fix(folderwatcher): ignore stale inotify descriptors

Assisted-by: Codex:GPT-5
Signed-off-by: thstyl2000 <18458458+thstyl2000@users.noreply.github.com>

Author: thstyl2000

src/gui/folderwatcher_linux.cpp

@@ -168,7 +168,13 @@ void FolderWatcherPrivate::slotReceivedNotification(int fd)
             || fileName.startsWith(".sync_")) {
             continue;
         }
-        const QString p = _watchToPath[event->wd] + '/' + fileName;
+        const auto watchPathIt = _watchToPath.constFind(event->wd);
+        if (watchPathIt == _watchToPath.cend()) {
+            qCDebug(lcFolderWatcher) << "Ignoring event for unknown watch descriptor" << event->wd << fileName;
+            continue;
+        }
+
+        const QString p = *watchPathIt + '/' + fileName;
         _parent->changeDetected(p);
 
         if ((event->mask & (IN_MOVED_TO | IN_CREATE))

test/testinotifywatcher.cpp

@@ -10,7 +10,19 @@
 
 #include <QtTest>
 
+#include <QSignalSpy>
+#include <QTemporaryDir>
+
+#include <array>
+#include <climits>
+#include <sys/inotify.h>
+#include <unistd.h>
+
+#define private public
+#define protected public
 #include "folderwatcher_linux.h"
+#undef protected
+#undef private
 #include "common/utility.h"
 
 using namespace OCC;
@@ -64,6 +76,41 @@ private slots:
         QVERIFY2(ok, "findFoldersBelow failed.");
     }
 
+    void testStaleWatchDescriptorIsIgnored()
+    {
+        QTemporaryDir root;
+        QVERIFY2(root.isValid(), "failed to create temp dir");
+        QVERIFY(QDir(root.path()).mkpath("sentinel"));
+
+        FolderWatcher watcher;
+        watcher.init(root.path());
+        const auto initialWatchCount = watcher.testLinuxWatchCount();
+        QSignalSpy pathChangedSpy(&watcher, &FolderWatcher::pathChanged);
+        pathChangedSpy.clear();
+        QVERIFY(!watcher._d->_watchToPath.contains(INT_MAX));
+
+        std::array<int, 2> pipeFds {};
+        QVERIFY(::pipe(pipeFds.data()) == 0);
+
+        QByteArray payload(sizeof(inotify_event) + sizeof("lib"), '\0');
+        auto *event = reinterpret_cast<inotify_event *>(payload.data());
+        event->wd = INT_MAX;
+        event->mask = IN_CREATE;
+        event->cookie = 0;
+        event->len = sizeof("lib");
+        memcpy(event->name, "lib", sizeof("lib"));
+
+        QCOMPARE(::write(pipeFds[1], payload.constData(), payload.size()), payload.size());
+        watcher._d->slotReceivedNotification(pipeFds[0]);
+
+        ::close(pipeFds[0]);
+        ::close(pipeFds[1]);
+
+        QCOMPARE(watcher.testLinuxWatchCount(), initialWatchCount);
+        QCOMPARE(pathChangedSpy.count(), 0);
+        QVERIFY(!watcher._d->_watchToPath.contains(INT_MAX));
+    }
+
     void cleanupTestCase() {
         if( _root.startsWith(QDir::tempPath() )) {
            system( QStringLiteral("rm -rf %1").arg(_root).toLocal8Bit() );