Re: [PATCH v2 0/2] Resolve feature conflict between NX and Stack guard

["Wang, Jian J" <jian.j.wang@intel.com>]

Regards,
Jian


> -----Original Message-----
> From: Ni, Ruiyu
> Sent: Wednesday, March 07, 2018 11:17 AM
> To: Wu, Hao A <hao.a.wu@intel.com>; edk2-devel@lists.01.org
> Cc: Wang, Jian J <jian.j.wang@intel.com>; Zeng, Star <star.zeng@intel.com>;
> Dong, Eric <eric.dong@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>
> Subject: Re: [PATCH v2 0/2] Resolve feature conflict between NX and Stack
> guard
> 
> On 3/6/2018 9:33 PM, Hao Wu wrote:
> > V2 changes:
> >
> > A. Use Hoblib APIs to get the base of stack from Hob.
> > B. Remove unnecessary local variable used in function
> >     InitializeDxeNxMemoryProtectionPolicy().
> >
> > V1 history:
> >
> > If enabled, NX memory protection feature will mark some types of active
> > memory as NX (non-executable), which includes the first page of the stack.
> > This will overwrite the attributes of the first page of the stack if the
> > stack guard feature is also enabled.
> >
> > The series will override the attributes setting to the first page of the
> > stack by adding back the 'EFI_MEMORY_RP' attribute when the stack guard
> > feature is enabled.
> >
> > Cc: Jian J Wang <jian.j.wang@intel.com>
> > Cc: Star Zeng <star.zeng@intel.com>
> > Cc: Eric Dong <eric.dong@intel.com>
> > Cc: Jiewen Yao <jiewen.yao@intel.com>
> > Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> >
> > Hao Wu (2):
> >    MdeModulePkg/Core: Refine handling NULL detection in NX setting
> >    MdeModulePkg/Core: Fix feature conflict between NX and Stack guard
> >
> >   MdeModulePkg/Core/Dxe/DxeMain.inf             |  4 +-
> >   MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c | 74
> +++++++++++++++++++++++----
> >   2 files changed, 67 insertions(+), 11 deletions(-)
> >
> 
>        if (MemoryMapEntry->PhysicalStart == 0 &&
>            PcdGet8 (PcdNullPointerDetectionPropertyMask) != 0) {
> 
>          ASSERT (MemoryMapEntry->NumberOfPages > 0);
>          //
>          // Add EFI_MEMORY_RP attribute for page 0 if NULL pointer
> detection is
>          // enabled.
>          //
> [Ray] 1. I prefer to move the above comments before the "if (...)".
> 
>          SetUefiImageMemoryAttributes (
>            0,
>            EFI_PAGES_TO_SIZE (1),
>            EFI_MEMORY_RP | Attributes);
>        }
> 
>        if (StackBase != 0 &&
>            (StackBase >= MemoryMapEntry->PhysicalStart &&
>             StackBase <  MemoryMapEntry->PhysicalStart +
>                          LShiftU64 (MemoryMapEntry->NumberOfPages,
> EFI_PAGE_SHIFT)) &&
>            PcdGetBool (PcdCpuStackGuard)) {
> 
>          //
>          // Add EFI_MEMORY_RP attribute for the first page of the stack
> if stack
>          // guard is enabled.
>          //
>          SetUefiImageMemoryAttributes (
>            StackBase,
>            EFI_PAGES_TO_SIZE (1),
>            EFI_MEMORY_RP | Attributes);
> [Ray] 2. The StackBase is directly used here. So do we need to check
> whether it's page aligned? Do we need to check whether the range
> [StackBase, StackBase + 4KB) is inside the MemoryMapEntry?
>        }

If PcdCpuStackGuard is TRUE, I think the owner who allocates memory for StackBase
should make sure all the conditions you mentioned, but not here.

> 
> --
> Thanks,
> Ray