StandaloneMmPkg/Core: Limit FwVol encapsulation section recursion

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>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>

1 files changed, 14 insertions, 2 deletions

diff --git a/StandaloneMmPkg/Core/FwVol.c b/StandaloneMmPkg/Core/FwVol.c
index 1f6d7714ba..e1e20ffd14 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;

     }