Re: LDAP authenticated session terminated by signal 11: Segmentation fault, PostgresSQL server terminates other active server processes

On Thu, Mar 07, 2019 at 10:45:56AM +1300, Thomas Munro wrote:
> On Wed, Feb 27, 2019 at 11:28 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Thomas Munro <thomas(dot)munro(at)gmail(dot)com> writes:
> > > I don't see pthread_is_threaded_np() on any non-Apple systems in my
> > > lab.
> >
> > Yeah, I thought that might be a Mac thing. I wonder if POSIX has any
> > usable equivalent.
>
> I don't see anything like that (the concept doesn't seem very
> portable).

I'm not aware of one.

> > > Clearly libdap_r is *capable* of creating threads: it contains a
> > > function ldap_pvt_thread_create(), and we can see that slapd and other
> > > OpenLDAP things use that, but AFAICT that's a private facility not
> > > intended for end users to call, so there's no danger if you just use
> > > the documented LDAP client API.
> >
> > That seems promising, but I'd sure be happier if we could cross-check
> > that there's still just one thread at the completion of authentication.
>
> Ok, here's that patch again with a commit message and with the
> configure version warning removed, and a make-sure-we're-not-threaded
> patch for FreeBSD.
>
> I'm not sure what to do about the LDAP test in
> contrib/dblink/sql/dblink.sql. Do we still want this?

Mike, does the dblink test suite not fail on your system? It's designed to
catch this exact problem.

Has anyone else reproduced this?

> I propose this for master only, for now. I also think it'd be nice to
> consider back-patching it after a while, especially since this
> reported broke on CentOS/RHEL7, a pretty popular OS that'll be around
> for a good while. Hmm, I wonder if it's OK to subtly change library
> dependencies in a minor release; I don't see any problem with it since
> I expect both variants to be provided by the same package in every
> distro but we'd certainly want to highlight this to the package
> maintainers if we did it.

It's not great to change library dependencies in a minor release. If every
RHEL 7 installation can crash this way, changing the dependencies is probably
the least bad thing.