Reduce memory reallocations in QTextTablePrivate::update()

This fixes oss-fuzz issue 21100.

Task-number: QTBUG-85139
Pick-to: 5.15
Change-Id: I635c1fa9b16dd527e568ec1e98ea7cac73977020
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

2 files changed, 6 insertions, 14 deletions

diff --git a/src/gui/text/qtexttable.cpp b/src/gui/text/qtexttable.cpp
index d4ed4411bc..951408052d 100644
--- a/src/gui/text/qtexttable.cpp
+++ b/src/gui/text/qtexttable.cpp
@@ -318,13 +318,6 @@ QTextFrame::iterator QTextTableCell::end() const
     Destroys the table cell.
 */
 
-QTextTablePrivate::~QTextTablePrivate()
-{
-    if (grid)
-        free(grid);
-}
-
-
 QTextTable *QTextTablePrivate::createTable(QTextDocumentPrivate *pieceTable, int pos, int rows, int cols, const QTextTableFormat &tableFormat)
 {
     QTextTableFormat fmt = tableFormat;
@@ -446,8 +439,7 @@ void QTextTablePrivate::update() const
     nRows = (cells.size() + nCols-1)/nCols;
 //     qDebug(">>>> QTextTablePrivate::update, nRows=%d, nCols=%d", nRows, nCols);
 
-    grid = q_check_ptr((int *)realloc(grid, nRows*nCols*sizeof(int)));
-    memset(grid, 0, nRows*nCols*sizeof(int));
+    grid.assign(nRows * nCols, 0);
 
     QTextDocumentPrivate *p = pieceTable;
     QTextFormatCollection *c = p->formatCollection();
@@ -470,8 +462,7 @@ void QTextTablePrivate::update() const
         cellIndices[i] = cell;
 
         if (r + rowspan > nRows) {
-            grid = q_check_ptr((int *)realloc(grid, sizeof(int)*(r + rowspan)*nCols));
-            memset(grid + (nRows*nCols), 0, sizeof(int)*(r+rowspan-nRows)*nCols);
+            grid.resize((r + rowspan) * nCols, 0);
             nRows = r + rowspan;
         }
 
diff --git a/src/gui/text/qtexttable_p.h b/src/gui/text/qtexttable_p.h
index 7dcab6c147..20ff67d1f9 100644
--- a/src/gui/text/qtexttable_p.h
+++ b/src/gui/text/qtexttable_p.h
@@ -55,14 +55,15 @@
 #include "private/qtextobject_p.h"
 #include "private/qtextdocument_p.h"
 
+#include <vector>
+
 QT_BEGIN_NAMESPACE
 
 class QTextTablePrivate : public QTextFramePrivate
 {
     Q_DECLARE_PUBLIC(QTextTable)
 public:
-    QTextTablePrivate(QTextDocument *document) : QTextFramePrivate(document), grid(nullptr), nRows(0), nCols(0), dirty(true), blockFragmentUpdates(false) {}
-    ~QTextTablePrivate();
+    QTextTablePrivate(QTextDocument *document) : QTextFramePrivate(document), nRows(0), nCols(0), dirty(true), blockFragmentUpdates(false) {}
 
     static QTextTable *createTable(QTextDocumentPrivate *, int pos, int rows, int cols, const QTextTableFormat &tableFormat);
     void fragmentAdded(QChar type, uint fragment) override;
@@ -76,7 +77,7 @@ public:
     // symmetric to cells array and maps to indecs in grid,
     // used for fast-lookup for row/column by fragment
     mutable QList<int> cellIndices;
-    mutable int *grid;
+    mutable std::vector<int> grid;
     mutable int nRows;
     mutable int nCols;
     mutable bool dirty;