a13f78144a
This fixes a crash while parsing an XML file with garbage data, the file starts with '<' then garbage data: - The loop in the parse() keeps iterating until it hits "case 262:", which calls fastScanName() - fastScanName() iterates over the text buffer scanning for the attribute name (e.g. "xml:lang"), until it finds ':' - Consider a Value val, fastScanName() is called on it, it would set val.prefix to a number > val.len, then it would hit the 4096 condition and return (returned 0, now it returns the equivalent of std::null_opt), which means that val.len doesn't get modified, making it smaller than val.prefix - The code would try constructing an XmlStringRef with negative length, which would hit an assert in one of QStringView's constructors Add an assert to the XmlStringRef constructor. Add unittest based on the file from the bug report. Later on I will replace FastScanNameResult with std::optional<qsizetype> (std::optional is C++17, which isn't required by Qt 5.15, and we want to backport this fix). Credit to OSS-Fuzz. Fixes: QTBUG-109781 Fixes: QTBUG-114829 Change-Id: I455a5eeb47870c2ac9ffd0cbcdcd99c1ae2dd374 Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io> (cherry picked from commit 6326bec46a618c72feba4a2bb994c4d475050aed) Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>