Windows: guard against closing the connection while processing incoming data

Before the patch we could end up using an already deleted
QWinOverlappedIoNotifier instance if the incoming queue has more than
one message, and the user decides to close the connection (and so delete
the notifier) before processing all of them.

This patch adds an explicit check that the QWinOverlappedIoNotifier
instance is still valid.

This commit amends f3a306a30fc4f40d1c96fee0ed44517fe8b43d76

Task-number: QTBUG-101444
Change-Id: Ieae622d248629827ed627bc9c17f7b5be491b717
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>
(cherry picked from commit 089f1cd197e93c216aae094ffbca2b4beacf57b8)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/serialport/qwinoverlappedionotifier.cpp b/src/serialport/qwinoverlappedionotifier.cpp
index 65d63bba..06f2b614 100644
--- a/src/serialport/qwinoverlappedionotifier.cpp
+++ b/src/serialport/qwinoverlappedionotifier.cpp
@@ -382,9 +382,12 @@ void QWinOverlappedIoNotifierPrivate::_q_notified()
         QQueue<IOResult> values;
         results.swap(values);
         ReleaseMutex(hResultsMutex);
-        while (!values.empty()) {
+        // 'q' can go out of scope if the user decides to close the serial port
+        // while processing some answer. So we need to guard against that.
+        QPointer<QWinOverlappedIoNotifier> qptr(q);
+        while (!values.empty() && qptr) {
             IOResult ioresult = values.dequeue();
-            emit q->notified(ioresult.numberOfBytes, ioresult.errorCode, ioresult.overlapped);
+            emit qptr->notified(ioresult.numberOfBytes, ioresult.errorCode, ioresult.overlapped);
         }
     }
 }