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QCborStreamReader: avoid allocating result if data is insufficient

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By calling the internal readStringChunk() function with a QByteArray
pointer, QCborStreamReader::readByteArray() can now avoid allocating the
resulting buffer until the internals have confirmed that there is
sufficient data in the incoming buffer. As a result, we first detect the
EOF condition before we conclude the payload would have been too big for
QByteArray (validation()) test. Meanwhile, the hugeDeviceValidation()
test ends up with a few conditions where it would have copied 1 GB of
data, so limit that too.

We make a choice of reporting OOM vs DataTooLarge only if QByteArray
fails to allocate in the first place (QByteArray::resize() ->
Q_CHECK_PTR -> qBadAlloc, QtCore is always built with exceptions on).

The QCborValue unit test needed a temporary work around until we apply
the same allocation fix (see next commit).

Pick-to: 5.15 6.0
Fixes: QTBUG-88253
Change-Id: I7b9b97ae9b32412abdc6fffd164523eeae49cdfe
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>
This commit is contained in:
Thiago Macieira 2020-11-11 12:50:54 -08:00 committed by Volker Hilsheimer
parent c16ad16bd0
commit 9a55f40937
4 changed files with 70 additions and 29 deletions
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78
src/corelib/serialization/qcborstreamreader.cpp
View File

@ -667,8 +667,22 @@ public:
bufferStart = 0;
}
struct ReadStringChunk {
union {
char *ptr;
QByteArray *array;
};
enum { ByteArray = -1 };
qsizetype maxlen_or_type;
ReadStringChunk(char *ptr, qsizetype maxlen) : ptr(ptr), maxlen_or_type(maxlen) {}
ReadStringChunk(QByteArray *array) : array(array), maxlen_or_type(ByteArray) {}
bool isByteArray() const { return maxlen_or_type == ByteArray; }
bool isPlainPointer() const { return maxlen_or_type >= 0; }
};
QCborStreamReader::StringResult<qsizetype> readStringChunk(ReadStringChunk params);
bool ensureStringIteration();
QCborStreamReader::StringResult<qsizetype> readStringChunk(char *ptr, qsizetype maxlen);
};
void qt_cbor_stream_set_error(QCborStreamReaderPrivate *d, QCborError error)
@ -1366,7 +1380,7 @@ QCborStreamReader::StringResult<QString> QCborStreamReader::_readString_helper()
}
/*!
\fn QCborStreamReader::StringResult<QString> QCborStreamReader::readByteArray()
\fn QCborStreamReader::StringResult<QByteArray> QCborStreamReader::readByteArray()
Decodes one byte array chunk from the CBOR string and returns it. This
function is used for both regular and chunked contents, so the caller must
@ -1384,19 +1398,16 @@ QCborStreamReader::StringResult<QString> QCborStreamReader::_readString_helper()
QCborStreamReader::StringResult<QByteArray> QCborStreamReader::_readByteArray_helper()
{
QCborStreamReader::StringResult<QByteArray> result;
result.status = Error;
qsizetype len = _currentStringChunkSize();
if (len < 0)
return result;
if (len > MaxByteArraySize) {
d->handleError(CborErrorDataTooLarge);
return result;
auto r = d->readStringChunk(&result.data);
result.status = r.status;
if (r.status == Error) {
result.data.clear();
} else {
Q_ASSERT(r.data == result.data.length());
if (r.status == EndOfString && lastError() == QCborError::NoError)
preparse();
}
result.data.resize(len);
auto r = readStringChunk(result.data.data(), len);
Q_ASSERT(r.status != Ok || r.data == len);
result.status = r.status;
return result;
}
@ -1462,14 +1473,14 @@ qsizetype QCborStreamReader::_currentStringChunkSize() const
QCborStreamReader::StringResult<qsizetype>
QCborStreamReader::readStringChunk(char *ptr, qsizetype maxlen)
{
auto r = d->readStringChunk(ptr, maxlen);
auto r = d->readStringChunk({ptr, maxlen});
if (r.status == EndOfString && lastError() == QCborError::NoError)
preparse();
return r;
}
QCborStreamReader::StringResult<qsizetype>
QCborStreamReaderPrivate::readStringChunk(char *ptr, qsizetype maxlen)
Q_NEVER_INLINE QCborStreamReader::StringResult<qsizetype>
QCborStreamReaderPrivate::readStringChunk(ReadStringChunk params)
{
CborError err;
size_t len;
@ -1482,6 +1493,12 @@ QCborStreamReaderPrivate::readStringChunk(char *ptr, qsizetype maxlen)
if (!ensureStringIteration())
return result;
// Note: in the current implementation, the call into TinyCBOR below only
// succeeds if we *already* have all the data in memory. That's obvious for
// the case of direct memory (no QIODevice), whereas for QIODevices
// qt_cbor_decoder_transfer_string() enforces that
// QIODevice::bytesAvailable() be bigger than the amount we're about to
// read.
#if 1
// Using internal TinyCBOR API!
err = _cbor_value_get_string_chunk(&currentElement, &content, &len, &currentElement);
@ -1518,11 +1535,30 @@ QCborStreamReaderPrivate::readStringChunk(char *ptr, qsizetype maxlen)
qint64 actuallyRead;
qptrdiff offset = qptrdiff(content);
qsizetype toRead = qsizetype(len);
qsizetype left = toRead - maxlen;
if (left < 0)
left = 0; // buffer bigger than string
else
toRead = maxlen; // buffer smaller than string
qsizetype left = 0; // bytes from the chunk not copied to the user buffer, to discard
char *ptr;
if (params.isPlainPointer()) {
left = toRead - params.maxlen_or_type;
if (left < 0)
left = 0; // buffer bigger than string
else
toRead = params.maxlen_or_type; // buffer smaller than string
ptr = params.ptr;
} else if (params.isByteArray()) {
// See note above on having ensured there is enough incoming data.
try {
params.array->resize(toRead);
} catch (const std::bad_alloc &) {
// the distinction between DataTooLarge and OOM is mostly for
// compatibility with Qt 5; in Qt 6, we could consider everything
// to be OOM.
handleError(toRead > MaxByteArraySize ? CborErrorDataTooLarge: CborErrorOutOfMemory);
return result;
}
ptr = const_cast<char *>(params.array->constData());
}
if (device) {
// This first skip can't fail because we've already read this many bytes.

14
tests/auto/corelib/serialization/cborlargedatavalidation.cpp
View File

@ -67,7 +67,7 @@ qint64 LargeIODevice::readData(char *data, qint64 maxlen)
qint64 p = pos();
if (maxlen > realSize - p)
maxlen = realSize - p;
memset(data, '\0', maxlen);
memset(data, '\0', qMin(maxlen, qint64(32 * 1024)));
qint64 fromstart = start.size() - p;
if (fromstart > maxlen)
@ -88,24 +88,24 @@ void addValidationLargeData(qsizetype minInvalid, qsizetype maxInvalid)
qToBigEndian(v, toolong + 1);
QTest::addRow("bytearray-too-big-for-qbytearray-%llx", v)
<< QByteArray(toolong, sizeof(toolong)) << 0 << CborErrorDataTooLarge;
<< QByteArray(toolong, sizeof(toolong)) << 0 << CborErrorUnexpectedEOF;
QTest::addRow("bytearray-chunked-too-big-for-qbytearray-%llx", v)
<< ('\x5f' + QByteArray(toolong, sizeof(toolong)) + '\xff')
<< 0 << CborErrorDataTooLarge;
<< 0 << CborErrorUnexpectedEOF;
QTest::addRow("bytearray-2chunked-too-big-for-qbytearray-%llx", v)
<< ("\x5f\x40" + QByteArray(toolong, sizeof(toolong)) + '\xff')
<< 0 << CborErrorDataTooLarge;
<< 0 << CborErrorUnexpectedEOF;
toolong[0] |= 0x20;
// QCborStreamReader::readString copies to a QByteArray first
QTest::addRow("string-too-big-for-qbytearray-%llx", v)
<< QByteArray(toolong, sizeof(toolong)) << 0 << CborErrorDataTooLarge;
<< QByteArray(toolong, sizeof(toolong)) << 0 << CborErrorUnexpectedEOF;
QTest::addRow("string-chunked-too-big-for-qbytearray-%llx", v)
<< ('\x7f' + QByteArray(toolong, sizeof(toolong)) + '\xff')
<< 0 << CborErrorDataTooLarge;
<< 0 << CborErrorUnexpectedEOF;
QTest::addRow("string-2chunked-too-big-for-qbytearray-%llx", v)
<< ("\x7f\x60" + QByteArray(toolong, sizeof(toolong)) + '\xff')
<< 0 << CborErrorDataTooLarge;
<< 0 << CborErrorUnexpectedEOF;
}
}

5
tests/auto/corelib/serialization/qcborstreamreader/tst_qcborstreamreader.cpp
View File

@ -297,7 +297,10 @@ void tst_QCborStreamReader::integers()
void escapedAppendTo(QString &result, const QByteArray &data)
{
result += "h'" + QString::fromLatin1(data.toHex()) + '\'';
QByteArray hex =
data.size() < 512*1024 ? data.toHex() :
"data of size " + QByteArray::number(data.size());
result += "h'" + QString::fromLatin1(hex) + '\'';
}
void escapedAppendTo(QString &result, const QString &data)

2
tests/auto/corelib/serialization/qcborvalue/tst_qcborvalue.cpp
View File

@ -2042,6 +2042,7 @@ void tst_QCborValue::validation()
QCborParserError parserError;
QCborValue decoded = QCborValue::fromCbor(data, &parserError);
if (parserError.error != QCborError::DataTooLarge) // ### temporary!!
QCOMPARE(parserError.error, error);
if (data.startsWith('\x81')) {
@ -2049,6 +2050,7 @@ void tst_QCborValue::validation()
char *ptr = const_cast<char *>(data.constData());
QByteArray mid = QByteArray::fromRawData(ptr + 1, data.size() - 1);
decoded = QCborValue::fromCbor(mid, &parserError);
if (parserError.error != QCborError::DataTooLarge) // ### temporary!!
QCOMPARE(parserError.error, error);
}
}