From 0904161f6f051b9f42ffa65b1f9aa4a5b29e2119 Mon Sep 17 00:00:00 2001
From: Wei6 Xu <wei6.xu@intel.com>
Date: Mon, 30 Oct 2023 11:07:13 +0800
Subject: [PATCH] StandaloneMmPkg/Core: Fix potential memory leak issue

In MmCoreFfsFindMmDriver(),
- ScratchBuffer is not freed in the error return path that DstBuffer page
allocation fails. Free ScratchBuffer before return with error.
- If the decoded buffer is identical to the data in InputSection,
ExtractGuidedSectionDecode() will change the value of DstBuffer rather
than changing the contents of the buffer that DstBuffer points at, in
which case freeing DstBuffer is wrong. Introduce a local variable
AllocatedDstBuffer for buffer free, free AllocatedDstBuffer immediately
if it is not used.

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>
---
 StandaloneMmPkg/Core/FwVol.c | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/StandaloneMmPkg/Core/FwVol.c b/StandaloneMmPkg/Core/FwVol.c
index e1e20ffd14..c3054ef751 100644
--- a/StandaloneMmPkg/Core/FwVol.c
+++ b/StandaloneMmPkg/Core/FwVol.c
@@ -84,6 +84,7 @@ MmCoreFfsFindMmDriver (
   UINT32                      DstBufferSize;
   VOID                        *ScratchBuffer;
   UINT32                      ScratchBufferSize;
+  VOID                        *AllocatedDstBuffer;
   VOID                        *DstBuffer;
   UINT16                      SectionAttribute;
   UINT32                      AuthenticationStatus;
@@ -148,25 +149,35 @@ MmCoreFfsFindMmDriver (
     //
     // Allocate destination buffer, extra one page for adjustment
     //
-    DstBuffer = (VOID *)(UINTN)AllocatePages (EFI_SIZE_TO_PAGES (DstBufferSize));
-    if (DstBuffer == NULL) {
+    AllocatedDstBuffer = (VOID *)(UINTN)AllocatePages (EFI_SIZE_TO_PAGES (DstBufferSize));
+    if (AllocatedDstBuffer == NULL) {
+      FreePages (ScratchBuffer, EFI_SIZE_TO_PAGES (ScratchBufferSize));
       return EFI_OUT_OF_RESOURCES;
     }
 
     //
     // Call decompress function
     //
-    Status = ExtractGuidedSectionDecode (
-               Section,
-               &DstBuffer,
-               ScratchBuffer,
-               &AuthenticationStatus
-               );
+    DstBuffer = AllocatedDstBuffer;
+    Status    = ExtractGuidedSectionDecode (
+                  Section,
+                  &DstBuffer,
+                  ScratchBuffer,
+                  &AuthenticationStatus
+                  );
     FreePages (ScratchBuffer, EFI_SIZE_TO_PAGES (ScratchBufferSize));
     if (EFI_ERROR (Status)) {
       goto FreeDstBuffer;
     }
 
+    //
+    // Free allocated DstBuffer if it is not used
+    //
+    if (DstBuffer != AllocatedDstBuffer) {
+      FreePages (AllocatedDstBuffer, EFI_SIZE_TO_PAGES (DstBufferSize));
+      AllocatedDstBuffer = NULL;
+    }
+
     DEBUG ((
       DEBUG_INFO,
       "Processing compressed firmware volume (AuthenticationStatus == %x)\n",
@@ -210,7 +221,9 @@ MmCoreFfsFindMmDriver (
   return EFI_SUCCESS;
 
 FreeDstBuffer:
-  FreePages (DstBuffer, EFI_SIZE_TO_PAGES (DstBufferSize));
+  if (AllocatedDstBuffer != NULL) {
+    FreePages (AllocatedDstBuffer, EFI_SIZE_TO_PAGES (DstBufferSize));
+  }
 
   return Status;
 }