fixed heap use after free vulnerability CVE-2021-21900

as reported in TALOS-2021-1351 / CVE-2021-21900,
DRW_TableEntry::parseCode had the potential to trigger an use after free exception with a malformed DXF file.

ChangeLog.txt

@@ -24,6 +24,7 @@
 - Option to disable the automatic search for updates.
 - [smart-pattern/valentina#153] To add text search bar in History window.
 - Improve for a search bar.
+- Backport fix vulnerability CVE-2021-21900.
 
 # Valentina 0.7.49 July 1, 2021
 - Fix crash.

src/libs/vdxf/libdxfrw/drw_objects.cpp

@@ -48,26 +48,46 @@ void DRW_TableEntry::parseCode(int code, dxfReader *reader){
     case 1011:
     case 1012:
     case 1013:
-        curr = new DRW_Variant();
+        // don't trust in X, Y, Z order!
-        curr->addCoord();
+        if (curr != nullptr)
+        {
             curr->setCoordX(reader->getDouble());
-        curr->code = code;
+        }
+        else
+        {
+            curr = new DRW_Variant( code, DRW_Coord( reader->getDouble(), 0.0, 0.0));
             extData.push_back(curr);
+        }
         break;
     case 1020:
     case 1021:
     case 1022:
     case 1023:
-        if (curr)
+        // don't trust in X, Y, Z order!
+        if (curr != nullptr)
+        {
             curr->setCoordY(reader->getDouble());
+        }
+        else
+        {
+            curr = new DRW_Variant(code, DRW_Coord( 0.0, reader->getDouble(), 0.0));
+                                   extData.push_back(curr);
+        }
         break;
     case 1030:
     case 1031:
     case 1032:
     case 1033:
-        if (curr)
+        // don't trust in X, Y, Z order!
+        if (curr != nullptr)
+        {
             curr->setCoordZ(reader->getDouble());
-        curr=nullptr;
+        }
+        else
+        {
+            curr = new DRW_Variant(code, DRW_Coord(0.0, 0.0, reader->getDouble()));
+            extData.push_back(curr);
+        }
         break;
     case 1040:
     case 1041:

src/libs/vdxf/libdxfrw/drw_objects.h

@@ -54,20 +54,15 @@ namespace DRW {
 */
 class DRW_TableEntry {
 public:
-    //initializes default values
     DRW_TableEntry()
-        : tType(DRW::UNKNOWNT),
-          handle(),
-          parentHandle(0),
-          name(),
-          flags(0),
-          extData(),
-          curr(nullptr)
     {}
 
-    virtual~DRW_TableEntry() {
+    virtual~DRW_TableEntry()
-        for (std::vector<DRW_Variant*>::iterator it=extData.begin(); it!=extData.end(); ++it)
+    {
+        for (std::vector<DRW_Variant*>::iterator it = extData.begin(); it != extData.end(); ++it)
+        {
             delete *it;
+        }
 
         extData.clear();
     }
@@ -79,34 +74,45 @@ public:
           name(e.name),
           flags(e.flags),
           extData(),
-          curr(e.curr)
+          curr(nullptr)
     {
-        for (std::vector<DRW_Variant*>::const_iterator it=e.extData.begin(); it!=e.extData.end(); ++it){
+        for (std::vector<DRW_Variant*>::const_iterator it = e.extData.begin(); it != e.extData.end(); ++it)
-            extData.push_back(new DRW_Variant(*(*it)));
+        {
+            DRW_Variant *src = *it;
+            DRW_Variant *dst = new DRW_Variant(*src);
+            extData.push_back(dst);
+            if (src == e.curr)
+            {
+                curr = dst;
+            }
         }
     }
 
 protected:
     void parseCode(int code, dxfReader *reader);
-    void reset(){
+    void reset()
+    {
         flags = 0;
-        for (std::vector<DRW_Variant*>::iterator it=extData.begin(); it!=extData.end(); ++it)
+        for (std::vector<DRW_Variant*>::iterator it = extData.begin(); it != extData.end(); ++it)
+        {
             delete *it;
+        }
         extData.clear();
+        curr = nullptr;
     }
 
 public:
-    enum DRW::TTYPE tType;     /*!< enum: entity type, code 0 */
+    enum DRW::TTYPE tType {DRW::UNKNOWNT};  /*!< enum: entity type, code 0 */
-    duint32 handle;            /*!< entity identifier, code 5 */
+    duint32 handle {0};                     /*!< entity identifier, code 5 */
-    int parentHandle;          /*!< Soft-pointer ID/handle to owner object, code 330 */
+    int parentHandle {0};                   /*!< Soft-pointer ID/handle to owner object, code 330 */
-    UTF8STRING name;           /*!< entry name, code 2 */
+    UTF8STRING name{};                      /*!< entry name, code 2 */
-    int flags;                 /*!< Flags relevant to entry, code 70 */
+    int flags {0};                          /*!< Flags relevant to entry, code 70 */
-    std::vector<DRW_Variant*> extData; /*!< FIFO list of extended data, codes 1000 to 1071*/
+    std::vector<DRW_Variant*> extData{};    /*!< FIFO list of extended data, codes 1000 to 1071*/
 
 private:
     DRW_TableEntry &operator=(const DRW_TableEntry &) Q_DECL_EQ_DELETE;
     // cppcheck-suppress unsafeClassCanLeak
-    DRW_Variant* curr;
+    DRW_Variant* curr{nullptr};
 };