Re: [MdeModulePkg] SetVirtualAddressMap() crashed due to DxeReportStatusCodeLib assuming the state of the BootService Memory at runtime.


Andrew Fish
 

On Aug 10, 2016, at 6:53 PM, Zeng, Star <star.zeng@intel.com> wrote:

If a DXE_RUNTIME_DRIVER driver just wants to report status code at boot phase and links to DxeReportStatusCodeLib, is it a bug?

How about just to add notes for DxeReportStatusCodeLib like DxePcdLib.inf?
Star,

This is point about lack of rules around this. I think the difference is the PCD protocol is defined as boot service only. I guess you could argue that depending on how things are constructed you could access some (FixedAtBuild) PCD things at runtime.

I don't think it is a good idea to produce a runtime service that does not work at runtime. Mike seems to agree.

But I agree better rules about this would be helpful.

Thanks,

Andrew Fish

DxePcdLib.inf:
"
# Note: A driver of type DXE_RUNTIME_DRIVER and DXE_SMM_DRIVER can only use this DxePcdLib
# in their initialization without any issues to access Dynamic and DynamicEx PCD. They can't
# access Dynamic and DynamicEx PCD in the implementation of runtime services and SMI handlers.
# Because EFI_PCD_PROTOCOL is DXE protocol that is not aviable in OS runtime phase.
"

Thanks,
Star
-----Original Message-----
From: afish@apple.com [mailto:afish@apple.com]
Sent: Thursday, August 11, 2016 3:04 AM
To: Kinney, Michael D <michael.d.kinney@intel.com>
Cc: Zeng, Star <star.zeng@intel.com>; edk2-devel <edk2-devel@lists.01.org>
Subject: Re: [edk2] [MdeModulePkg] SetVirtualAddressMap() crashed due to DxeReportStatusCodeLib assuming the state of the BootService Memory at runtime.


On Aug 10, 2016, at 11:02 AM, Kinney, Michael D <michael.d.kinney@intel.com> wrote:



-----Original Message-----
From: afish@apple.com [mailto:afish@apple.com]
Sent: Wednesday, August 10, 2016 10:35 AM
To: Kinney, Michael D <michael.d.kinney@intel.com>
Cc: Zeng, Star <star.zeng@intel.com>; edk2-devel
<edk2-devel@lists.01.org>
Subject: Re: [edk2] [MdeModulePkg] SetVirtualAddressMap() crashed due
to DxeReportStatusCodeLib assuming the state of the BootService Memory at runtime.


On Aug 10, 2016, at 10:22 AM, Kinney, Michael D <michael.d.kinney@intel.com> wrote:

Hi Andrew,

I am staring at the code. Something is not right here, but I am
concerned that there are use cases I am not considering yet. Here
is my analysis so far.

Here are the lib instances I see:
(ignoring IntelFramework ones for the purposes of this discussion).

MdeModulePkg\Library\DxeReportStatusCodeLib\DxeReportStatusCodeLib.inf(25):
LIBRARY_CLASS = ReportStatusCodeLib|DXE_CORE DXE_DRIVER
DXE_RUNTIME_DRIVER
DXE_SAL_DRIVER DXE_SMM_DRIVER UEFI_APPLICATION UEFI_DRIVER SMM_CORE

MdeModulePkg\Library\PeiReportStatusCodeLib\PeiReportStatusCodeLib.inf(27):
LIBRARY_CLASS = ReportStatusCodeLib|SEC PEIM PEI_CORE

MdeModulePkg\Library\RuntimeDxeReportStatusCodeLib\RuntimeDxeReportSt
atusCodeLib.inf(
23):
LIBRARY_CLASS = ReportStatusCodeLib|DXE_RUNTIME_DRIVER
DXE_SAL_DRIVER

MdeModulePkg\Library\SmmReportStatusCodeLib\SmmReportStatusCodeLib.inf(26):
LIBRARY_CLASS = ReportStatusCodeLib|DXE_SMM_DRIVER SMM_CORE

MdePkg\Library\BaseReportStatusCodeLibNull\BaseReportStatusCodeLibNull.inf(23):
LIBRARY_CLASS = ReportStatusCodeLib

* The BASE one that is a Null instance makes sense when disabling
Report Status
Code.
* The PEI one makes sense for its module compatibility.
* The SMM one also makes sense its module compatibility.
* And the RuntimeDxe one also makes sense its module compatibility.
* The DXE one seems to be over specified and if we reduced its
module compatibility, the SMM and RuntimeDxe lib instances can be
used to cover those module types.

When I look at the source code in DxeReportStatusCodeLib, I see
comments that describe the use case where a module is dispatched
before the Report Status Code Protocol is available.

The use case you are describing is when the first call to Report
Status Code by a module occurs after ExitBootServices(). In that
case, we depend on the Boot Services table being zeroed to exit early.

I agree that no component should depend on Boot Services table being
cleared to zeros at ExitBootServices(). It is legal from UEFI/PI
spec to not zero at all, or in your example, fill with a pattern
other than zeros.

It appears that the use case of first call to Report Status Code
after
ExitBootServices() is not covered by the DXE lib instance, and we
have just been getting lucky due to zeroing behavior of boot services table.

I can think of a couple options:

* Update DXE INF to remove the DXE Runtime, DXE SAL, SMM, SMM Core
module types. This may break platform builds if a platform is using
this lib mapping for modules of the types being removed. However,
those could be considered platform DSC bugs.

* Update DXE lib instance to add ExitBootServices() and
SetVirtualAddressMap() events. However, this would basically make
the DXE lib instance the same as the DXE Runtime instance and would
increase size of non-RT components.

I would prefer the first option, but we would need to do some
testing to see how many platform DSC files break.
Mike,

That seems to make the most sense, but I too was worried about compatibility.

I tried adding the UefiRuntimeLib to just fail calls at Runtime, but
that breaks the build as DXE_CORE does not support UefiRuntimeLib.

I guess one option would be to only add the ExitBootServices event
and fail calls at runtime?
I agree this would remove the assumption that the boot services table is zeroed.
However, the only way this function can be called after
ExitBootServices() is if the module is DXE_RUNTIME_DRIVER,
DXE_SAL_DRIVER, or DXE_SMM_DRIVER. If a module is one of these types
and they call Report Status Code, then they would want the status code
to go out. The current behavior of this lib instance silently ignores
all status codes after ExitBootServices(). This silent filtering is
not good, and may be a good reason to move ahead with the first option and fix the platform DSC files.
Mike,

I have to admit the assumption that it works at runtime is how I hit this issue in the first place so I'm fine with restricting the usage.

I guess the rule is:
1) For BootServices only libraries it is OK to map as Runtime Services as there is an assumption that the calls will only be made at boot services time.
2) For RuntimeServices libraries they should always work.

I think the issue was a RT library that was coded with 1) assumptions. I have to admit I don't know that we do a good job of documenting this kind of thing.

It also brings up the point of maybe it would be better to list fewer things as SMM from a security audit point of view. Maybe it would be worthing it to add runtime checks that fail for things marked SMM that are in bucket 1)?

Thanks,

Andrew Fish


Thanks,

Andrew Fish

Mike

-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf
Of Andrew Fish
Sent: Tuesday, August 9, 2016 7:50 AM
To: Zeng, Star <star.zeng@intel.com>
Cc: edk2-devel <edk2-devel@lists.01.org>
Subject: Re: [edk2] [MdeModulePkg] SetVirtualAddressMap() crashed
due to DxeReportStatusCodeLib assuming the state of the BootService Memory at runtime.


On Aug 8, 2016, at 7:26 PM, Zeng, Star <star.zeng@intel.com> wrote:

On 2016/8/9 10:07, Andrew Fish wrote:

On Aug 8, 2016, at 6:21 PM, Zeng, Star <star.zeng@intel.com> wrote:

Andrew,

Should MdeModulePkg/Library/RuntimeDxeReportStatusCodeLib be
used for your case
if there are really runtime status code reporting needed?
Star,

If the Library instance does not fully support
DXE_RUNTIME_DRIVER, why is it
listed in the LIBRARY_CLASS as supported?

This kind of library can support DXE_RUNTIME_DRIVER at boot time,
for example
UefiHiiLib, UefiHiiServicesLib, UefiBootServicesTableLib, DxePcdLib and etc.
Star,

I understand giving access to Boot Services resources to a Runtime
Driver for its constructor. I think the difference here is the
DxeReportStatusCodeLib is
abstracting
a runtime service, but not doing it in a way to really works
properly at runtime
in
all cases. I would expect that a library abstraction a runtime
feature would work
at
runtime. Which is why I ended up with a "bad" mapping in the first place.

Thanks,

Andrew Fish


https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Library/Dx
eReportStatusCod
eLib/DxeReportStatusCodeLib.inf#L25

LIBRARY_CLASS = ReportStatusCodeLib|DXE_CORE DXE_DRIVER
DXE_RUNTIME_DRIVER DXE_SAL_DRIVER DXE_SMM_DRIVER UEFI_APPLICATION
UEFI_DRIVER SMM_CORE

Actually I tried to add the UefiRuntimeDriverLib and the build
failed as
UefiRuntimeDriverLib was not supported for the DXE_CORE type. Maybe
the bug is
this
library instance lists DXE_RUNTIME_DRIVER, DXE_SAL_DRIVER and
DXE_SMM_DRIVER when
it
has special case code to support DXE_CORE? Maybe this library is
trying to do too many things?

What ReportStatusCodeLib would you recommend to link with RuntimeDxe driver:
https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Runti
meDxe/RuntimeDxe
.inf

[LibraryClasses.common.DXE_CORE]
ReportStatusCodeLib|MdeModulePkg/Library/DxeReportStatusCodeLib/DxeRe
ReportStatusCodeLib|portStatusCodeLi
b.inf

[LibraryClasses.common.DXE_RUNTIME_DRIVER]
ReportStatusCodeLib|MdeModulePkg/Library/RuntimeDxeReportStatusCodeLi
ReportStatusCodeLib|b/RuntimeDxeRepo
rtStatusCodeLib.inf

[LibraryClasses.common.UEFI_DRIVER]
ReportStatusCodeLib|MdeModulePkg/Library/DxeReportStatusCodeLib/DxeRe
ReportStatusCodeLib|portStatusCodeLi
b.inf

[LibraryClasses.common.DXE_DRIVER]
ReportStatusCodeLib|MdeModulePkg/Library/DxeReportStatusCodeLib/DxeRe
ReportStatusCodeLib|portStatusCodeLi
b.inf

[LibraryClasses.common.UEFI_APPLICATION]
ReportStatusCodeLib|MdeModulePkg/Library/DxeReportStatusCodeLib/DxeRe
ReportStatusCodeLib|portStatusCodeLi
b.inf

Thanks,
Star


Thanks,

Andrew Fish

Thanks,
Star
-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On
Behalf Of Andrew
Fish
Sent: Tuesday, August 9, 2016 7:08 AM
To: edk2-devel <edk2-devel@lists.01.org>
Subject: [edk2] [MdeModulePkg] SetVirtualAddressMap() crashed
due to
DxeReportStatusCodeLib assuming the state of the BootService Memory at runtime.

I was messing about with an ExitBootServices test that fills
boot services
memory
with 0xAFAFAFAFAFAFAFAF (It was Vincent's idea to use my Initials
but it has the handy property of being a non-cononical address and
causes on GP fault on X64) and
SetVirtualAddressMap() started crashing.

It looks like this code is assuming the 1st call to ReportStatus
code will not
happen at runtime. This is not the case for the RuntimeDxe driver.
https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Library/Dx
eReportStatusCod
eLib/ReportStatusCodeLib.c#L43
VOID
InternalGetReportStatusCode (
VOID
)
{
EFI_STATUS Status;

if (mReportStatusCodeLibStatusCodeProtocol != NULL) { return; }

//
// Check gBS just in case ReportStatusCode is called before gBS is initialized.
//
if (gBS != NULL && gBS->LocateProtocol != NULL) { Status =
gBS->LocateProtocol (&gEfiStatusCodeRuntimeProtocolGuid, NULL,
(VOID**)
&mReportStatusCodeLibStatusCodeProtocol);
if (EFI_ERROR (Status)) {
mReportStatusCodeLibStatusCodeProtocol = NULL; } } }

I'm guessing this seems to work due
to:https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Core/Dx
e/DxeMain/DxeMai
n.c#L803

//
// Zero out the Boot Service Table // ZeroMem (gBS, sizeof
(EFI_BOOT_SERVICES));


Thus if I'm looking at this code correctly it only looks like it
works at
Runtime
since it is depending on the value of a boot services memory buffer not changing.
This is not a valid assumption as that code is owned by the caller
of ExitBootServices, so it should be legal for my test to change the value.

I wanted to get a few more eyes on this prior to filling a bug?

Thanks,

Andrew Fish


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