QLockFile: fix deadlock when the lock file is corrupted

[ChangeLog][QtCore][QLockFile] Fixed a deadlock when the lock file
is corrupted.

Task-number: QTBUG-44771
Change-Id: Ic490b09d70ff1cc1733b64949889a73720b2d0f3
Reviewed-by: David Faure <david.faure@kdab.com>

3 files changed, 33 insertions, 16 deletions

diff --git a/src/corelib/io/qlockfile_unix.cpp b/src/corelib/io/qlockfile_unix.cpp
index bf1015a7be..dc9f8f73c4 100644
--- a/src/corelib/io/qlockfile_unix.cpp
+++ b/src/corelib/io/qlockfile_unix.cpp
@@ -181,11 +181,11 @@ bool QLockFilePrivate::isApparentlyStale() const
 {
     qint64 pid;
     QString hostname, appname;
-    if (!getLockInfo(&pid, &hostname, &appname))
-        return false;
-    if (hostname.isEmpty() || hostname == QString::fromLocal8Bit(localHostName())) {
-        if (::kill(pid, 0) == -1 && errno == ESRCH)
-            return true; // PID doesn't exist anymore
+    if (getLockInfo(&pid, &hostname, &appname)) {
+        if (hostname.isEmpty() || hostname == QString::fromLocal8Bit(localHostName())) {
+            if (::kill(pid, 0) == -1 && errno == ESRCH)
+                return true; // PID doesn't exist anymore
+        }
     }
     const qint64 age = QFileInfo(fileName).lastModified().msecsTo(QDateTime::currentDateTime());
     return staleLockTime > 0 && age > staleLockTime;
diff --git a/src/corelib/io/qlockfile_win.cpp b/src/corelib/io/qlockfile_win.cpp
index f9f29090d7..3587c7bffe 100644
--- a/src/corelib/io/qlockfile_win.cpp
+++ b/src/corelib/io/qlockfile_win.cpp
@@ -115,21 +115,21 @@ bool QLockFilePrivate::isApparentlyStale() const
 {
     qint64 pid;
     QString hostname, appname;
-    if (!getLockInfo(&pid, &hostname, &appname))
-        return false;
 
     // On WinRT there seems to be no way of obtaining information about other
     // processes due to sandboxing
 #ifndef Q_OS_WINRT
-    if (hostname == QString::fromLocal8Bit(localHostName())) {
-        HANDLE procHandle = ::OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, pid);
-        if (!procHandle)
-            return true;
-        // We got a handle but check if process is still alive
-        DWORD dwR = ::WaitForSingleObject(procHandle, 0);
-        ::CloseHandle(procHandle);
-        if (dwR == WAIT_TIMEOUT)
-            return true;
+    if (getLockInfo(&pid, &hostname, &appname)) {
+        if (hostname == QString::fromLocal8Bit(localHostName())) {
+            HANDLE procHandle = ::OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, pid);
+            if (!procHandle)
+                return true;
+            // We got a handle but check if process is still alive
+            DWORD dwR = ::WaitForSingleObject(procHandle, 0);
+            ::CloseHandle(procHandle);
+            if (dwR == WAIT_TIMEOUT)
+                return true;
+        }
     }
 #endif // !Q_OS_WINRT
     const qint64 age = QFileInfo(fileName).lastModified().msecsTo(QDateTime::currentDateTime());
diff --git a/tests/auto/corelib/io/qlockfile/tst_qlockfile.cpp b/tests/auto/corelib/io/qlockfile/tst_qlockfile.cpp
index 77bef94550..12bea6769c 100644
--- a/tests/auto/corelib/io/qlockfile/tst_qlockfile.cpp
+++ b/tests/auto/corelib/io/qlockfile/tst_qlockfile.cpp
@@ -58,6 +58,7 @@ private slots:
     void staleLongLockFromBusyProcess();
     void staleLockRace();
     void noPermissions();
+    void corruptedLockFile();
 
 public:
     QString m_helperApp;
@@ -415,5 +416,21 @@ void tst_QLockFile::noPermissions()
     QCOMPARE(int(lockFile.error()), int(QLockFile::PermissionError));
 }
 
+void tst_QLockFile::corruptedLockFile()
+{
+    const QString fileName = dir.path() + "/corruptedLockFile";
+
+    {
+        // Create a empty file. Typically the result of a computer crash or hard disk full.
+        QFile file(fileName);
+        QVERIFY(file.open(QFile::WriteOnly));
+    }
+
+    QLockFile secondLock(fileName);
+    secondLock.setStaleLockTime(100);
+    QVERIFY(secondLock.tryLock(10000));
+    QCOMPARE(int(secondLock.error()), int(QLockFile::NoError));
+}
+
 QTEST_MAIN(tst_QLockFile)
 #include "tst_qlockfile.moc"