Fix crashes when creating large documents

Compact an object in regular intervals when inserting
data into it, to avoid the object becoming huge.
Compact an object/array before inserting into another
array or object.
Check that the document doesn't get so big it's overflowing
the internal data structures.

Task-number: QTBUG-29288
Change-Id: Id39d80dac1e7d5a11f40819f41b4b336bce16947
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/json/qjson.cpp

@@ -149,6 +149,10 @@ bool Data::valid() const
 int Base::reserveSpace(uint dataSize, int posInTable, uint numItems, bool replace)
 {
     Q_ASSERT(posInTable >= 0 && posInTable <= (int)length);
+    if (size + dataSize >= Value::MaxSize) {
+        qWarning("QJson: Document too large to store in data structure %d %d %d", (uint)size, dataSize, Value::MaxSize);
+        return 0;
+    }
 
     offset off = tableOffset;
     // move table to new position
@@ -334,7 +338,7 @@ bool Value::isValid(const Base *b) const
 /*!
     \internal
  */
-int Value::requiredStorage(const QJsonValue &v, bool *compressed)
+int Value::requiredStorage(QJsonValue &v, bool *compressed)
 {
     *compressed = false;
     switch (v.t) {
@@ -351,6 +355,11 @@ int Value::requiredStorage(const QJsonValue &v, bool *compressed)
     }
     case QJsonValue::Array:
     case QJsonValue::Object:
+        if (v.d && v.d->compactionCounter) {
+            v.detach();
+            v.d->compact();
+            v.base = static_cast<QJsonPrivate::Base *>(v.d->header->root());
+        }
         return v.base ? v.base->size : sizeof(QJsonPrivate::Base);
     case QJsonValue::Undefined:
     case QJsonValue::Null:

src/corelib/json/qjson_p.h

@@ -543,6 +543,9 @@ public:
 class Value
 {
 public:
+    enum {
+        MaxSize = (1<<27) - 1
+    };
     union {
         uint _dummy;
         qle_bitfield<0, 3> type;
@@ -564,7 +567,7 @@ public:
 
     bool isValid(const Base *b) const;
 
-    static int requiredStorage(const QJsonValue &v, bool *compressed);
+    static int requiredStorage(QJsonValue &v, bool *compressed);
     static uint valueToStore(const QJsonValue &v, uint offset);
     static void copyData(const QJsonValue &v, char *dest, bool compressed);
 };

src/corelib/json/qjsonarray.cpp

@@ -391,9 +391,10 @@ QJsonValue QJsonArray::takeAt(int i)
 void QJsonArray::insert(int i, const QJsonValue &value)
 {
     Q_ASSERT (i >= 0 && i <= (a ? (int)a->length : 0));
+    QJsonValue val = value;
 
     bool compressed;
-    int valueSize = QJsonPrivate::Value::requiredStorage(value, &compressed);
+    int valueSize = QJsonPrivate::Value::requiredStorage(val, &compressed);
 
     detach(valueSize + sizeof(QJsonPrivate::Value));
 
@@ -401,13 +402,16 @@ void QJsonArray::insert(int i, const QJsonValue &value)
         a->tableOffset = sizeof(QJsonPrivate::Array);
 
     int valueOffset = a->reserveSpace(valueSize, i, 1, false);
+    if (!valueOffset)
+        return;
+
     QJsonPrivate::Value &v = (*a)[i];
-    v.type = (value.t == QJsonValue::Undefined ? QJsonValue::Null : value.t);
+    v.type = (val.t == QJsonValue::Undefined ? QJsonValue::Null : val.t);
     v.latinOrIntValue = compressed;
     v.latinKey = false;
-    v.value = QJsonPrivate::Value::valueToStore(value, valueOffset);
+    v.value = QJsonPrivate::Value::valueToStore(val, valueOffset);
     if (valueSize)
-        QJsonPrivate::Value::copyData(value, (char *)a + valueOffset, compressed);
+        QJsonPrivate::Value::copyData(val, (char *)a + valueOffset, compressed);
 }
 
 /*!
@@ -437,9 +441,10 @@ void QJsonArray::insert(int i, const QJsonValue &value)
 void QJsonArray::replace(int i, const QJsonValue &value)
 {
     Q_ASSERT (a && i >= 0 && i < (int)(a->length));
+    QJsonValue val = value;
 
     bool compressed;
-    int valueSize = QJsonPrivate::Value::requiredStorage(value, &compressed);
+    int valueSize = QJsonPrivate::Value::requiredStorage(val, &compressed);
 
     detach(valueSize);
 
@@ -447,13 +452,16 @@ void QJsonArray::replace(int i, const QJsonValue &value)
         a->tableOffset = sizeof(QJsonPrivate::Array);
 
     int valueOffset = a->reserveSpace(valueSize, i, 1, true);
+    if (!valueOffset)
+        return;
+
     QJsonPrivate::Value &v = (*a)[i];
-    v.type = (value.t == QJsonValue::Undefined ? QJsonValue::Null : value.t);
+    v.type = (val.t == QJsonValue::Undefined ? QJsonValue::Null : val.t);
     v.latinOrIntValue = compressed;
     v.latinKey = false;
-    v.value = QJsonPrivate::Value::valueToStore(value, valueOffset);
+    v.value = QJsonPrivate::Value::valueToStore(val, valueOffset);
     if (valueSize)
-        QJsonPrivate::Value::copyData(value, (char *)a + valueOffset, compressed);
+        QJsonPrivate::Value::copyData(val, (char *)a + valueOffset, compressed);
 
     ++d->compactionCounter;
     if (d->compactionCounter > 32u && d->compactionCounter >= unsigned(a->length) / 2u)

src/corelib/json/qjsondocument.h

@@ -67,7 +67,8 @@ struct Q_CORE_EXPORT QJsonParseError
         IllegalUTF8String,
         UnterminatedString,
         MissingObject,
-        DeepNesting
+        DeepNesting,
+        DocumentTooLarge
     };
 
     QString    errorString() const;

src/corelib/json/qjsonobject.cpp

@@ -317,9 +317,10 @@ QJsonObject::iterator QJsonObject::insert(const QString &key, const QJsonValue &
         remove(key);
         return end();
     }
+    QJsonValue val = value;
 
     bool latinOrIntValue;
-    int valueSize = QJsonPrivate::Value::requiredStorage(value, &latinOrIntValue);
+    int valueSize = QJsonPrivate::Value::requiredStorage(val, &latinOrIntValue);
 
     bool latinKey = QJsonPrivate::useCompressed(key);
     int valueOffset = sizeof(QJsonPrivate::Entry) + QJsonPrivate::qStringSize(key, latinKey);
@@ -335,16 +336,21 @@ QJsonObject::iterator QJsonObject::insert(const QString &key, const QJsonValue &
     if (keyExists)
         ++d->compactionCounter;
 
-    o->reserveSpace(requiredSize, pos, 1, keyExists);
+    uint off = o->reserveSpace(requiredSize, pos, 1, keyExists);
+    if (!off)
+        return end();
 
     QJsonPrivate::Entry *e = o->entryAt(pos);
-    e->value.type = value.t;
+    e->value.type = val.t;
     e->value.latinKey = latinKey;
     e->value.latinOrIntValue = latinOrIntValue;
-    e->value.value = QJsonPrivate::Value::valueToStore(value, (char *)e - (char *)o + valueOffset);
+    e->value.value = QJsonPrivate::Value::valueToStore(val, (char *)e - (char *)o + valueOffset);
     QJsonPrivate::copyString((char *)(e + 1), key, latinKey);
     if (valueSize)
-        QJsonPrivate::Value::copyData(value, (char *)e + valueOffset, latinOrIntValue);
+        QJsonPrivate::Value::copyData(val, (char *)e + valueOffset, latinOrIntValue);
+
+    if (d->compactionCounter > 32u && d->compactionCounter >= unsigned(o->length) / 2u)
+        compact();
 
     return iterator(this, pos);
 }

src/corelib/json/qjsonparser.cpp

@@ -76,6 +76,7 @@ QT_BEGIN_NAMESPACE
 #define JSONERR_UTERM_STR   QT_TRANSLATE_NOOP("QJsonParseError", "unterminated string")
 #define JSONERR_MISS_OBJ    QT_TRANSLATE_NOOP("QJsonParseError", "object is missing after a comma")
 #define JSONERR_DEEP_NEST   QT_TRANSLATE_NOOP("QJsonParseError", "too deeply nested document")
+#define JSONERR_DOC_LARGE   QT_TRANSLATE_NOOP("QJsonParseError", "too large document")
 
 /*!
     \class QJsonParseError
@@ -105,6 +106,7 @@ QT_BEGIN_NAMESPACE
     \value UnterminatedString       A string wasn't terminated with a quote
     \value MissingObject            An object was expected but couldn't be found
     \value DeepNesting              The JSON document is too deeply nested for the parser to parse it
+    \value DocumentTooLarge         The JSON document is too large for the parser to parse it
 */
 
 /*!
@@ -173,6 +175,9 @@ QString QJsonParseError::errorString() const
     case DeepNesting:
         sz = JSONERR_DEEP_NEST;
         break;
+    case DocumentTooLarge:
+        sz = JSONERR_DOC_LARGE;
+        break;
     }
 #ifndef QT_BOOTSTRAPPED
     return QCoreApplication::translate("QJsonParseError", sz);
@@ -579,6 +584,10 @@ bool Parser::parseValue(QJsonPrivate::Value *val, int baseOffset)
         return false;
     case Quote: {
         val->type = QJsonValue::String;
+        if (current - baseOffset >= Value::MaxSize) {
+            lastError = QJsonParseError::DocumentTooLarge;
+            return false;
+        }
         val->value = current - baseOffset;
         bool latin1;
         if (!parseString(&latin1))
@@ -590,6 +599,10 @@ bool Parser::parseValue(QJsonPrivate::Value *val, int baseOffset)
     }
     case BeginArray:
         val->type = QJsonValue::Array;
+        if (current - baseOffset >= Value::MaxSize) {
+            lastError = QJsonParseError::DocumentTooLarge;
+            return false;
+        }
         val->value = current - baseOffset;
         if (!parseArray())
             return false;
@@ -598,6 +611,10 @@ bool Parser::parseValue(QJsonPrivate::Value *val, int baseOffset)
         return true;
     case BeginObject:
         val->type = QJsonValue::Object;
+        if (current - baseOffset >= Value::MaxSize) {
+            lastError = QJsonParseError::DocumentTooLarge;
+            return false;
+        }
         val->value = current - baseOffset;
         if (!parseObject())
             return false;
@@ -707,6 +724,10 @@ bool Parser::parseNumber(QJsonPrivate::Value *val, int baseOffset)
 
     int pos = reserveSpace(sizeof(double));
     *(quint64 *)(data + pos) = qToLittleEndian(ui);
+    if (current - baseOffset >= Value::MaxSize) {
+        lastError = QJsonParseError::DocumentTooLarge;
+        return false;
+    }
     val->value = pos - baseOffset;
     val->latinOrIntValue = false;