MdeModulePkg FvSimpleFileSystemDxe: Fix memory leak in Read function

FvSimpleFileSystem on read always allocates a FileBuffer, and never frees
it. This causes memory leaks. It is especially bad for reading scripts
line-by-line. In some cases memory leak can exceed 1GB.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Vladimir Olovyannikiov <vladimir.olovyannikov@broadcom.com>
Reviewed-by: Star Zeng <star.zeng@intel.com>

MdeModulePkg/Universal/FvSimpleFileSystemDxe/FvSimpleFileSystem.c

@@ -704,6 +704,7 @@ FvSimpleFileSystemRead (
 
     Status = FvFsReadFile (File->Instance->FvProtocol, File->FvFileInfo, &FileSize, &FileBuffer);
     if (EFI_ERROR (Status)) {
+      FreePool (FileBuffer);
       return EFI_DEVICE_ERROR;
     }
 
@@ -714,6 +715,8 @@ FvSimpleFileSystemRead (
     CopyMem (Buffer, (UINT8*)FileBuffer + File->Position, *BufferSize);
     File->Position += *BufferSize;
 
+    FreePool (FileBuffer);
+
     return EFI_SUCCESS;
   }
 }