Re: [PATCH] obexd: Fix null pointer dereference.

Matias Karhumaa
2017-06-22T10:20:25Z

On Thu, Jun 22, 2017 at 09:18:10AM +0300, Johan Hedberg wrote:
> Hi Matias,
>
> On Thu, Jun 22, 2017, Matias Karhumaa wrote:
> > > >> It seems to me that the bug is with opp.c passing the service_data to
> > > >> manager_request_authorization(), and service_data is expected to be the
> > > >> obex_transfer object. However, currently the code creates this object
> > > >> only upon CONNECT (in opp_connect).
> > > >>
> > > >> I think one possible way to solve this would be to trigger a call to
> > > >> os->service->connect if CONNECT hasn't been explicitly issued, however
> > > >> then the code needs to track this in some other way since service_data
> > > >> seems too unreliable.
> > >
> > > How about the following:
> > >
> > > https://gist.github.com/Vudentz/1736d6af9608b9332b93858d92a3feff
> >
> > Your fix seems solid to me and fixes the crash with OPP. I checked ftp.c
> > also and saw potentially similar problem in ftp_chkput. Should we call
> > os->service->connect also in case of OBEX_FTP?
>
> OPP is the only service where the specification allows skipping the
> connect step. This is why os->service gets pre-initialized to OPP (in
> the obex_session_start function). Also, if the OPP plugin isn't
> available os->service will be NULL before CONNECT, and that's something
> the code already seems to check for (e.g. in cmd_put). So unless I've
> misunderstood something, you shouldn't be able get to a situation where
> os->service points at FTP but CONNECT hasn't been issued.

Ok, understood. Actually I tried to do FTP PUT without CONNECT and I can
confirm that it works as you explained.

I will create a patch from the gist.

Best regards,
Matias Karhumaa