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Avoid assert or crash on plateauing transfer table

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If the same value repeats many times the values y1 and y2
can end up being the same cauing an assert or division by 0.

Fixes oss-fuzz 42535976. Credit to OSS-Fuzz for finding the case.

Change-Id: I30afd5cd61163c51949a8c13d4034f4bc11d27a7
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
(cherry picked from commit aa1293f043f5df34ee7501efda6a6a2e8da5fa99)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
This commit is contained in:
Allan Sandfeld Jensen 2024-10-25 11:34:08 +02:00 committed by Qt Cherry-pick Bot
parent a6ffdfec98
commit f0c51f8f83
1 changed files with 2 additions and 2 deletions
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4
src/gui/painting/qcolortransfertable_p.h
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@ -111,7 +111,7 @@ public:
return x; return x;
} }
// Apply inverse, optimized by giving a previous result a value < x. // Apply inverse, optimized by giving a previous result for a value < x.
float applyInverse(float x, float resultLargerThan = 0.0f) const float applyInverse(float x, float resultLargerThan = 0.0f) const
{ {
Q_ASSERT(resultLargerThan >= 0.0f && resultLargerThan <= 1.0f); Q_ASSERT(resultLargerThan >= 0.0f && resultLargerThan <= 1.0f);
@ -191,7 +191,7 @@ private:
template<typename T> template<typename T>
static float inverseLookup(float needle, float resultLargerThan, const QList<T> &table, quint32 tableMax) static float inverseLookup(float needle, float resultLargerThan, const QList<T> &table, quint32 tableMax)
{ {
uint32_t i = static_cast<uint32_t>(resultLargerThan * tableMax); uint32_t i = qMax(static_cast<uint32_t>(resultLargerThan * tableMax), 1U) - 1;
auto it = std::lower_bound(table.cbegin() + i, table.cend(), needle); auto it = std::lower_bound(table.cbegin() + i, table.cend(), needle);
i = it - table.cbegin(); i = it - table.cbegin();
if (i == 0) if (i == 0)