Revision control
++ // Copyright (C) 2016 The Qt Company Ltd.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
++ // Qt-Security score:significant
++
++ #include "qv4compilationunitmapper_p.h"
++
++ #include <private/qcore_unix_p.h>
++ #include <private/qv4compileddata_p.h>
++
++ #include <QtCore/qscopeguard.h>
++ #include <QtCore/qdatetime.h>
++
++ #include <functional>
++ #include <sys/mman.h>
++
++ QT_BEGIN_NAMESPACE
++
++ using namespace QV4;
++
++ CompiledData::Unit *CompilationUnitMapper::open(const QString &cacheFileName, const QDateTime &sourceTimeStamp, QString *errorString)
++ {
++ close();
++
++ int fd = qt_safe_open(QFile::encodeName(cacheFileName).constData(), O_RDONLY);
++ if (fd == -1) {
++ *errorString = qt_error_string(errno);
++ return nullptr;
++ }
++
++ auto cleanup = qScopeGuard([fd]{
++ qt_safe_close(fd) ;
++ });
++
++ CompiledData::Unit header;
++ qint64 bytesRead = qt_safe_read(fd, reinterpret_cast<char *>(&header), sizeof(header));
++
++ if (bytesRead != sizeof(header)) {
++ *errorString = QStringLiteral("File too small for the header fields");
++ return nullptr;
++ }
++
++ if (!header.verifyHeader(sourceTimeStamp, errorString))
++ return nullptr;
++
++ // Data structure and qt version matched, so now we can access the rest of the file safely.
++
++ length = static_cast<size_t>(lseek(fd, 0, SEEK_END));
++ /* Error out early on file corruption. We assume we can read header.unitSize bytes
++ later (even before verifying the checksum), potentially causing out-of-bound
++ reads
++ Also, no need to wait until checksum verification if we know beforehand
++ that the cached unit is bogus
++ */
++ if (length != header.unitSize) {
++ *errorString = QStringLiteral("Potential file corruption, file too small");
++ return nullptr;
++ }
++
++ void *ptr = mmap(nullptr, length, PROT_READ, MAP_SHARED, fd, /*offset*/0);
++ if (ptr == MAP_FAILED) {
++ *errorString = qt_error_string(errno);
++ return nullptr;
++ }
++ dataPtr = ptr;
++
++ return reinterpret_cast<CompiledData::Unit*>(dataPtr);
++ }
++
++ void CompilationUnitMapper::close()
++ {
++ // Do not unmap the data here.
++ if (dataPtr != nullptr) {
++ // Do not unmap cache files that are built with the StaticData flag. That's the majority of
++ // them and it's necessary to benefit from the QString literal optimization. There might
++ // still be QString instances around that point into that memory area. The memory is backed
++ // on the disk, so the kernel is free to release the pages and all that remains is the
++ // address space allocation.
++ if (!(reinterpret_cast<CompiledData::Unit*>(dataPtr)->flags & CompiledData::Unit::StaticData))
++ munmap(dataPtr, length);
++ }
++ dataPtr = nullptr;
++ }
++
++ QT_END_NAMESPACE