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

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

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