Major changes:
- Added pooled + elastic work item model with retry/backoff (MAX_WI_RETRIES). removed semaphore usage.
- Introduced two completion threads to reduce contention and latency under heavy IO.
- Added BytesCompleted (per IRP) and ActualBytes (per fragment) for correct short read/write accounting. total read/write stats now reflect real transferred bytes instead of requested length.
- Moved decryption of read fragments into IO thread. completion threads now only finalize IRPs (reduces race window and simplifies flow).
- Deferred final IRP completion via FinalizeOriginalIrp to avoid inline IoCompleteRequest re-entrancy. added safe OOM inline fallback.
- Implemented work item pool drain & orderly shutdown (ActiveWorkItems + NoActiveWorkItemsEvent) with robust stop protocol.
- Replaced semaphore-based work item acquisition with spin lock + free list + event (WorkItemAvailableEvent). added exponential backoff for transient exhaustion.
- Added elastic (on-demand) work item allocation with pool vs dynamic origin tracking (FromPool).
- Added FreeCompletionWorkItemPool() for symmetric cleanup; ensured all threads are explicitly awakened during stop.
- Added second completion thread replacing single CompletionThread.
- Hardened UpdateBuffer: fixed parameter name typo, added bounds/overflow checks using IntSafe (ULongLongAdd), validated Count, guarded sector end computation.
- Fixed GPT/system region write protection logic to pass correct length instead of end offset.
- Ensured ASSERTs use fragment‑relative bounds (cast + length) and avoided mixed 64/32 comparisons.
- Added MAX_WI_RETRIES constant. added WiRetryCount field in EncryptedIoRequest.
- Ensured RemoveLock is released only after all queue/accounting updates (OnItemCompleted).
- Reset/read-ahead logic preserved. read-ahead trigger now based on actual completion & zero pending fragment count.
- General refactoring, clearer separation of concerns (TryAcquireCompletionWorkItem / FinalizeOriginalIrp / HandleCompleteOriginalIrp).
Safety / correctness improvements:
- Accurate short read handling (STATUS_END_OF_FILE with true byte count).
- Eliminated risk of double free or premature RemoveLock release on completion paths.
- Prevented potential overflow in sector end arithmetic.
- Reduced contention and potential deadlock scenarios present with previous semaphore wait path.
- Document HIGH_LEVEL constraints and rationale for pre-building a nonpaged scratch MDL.
- Allocate contiguous scratch buffer with conservative PFN cap (0x7FFFFFFFFFF) and fall back to unlimited cap if needed.
- Replace ASSERT with TC_BUG_CHECK for validation of write MDL mapping at HIGH_LEVEL.
- Safely copy PFNs from prebuilt MDL into caller MDL: compute dst/src page counts, check capacity, copy exact PFNs and retarget MDL header fields (preserve MdlFlags).
- Make DumpData cleanup defensive in unload path.
- comments improvements for clarity and maintainability.
* Prefer allocations to be non-executable
* Remove and reimplement DDIs inappropriately called inside HIGH_LEVEL IRQL routines
* Refactor hibernate context to be passed around in the passed FILTER_EXTENSION pointer rather than global
Replaced hardcoded 0x56455241 ('VERA') with TC_HEADER_MAGIC for better readability and maintainability.
Also replaced 0x5645524142455854 with TC_BOOT_DRIVE_FILTER_EXTENSION_MAGIC and added 'ULL' suffix for 64-bit safety.
Now we properly honor the AllowDefrag configuration.
This regression introduced other issues because, in order to allow defragmentation, we must provide Windows with an actual physical disk number. As a result, we assign the number of the physical disk where the VeraCrypt volume resides. This, in turn, causes Windows to send IOCTLs directly to this disk instead of to VeraCrypt. If these IOCTLs return values and properties not supported by VeraCrypt, inconsistencies arise, leading to failures.
* refactor: use UNMOUNT instead of DISMOUNT in code
This change updates the term DISMOUNT in constants to UNMOUNT.
Other occurrences (e.g. variable names) are left alone for now.
* refactor(ui): use unmount instead of dismount
This change updates the GUI text and replaces dismount with unmount.
* docs: update term dismount -> unmount
* refactor(cmdline): add unmount
This change adds an argument 'unmount' for command line usage, while
trying to deprecate the old disnount argument.
The current dismount argument/flag will still work to not introduce
a breaking change.
* docs: mention that /dismount is deprecated
This change fixes the shorthand version of the argument /unmount
It also adds back the info for /dismount and that it is deprecated.
- Made the maximum work items count configurable to allow flexibility based on system needs.
- Increased the default value of max work items count to 1024 to better handle high-throughput scenarios.
- Queue write IRPs in system worker thread to avoid potential deadlocks in write scenarios.
Reduce the critical section protected by spinlock to only cover the list manipulation operation. Move the ActiveWorkItems counter decrement outside the spinlock using InterlockedDecrement, and separate event signaling from the locked section.
This change minimizes time spent at raised IRQL (DISPATCH_LEVEL) and reduces potential for lock contention.
There was a deadlock issue in the driver caused by the CompletionThreadProc function in EncryptedIoQueue.c:
https://sourceforge.net/p/veracrypt/discussion/general/thread/f6e7f623d0/?page=20&limit=25#8362
The driver uses a single thread (CompletionThreadProc) to process IRP completions. When IoCompleteRequest is called within this thread, it can result in new IRPs being generated (e.g., for pagefile operations) that are intercepted by the driver and queued back into the CompletionThreadQueue. Since CompletionThreadProc is the only thread processing this queue and is waiting on IoCompleteRequest, these new IRPs are not handled, leading to a system freeze.
To resolve this issue, the following changes have been made:
Deferred IRP Completion Using Pre-allocated Work Items:
- Introduced a pool of pre-allocated work items (COMPLETE_IRP_WORK_ITEM) to handle IRP completions without causing additional resource allocations that could trigger new IRPs.
- The CompletionThreadProc now queues IRP completions to these work items, which are processed in a different context using IoQueueWorkItem, preventing re-entrant IRPs from blocking the completion thread.
Thread-Safe Work Item Pool Management:
- Implemented a thread-safe mechanism using a semaphore (WorkItemSemaphore), spin lock (WorkItemLock), and a free list (FreeWorkItemsList) to manage the pool of work items.
- Threads acquire and release work items safely, and if all work items are busy, threads wait until one becomes available.
Reference Counting and Improved Stop Handling:
- Added an ActiveWorkItems counter to track the number of active work items.
- Modified EncryptedIoQueueStop to wait for all active work items to complete before proceeding with cleanup, ensuring a clean shutdown.
These changes address the deadlock issue by preventing CompletionThreadProc from being blocked by re-entrant IRPs generated during IoCompleteRequest. By deferring IRP completion to a different context using pre-allocated work items and managing resources properly, we avoid the deadlock and ensure that all IRPs are processed correctly.
Mounir IDRASSI
Charlie
Mounir IDRASSI
Bernard Ladenthin
Helmut K. C. Tessarek