[edk2-devel] [PATCH v5 06/28] MdeModulePkg: Apply Protections to the HOB List

[Taylor Beebe]

Because the platform memory protection settings will be stored
in the HOB, the HOB list should be marked read-only and non-executable
as soon as possible in boot.

This patch page-aligns the allocated HOB list in DXE and marks
it RO/NX during memory protection initialization.

Signed-off-by: Taylor Beebe <taylor.d.beebe at gmail.com>
Cc: Jian J Wang <jian.j.wang at intel.com>
Cc: Liming Gao <gaoliming at byosoft.com.cn>
Cc: Dandan Bi <dandan.bi at intel.com>
---
 MdeModulePkg/Core/Dxe/Gcd/Gcd.c               | 18 ++++++------
 MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c | 29 ++++++++++++++++++++
 2 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/MdeModulePkg/Core/Dxe/Gcd/Gcd.c b/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
index 792cd2e0af23..72bd036eab1e 100644
--- a/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
+++ b/MdeModulePkg/Core/Dxe/Gcd/Gcd.c
@@ -2764,21 +2764,21 @@ CoreInitializeGcdServices (
   }
 
   //
-  // Relocate HOB List to an allocated pool buffer.
+  // Relocate HOB List to allocated pages.
   // The relocation should be at after all the tested memory resources added
   // (except the memory space that covers HOB List) to the memory services,
   // because the memory resource found in CoreInitializeMemoryServices()
   // may have not enough remaining resource for HOB List.
   //
-  NewHobList = AllocateCopyPool (
-                 (UINTN)PhitHob->EfiFreeMemoryBottom - (UINTN)(*HobStart),
-                 *HobStart
-                 );
-  ASSERT (NewHobList != NULL);
-
-  *HobStart = NewHobList;
-  gHobList  = NewHobList;
+  NewHobList = AllocatePages (EFI_SIZE_TO_PAGES ((UINTN)PhitHob->EfiFreeMemoryBottom - (UINTN)(*HobStart)));
+  if (NewHobList != NULL) {
+    CopyMem (NewHobList, *HobStart, (UINTN)PhitHob->EfiFreeMemoryBottom - (UINTN)(*HobStart));
+    *HobStart = NewHobList;
+  } else {
+    ASSERT (NewHobList != NULL);
+  }
 
+  gHobList = *HobStart;
   if (MemorySpaceMapHobList != NULL) {
     //
     // Add and allocate the memory space that covers HOB List to the memory services
diff --git a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
index 7cc829b17402..94ed3111688b 100644
--- a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
+++ b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
@@ -967,6 +967,32 @@ InitializeDxeNxMemoryProtectionPolicy (
   }
 }
 
+/**
+  Mark the HOB list as read-only and non-executable.
+**/
+STATIC
+VOID
+ProtectHobList (
+  VOID
+  )
+{
+  EFI_PEI_HOB_POINTERS  Hob;
+
+  Hob.Raw = GetHobList ();
+
+  // Find the end of the HOB list.
+  while (!END_OF_HOB_LIST (Hob)) {
+    Hob.Raw = GET_NEXT_HOB (Hob);
+  }
+
+  // Protect the HOB list.
+  SetUefiImageMemoryAttributes (
+    (UINTN)gHobList,
+    ALIGN_VALUE (((UINTN)Hob.Raw + GET_HOB_LENGTH (Hob)) - (UINTN)GetHobList (), EFI_PAGE_SIZE),
+    EFI_MEMORY_XP | EFI_MEMORY_RO
+    );
+}
+
 /**
   A notification for CPU_ARCH protocol.
 
@@ -1007,6 +1033,9 @@ MemoryProtectionCpuArchProtocolNotify (
   //
   HeapGuardCpuArchProtocolNotify ();
 
+  // Mark the HOB list XP and RO.
+  ProtectHobList ();
+
   if (mImageProtectionPolicy == 0) {
     goto Done;
   }
-- 
2.42.0.windows.2



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