ofz#827 avoid oom in xpms

Change-Id: I323be5e042e0ccb21956def70a8c481833f43998

vcl/source/filter/ixpm/xpmread.cxx

@@ -160,6 +160,10 @@ ReadState XPMReader::ReadXPM( Graphic& rGraphic )
                 mbStatus = false;
             if ( ( mnWidth * mnCpp ) >= XPMSTRINGBUF )
                 mbStatus = false;
+            //xpms are a minimum of one character (one byte) per pixel, so if the file isn't
+            //even that long, its not all there
+            if (mrIStm.remainingSize() < static_cast<sal_uInt64>(mnWidth) * mnHeight)
+                mbStatus = false;
             if ( mbStatus && mnWidth && mnHeight && mnColors && mnCpp )
             {
                 mnIdentifier = XPMCOLORS;