel.com>; Carsey, Jaben <jaben.carsey@intel.com>
> Subject: Re: [PATCH v2 4/6] BaseTools/DevicePath: use MAX_UINT16 as default device path max size
> 
> On Wed, 5 Dec 2018 at 01:04, Gao, Liming <liming.gao@intel.com> wrote:
> >
> > Laszlo:
> >   I agree with you. MAX_UINT32 is more comfortable.
> >
> 
> Liming,
> 
> No definitions for MAX_UINT32 exist currently in BaseTools, so I will
> have to add the following:
> 
> diff --git a/BaseTools/Source/C/Common/CommonLib.h
> b/BaseTools/Source/C/Common/CommonLib.h
> index b1c6c00a3478..1c40180329c4 100644
> --- a/BaseTools/Source/C/Common/CommonLib.h
> +++ b/BaseTools/Source/C/Common/CommonLib.h
> @@ -23,6 +23,7 @@ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND,
> EITHER EXPRESS OR IMPLIED.
>  #define MAX_LONG_FILE_PATH 500
> 
>  #define MAX_UINT64 ((UINT64)0xFFFFFFFFFFFFFFFFULL)
> +#define MAX_UINT32 ((UINT32)0xFFFFFFFFULL)
>  #define MAX_UINT16  ((UINT16)0xFFFF)
>  #define MAX_UINT8   ((UINT8)0xFF)
>  #define ARRAY_SIZE(Array) (sizeof (Array) / sizeof ((Array)[0]))
> 
> Does your Reviewed-by cover that as well?
> 
> 
> 
> 
> > >-----Original Message-----
> > >From: Laszlo Ersek [mailto:lersek@redhat.com]
> > >Sent: Monday, December 03, 2018 9:06 PM
> > >To: Ard Biesheuvel <ard.biesheuvel@linaro.org>; edk2-devel@lists.01.org
> > >Cc: Zhu, Yonghong <yonghong.zhu@intel.com>; Gao, Liming
> > ><liming.gao@intel.com>; Feng, Bob C <bob.c.feng@intel.com>; Carsey, Jaben
> > ><jaben.carsey@intel.com>
> > >Subject: Re: [PATCH v2 4/6] BaseTools/DevicePath: use MAX_UINT16 as
> > >default device path max size
> > >
> > >On 11/30/18 23:45, Ard Biesheuvel wrote:
> > >> Replace the default size limit of IsDevicePathValid() with a value
> > >> that does not depend on the native word size of the build host.
> > >>
> > >> 64 KB seems sufficient as the upper bound of a device path handled
> > >> by UEFI.
> > >>
> > >> Contributed-under: TianoCore Contribution Agreement 1.1
> > >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > >> Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
> > >> ---
> > >>  BaseTools/Source/C/DevicePath/DevicePathUtilities.c | 4 ++--
> > >>  1 file changed, 2 insertions(+), 2 deletions(-)
> > >>
> > >> diff --git a/BaseTools/Source/C/DevicePath/DevicePathUtilities.c
> > >b/BaseTools/Source/C/DevicePath/DevicePathUtilities.c
> > >> index d4ec2742b7c8..ba7f83e53070 100644
> > >> --- a/BaseTools/Source/C/DevicePath/DevicePathUtilities.c
> > >> +++ b/BaseTools/Source/C/DevicePath/DevicePathUtilities.c
> > >> @@ -62,7 +62,7 @@ IsDevicePathValid (
> > >>    ASSERT (DevicePath != NULL);
> > >>
> > >>    if (MaxSize == 0) {
> > >> -    MaxSize = MAX_UINTN;
> > >> +    MaxSize = MAX_UINT16;
> > >>   }
> > >>
> > >>    //
> > >> @@ -78,7 +78,7 @@ IsDevicePathValid (
> > >>        return FALSE;
> > >>      }
> > >>
> > >> -    if (NodeLength > MAX_UINTN - Size) {
> > >> +    if (NodeLength > MAX_UINT16 - Size) {
> > >>        return FALSE;
> > >>      }
> > >>      Size += NodeLength;
> > >>
> > >
> > >I'm somewhat undecided about this patch.
> > >
> > >(1) IsDevicePathValid() also exists in:
> > >
> > >- MdePkg/Library/UefiDevicePathLib/DevicePathUtilities.c
> > >- MdePkg/Library/UefiDevicePathLibDevicePathProtocol/UefiDevicePathLib.c
> > >
> > >Both have:
> > >
> > >  if (MaxSize == 0) {
> > >    MaxSize = MAX_UINTN;
> > >  }
> > >
> > >Relative to those, this change departs quite strongly.
> > >
> > >
> > >(2) In addition, a single device path node may extend up to 64KB. That
> > >would be pathologic, yes, but the option is there.
> > >
> > >
> > >... Of course, we are discussing theoretical limits. Still I'd feel more
> > >comfortable with MAX_UINT32. Lifting the limit from 64K to 4G wouldn't
> > >cost us anything (in development effort), it would be a no-op on 32-bit
> > >build hosts, it would be a theoretical-only change on 64-bit build
> > >hosts, and it would leave us with a larger "safety margin".
> > >
> > >I won't insist, but I thought I should raise this. (Sorry if this has
> > >been discussed under v1 already.) If you agree, no need to repost (from
> > >my side anyway) just for this.
> > >
> > >With or without the update:
> > >
> > >Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> > >
> > >Thanks
> > >Laszlo