QFileSystemEngine/Unix: avoid removing WasDeletedFlag

As the comment says, the flag can only come from a prior call that used
fstat() on the file descriptor, so don't remove it when we couldn't have
added it in the first place.

Pick-to: 6.10 6.9 6.8
Fixes: QTBUG-137438
Change-Id: Ia75e29d28665c334dea6fffdb498a99c416bc3ac
Reviewed-by: Lars Schmertmann <[email protected]>
Reviewed-by: Ahmad Samir <[email protected]>
Reviewed-by: Edward Welbourne <[email protected]>

3 files changed, 72 insertions, 0 deletions

diff --git a/src/corelib/io/qfilesystemengine_unix.cpp b/src/corelib/io/qfilesystemengine_unix.cpp
index 6f995fe082e..5a0be1d895e 100644
--- a/src/corelib/io/qfilesystemengine_unix.cpp
+++ b/src/corelib/io/qfilesystemengine_unix.cpp
@@ -893,6 +893,12 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
 {
     Q_CHECK_FILE_NAME(entry, false);
 
+    // Detection of WasDeletedAttribute is imperfect: in general, if we can
+    // successfully stat() or access() a file, it hasn't been deleted (though
+    // there are exceptions, like /proc/XXX/fd/ entries on Linux). So we have
+    // to restore this flag in case we fail to stat() anything.
+    auto hadBeenDeleted = data.entryFlags & QFileSystemMetaData::WasDeletedAttribute;
+
 #if defined(Q_OS_DARWIN)
     if (what & (QFileSystemMetaData::BundleType | QFileSystemMetaData::CaseSensitive)) {
         if (!data.hasFlags(QFileSystemMetaData::DirectoryType))
@@ -1103,6 +1109,11 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
     if (entryErrno != 0) {
         what &= ~QFileSystemMetaData::LinkType; // don't clear link: could be broken symlink
         data.clearFlags(what);
+
+        // see comment at the top
+        data.entryFlags |= hadBeenDeleted;
+        data.knownFlagsMask |= hadBeenDeleted;
+
         return false;
     }
     return true;
diff --git a/tests/auto/corelib/io/qfile/tst_qfile.cpp b/tests/auto/corelib/io/qfile/tst_qfile.cpp
index 781f64a31ab..66c3db2e2f0 100644
--- a/tests/auto/corelib/io/qfile/tst_qfile.cpp
+++ b/tests/auto/corelib/io/qfile/tst_qfile.cpp
@@ -228,6 +228,7 @@ private slots:
     void getCharFF();
     void remove_and_exists();
     void removeOpenFile();
+    void removedFileDoesntExist();
     void fullDisk();
     void writeLargeDataBlock_data();
     void writeLargeDataBlock();
@@ -2526,6 +2527,37 @@ void tst_QFile::removeOpenFile()
     }
 }
 
+void tst_QFile::removedFileDoesntExist()
+{
+#ifdef Q_OS_WIN
+    QSKIP("Not relevant for Windows - can't remove still-open files");
+#endif
+    QFile::remove("remove_unclosed.txt");
+    QFile f("remove_unclosed.txt");
+    QVERIFY(!f.exists());
+    bool opened = f.open(QIODevice::ReadWrite | QIODevice::Unbuffered);
+    QVERIFY(opened);
+    f.write("blah blah blah");
+
+    QVERIFY(f.exists());
+
+    // delete by path, not using f.remove() (that's tested above)
+    QVERIFY(QFile::remove(f.fileName()));
+    QVERIFY(!QFile::exists(f.fileName()));
+    QVERIFY(!f.exists());
+
+#ifdef Q_OS_LINUX
+    QString procPath = u"/proc/self/fd/"_s;
+    if (QFile::exists(procPath)) {
+        // reopen the deleted file
+        procPath += QString::number(f.handle());
+        QFile f2(procPath);
+        QVERIFY(f2.open(QIODevice::ReadOnly));
+        QVERIFY(!f2.exists());
+    }
+#endif
+}
+
 void tst_QFile::fullDisk()
 {
     QFile file("/dev/full");
diff --git a/tests/auto/corelib/io/qfileinfo/tst_qfileinfo.cpp b/tests/auto/corelib/io/qfileinfo/tst_qfileinfo.cpp
index 761f0552eec..e2190477441 100644
--- a/tests/auto/corelib/io/qfileinfo/tst_qfileinfo.cpp
+++ b/tests/auto/corelib/io/qfileinfo/tst_qfileinfo.cpp
@@ -141,6 +141,7 @@ private slots:
 
     void exists_data();
     void exists();
+    void deletedFileLinuxProcExists();
 
     void absolutePath_data();
     void absolutePath();
@@ -615,6 +616,34 @@ void tst_QFileInfo::exists()
         QVERIFY(!exists);
 }
 
+void tst_QFileInfo::deletedFileLinuxProcExists()
+{
+#ifdef Q_OS_LINUX
+    static const char msg[] = "Hello, World\n";
+    QFileInfo fi("/proc/self/fd/");
+    if (!fi.isDir())
+        QSKIP("/proc appears not to be mounted");
+
+    QFile f("removed_file.txt");
+    QVERIFY(f.open(QIODevice::ReadWrite | QIODevice::Unbuffered));
+    f.write(msg, strlen(msg));
+
+    fi.setFile(fi.filePath() + QString::number(f.handle()));
+    QVERIFY(fi.exists());
+    QCOMPARE(fi.size(), strlen(msg));
+
+    QFile::remove("removed_file.txt");
+    fi.refresh();
+    QVERIFY(fi.exists());
+
+    fi.refresh();
+    QCOMPARE(fi.size(), strlen(msg));   // this stats, so may change flags
+    QVERIFY(fi.exists());
+#else
+    QSKIP("Linux-only test");
+#endif
+}
+
 void tst_QFileInfo::absolutePath_data()
 {
     QTest::addColumn<QString>("file");