Wireshark · Ethereal-dev: Re: [Ethereal-dev] Exception in pdml

[Guy Harris <gharris@xxxxxxxxx>]

Wesley Shields wrote:

> I've done some digging through the archives and can only find minimal 
> mention of this issue.  The most specific email[1] I can find that fits 
> this issue is from 3/28/04 (there have been others but they don't 
> specifically mention a negative value).  If a field_info struct has a 
> negative length value an exception will eventually be thrown because it 
> can not ensure the block of data is contiguous before printing it out. I 
> believe that throwing an exception is not always desired, as automated 
> processes will stop early.  Ideally, an invalid value should be noted 
> and processing should continue.

No, ideally, an invalid value shouldn't *exist*.  A field_info structure 
shouldn't *have* a negative value.

There was a bug in the Mobile IPv6 code that caused that to happen; I 
checked in a fix a couple of days after that message was sent.

I have a change that will cause Ethereal to abort if a dissector 
attempts to create a field with a negative length or set the length to a 
negative value, so that bugs of that sort will be caught.  I'm testing 
it now with a collection of captures I have, in order to see whether any 
dissectors have bugs of that sort; once the testing is done, and any 
dissectors it finds bugs in are fixed, I'll check that in.