Resolves: ofz#424 guard against broken dxary length

Change-Id: Ia2569e963edd75cd6c27399d33e73bafe8b3f073
Reviewed-on: https://gerrit.libreoffice.org/33319Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/source/gdi/svmconverter.cxx

@@ -939,6 +939,7 @@ void SVMConverter::ImplConvertFromSVM1( SvStream& rIStm, GDIMetaFile& rMtf )
                     OUString aStr(OStringToOUString(aByteStr, eActualCharSet));
 
                     std::unique_ptr<long[]> pDXAry;
+                    sal_Int32 nDXAryLen = 0;
                     if (nAryLen > 0)
                     {
                         const size_t nMinRecordSize = sizeof(sal_Int32);
@@ -952,36 +953,50 @@ void SVMConverter::ImplConvertFromSVM1( SvStream& rIStm, GDIMetaFile& rMtf )
 
                         sal_Int32 nStrLen( aStr.getLength() );
 
-                        pDXAry.reset(new long[ std::max( nAryLen, nStrLen ) ]);
+                        nDXAryLen = std::max(nAryLen, nStrLen);
 
-                        for (sal_Int32 j = 0; j < nAryLen; ++j)
-                            rIStm.ReadInt32( nTmp ), pDXAry[ j ] = nTmp;
-
-                        // #106172# Add last DX array elem, if missing
-                        if( nAryLen != nStrLen )
+                        if (nDXAryLen < nLen)
+                        {
+                            //MetaTextArrayAction ctor expects pDXAry to be >= nLen if set, so if this can't
+                            //be achieved, don't read it, it's utterly broken.
+                            SAL_WARN("vcl.gdi", "dxary too short, discarding completely");
+                            rIStm.SeekRel(sizeof(sal_Int32) * nDXAryLen);
+                            nLen = 0;
+                            nIndex = 0;
+                        }
+                        else
                         {
-                            if( nAryLen+1 == nStrLen )
+                            pDXAry.reset(new long[nDXAryLen]);
+
+                            for (sal_Int32 j = 0; j < nAryLen; ++j)
+                                rIStm.ReadInt32( nTmp ), pDXAry[ j ] = nTmp;
+
+                            // #106172# Add last DX array elem, if missing
+                            if( nAryLen != nStrLen )
                             {
-                                std::unique_ptr<long[]> pTmpAry(new long[nStrLen]);
-
-                                aFontVDev->GetTextArray( aStr, pTmpAry.get(), nIndex, nLen );
-
-                                // now, the difference between the
-                                // last and the second last DX array
-                                // is the advancement for the last
-                                // glyph. Thus, to complete our meta
-                                // action's DX array, just add that
-                                // difference to last elem and store
-                                // in very last.
-                                if( nStrLen > 1 )
-                                    pDXAry[ nStrLen-1 ] = pDXAry[ nStrLen-2 ] + pTmpAry[ nStrLen-1 ] - pTmpAry[ nStrLen-2 ];
-                                else
-                                    pDXAry[ nStrLen-1 ] = pTmpAry[ nStrLen-1 ]; // len=1: 0th position taken to be 0
-                            }
+                                if( nAryLen+1 == nStrLen )
+                                {
+                                    std::unique_ptr<long[]> pTmpAry(new long[nStrLen]);
+
+                                    aFontVDev->GetTextArray( aStr, pTmpAry.get(), nIndex, nLen );
+
+                                    // now, the difference between the
+                                    // last and the second last DX array
+                                    // is the advancement for the last
+                                    // glyph. Thus, to complete our meta
+                                    // action's DX array, just add that
+                                    // difference to last elem and store
+                                    // in very last.
+                                    if( nStrLen > 1 )
+                                        pDXAry[ nStrLen-3 ] = pDXAry[ nStrLen-2 ] + pTmpAry[ nStrLen-1 ] - pTmpAry[ nStrLen-2 ];
+                                    else
+                                        pDXAry[ nStrLen-1 ] = pTmpAry[ nStrLen-1 ]; // len=1: 0th position taken to be 0
+                                }
 #ifdef DBG_UTIL
-                            else
-                                OSL_FAIL("More than one DX array element missing on SVM import");
+                                else
+                                    OSL_FAIL("More than one DX array element missing on SVM import");
 #endif
+                            }
                         }
                     }
                     if ( nUnicodeCommentActionNumber == i )