fix: harden Ext2Mgr mount assigns and Ext2Srv pipe accept

Ext2Mgr/IMPROVEMENTS.md

@@ -0,0 +1,55 @@
+# Ext2Mgr / Ext2Srv — classic stack improvements
+
+Fixes and service changes that apply to the **regular** MFC **Ext2 Volume Manager** (`Ext2Mgr/`) and/or **Ext2Srv**, independent of the Iced port.
+
+Rebuild Ext2Mgr / reinstall Ext2Srv (`Scripts\build.ps1`, `Scripts\install_driver.ps1`) to pick these up. Optional Iced GUI comparisons live on the `ext2mgr-iced` branch under `ext2mgr_iced/PORT_IMPROVEMENTS.md`.
+
+---
+
+## Ext2Mgr (`Ext2Mgr/`)
+
+### Change Drive Letters — crash on non-EXT / Session Manager
+
+**Symptom:** Choosing **Session Manager DOS Devices** (or temporary DOS devices) for an NTFS/FAT partition could crash Ext2Mgr.
+
+**Cause:** `CMountPoints::AddMountPoint` in `MountPoints.cpp`:
+
+1. On successful Session Manager registry write it called `EndDialog(0)` **without returning**, so execution continued.
+2. It always ran `Ext2QueryExt2Property(Handle, EVP)` to store Ext2Fsd automount properties.
+3. For a **partition-selected** native volume, `EVP` stayed **NULL** (only set from `m_Volume` or an EXT `m_Part->Volume` branch) → null dereference.
+
+**Fix:**
+
+- `return TRUE` immediately after a successful Session Manager assign + `EndDialog`.
+- If `EVP` is NULL, **skip** the Ext2 property IOCTL path and only assign the DOS letter (`Ext2AssignDrvLetter`), then update letter masks / notify.
+
+**Note:** Classic assign remains `DefineDosDevice` to `\Device\HarddiskVolumeN` (same path Session Manager uses). This fix is **crash safety** only.
+
+---
+
+## Ext2Srv (`Ext2Srv/`)
+
+These pipe-server changes help **both** Ext2Mgr and `ext2mgr_iced` (temporary EXT letter ops via `\\.\pipe\EXT2MGR_PSRV`).
+
+| Change | File | What |
+|--------|------|------|
+| Dual idle pipe listeners | `Ext2Pipe.cpp` (`Ext2StartPipeSrv`) | Second `Ext2PipeEngine` thread so reconnect / overlap rarely hits `ERROR_PIPE_BUSY` |
+| Soft create retries | `Ext2Pipe.cpp` (`Ext2PipeEngine`) | Cap create failures at 3×50ms (+ short sleep) instead of long backoff storms |
+| No `FILE_FLAG_WRITE_THROUGH` | `Ext2Pipe.cpp` (`Ext2CreatePipe`) | Dropped on tiny IPC messages; measured after reinstall (2026-07-28): cold connect median ~0.7 ms, burst reconnect ~0.2 ms, `QUERY_DRV` ~0.1 ms (query-only probe) |
+
+---
+
+## Intentionally not changed here
+
+| Topic | Status |
+|-------|--------|
+| Mount Manager for NTFS in classic Ext2Mgr | Not needed for Explorer when Session Manager / DosDevice targets `\Device\HarddiskVolumeN`. Classic UI still forces DosDev (`#if TRUE` in `MountPoints.cpp`). |
+| EXT-only “Assign Drive Letter” gating | Iced-only (classic still offers assign more broadly and can wait on Ext2Srv). |
+| Dead-letter detection breadth | Iced lists more orphans; classic logic unchanged. |
+
+---
+
+## Related docs
+
+- [`../README.md`](../README.md) — fork build/install scripts and driver changelog
+- `ext2mgr_iced/` on branch `ext2mgr-iced` — optional Iced GUI port

Ext2Mgr/MountPoints.cpp

@@ -123,6 +123,7 @@ CMountPoints::AddMountPoint(
         if (Ext2SetRegistryMountPoint(&drvChar, devPath, bRegistry)) {
             Ext2AssignDrvLetter(drvLetter, devPath, FALSE);
             EndDialog(0);
+            return TRUE;
         } else {
             str.Format("Failed to modify registry: SYSTEM\\CurrentControlSet\\Control\\Session Manager\\DOS Devices\n");
             AfxMessageBox(str, MB_OK|MB_ICONWARNING);
@@ -152,7 +153,42 @@ CMountPoints::AddMountPoint(
         }
     }
 
-    /* create an entry in regisgtry */
+    /* Ext2 property IOCTL — only for EXT volumes (EVP non-NULL).
+       NTFS/FAT hit this path via Change Drive Letters and used to crash
+       on Ext2QueryExt2Property(NULL). Assign the DOS letter only. */
+    if (!EVP) {
+        rc = Ext2AssignDrvLetter(drvLetter, devPath, bMountMgr);
+        if (!rc && !bMountMgr) {
+            CString str;
+            str.Format("Failed to assign new drive letter %c:\n", drvChar);
+            AfxMessageBox(str, MB_OK|MB_ICONWARNING);
+            return FALSE;
+        }
+        if (rc) {
+            m_bUpdated = TRUE;
+            if (m_Part) {
+                m_Part->DrvLetters |= letterMask;
+                if (m_Part->Volume) {
+                    m_Part->Volume->DrvLetters |= letterMask;
+                }
+                InitializeList(m_Part->DrvLetters);
+            }
+            if (m_Volume) {
+                m_Volume->DrvLetters |= letterMask;
+                InitializeList(m_Volume->DrvLetters);
+            }
+            if (m_Cdrom) {
+                m_Cdrom->DrvLetters |= letterMask;
+                InitializeList(m_Cdrom->DrvLetters);
+            }
+            m_MainDlg->SendMessage(
+                        WM_MOUNTPOINT_NOTIFY,
+                        'DA', (LPARAM)drvLetter->Letter);
+        }
+        return rc;
+    }
+
+    /* create an entry in registry (EXT only) */
     {
 
         NT::NTSTATUS status;

Ext2Srv/Ext2Pipe.cpp

@@ -151,8 +151,8 @@ Ext2CreatePipe()
 
     sa = Ext2CreateSA();
 
-    ap->p = CreateNamedPipe( _T(EXT2_MGR_SRV), PIPE_ACCESS_DUPLEX |
-                              FILE_FLAG_WRITE_THROUGH /* | ACCESS_SYSTEM_SECURITY */,
+    ap->p = CreateNamedPipe( _T(EXT2_MGR_SRV), PIPE_ACCESS_DUPLEX,
+                              /* no WRITE_THROUGH: tiny IPC messages; measure if needed */
                               PIPE_TYPE_BYTE | PIPE_READMODE_BYTE |
                               PIPE_WAIT /* PIPE_REJECT_REMOTE_CLIENTS */ ,
                               PIPE_UNLIMITED_INSTANCES,
@@ -429,21 +429,23 @@ Ext2PipeEngine(VOID *arg)
         /* create named pipe */
         ap = Ext2CreatePipe();
         if (NULL == ap) {
-            if (times++ < 10) {
-                Sleep(250 * times);
+            if (times++ < 3) {
+                Sleep(50);
                 goto retry;
             }
+            Sleep(100);
             continue;
         }
 
         /* ASSD_PIPE is valid or not */
         if (!ap->p || ap->p == INVALID_HANDLE_VALUE ||
             !ap->e || ap->e == INVALID_HANDLE_VALUE) {
             Ext2DestroyPipe(ap);
-            if (times++ < 10) {
-                Sleep(500);
+            if (times++ < 3) {
+                Sleep(50);
                 goto retry;
             }
+            Sleep(100);
             continue;
         }
 
@@ -498,6 +500,9 @@ DWORD Ext2StartPipeSrv()
         rc = WaitForSingleObject(g_wait, 1000*1);
     } while (rc == WAIT_TIMEOUT);
 
+    /* Second idle listener so a reconnect/overlap rarely hits PIPE_BUSY. */
+    _beginthread(Ext2PipeEngine, 0, NULL);
+
     return 0;
 }
 

Ext2Srv/Ext2Srv.cpp

@@ -318,13 +318,14 @@ Ext2SetupService(BOOL bInstall)
     if (bInstall) {
 
         // now create service entry for Ext2Mgr
+        // Note: SERVICE_INTERACTIVE_PROCESS removed - interactive services are deprecated
+        // and don't work on modern Windows (can't create named pipes accessible to user sessions)
         hService = CreateService(
                 hManager,                   // SCManager database
                 _T("Ext2Srv"),                 // name of service
                 _T("Ext2Fsd Service Manager"), // name to display
                 SERVICE_ALL_ACCESS,	        // desired access
-                SERVICE_WIN32_OWN_PROCESS | // service type
-                SERVICE_INTERACTIVE_PROCESS,
+                SERVICE_WIN32_OWN_PROCESS, // service type (removed SERVICE_INTERACTIVE_PROCESS)
                 SERVICE_AUTO_START,	        // start type
                 SERVICE_ERROR_NORMAL,       // error control type
 				Target,	                    // service's binary

Ext2Srv/Ext2Srv.rc

@@ -66,8 +66,8 @@ LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
 //
 
 VS_VERSION_INFO VERSIONINFO
- FILEVERSION 1,4,71,1
- PRODUCTVERSION 1,4,71,1
+ FILEVERSION 1,4,71,2
+ PRODUCTVERSION 1,4,71,2
  FILEFLAGSMASK 0x3fL
 #ifdef _DEBUG
  FILEFLAGS 0x1L
@@ -85,12 +85,12 @@ BEGIN
             VALUE "Comments", "Bo Branten <bosse@accum.se>"
             VALUE "CompanyName", "Ext2Fsd Group (www.ext2fsd.com)"
             VALUE "FileDescription", "Ext2Fsd Service"
-            VALUE "FileVersion", "1.4.71.1"
+            VALUE "FileVersion", "1.4.71.2"
             VALUE "InternalName", "Ext2Srv"
             VALUE "LegalCopyright", "Copyright (C) 2002-2017 Matt Wu <matt@ext2fsd.com>"
             VALUE "OriginalFilename", "Ext2Srv.exe"
             VALUE "ProductName", "Ext2Fsd Service"
-            VALUE "ProductVersion", "1.4.71.1"
+            VALUE "ProductVersion", "1.4.71.2"
         END
     END
     BLOCK "VarFileInfo"