UefiCpuPkg/CpuMpPei: Enable paging and set NP flag to avoid TOCTOU (CVE-2019-11098)

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=1614

To avoid the TOCTOU, enable paging and set Not Present flag so when
access any code in the flash range, it will trigger #PF exception.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Rahul Kumar <rahul1.kumar@intel.com>
Signed-off-by: Guomin Jiang <guomin.jiang@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

2 files changed, 30 insertions, 5 deletions

diff --git a/UefiCpuPkg/CpuMpPei/CpuMpPei.inf b/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
index f4d11b861f..7e511325d8 100644
--- a/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
+++ b/UefiCpuPkg/CpuMpPei/CpuMpPei.inf
@@ -46,6 +46,9 @@
   BaseMemoryLib

   CpuLib

 

+[Guids]

+  gEdkiiMigratedFvInfoGuid                                             ## SOMETIMES_CONSUMES     ## HOB

+

 [Ppis]

   gEfiPeiMpServicesPpiGuid                      ## PRODUCES

   gEfiSecPlatformInformationPpiGuid             ## SOMETIMES_CONSUMES

diff --git a/UefiCpuPkg/CpuMpPei/CpuPaging.c b/UefiCpuPkg/CpuMpPei/CpuPaging.c
index 3bf0574b34..8ab7dfcce3 100644
--- a/UefiCpuPkg/CpuMpPei/CpuPaging.c
+++ b/UefiCpuPkg/CpuMpPei/CpuPaging.c
@@ -12,6 +12,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 #include <Library/MemoryAllocationLib.h>

 #include <Library/CpuLib.h>

 #include <Library/BaseLib.h>

+#include <Guid/MigratedFvInfo.h>

 

 #include "CpuMpPei.h"

 

@@ -602,9 +603,11 @@ MemoryDiscoveredPpiNotifyCallback (
   IN VOID                       *Ppi

   )

 {

-  EFI_STATUS  Status;

-  BOOLEAN     InitStackGuard;

-  BOOLEAN     InterruptState;

+  EFI_STATUS              Status;

+  BOOLEAN                 InitStackGuard;

+  BOOLEAN                 InterruptState;

+  EDKII_MIGRATED_FV_INFO  *MigratedFvInfo;

+  EFI_PEI_HOB_POINTERS    Hob;

 

   if (PcdGetBool (PcdMigrateTemporaryRamFirmwareVolumes)) {

     InterruptState = SaveAndDisableInterrupts ();

@@ -619,9 +622,14 @@ MemoryDiscoveredPpiNotifyCallback (
   // the task switch (for the sake of stack switch).

   //

   InitStackGuard = FALSE;

-  if (IsIa32PaeSupported () && PcdGetBool (PcdCpuStackGuard)) {

+  Hob.Raw = NULL;

+  if (IsIa32PaeSupported ()) {

+    Hob.Raw  = GetFirstGuidHob (&gEdkiiMigratedFvInfoGuid);

+    InitStackGuard = PcdGetBool (PcdCpuStackGuard);

+  }

+

+  if (InitStackGuard || Hob.Raw != NULL) {

     EnablePaging ();

-    InitStackGuard = TRUE;

   }

 

   Status = InitializeCpuMpWorker ((CONST EFI_PEI_SERVICES **)PeiServices);

@@ -631,6 +639,20 @@ MemoryDiscoveredPpiNotifyCallback (
     SetupStackGuardPage ();

   }

 

+  while (Hob.Raw != NULL) {

+    MigratedFvInfo = GET_GUID_HOB_DATA (Hob);

+

+    //

+    // Enable #PF exception, so if the code access SPI after disable NEM, it will generate

+    // the exception to avoid potential vulnerability.

+    //

+    ConvertMemoryPageAttributes (MigratedFvInfo->FvOrgBase, MigratedFvInfo->FvLength, 0);

+

+    Hob.Raw = GET_NEXT_HOB (Hob);

+    Hob.Raw = GetNextGuidHob (&gEdkiiMigratedFvInfoGuid, Hob.Raw);

+  }

+  CpuFlushTlb ();

+

   return Status;

 }