[edk2-devel] [PATCH v3 1/4] StandaloneMmPkg/Core: Limit FwVol encapsulation section recursion

["Xu, Wei6" <wei6.xu@intel.com>]

MmCoreFfsFindMmDriver() is called recursively for encapsulation sections.
Currently this recursion is not limited. Introduce a new PCD
(fixed-at-build, or patchable-in-module), and make MmCoreFfsFindMmDriver()
track the section nesting depth against that PCD.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Wei6 Xu <wei6.xu@intel.com>
---
 StandaloneMmPkg/Core/FwVol.c              | 16 ++++++++++++++--
 StandaloneMmPkg/Core/StandaloneMmCore.c   |  5 +++--
 StandaloneMmPkg/Core/StandaloneMmCore.inf |  3 +++
 StandaloneMmPkg/StandaloneMmPkg.dec       |  5 +++++
 4 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/StandaloneMmPkg/Core/FwVol.c b/StandaloneMmPkg/Core/FwVol.c
index 1f6d7714ba97..e1e20ffd14ac 100644
--- a/StandaloneMmPkg/Core/FwVol.c
+++ b/StandaloneMmPkg/Core/FwVol.c
@@ -48,6 +48,9 @@ FvIsBeingProcessed (
   MM driver and return its PE32 image.
 
   @param [in] FwVolHeader   Pointer to memory mapped FV
+  @param [in] Depth         Nesting depth of encapsulation sections. Callers
+                            different from MmCoreFfsFindMmDriver() are
+                            responsible for passing in a zero Depth.
 
   @retval  EFI_SUCCESS            Success.
   @retval  EFI_INVALID_PARAMETER  Invalid parameter.
@@ -55,11 +58,15 @@ FvIsBeingProcessed (
   @retval  EFI_OUT_OF_RESOURCES   Out of resources.
   @retval  EFI_VOLUME_CORRUPTED   Firmware volume is corrupted.
   @retval  EFI_UNSUPPORTED        Operation not supported.
+  @retval  EFI_ABORTED            Recursion aborted because Depth has been
+                                  greater than or equal to
+                                  PcdFwVolMmMaxEncapsulationDepth.
 
 **/
 EFI_STATUS
 MmCoreFfsFindMmDriver (
-  IN  EFI_FIRMWARE_VOLUME_HEADER  *FwVolHeader
+  IN  EFI_FIRMWARE_VOLUME_HEADER  *FwVolHeader,
+  IN  UINT32                      Depth
   )
 {
   EFI_STATUS                  Status;
@@ -84,6 +91,11 @@ MmCoreFfsFindMmDriver (
 
   DEBUG ((DEBUG_INFO, "MmCoreFfsFindMmDriver - 0x%x\n", FwVolHeader));
 
+  if (Depth >= PcdGet32 (PcdFwVolMmMaxEncapsulationDepth)) {
+    DEBUG ((DEBUG_ERROR, "%a: recursion aborted due to nesting depth\n", __func__));
+    return EFI_ABORTED;
+  }
+
   if (FvHasBeenProcessed (FwVolHeader)) {
     return EFI_SUCCESS;
   }
@@ -172,7 +184,7 @@ MmCoreFfsFindMmDriver (
     }
 
     InnerFvHeader = (VOID *)(Section + 1);
-    Status        = MmCoreFfsFindMmDriver (InnerFvHeader);
+    Status        = MmCoreFfsFindMmDriver (InnerFvHeader, Depth + 1);
     if (EFI_ERROR (Status)) {
       goto FreeDstBuffer;
     }
diff --git a/StandaloneMmPkg/Core/StandaloneMmCore.c b/StandaloneMmPkg/Core/StandaloneMmCore.c
index d221f1d1115d..523ea0a632a1 100644
--- a/StandaloneMmPkg/Core/StandaloneMmCore.c
+++ b/StandaloneMmPkg/Core/StandaloneMmCore.c
@@ -11,7 +11,8 @@
 
 EFI_STATUS
 MmCoreFfsFindMmDriver (
-  IN  EFI_FIRMWARE_VOLUME_HEADER  *FwVolHeader
+  IN  EFI_FIRMWARE_VOLUME_HEADER  *FwVolHeader,
+  IN  UINT32                      Depth
   );
 
 EFI_STATUS
@@ -643,7 +644,7 @@ StandaloneMmMain (
   //
   DEBUG ((DEBUG_INFO, "Mm Dispatch StandaloneBfvAddress - 0x%08x\n", gMmCorePrivate->StandaloneBfvAddress));
   if (gMmCorePrivate->StandaloneBfvAddress != 0) {
-    MmCoreFfsFindMmDriver ((EFI_FIRMWARE_VOLUME_HEADER *)(UINTN)gMmCorePrivate->StandaloneBfvAddress);
+    MmCoreFfsFindMmDriver ((EFI_FIRMWARE_VOLUME_HEADER *)(UINTN)gMmCorePrivate->StandaloneBfvAddress, 0);
     MmDispatcher ();
   }
 
diff --git a/StandaloneMmPkg/Core/StandaloneMmCore.inf b/StandaloneMmPkg/Core/StandaloneMmCore.inf
index c44b9ff33303..02ecd68f37e2 100644
--- a/StandaloneMmPkg/Core/StandaloneMmCore.inf
+++ b/StandaloneMmPkg/Core/StandaloneMmCore.inf
@@ -76,6 +76,9 @@ [Guids]
   gEfiEventExitBootServicesGuid
   gEfiEventReadyToBootGuid
 
+[Pcd]
+  gStandaloneMmPkgTokenSpaceGuid.PcdFwVolMmMaxEncapsulationDepth    ##CONSUMES
+
 #
 # This configuration fails for CLANGPDB, which does not support PIE in the GCC
 # sense. Such however is required for ARM family StandaloneMmCore
diff --git a/StandaloneMmPkg/StandaloneMmPkg.dec b/StandaloneMmPkg/StandaloneMmPkg.dec
index 46784d94e421..c43632d6d8ae 100644
--- a/StandaloneMmPkg/StandaloneMmPkg.dec
+++ b/StandaloneMmPkg/StandaloneMmPkg.dec
@@ -48,3 +48,8 @@ [Guids]
   gEfiStandaloneMmNonSecureBufferGuid      = { 0xf00497e3, 0xbfa2, 0x41a1, { 0x9d, 0x29, 0x54, 0xc2, 0xe9, 0x37, 0x21, 0xc5 }}
   gEfiArmTfCpuDriverEpDescriptorGuid       = { 0x6ecbd5a1, 0xc0f8, 0x4702, { 0x83, 0x01, 0x4f, 0xc2, 0xc5, 0x47, 0x0a, 0x51 }}
 
+[PcdsFixedAtBuild, PcdsPatchableInModule]
+  ## Maximum permitted encapsulation levels of sections in a firmware volume,
+  #  in the MM phase. Minimum value is 1. Sections nested more deeply are rejected.
+  # @Prompt Maximum permitted FwVol section nesting depth (exclusive) in MM.
+  gStandaloneMmPkgTokenSpaceGuid.PcdFwVolMmMaxEncapsulationDepth|0x10|UINT32|0x00000001
-- 
2.29.2.windows.2



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