fix: hardening of INI file handling for multi instances workflows

src/Config/Config.cpp

@@ -251,6 +251,48 @@ bool ReleaseFileLock(HANDLE hFile, OVERLAPPED& rOvrLpd)
     return bUnLocked;
 }
 
+// ============================================================================
+//
+//  Cross-instance INI save serialization
+//
+static HANDLE s_hMtxIniFileSave = NULL;
+
+static unsigned long _HashIniPath(LPCWSTR path)
+{
+    unsigned long hash = 5381;
+    for (; *path; ++path) {
+        WCHAR ch = *path;
+        if (ch >= L'A' && ch <= L'Z') { ch += 32; }
+        if (ch == L'/') { ch = L'\\'; }
+        hash = ((hash << 5) + hash) ^ (unsigned long)ch;
+    }
+    return hash;
+}
+
+extern "C" void InitIniFileSaveMutex(void)
+{
+    if (Path_IsEmpty(Paths.IniFile)) {
+        return;
+    }
+    if (IS_VALID_HANDLE(s_hMtxIniFileSave)) {
+        CloseHandle(s_hMtxIniFileSave);
+        s_hMtxIniFileSave = NULL;
+    }
+    WCHAR szMutexName[80];
+    unsigned long const hash = _HashIniPath(Path_Get(Paths.IniFile));
+    StringCchPrintfW(szMutexName, COUNTOF(szMutexName),
+                     L"Local\\Notepad3_INI_%08lX", hash);
+    s_hMtxIniFileSave = CreateMutexW(NULL, FALSE, szMutexName);
+}
+
+extern "C" void CloseIniFileSaveMutex(void)
+{
+    if (IS_VALID_HANDLE(s_hMtxIniFileSave)) {
+        CloseHandle(s_hMtxIniFileSave);
+        s_hMtxIniFileSave = NULL;
+    }
+}
+
 // ============================================================================
 
 static CSimpleIni s_TMPINI(s_bIsUTF8, s_bUseMultiKey, s_bUseMultiLine);
@@ -2437,6 +2479,15 @@ bool SaveAllSettings(bool bForceSaveSettings)
         return false;
     }
 
+    // Cross-instance serialization: acquire mutex so only one instance
+    // performs the load-modify-save cycle at a time.
+    DWORD dwMtxWait = WAIT_OBJECT_0;
+    if (IS_VALID_HANDLE(s_hMtxIniFileSave)) {
+        dwMtxWait = WaitForSingleObject(s_hMtxIniFileSave, 10000);
+    }
+    // Force fresh reload from disk to pick up changes from other instances
+    ResetIniFileCache();
+
     WCHAR tchMsg[80];
     GetLngString(IDS_MUI_SAVINGSETTINGS, tchMsg, COUNTOF(tchMsg));
 
@@ -2489,6 +2540,13 @@ bool SaveAllSettings(bool bForceSaveSettings)
 
     Globals.bIniFileFromScratch = false; // INI has content now
 
+    // Release cross-instance save mutex (INI is flushed to disk)
+    if (IS_VALID_HANDLE(s_hMtxIniFileSave)) {
+        if (dwMtxWait == WAIT_OBJECT_0 || dwMtxWait == WAIT_ABANDONED) {
+            ReleaseMutex(s_hMtxIniFileSave);
+        }
+    }
+
     // maybe separate INI files for Style-Themes
     if (Globals.uCurrentThemeIndex > 0) {
         Style_SaveSettings(bForceSaveSettings);

src/Config/Config.h

@@ -36,6 +36,9 @@ bool SaveWindowPositionSettings(bool bClearSettings);
 bool SaveAllSettings(bool bForceSaveSettings);
 void CmdSaveSettingsNow();
 
+void InitIniFileSaveMutex(void);
+void CloseIniFileSaveMutex(void);
+
 bool OpenSettingsFile(LPCSTR fctname);
 bool CloseSettingsFile(LPCSTR fctname, bool bSaveSettings);
 

src/Notepad3.c

@@ -1149,6 +1149,8 @@ int WINAPI wWinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance,
     }
     LoadSettings();
 
+    InitIniFileSaveMutex();
+
     PrivateSetCurrentProcessExplicitAppUserModelID(Settings2.AppUserModelID);
 
     (void)CoInitializeEx(NULL, COINIT_APARTMENTTHREADED | COINIT_SPEED_OVER_MEMORY);
@@ -3385,6 +3387,7 @@ LRESULT MsgEndSession(HWND hwnd, UINT umsg, WPARAM wParam, LPARAM lParam)
 
         // call SaveAllSettings() when Globals.hwndToolbar is still valid
         SaveAllSettings(false);
+        CloseIniFileSaveMutex();
 
         // Remove tray icon in any case
         ShowNotifyIcon(hwnd, false);