From 6bc2ea5d2b0b6fbfe2ba62cdb425d6dc0992b10f Mon Sep 17 00:00:00 2001
From: Valentin Radu <valentin.radu@valinet.ro>
Date: Mon, 20 Mar 2023 23:58:32 +0200
Subject: [PATCH] All: Fix crash when attempting to hook function on older OS
 builds

`RtlQueryFeatureConfiguration` is not available on old Windows 10
builds, like 17763 (LTSC 2019).
Related issue: https://github.com/valinet/ExplorerPatcher/discussions/1142
---
 ExplorerPatcher/dllmain.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/ExplorerPatcher/dllmain.c b/ExplorerPatcher/dllmain.c
index 5b85cd6c0..eff4795cf 100644
--- a/ExplorerPatcher/dllmain.c
+++ b/ExplorerPatcher/dllmain.c
@@ -10161,15 +10161,17 @@ DWORD Inject(BOOL bIsExplorer)
     }
 
     RtlQueryFeatureConfigurationFunc = GetProcAddress(GetModuleHandleW(L"ntdll.dll"), "RtlQueryFeatureConfiguration");
-    rv = funchook_prepare(
-        funchook,
-        (void**)&RtlQueryFeatureConfigurationFunc,
-        RtlQueryFeatureConfigurationHook
-    );
-    if (rv != 0)
-    {
-        FreeLibraryAndExitThread(hModule, rv);
-        return FALSE;
+    if (RtlQueryFeatureConfigurationFunc) {
+        rv = funchook_prepare(
+            funchook,
+            (void**)&RtlQueryFeatureConfigurationFunc,
+            RtlQueryFeatureConfigurationHook
+        );
+        if (rv != 0)
+        {
+            FreeLibraryAndExitThread(hModule, rv);
+            return FALSE;
+        }
     }
     printf("Setup ntdll functions done\n");