From 1ce48bf0400a708e94293e598103d810457cf1a8 Mon Sep 17 00:00:00 2001
From: Download-Fritz <download-fritz@outlook.com>
Date: Fri, 19 Oct 2018 14:10:46 +0200
Subject: [PATCH] OcMachoLib: Verify FileSize can handle at least the header
 and the minimal LC size.

---
 Library/OcMachoLib/Header.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/Library/OcMachoLib/Header.c b/Library/OcMachoLib/Header.c
index 8582e223..df88bd76 100644
--- a/Library/OcMachoLib/Header.c
+++ b/Library/OcMachoLib/Header.c
@@ -37,6 +37,7 @@ MachoInitializeContext (
   OUT OC_MACHO_CONTEXT      *Context
   )
 {
+  UINTN                   MinCommandsSize;
   UINTN                   TopOfCommands;
   UINTN                   Index;
   CONST MACH_LOAD_COMMAND *Command;
@@ -44,8 +45,11 @@ MachoInitializeContext (
   //
   // Verify MACH-O Header sanity.
   //
-  TopOfCommands = ((UINTN)MachHeader->Commands + MachHeader->CommandsSize);
-  if ((MachHeader->Signature != MACH_HEADER_64_SIGNATURE)
+  TopOfCommands   = ((UINTN)MachHeader->Commands + MachHeader->CommandsSize);
+  MinCommandsSize = (MachHeader->NumberOfCommands * sizeof (*MachHeader->Commands));
+  if ((FileSize < sizeof (*MachHeader))
+   || (MachHeader->Signature != MACH_HEADER_64_SIGNATURE)
+   || (MachHeader->CommandsSize < MinCommandsSize)
    || (TopOfCommands > ((UINTN)MachHeader + FileSize))) {
     return FALSE;
   }