Package: qt4-x11 / 4:4.8.7+dfsg-18

Better-handling-of-invalid-font-tables.patch Patch series | download
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From 0a2f2382541424726168804be2c90b91381608c6 Mon Sep 17 00:00:00 2001
From: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>
Date: Fri, 10 Jul 2015 13:22:32 +0200
Subject: [PATCH] Better handling of invalid font tables

Specifically when reading files with broken cmap tables, we could
get some undeterministic results. We handle this more gracefully
by verifying that the offsets are sane and bailing out early if not.
This replaces the current pattern throughout the font engine for
consistency.

This is a back-port of 4a1e5dbade4bab55f39bd368480dcca9a11e4b38
from Qt 5.

Change-Id: If4172b9ef0808801c8e27ffaad962535afe572ed
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>
---
 src/gui/text/qfontengine.cpp     | 212 +++++++++++++++++++++++++++++----------
 src/gui/text/qfontengine_mac.mm  |  11 +-
 src/gui/text/qfontengine_mac_p.h |   1 +
 src/gui/text/qfontengine_p.h     |   2 +-
 src/gui/text/qfontengine_qpa.cpp |  12 +--
 src/gui/text/qfontengine_qpf.cpp |  12 +--
 src/gui/text/qfontengine_s60.cpp |   9 +-
 src/gui/text/qfontengine_s60_p.h |   1 +
 src/gui/text/qfontengine_win.cpp |  22 ++--
 src/gui/text/qfontengine_win_p.h |   1 +
 10 files changed, 198 insertions(+), 85 deletions(-)

diff --git a/src/gui/text/qfontengine.cpp b/src/gui/text/qfontengine.cpp
index 67b8798..3f7d831 100644
--- a/src/gui/text/qfontengine.cpp
+++ b/src/gui/text/qfontengine.cpp
@@ -69,6 +69,16 @@ static inline bool qtransform_equals_no_translate(const QTransform &a, const QTr
     }
 }
 
+template<typename T>
+static inline bool qSafeFromBigEndian(const uchar *source, const uchar *end, T *output)
+{
+    if (source + sizeof(T) > end)
+        return false;
+
+    *output = qFromBigEndian<T>(source);
+    return true;
+}
+
 // Harfbuzz helper functions
 
 static HB_Bool hb_stringToGlyphs(HB_Font font, const HB_UChar16 *string, hb_uint32 length, HB_Glyph *glyphs, hb_uint32 *numGlyphs, HB_Bool rightToLeft)
@@ -808,26 +818,38 @@ void QFontEngine::loadKerningPairs(QFixed scalingFactor)
         return;
 
     const uchar *table = reinterpret_cast<const uchar *>(tab.constData());
+    const uchar *end = table + tab.size();
+
+    quint16 version;
+    if (!qSafeFromBigEndian(table, end, &version))
+        return;
 
-    unsigned short version = qFromBigEndian<quint16>(table);
     if (version != 0) {
 //        qDebug("wrong version");
        return;
     }
 
-    unsigned short numTables = qFromBigEndian<quint16>(table + 2);
+    quint16 numTables;
+    if (!qSafeFromBigEndian(table + 2, end, &numTables))
+        return;
+
     {
         int offset = 4;
         for(int i = 0; i < numTables; ++i) {
-            if (offset + 6 > tab.size()) {
-//                qDebug("offset out of bounds");
-                goto end;
-            }
             const uchar *header = table + offset;
 
-            ushort version = qFromBigEndian<quint16>(header);
-            ushort length = qFromBigEndian<quint16>(header+2);
-            ushort coverage = qFromBigEndian<quint16>(header+4);
+            quint16 version;
+            if (!qSafeFromBigEndian(header, end, &version))
+                goto end;
+
+            quint16 length;
+            if (!qSafeFromBigEndian(header + 2, end, &length))
+                goto end;
+
+            quint16 coverage;
+            if (!qSafeFromBigEndian(header + 4, end, &coverage))
+                goto end;
+
 //            qDebug("subtable: version=%d, coverage=%x",version, coverage);
             if(version == 0 && coverage == 0x0001) {
                 if (offset + length > tab.size()) {
@@ -836,7 +858,10 @@ void QFontEngine::loadKerningPairs(QFixed scalingFactor)
                 }
                 const uchar *data = table + offset + 6;
 
-                ushort nPairs = qFromBigEndian<quint16>(data);
+                quint16 nPairs;
+                if (!qSafeFromBigEndian(data, end, &nPairs))
+                    goto end;
+
                 if(nPairs * 6 + 8 > length - 6) {
 //                    qDebug("corrupt table!");
                     // corrupt table
@@ -846,8 +871,21 @@ void QFontEngine::loadKerningPairs(QFixed scalingFactor)
                 int off = 8;
                 for(int i = 0; i < nPairs; ++i) {
                     QFontEngine::KernPair p;
-                    p.left_right = (((uint)qFromBigEndian<quint16>(data+off)) << 16) + qFromBigEndian<quint16>(data+off+2);
-                    p.adjust = QFixed(((int)(short)qFromBigEndian<quint16>(data+off+4))) / scalingFactor;
+
+                    quint16 tmp;
+                    if (!qSafeFromBigEndian(data + off, end, &tmp))
+                        goto end;
+
+                    p.left_right = uint(tmp) << 16;
+                    if (!qSafeFromBigEndian(data + off + 2, end, &tmp))
+                        goto end;
+
+                    p.left_right |= tmp;
+
+                    if (!qSafeFromBigEndian(data + off + 4, end, &tmp))
+                        goto end;
+
+                    p.adjust = QFixed(int(short(tmp))) / scalingFactor;
                     kerning_pairs.append(p);
                     off += 6;
                 }
@@ -872,26 +910,31 @@ int QFontEngine::glyphCount() const
     QByteArray maxpTable = getSfntTable(MAKE_TAG('m', 'a', 'x', 'p'));
     if (maxpTable.size() < 6)
         return 0;
-    return qFromBigEndian<quint16>(reinterpret_cast<const uchar *>(maxpTable.constData() + 4));
+
+    const uchar *source = reinterpret_cast<const uchar *>(maxpTable.constData() + 4);
+    const uchar *end = source + maxpTable.size();
+
+    quint16 count = 0;
+    qSafeFromBigEndian(source, end, &count);
+    return count;
 }
 
 const uchar *QFontEngine::getCMap(const uchar *table, uint tableSize, bool *isSymbolFont, int *cmapSize)
 {
     const uchar *header = table;
-    if (tableSize < 4)
-        return 0;
-
     const uchar *endPtr = table + tableSize;
 
     // version check
-    if (qFromBigEndian<quint16>(header) != 0)
+    quint16 version;
+    if (!qSafeFromBigEndian(header, endPtr, &version) || version != 0)
         return 0;
 
-    unsigned short numTables = qFromBigEndian<quint16>(header + 2);
-    const uchar *maps = table + 4;
-    if (maps + 8 * numTables > endPtr)
+    quint16 numTables;
+    if (!qSafeFromBigEndian(header + 2, endPtr, &numTables))
         return 0;
 
+    const uchar *maps = table + 4;
+
     enum {
         Invalid,
         AppleRoman,
@@ -906,8 +949,14 @@ const uchar *QFontEngine::getCMap(const uchar *table, uint tableSize, bool *isSy
     int tableToUse = -1;
     int score = Invalid;
     for (int n = 0; n < numTables; ++n) {
-        const quint16 platformId = qFromBigEndian<quint16>(maps + 8 * n);
-        const quint16 platformSpecificId = qFromBigEndian<quint16>(maps + 8 * n + 2);
+        quint16 platformId;
+        if (!qSafeFromBigEndian(maps + 8 * n, endPtr, &platformId))
+            return 0;
+
+        quint16 platformSpecificId;
+        if (!qSafeFromBigEndian(maps + 8 * n + 2, endPtr, &platformSpecificId))
+            return 0;
+
         switch (platformId) {
         case 0: // Unicode
             if (score < Unicode &&
@@ -961,20 +1010,30 @@ const uchar *QFontEngine::getCMap(const uchar *table, uint tableSize, bool *isSy
 resolveTable:
     *isSymbolFont = (symbolTable > -1);
 
-    unsigned int unicode_table = qFromBigEndian<quint32>(maps + 8*tableToUse + 4);
+    quint32 unicode_table;
+    if (!qSafeFromBigEndian(maps + 8 * tableToUse + 4, endPtr, &unicode_table))
+        return 0;
 
-    if (!unicode_table || unicode_table + 8 > tableSize)
+    if (!unicode_table)
         return 0;
 
     // get the header of the unicode table
     header = table + unicode_table;
 
-    unsigned short format = qFromBigEndian<quint16>(header);
-    unsigned int length;
-    if(format < 8)
-        length = qFromBigEndian<quint16>(header + 2);
-    else
-        length = qFromBigEndian<quint32>(header + 4);
+    quint16 format;
+    if (!qSafeFromBigEndian(header, endPtr, &format))
+        return 0;
+
+    quint32 length;
+    if (format < 8) {
+        quint16 tmp;
+        if (!qSafeFromBigEndian(header + 2, endPtr, &tmp))
+            return 0;
+        length = tmp;
+    } else {
+        if (!qSafeFromBigEndian(header + 4, endPtr, &length))
+            return 0;
+    }
 
     if (table + unicode_table + length > endPtr)
         return 0;
@@ -989,7 +1048,7 @@ resolveTable:
         // Check that none of the latin1 range are in the unicode table
         bool unicodeTableHasLatin1 = false;
         for (int uc=0x00; uc<0x100; ++uc) {
-            if (getTrueTypeGlyphIndex(selectedTable, uc) != 0) {
+            if (getTrueTypeGlyphIndex(selectedTable, length, uc) != 0) {
                 unicodeTableHasLatin1 = true;
                 break;
             }
@@ -999,7 +1058,7 @@ resolveTable:
         bool unicodeTableHasSymbols = false;
         if (!unicodeTableHasLatin1) {
             for (int uc=0xf000; uc<0xf100; ++uc) {
-                if (getTrueTypeGlyphIndex(selectedTable, uc) != 0) {
+                if (getTrueTypeGlyphIndex(selectedTable, length, uc) != 0) {
                     unicodeTableHasSymbols = true;
                     break;
                 }
@@ -1017,12 +1076,17 @@ resolveTable:
     return table + unicode_table;
 }
 
-quint32 QFontEngine::getTrueTypeGlyphIndex(const uchar *cmap, uint unicode)
+quint32 QFontEngine::getTrueTypeGlyphIndex(const uchar *cmap, int cmapSize, uint unicode)
 {
-    unsigned short format = qFromBigEndian<quint16>(cmap);
+    const uchar *end = cmap + cmapSize;
+    quint16 format;
+    if (!qSafeFromBigEndian(cmap, end, &format))
+        return 0;
+
     if (format == 0) {
-        if (unicode < 256)
-            return (int) *(cmap+6+unicode);
+        const uchar *ptr = cmap + 6 + unicode;
+        if (unicode < 256 && ptr < end)
+            return quint32(*ptr);
     } else if (format == 4) {
         /* some fonts come with invalid cmap tables, where the last segment
            specified end = start = rangeoffset = 0xffff, delta = 0x0001
@@ -1031,25 +1095,49 @@ quint32 QFontEngine::getTrueTypeGlyphIndex(const uchar *cmap, uint unicode)
         */
         if(unicode >= 0xffff)
             return 0;
-        quint16 segCountX2 = qFromBigEndian<quint16>(cmap + 6);
+
+        quint16 segCountX2;
+        if (!qSafeFromBigEndian(cmap + 6, end, &segCountX2))
+            return 0;
+
         const unsigned char *ends = cmap + 14;
+
         int i = 0;
-        for (; i < segCountX2/2 && qFromBigEndian<quint16>(ends + 2*i) < unicode; i++) {}
+        for (; i < segCountX2/2; ++i) {
+            quint16 codePoint;
+            if (!qSafeFromBigEndian(ends + 2 * i, end, &codePoint))
+                return 0;
+            if (codePoint >= unicode)
+                break;
+        }
 
         const unsigned char *idx = ends + segCountX2 + 2 + 2*i;
-        quint16 startIndex = qFromBigEndian<quint16>(idx);
 
+        quint16 startIndex;
+        if (!qSafeFromBigEndian(idx, end, &startIndex))
+            return 0;
         if (startIndex > unicode)
             return 0;
 
         idx += segCountX2;
-        qint16 idDelta = (qint16)qFromBigEndian<quint16>(idx);
+
+        quint16 tmp;
+        if (!qSafeFromBigEndian(idx, end, &tmp))
+            return 0;
+        qint16 idDelta = qint16(tmp);
+
         idx += segCountX2;
-        quint16 idRangeoffset_t = (quint16)qFromBigEndian<quint16>(idx);
+
+        quint16 idRangeoffset_t;
+        if (!qSafeFromBigEndian(idx, end, &idRangeoffset_t))
+            return 0;
 
         quint16 glyphIndex;
         if (idRangeoffset_t) {
-            quint16 id = qFromBigEndian<quint16>(idRangeoffset_t + 2*(unicode - startIndex) + idx);
+            quint16 id;
+            if (!qSafeFromBigEndian(idRangeoffset_t + 2 * (unicode - startIndex) + idx, end, &id))
+                return 0;
+
             if (id)
                 glyphIndex = (idDelta + id) % 0x10000;
             else
@@ -1059,13 +1147,19 @@ quint32 QFontEngine::getTrueTypeGlyphIndex(const uchar *cmap, uint unicode)
         }
         return glyphIndex;
     } else if (format == 6) {
-        quint16 tableSize = qFromBigEndian<quint16>(cmap + 2);
+        quint16 tableSize;
+        if (!qSafeFromBigEndian(cmap + 2, end, &tableSize))
+            return 0;
 
-        quint16 firstCode6 = qFromBigEndian<quint16>(cmap + 6);
+        quint16 firstCode6;
+        if (!qSafeFromBigEndian(cmap + 6, end, &firstCode6))
+            return 0;
         if (unicode < firstCode6)
             return 0;
 
-        quint16 entryCount6 = qFromBigEndian<quint16>(cmap + 8);
+        quint16 entryCount6;
+        if (!qSafeFromBigEndian(cmap + 8, end, &entryCount6))
+            return 0;
         if (entryCount6 * 2 + 10 > tableSize)
             return 0;
 
@@ -1074,9 +1168,14 @@ quint32 QFontEngine::getTrueTypeGlyphIndex(const uchar *cmap, uint unicode)
             return 0;
 
         quint16 entryIndex6 = unicode - firstCode6;
-        return qFromBigEndian<quint16>(cmap + 10 + (entryIndex6 * 2));
+
+        quint16 index = 0;
+        qSafeFromBigEndian(cmap + 10 + (entryIndex6 * 2), end, &index);
+        return index;
     } else if (format == 12) {
-        quint32 nGroups = qFromBigEndian<quint32>(cmap + 12);
+        quint32 nGroups;
+        if (!qSafeFromBigEndian(cmap + 12, end, &nGroups))
+            return 0;
 
         cmap += 16; // move to start of groups
 
@@ -1084,13 +1183,24 @@ quint32 QFontEngine::getTrueTypeGlyphIndex(const uchar *cmap, uint unicode)
         while (left <= right) {
             int middle = left + ( ( right - left ) >> 1 );
 
-            quint32 startCharCode = qFromBigEndian<quint32>(cmap + 12*middle);
+            quint32 startCharCode;
+            if (!qSafeFromBigEndian(cmap + 12 * middle, end, &startCharCode))
+                return 0;
+
             if(unicode < startCharCode)
                 right = middle - 1;
             else {
-                quint32 endCharCode = qFromBigEndian<quint32>(cmap + 12*middle + 4);
-                if(unicode <= endCharCode)
-                    return qFromBigEndian<quint32>(cmap + 12*middle + 8) + unicode - startCharCode;
+                quint32 endCharCode;
+                if (!qSafeFromBigEndian(cmap + 12 * middle + 4, end, &endCharCode))
+                    return 0;
+
+                if (unicode <= endCharCode) {
+                    quint32 index;
+                    if (!qSafeFromBigEndian(cmap + 12 * middle + 8, end, &index))
+                        return 0;
+
+                    return index + unicode - startCharCode;
+                }
                 left = middle + 1;
             }
         }
diff --git a/src/gui/text/qfontengine_mac.mm b/src/gui/text/qfontengine_mac.mm
index ba01f4c..460aa5f 100644
--- a/src/gui/text/qfontengine_mac.mm
+++ b/src/gui/text/qfontengine_mac.mm
@@ -625,7 +625,7 @@ bool QFontEngineMacMulti::canRender(const QChar *string, int len)
 }
 
 QFontEngineMac::QFontEngineMac(ATSUStyle baseStyle, ATSUFontID fontID, const QFontDef &def, QFontEngineMacMulti *multiEngine)
-    : fontID(fontID), multiEngine(multiEngine), cmap(0), symbolCMap(false)
+    : fontID(fontID), multiEngine(multiEngine), cmap(0), symbolCMap(false), cmapSize(0)
 {
     fontDef = def;
     ATSUCreateAndCopyStyle(baseStyle, &style);
@@ -747,22 +747,21 @@ bool QFontEngineMac::stringToCMap(const QChar *str, int len, QGlyphLayout *glyph
 {
     if (!cmap) {
         cmapTable = getSfntTable(MAKE_TAG('c', 'm', 'a', 'p'));
-        int size = 0;
-        cmap = getCMap(reinterpret_cast<const uchar *>(cmapTable.constData()), cmapTable.size(), &symbolCMap, &size);
+        cmap = getCMap(reinterpret_cast<const uchar *>(cmapTable.constData()), cmapTable.size(), &symbolCMap, &cmapSize);
         if (!cmap)
             return false;
     }
     if (symbolCMap) {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(str, i, len);
-            glyphs->glyphs[i] = getTrueTypeGlyphIndex(cmap, uc);
+            glyphs->glyphs[i] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
             if(!glyphs->glyphs[i] && uc < 0x100)
-                glyphs->glyphs[i] = getTrueTypeGlyphIndex(cmap, uc + 0xf000);
+                glyphs->glyphs[i] = getTrueTypeGlyphIndex(cmap, cmapSize, uc + 0xf000);
         }
     } else {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(str, i, len);
-            glyphs->glyphs[i] = getTrueTypeGlyphIndex(cmap, uc);
+            glyphs->glyphs[i] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
         }
     }
 
diff --git a/src/gui/text/qfontengine_mac_p.h b/src/gui/text/qfontengine_mac_p.h
index 7d70c24..844d421 100644
--- a/src/gui/text/qfontengine_mac_p.h
+++ b/src/gui/text/qfontengine_mac_p.h
@@ -108,6 +108,7 @@ private:
     qreal m_maxCharWidth;
     QFixed m_xHeight;
     QFixed m_averageCharWidth;
+    mutable int cmapSize;
 };
 
 class QFontEngineMacMulti : public QFontEngineMulti
diff --git a/src/gui/text/qfontengine_p.h b/src/gui/text/qfontengine_p.h
index f29ac47..9c3435f 100644
--- a/src/gui/text/qfontengine_p.h
+++ b/src/gui/text/qfontengine_p.h
@@ -247,7 +247,7 @@ public:
     QFontEngineGlyphCache *glyphCache(void *key, QFontEngineGlyphCache::Type type, const QTransform &transform) const;
 
     static const uchar *getCMap(const uchar *table, uint tableSize, bool *isSymbolFont, int *cmapSize);
-    static quint32 getTrueTypeGlyphIndex(const uchar *cmap, uint unicode);
+    static quint32 getTrueTypeGlyphIndex(const uchar *cmap, int cmapSize, uint unicode);
 
     static QByteArray convertToPostscriptFontFamilyName(const QByteArray &fontFamily);
 
diff --git a/src/gui/text/qfontengine_qpa.cpp b/src/gui/text/qfontengine_qpa.cpp
index 04f7b76..011d233 100644
--- a/src/gui/text/qfontengine_qpa.cpp
+++ b/src/gui/text/qfontengine_qpa.cpp
@@ -358,9 +358,9 @@ bool QFontEngineQPA::stringToCMap(const QChar *str, int len, QGlyphLayout *glyph
             unsigned int uc = getChar(str, i, len);
             if (mirrored)
                 uc = QChar::mirroredChar(uc);
-            glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc);
+            glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
             if(!glyphs->glyphs[glyph_pos] && uc < 0x100)
-                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc + 0xf000);
+                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc + 0xf000);
             ++glyph_pos;
         }
     } else {
@@ -368,7 +368,7 @@ bool QFontEngineQPA::stringToCMap(const QChar *str, int len, QGlyphLayout *glyph
             unsigned int uc = getChar(str, i, len);
             if (mirrored)
                 uc = QChar::mirroredChar(uc);
-            glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc);
+            glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
 #if 0 && defined(DEBUG_FONTENGINE)
             QChar c(uc);
             if (!findGlyph(glyphs[glyph_pos].glyph) && !seenGlyphs.contains(c))
@@ -511,16 +511,16 @@ bool QFontEngineQPA::canRender(const QChar *string, int len)
     if (symbol) {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(string, i, len);
-            glyph_t g = getTrueTypeGlyphIndex(cmap, uc);
+            glyph_t g = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
             if(!g && uc < 0x100)
-                g = getTrueTypeGlyphIndex(cmap, uc + 0xf000);
+                g = getTrueTypeGlyphIndex(cmap, cmapSize, uc + 0xf000);
             if (!g)
                 return false;
         }
     } else {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(string, i, len);
-            if (!getTrueTypeGlyphIndex(cmap, uc))
+            if (!getTrueTypeGlyphIndex(cmap, cmapSize, uc))
                 return false;
         }
     }
diff --git a/src/gui/text/qfontengine_qpf.cpp b/src/gui/text/qfontengine_qpf.cpp
index 8d5e71b..9087cff 100644
--- a/src/gui/text/qfontengine_qpf.cpp
+++ b/src/gui/text/qfontengine_qpf.cpp
@@ -577,9 +577,9 @@ bool QFontEngineQPF::stringToCMap(const QChar *str, int len, QGlyphLayout *glyph
     if (symbol) {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(str, i, len);
-            glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc);
+            glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
             if(!glyphs->glyphs[glyph_pos] && uc < 0x100)
-                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc + 0xf000);
+                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc + 0xf000);
             ++glyph_pos;
         }
     } else {
@@ -587,7 +587,7 @@ bool QFontEngineQPF::stringToCMap(const QChar *str, int len, QGlyphLayout *glyph
             unsigned int uc = getChar(str, i, len);
             if (mirrored)
                 uc = QChar::mirroredChar(uc);
-            glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc);
+            glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
 #if 0 && defined(DEBUG_FONTENGINE)
             QChar c(uc);
             if (!findGlyph(glyphs[glyph_pos].glyph) && !seenGlyphs.contains(c))
@@ -786,16 +786,16 @@ bool QFontEngineQPF::canRender(const QChar *string, int len)
     if (symbol) {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(string, i, len);
-            glyph_t g = getTrueTypeGlyphIndex(cmap, uc);
+            glyph_t g = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
             if(!g && uc < 0x100)
-                g = getTrueTypeGlyphIndex(cmap, uc + 0xf000);
+                g = getTrueTypeGlyphIndex(cmap, cmapSize, uc + 0xf000);
             if (!g)
                 return false;
         }
     } else {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(string, i, len);
-            if (!getTrueTypeGlyphIndex(cmap, uc))
+            if (!getTrueTypeGlyphIndex(cmap, cmapSize, uc))
                 return false;
         }
     }
diff --git a/src/gui/text/qfontengine_s60.cpp b/src/gui/text/qfontengine_s60.cpp
index 1da501a..b2bb561 100644
--- a/src/gui/text/qfontengine_s60.cpp
+++ b/src/gui/text/qfontengine_s60.cpp
@@ -77,6 +77,7 @@ QSymbianTypeFaceExtras::QSymbianTypeFaceExtras(CFont* cFont, COpenFont *openFont
     : m_cFont(cFont)
     , m_symbolCMap(false)
     , m_openFont(openFont)
+    , m_cmapSize(0)
 {
     if (!symbianFontTableApiAvailable()) {
         TAny *trueTypeExtension = NULL;
@@ -161,10 +162,9 @@ const uchar *QSymbianTypeFaceExtras::cmap() const
 {
     if (m_cmapTable.isNull()) {
         const QByteArray cmapTable = getSfntTable(MAKE_TAG('c', 'm', 'a', 'p'));
-        int size = 0;
         const uchar *cmap = QFontEngine::getCMap(reinterpret_cast<const uchar *>
-                (cmapTable.constData()), cmapTable.size(), &m_symbolCMap, &size);
-        m_cmapTable = QByteArray(reinterpret_cast<const char *>(cmap), size);
+                (cmapTable.constData()), cmapTable.size(), &m_symbolCMap, &m_cmapSize);
+        m_cmapTable = QByteArray(reinterpret_cast<const char *>(cmap), m_cmapSize);
     }
     return reinterpret_cast<const uchar *>(m_cmapTable.constData());
 }
@@ -324,6 +324,7 @@ bool QFontEngineS60::stringToCMap(const QChar *characters, int len, QGlyphLayout
     for (int i = 0; i < len; ++i) {
         const unsigned int uc = getChar(characters, i, len);
         *g++ = QFontEngine::getTrueTypeGlyphIndex(cmap,
+                                                  m_cmapSize,
                         (isRtl && !m_extras->isSymbolCMap()) ? QChar::mirroredChar(uc) : uc);
     }
 
@@ -463,7 +464,7 @@ bool QFontEngineS60::canRender(const QChar *string, int len)
     const unsigned char *cmap = m_extras->cmap();
     for (int i = 0; i < len; ++i) {
         const unsigned int uc = getChar(string, i, len);
-        if (QFontEngine::getTrueTypeGlyphIndex(cmap, uc) == 0)
+        if (QFontEngine::getTrueTypeGlyphIndex(cmap, m_cmapSize, uc) == 0)
             return false;
     }
     return true;
diff --git a/src/gui/text/qfontengine_s60_p.h b/src/gui/text/qfontengine_s60_p.h
index 17e2207..9e38570 100644
--- a/src/gui/text/qfontengine_s60_p.h
+++ b/src/gui/text/qfontengine_s60_p.h
@@ -93,6 +93,7 @@ private:
     // the Font Table API
     COpenFont *m_openFont;
     mutable MOpenFontTrueTypeExtension *m_trueTypeExtension;
+    mutable int m_cmapSize;
 };
 
 class QFontEngineS60 : public QFontEngine
diff --git a/src/gui/text/qfontengine_win.cpp b/src/gui/text/qfontengine_win.cpp
index bd9a437..6ad5eb4 100644
--- a/src/gui/text/qfontengine_win.cpp
+++ b/src/gui/text/qfontengine_win.cpp
@@ -215,9 +215,8 @@ void QFontEngineWin::getCMap()
     bool symb = false;
     if (ttf) {
         cmapTable = getSfntTable(qbswap<quint32>(MAKE_TAG('c', 'm', 'a', 'p')));
-        int size = 0;
         cmap = QFontEngine::getCMap(reinterpret_cast<const uchar *>(cmapTable.constData()),
-                       cmapTable.size(), &symb, &size);
+                       cmapTable.size(), &symb, &cmapSize);
     }
     if (!cmap) {
         ttf = false;
@@ -263,14 +262,14 @@ int QFontEngineWin::getGlyphIndexes(const QChar *str, int numChars, QGlyphLayout
         if (symbol) {
             for (; i < numChars; ++i, ++glyph_pos) {
                 unsigned int uc = getChar(str, i, numChars);
-                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc);
+                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
                 if (!glyphs->glyphs[glyph_pos] && uc < 0x100)
-                    glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc + 0xf000);
+                    glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc + 0xf000);
             }
         } else if (ttf) {
             for (; i < numChars; ++i, ++glyph_pos) {
                 unsigned int uc = getChar(str, i, numChars);
-                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, QChar::mirroredChar(uc));
+                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, QChar::mirroredChar(uc));
             }
         } else {
 #endif
@@ -296,14 +295,14 @@ int QFontEngineWin::getGlyphIndexes(const QChar *str, int numChars, QGlyphLayout
         if (symbol) {
             for (; i < numChars; ++i, ++glyph_pos) {
                 unsigned int uc = getChar(str, i, numChars);
-                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc);
+                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
                 if(!glyphs->glyphs[glyph_pos] && uc < 0x100)
-                    glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc + 0xf000);
+                    glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc + 0xf000);
             }
         } else if (ttf) {
             for (; i < numChars; ++i, ++glyph_pos) {
                 unsigned int uc = getChar(str, i, numChars);
-                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, uc);
+                glyphs->glyphs[glyph_pos] = getTrueTypeGlyphIndex(cmap, cmapSize, uc);
             }
         } else {
 #endif
@@ -335,6 +334,7 @@ QFontEngineWin::QFontEngineWin(const QString &name, HFONT _hfont, bool stockFont
     _name = name;
 
     cmap = 0;
+    cmapSize = 0;
     hfont = _hfont;
     logfont = lf;
     HDC hdc = shared_dc();
@@ -811,9 +811,9 @@ bool QFontEngineWin::canRender(const QChar *string,  int len)
     if (symbol) {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(string, i, len);
-            if (getTrueTypeGlyphIndex(cmap, uc) == 0) {
+            if (getTrueTypeGlyphIndex(cmap, cmapSize, uc) == 0) {
                 if (uc < 0x100) {
-                    if (getTrueTypeGlyphIndex(cmap, uc + 0xf000) == 0)
+                    if (getTrueTypeGlyphIndex(cmap, cmapSize, uc + 0xf000) == 0)
                         return false;
                 } else {
                     return false;
@@ -823,7 +823,7 @@ bool QFontEngineWin::canRender(const QChar *string,  int len)
     } else if (ttf) {
         for (int i = 0; i < len; ++i) {
             unsigned int uc = getChar(string, i, len);
-            if (getTrueTypeGlyphIndex(cmap, uc) == 0)
+            if (getTrueTypeGlyphIndex(cmap, cmapSize, uc) == 0)
                 return false;
         }
     } else {
diff --git a/src/gui/text/qfontengine_win_p.h b/src/gui/text/qfontengine_win_p.h
index 0c8df72..27f0355 100644
--- a/src/gui/text/qfontengine_win_p.h
+++ b/src/gui/text/qfontengine_win_p.h
@@ -144,6 +144,7 @@ public:
     mutable uint widthCacheSize;
     mutable QFixed *designAdvances;
     mutable int designAdvancesSize;
+    int cmapSize;
 
 private:
     bool hasCFFTable() const;
-- 
2.8.1