From cd3ef0bf7d64dfa15c80abe8aac5458cb157dbb4 Mon Sep 17 00:00:00 2001
From: Michael Maltsev <4129781+m417z@users.noreply.github.com>
Date: Sat, 5 Apr 2025 16:50:07 +0300
Subject: [PATCH] Graceful handling for invalid target function

---
 Source/SlimDetours/Disassembler.c | 4 ++--
 Source/SlimDetours/Transaction.c  | 7 +++++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/Source/SlimDetours/Disassembler.c b/Source/SlimDetours/Disassembler.c
index b378544e..74d8e626 100644
--- a/Source/SlimDetours/Disassembler.c
+++ b/Source/SlimDetours/Disassembler.c
@@ -1058,9 +1058,9 @@ Invalid(
     UNREFERENCED_PARAMETER(pDisasm);
     UNREFERENCED_PARAMETER(pEntry);
     UNREFERENCED_PARAMETER(pbDst);
+    UNREFERENCED_PARAMETER(pbSrc);
 
-    ASSERT(!"Invalid Instruction");
-    return pbSrc + 1;
+    return NULL;
 }
 
 static
diff --git a/Source/SlimDetours/Transaction.c b/Source/SlimDetours/Transaction.c
index 53b7705b..51845de4 100644
--- a/Source/SlimDetours/Transaction.c
+++ b/Source/SlimDetours/Transaction.c
@@ -360,6 +360,13 @@ SlimDetoursAttach(
 
         DETOUR_TRACE(" SlimDetoursCopyInstruction(%p,%p)\n", pbTrampoline, pbSrc);
         pbSrc = (PBYTE)SlimDetoursCopyInstruction(pbTrampoline, pbSrc, NULL, &lExtra);
+        if (pbSrc == NULL)
+        {
+            Status = STATUS_ILLEGAL_INSTRUCTION;
+            DETOUR_BREAK();
+            goto fail;
+        }
+
         DETOUR_TRACE(" SlimDetoursCopyInstruction() = %p (%d bytes)\n", pbSrc, (int)(pbSrc - pbOp));
         pbTrampoline += (pbSrc - pbOp) + lExtra;
         cbTarget = PtrOffset(pbTarget, pbSrc);