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Avoid overflow in some more qdatetime.cpp functions

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One multiplied TIME_T_MAX * MSECS_PER_SEC despite knowing this to be
too close for comfort to the bounds of qint64; but the comment
indicated it should have been using a 32-bit signed max in place of
TIME_T_MAX. Two others simply neglected to check for overflow.

Also use QRoundingDown::qMod() in one place to avoid needlessly
complicating arithmetic; and assert, in another, that we were never in
danger of overflowing anyway (thanks to an earlier isValid() check).
Restructured QDateTimePrivate::zoneMSecsToEpochMSecs() in the process
of catching its potential overflow.

Change-Id: I429321d90246ba922cccf09a4f028f03a514cb6b
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
This commit is contained in:
Edward Welbourne 2020-09-21 16:51:33 +02:00
parent 131c7009fa
commit 460d7c8780
1 changed files with 36 additions and 28 deletions
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64
src/corelib/time/qdatetime.cpp
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@ -47,6 +47,7 @@
#include "qset.h"
#include "qlocale.h"
#include "private/qcalendarmath_p.h"
#include "private/qdatetime_p.h"
#if QT_CONFIG(datetimeparser)
#include "private/qdatetimeparser_p.h"
@ -1957,6 +1958,7 @@ bool QTime::setHMS(int h, int m, int s, int ms)
return false;
}
mds = (h * SECS_PER_HOUR + m * SECS_PER_MIN + s) * MSECS_PER_SEC + ms;
Q_ASSERT(mds >= 0 && mds < MSECS_PER_DAY);
return true;
}
@ -2022,15 +2024,8 @@ int QTime::secsTo(QTime t) const
QTime QTime::addMSecs(int ms) const
{
QTime t;
if (isValid()) {
if (ms < 0) {
// %,/ not well-defined for -ve, so always work with +ve.
int negdays = (MSECS_PER_DAY - ms) / MSECS_PER_DAY;
t.mds = (ds() + ms + negdays * MSECS_PER_DAY) % MSECS_PER_DAY;
} else {
t.mds = (ds() + ms) % MSECS_PER_DAY;
}
}
if (isValid())
t.mds = QRoundingDown::qMod(ds() + ms, MSECS_PER_DAY);
return t;
}
@ -2690,8 +2685,18 @@ static void msecsToTime(qint64 msecs, QDate *date, QTime *time)
// Converts a date/time value into msecs
static qint64 timeToMSecs(QDate date, QTime time)
{
return ((date.toJulianDay() - JULIAN_DAY_FOR_EPOCH) * MSECS_PER_DAY)
+ time.msecsSinceStartOfDay();
qint64 days = date.toJulianDay() - JULIAN_DAY_FOR_EPOCH;
qint64 msecs, dayms = time.msecsSinceStartOfDay();
if (days < 0 && dayms > 0) {
++days;
dayms -= MSECS_PER_DAY;
}
if (mul_overflow(days, std::integral_constant<qint64, MSECS_PER_DAY>(), &msecs)
|| add_overflow(msecs, dayms, &msecs)) {
using Bound = std::numeric_limits<qint64>;
return days < 0 ? Bound::min() : Bound::max();
}
return msecs;
}
/*!
@ -2753,8 +2758,10 @@ static auto computeSystemMillisRange()
// MS's end-of-range, end of year 3000:
{ 3000, Q_INT64_C(32535215999999) },
};
// Assume we do at least reach the end of 32-bit time_t:
qint64 stop = quint64(TIME_T_MAX) * MSECS_PER_SEC - 1 + MSECS_PER_SEC;
// Assume we do at least reach the end of a signed 32-bit time_t (since
// our actual time_t is bigger than that):
qint64 stop =
quint64(std::numeric_limits<qint32>::max()) * MSECS_PER_SEC - 1 + MSECS_PER_SEC;
// Cleared if first pass round loop fails:
bool stopMax = true;
for (const auto c : ends) {
@ -3424,26 +3431,27 @@ inline qint64 QDateTimePrivate::zoneMSecsToEpochMSecs(qint64 zoneMSecs, const QT
// Get the effective data from QTimeZone
DaylightStatus dst = hint ? *hint : UnknownDaylightTime;
QTimeZonePrivate::Data data = zone.d->dataForLocalTime(zoneMSecs, int(dst));
if (data.offsetFromUtc == QTimeZonePrivate::invalidSeconds()) {
if (hint)
*hint = QDateTimePrivate::UnknownDaylightTime;
if (abbreviation)
*abbreviation = QString();
const bool badDateTime = data.offsetFromUtc == QTimeZonePrivate::invalidSeconds();
Q_ASSERT(badDateTime
|| zone.d->offsetFromUtc(data.atMSecsSinceEpoch) == data.offsetFromUtc);
if (hint) {
*hint = badDateTime
? QDateTimePrivate::UnknownDaylightTime
: (data.daylightTimeOffset
? QDateTimePrivate::DaylightTime
: QDateTimePrivate::StandardTime);
}
if (abbreviation)
*abbreviation = badDateTime ? QString() : data.abbreviation;
qint64 msecs;
if (badDateTime ||
add_overflow(data.offsetFromUtc * MSECS_PER_SEC, data.atMSecsSinceEpoch, &msecs)) {
if (zoneDate)
*zoneDate = QDate();
if (zoneTime)
*zoneTime = QTime();
} else {
Q_ASSERT(zone.d->offsetFromUtc(data.atMSecsSinceEpoch) == data.offsetFromUtc);
msecsToTime(data.atMSecsSinceEpoch + data.offsetFromUtc * MSECS_PER_SEC,
zoneDate, zoneTime);
if (hint) {
*hint = data.daylightTimeOffset
? QDateTimePrivate::DaylightTime
: QDateTimePrivate::StandardTime;
}
if (abbreviation)
*abbreviation = data.abbreviation;
msecsToTime(msecs, zoneDate, zoneTime);
}
return data.atMSecsSinceEpoch;
}