Improve robustness of qml disk caching

Perform various basic checks before proceeding to load an existing cache file,
including the qt version, architecture, data structure version and others.

Change-Id: Ie822b056e944ac120643aad260e97f62616688bf
Reviewed-by: Erik Verbruggen <erik.verbruggen@qt.io>

1 files changed, 50 insertions, 5 deletions

diff --git a/src/qml/compiler/qv4compileddata.cpp b/src/qml/compiler/qv4compileddata.cpp
index 1bcd6892d2..965924262d 100644
--- a/src/qml/compiler/qv4compileddata.cpp
+++ b/src/qml/compiler/qv4compileddata.cpp
@@ -331,20 +331,56 @@ bool CompilationUnit::saveToDisk(QString *errorString)
     return true;
 }
 
-bool CompilationUnit::loadFromDisk(const QUrl &url, QString *errorString)
+bool CompilationUnit::loadFromDisk(const QUrl &url, EvalISelFactory *iselFactory, QString *errorString)
 {
     if (!url.isLocalFile()) {
         *errorString = QStringLiteral("File has to be a local file.");
         return false;
     }
 
-    QScopedPointer<QFile> cacheFile(new QFile(url.toLocalFile() + QLatin1Char('c')));
+    const QString sourcePath = url.toLocalFile();
+    QScopedPointer<QFile> cacheFile(new QFile(sourcePath + QLatin1Char('c')));
 
     if (!cacheFile->open(QIODevice::ReadOnly)) {
         *errorString = cacheFile->errorString();
         return false;
     }
 
+    {
+        CompiledData::Unit header;
+        qint64 bytesRead = cacheFile->read(reinterpret_cast<char *>(&header), sizeof(header));
+
+        if (bytesRead != sizeof(header)) {
+            *errorString = QStringLiteral("File too small for the header fields");
+            return false;
+        }
+
+        if (strncmp(header.magic, CompiledData::magic_str, sizeof(header.magic))) {
+            *errorString = QStringLiteral("Magic bytes in the header do not match");
+            return false;
+        }
+
+        if (header.version != quint32(QV4_DATA_STRUCTURE_VERSION)) {
+            *errorString = QString::fromUtf8("V4 data structure version mismatch. Found %1 expected %2").arg(header.version, 0, 16).arg(QV4_DATA_STRUCTURE_VERSION, 0, 16);
+            return false;
+        }
+
+        if (header.qtVersion != quint32(QT_VERSION)) {
+            *errorString = QString::fromUtf8("Qt version mismatch. Found %1 expected %2").arg(header.qtVersion, 0, 16).arg(QT_VERSION, 0, 16);
+            return false;
+        }
+
+        {
+            QFileInfo sourceCode(sourcePath);
+            if (sourceCode.exists() && sourceCode.lastModified().toMSecsSinceEpoch() != header.sourceTimeStamp) {
+                *errorString = QStringLiteral("QML source file has a different time stamp than cached file.");
+                return false;
+            }
+        }
+
+    }
+    // Data structure and qt version matched, so now we can access the rest of the file safely.
+
     uchar *cacheData = cacheFile->map(/*offset*/0, cacheFile->size());
     if (!cacheData) {
         *errorString = cacheFile->errorString();
@@ -354,13 +390,22 @@ bool CompilationUnit::loadFromDisk(const QUrl &url, QString *errorString)
     QScopedValueRollback<const Unit *> dataPtrChange(data, reinterpret_cast<const Unit *>(cacheData));
 
     {
-        QFileInfo sourceCode(url.toLocalFile());
-        if (sourceCode.exists() && sourceCode.lastModified().toMSecsSinceEpoch() != data->sourceTimeStamp) {
-            *errorString = QStringLiteral("QML source file has a different time stamp than cached file.");
+        const QString foundArchitecture = stringAt(data->architectureIndex);
+        const QString expectedArchitecture = QSysInfo::buildAbi();
+        if (foundArchitecture != expectedArchitecture) {
+            *errorString = QString::fromUtf8("Architecture mismatch. Found %1 expected %2").arg(foundArchitecture).arg(expectedArchitecture);
             return false;
         }
     }
 
+    {
+        const QString foundCodeGenerator = stringAt(data->codeGeneratorIndex);
+        const QString expectedCodeGenerator = iselFactory->codeGeneratorName;
+        if (foundCodeGenerator != expectedCodeGenerator) {
+            *errorString = QString::fromUtf8("Code generator mismatch. Found code generated by %1 but expected %2").arg(foundCodeGenerator).arg(expectedCodeGenerator);
+            return false;
+        }
+    }
 
     if (!memoryMapCode(errorString))
         return false;