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Fix abortive close and use-after-free on Windows resource close - #3221
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FULL DISCLOSURE: this was written by LLMs, though with significant back and forth from me. I'm not a Windows dev, so I'm not super qualified to review the changes. It did pass the tests on a Windows VM. No UART to test on the VM though. As the changed zlib-gzip-test shows, this can prevent the last written data from being delivered across the pipe if it gets closed. (Though arguably still better than a use-after-free ;)) If we want pipes on windows to act the same as they do on Linux, we would need some special handling for it. Let me know if you think this is important, and I can follow up with some options. |
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No actionable comments were generated in the recent review. 🎉 ℹ️ Recent review info⚙️ Run configurationConfiguration used: Organization UI Review profile: CHILL Plan: Advanced Run ID: 📒 Files selected for processing (7)
Included review availability: Your plan provides up to 4 included reviews per hour; 3 remain after this review. WalkthroughThe change adds ChangesWindows overlapped I/O
Gzip test input handling
Priority: ⬆️ High Estimated code review effort: 3 (Moderate) | ~30 minutes Merge Risk: ⚪ Minimal · up to No concrete merge-blocking risk remains: Windows TCP writes preserve partial-send and backpressure behavior. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 10.71% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 56 functions across 9 files. (2 skipped: 2 unsupported.)
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Inline comments:
In `@src/resources/pipe_win.cc`:
- Line 85: Update WritePipeResource::send and the PRIMITIVE(write) path so
ERROR_IO_PENDING does not return the full buffer length before the overlapped
write completes. Retain overlapped_.cancel_and_wait(handle_) for
resource-lifetime safety, then await completion and return the full count only
on successful completion; otherwise propagate cancellation or failure as a short
write or error.
In `@src/resources/tcp_win.cc`:
- Line 157: Update TcpSocketResource::do_close to stop canceling pending TCP
writes via write_overlapped_.cancel_and_wait; retain reaping of pending WSARecv
operations, and allow an outstanding WSASend to complete naturally before
closesocket.
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📒 Files selected for processing (9)
src/event_sources/event_win.ccsrc/event_sources/event_win.hsrc/resources/pipe_win.ccsrc/resources/tcp_win.ccsrc/resources/uart_win.ccsrc/resources/udp_win.cctests/pipe-close-pending-write-test-compiler.toittests/tcp-write-close-test.toittests/zlib-gzip-test.toit
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Every Toit TCP socket keeps an overlapped WSARecv armed, and calling closesocket with one pending is an abortive close: the peer gets an RST and loses data it has not read yet. So `write` followed by `close` lost the payload on Windows while working on Linux and macOS. More generally, closing a handle cancels its pending overlapped operations, but the completion can be written into the OVERLAPPED after the close returns, when the resource has already been freed. Measured: almost always for pipe reads, on the peer's close for pending pipe writes, and a few percent of the time for UDP and TCP receives. Add WindowsOverlapped, which records whether the last operation issued with an OVERLAPPED started, and cancels and waits for it before the TCP, UDP, pipe and UART resources close their handles. An operation that fails synchronously is not waited for: the OVERLAPPED is not meaningful then, and waiting would hang. Cancellation completes promptly (under 0.2ms measured), so the wait on the event thread is bounded. Pipe and UART writes still report success once queued, so a write that is pending when the pipe or port is closed is now cancelled and its data is lost. Before, it was delivered, but its completion wrote into freed memory. TCP writes are not affected. zlib-gzip-test wrote to gzip's stdin and closed it immediately; give gzip a file instead. Add tests/tcp-write-close-test.toit, which writes and closes while the peer is not reading yet. It received 0 of 4101 bytes on Windows before this change. Add tests/pipe-close-pending-write-test-compiler.toit, which closes a child's stdin with a write pending and reallocates the freed memory. The stale completion wrote STATUS_PIPE_BROKEN into it on Windows before this change.
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Closing Windows TCP sockets with an overlapped receive armed can reset the peer and discard unread data. Closing TCP, UDP, pipe, and UART handles also allows pending completions to write into freed
OVERLAPPEDstructures.Add
WindowsOverlappedto track successfully issued operations and cancel/reap them before destroying their handles, events, and resources. Synchronous failures are not waited on, because no operation was started.TCP writes now use nonblocking
sendandFD_WRITEreadiness. Each primitive call retriessenddirectly; no cached write-readiness flag can overwrite anFD_WRITEnotification that arrives as a blocked send returns. They report only bytes accepted by the transport, handle partial writes and backpressure, and leave no queuedWSASendfor close to cancel. This also corrects the address length passed toconnectand closes the auxiliary socket event. Waiting for a pending send inside the shared event thread would stall unrelated I/O; nonblocking sends avoid that dependency. See Microsoft's send semantics.Add
pipe.write-resultto return the actual completed byte count, null while pending, or an asynchronous error. The existing write primitive retains its queued-count behavior for package compatibility. pkg-host#101 uses the new primitive to suspend the writing task until completion, serialize concurrent writers, and propagate cancellation/errors. Preventing pipe write-then-close data loss requires that companion package update. It remains draft until an SDK release includes the new primitive and its minimum SDK requirement can be updated.UART writes and older host packages still report queued writes; closing them may cancel pending data. The gzip test retains file input while the SDK tests use the released host package.
Validation:
FD_WRITEhandling before a would-block send returns: the original implementation fails to retry on a writable socket; the updated implementation accepts the next byte.