QFileSystemEngine: verify that the file name isn't empty

Making system calls with empty file names is not a good idea. When you
run qmake $srcdir, you see this in strace:

 stat("", 0x7ffed229e250)                = -1 ENOENT (No such file or directory)
(twice)

I've also inlined the isEmpty() function for better code generation.

Some functions take QSystemError and some don't. That needs to be
corrected at some point, possibly with something like std::expected.

Change-Id: I1eba2b016de74620bfc8fffd14ccbfa162f93631
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

src/corelib/io/qfilesystemengine_unix.cpp

@@ -95,6 +95,13 @@ static int statx(int dirfd, const char *pathname, int flag, unsigned mask, struc
 
 QT_BEGIN_NAMESPACE
 
+#define emptyFileEntryWarning() emptyFileEntryWarning_(QT_MESSAGELOG_FILE, QT_MESSAGELOG_LINE, QT_MESSAGELOG_FUNC)
+static void emptyFileEntryWarning_(const char *file, int line, const char *function)
+{
+    QMessageLogger(file, line, function).warning("Empty filename passed to function");
+    errno = EINVAL;
+}
+
 #if defined(Q_OS_DARWIN)
 static inline bool hasResourcePropertyFlag(const QFileSystemMetaData &data,
                                            const QFileSystemEntry &entry,
@@ -602,6 +609,9 @@ void QFileSystemMetaData::fillFromDirEnt(const QT_DIRENT &entry)
 //static
 QFileSystemEntry QFileSystemEngine::getLinkTarget(const QFileSystemEntry &link, QFileSystemMetaData &data)
 {
+    if (Q_UNLIKELY(link.isEmpty()))
+        return emptyFileEntryWarning(), link;
+
     QByteArray s = qt_readlink(link.nativeFilePath().constData());
     if (s.length() > 0) {
         QString ret;
@@ -666,7 +676,9 @@ QFileSystemEntry QFileSystemEngine::getLinkTarget(const QFileSystemEntry &link,
 //static
 QFileSystemEntry QFileSystemEngine::canonicalName(const QFileSystemEntry &entry, QFileSystemMetaData &data)
 {
-    if (entry.isEmpty() || entry.isRoot())
+    if (Q_UNLIKELY(entry.isEmpty()))
+        return emptyFileEntryWarning(), entry;
+    if (entry.isRoot())
         return entry;
 
 #if !defined(Q_OS_MAC) && !defined(Q_OS_QNX) && !defined(Q_OS_ANDROID) && !defined(Q_OS_HAIKU) && _POSIX_VERSION < 200809L
@@ -733,6 +745,8 @@ QFileSystemEntry QFileSystemEngine::canonicalName(const QFileSystemEntry &entry,
 //static
 QFileSystemEntry QFileSystemEngine::absoluteName(const QFileSystemEntry &entry)
 {
+    if (Q_UNLIKELY(entry.isEmpty()))
+        return emptyFileEntryWarning(), entry;
     if (entry.isAbsolute() && entry.isClean())
         return entry;
 
@@ -766,6 +780,9 @@ QFileSystemEntry QFileSystemEngine::absoluteName(const QFileSystemEntry &entry)
 //static
 QByteArray QFileSystemEngine::id(const QFileSystemEntry &entry)
 {
+    if (Q_UNLIKELY(entry.isEmpty()))
+        return emptyFileEntryWarning(), QByteArray();
+
     QT_STATBUF statResult;
     if (QT_STAT(entry.nativeFilePath().constData(), &statResult)) {
         if (errno != ENOENT)
@@ -873,6 +890,9 @@ QString QFileSystemEngine::bundleName(const QFileSystemEntry &entry)
 bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemMetaData &data,
         QFileSystemMetaData::MetaDataFlags what)
 {
+    if (Q_UNLIKELY(entry.isEmpty()))
+        return emptyFileEntryWarning(), false;
+
 #if defined(Q_OS_DARWIN)
     if (what & QFileSystemMetaData::BundleType) {
         if (!data.hasFlags(QFileSystemMetaData::DirectoryType))
@@ -1083,6 +1103,8 @@ static bool createDirectoryWithParents(const QByteArray &nativeName, bool should
 bool QFileSystemEngine::createDirectory(const QFileSystemEntry &entry, bool createParents)
 {
     QString dirName = entry.filePath();
+    if (Q_UNLIKELY(dirName.isEmpty()))
+        return emptyFileEntryWarning(), false;
 
     // Darwin doesn't support trailing /'s, so remove for everyone
     while (dirName.size() > 1 && dirName.endsWith(QLatin1Char('/')))
@@ -1101,6 +1123,9 @@ bool QFileSystemEngine::createDirectory(const QFileSystemEntry &entry, bool crea
 //static
 bool QFileSystemEngine::removeDirectory(const QFileSystemEntry &entry, bool removeEmptyParents)
 {
+    if (Q_UNLIKELY(entry.isEmpty()))
+        return emptyFileEntryWarning(), false;
+
     if (removeEmptyParents) {
         QString dirName = QDir::cleanPath(entry.filePath());
         for (int oldslash = 0, slash=dirName.length(); slash > 0; oldslash = slash) {
@@ -1124,6 +1149,8 @@ bool QFileSystemEngine::removeDirectory(const QFileSystemEntry &entry, bool remo
 //static
 bool QFileSystemEngine::createLink(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error)
 {
+    if (Q_UNLIKELY(source.isEmpty() || target.isEmpty()))
+        return emptyFileEntryWarning(), false;
     if (::symlink(source.nativeFilePath().constData(), target.nativeFilePath().constData()) == 0)
         return true;
     error = QSystemError(errno, QSystemError::StandardLibraryError);
@@ -1158,6 +1185,8 @@ bool QFileSystemEngine::renameFile(const QFileSystemEntry &source, const QFileSy
 {
     QFileSystemEntry::NativePath srcPath = source.nativeFilePath();
     QFileSystemEntry::NativePath tgtPath = target.nativeFilePath();
+    if (Q_UNLIKELY(srcPath.isEmpty() || tgtPath.isEmpty()))
+        return emptyFileEntryWarning(), false;
 
 #if defined(RENAME_NOREPLACE) && (QT_CONFIG(renameat2) || defined(SYS_renameat2))
     if (renameat2(AT_FDCWD, srcPath, AT_FDCWD, tgtPath, RENAME_NOREPLACE) == 0)
@@ -1227,6 +1256,8 @@ bool QFileSystemEngine::renameFile(const QFileSystemEntry &source, const QFileSy
 //static
 bool QFileSystemEngine::renameOverwriteFile(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error)
 {
+    if (Q_UNLIKELY(source.isEmpty() || target.isEmpty()))
+        return emptyFileEntryWarning(), false;
     if (::rename(source.nativeFilePath().constData(), target.nativeFilePath().constData()) == 0)
         return true;
     error = QSystemError(errno, QSystemError::StandardLibraryError);
@@ -1236,6 +1267,8 @@ bool QFileSystemEngine::renameOverwriteFile(const QFileSystemEntry &source, cons
 //static
 bool QFileSystemEngine::removeFile(const QFileSystemEntry &entry, QSystemError &error)
 {
+    if (Q_UNLIKELY(entry.isEmpty()))
+        return emptyFileEntryWarning(), false;
     if (unlink(entry.nativeFilePath().constData()) == 0)
         return true;
     error = QSystemError(errno, QSystemError::StandardLibraryError);
@@ -1270,8 +1303,10 @@ static mode_t toMode_t(QFile::Permissions permissions)
 //static
 bool QFileSystemEngine::setPermissions(const QFileSystemEntry &entry, QFile::Permissions permissions, QSystemError &error, QFileSystemMetaData *data)
 {
-    mode_t mode = toMode_t(permissions);
+    if (Q_UNLIKELY(entry.isEmpty()))
+        return emptyFileEntryWarning(), false;
 
+    mode_t mode = toMode_t(permissions);
     bool success = ::chmod(entry.nativeFilePath().constData(), mode) == 0;
     if (success && data) {
         data->entryFlags &= ~QFileSystemMetaData::Permissions;

src/corelib/io/qfilesystementry.cpp

@@ -331,11 +331,6 @@ bool QFileSystemEntry::isRoot() const
     return isRootPath(m_filePath);
 }
 
-bool QFileSystemEntry::isEmpty() const
-{
-    return m_filePath.isEmpty() && m_nativeFilePath.isEmpty();
-}
-
 // private methods
 
 void QFileSystemEntry::findLastSeparator() const

src/corelib/io/qfilesystementry_p.h

@@ -98,7 +98,10 @@ public:
 #endif
     bool isRoot() const;
 
-    bool isEmpty() const;
+    bool isEmpty() const
+    {
+        return m_filePath.isEmpty() && m_nativeFilePath.isEmpty();
+    }
     void clear()
     {
         *this = QFileSystemEntry();