From 056865f59a0a04e4fe180deb562c4424fefc0bd5 Mon Sep 17 00:00:00 2001
From: John Reiser <jreiser@BitWagon.com>
Date: Tue, 4 Jun 2024 08:55:46 -0700
Subject: [PATCH] Detect bad placement of LINK segment

https://github.com/upx/upx/issues/827
	modified:   p_mach.cpp
---
 src/p_mach.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/p_mach.cpp b/src/p_mach.cpp
index a26ac67a..3a66c617 100644
--- a/src/p_mach.cpp
+++ b/src/p_mach.cpp
@@ -1754,6 +1754,10 @@ tribool PackMachBase<T>::canUnpack()
         else { // PackHeader follows loader at __LINKEDIT
             if ((off_t)bufsize > (fi->st_size() - offLINK)) {
                 bufsize = fi->st_size() - offLINK;
+                if (bufsize < sizeof(struct b_info)) {
+                    throwCantUnpack("bad offLINK %p %p",
+                        (void *)offLINK, (void *)file_size);
+                }
             }
             fi->seek(offLINK, SEEK_SET);
         }