Horton

Re: Worth using personality(ADDR_NO_RANDOMIZE) for EXEC_BACKEND on linux?

Andres Freund <andres@anarazel.de>

View thread View on postgr.es
From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andrew Dunstan <andrew@dunslane.net>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2021-08-09T18:04:07Z
Lists: pgsql-hackers 
Hi,

On 2021-08-09 13:54:25 -0400, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > On 2021-08-09 13:43:03 -0400, Robert Haas wrote:
> >> On Mon, Aug 9, 2021 at 1:30 PM Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> > How common is to get a failure?  I know I've run tests under
> > EXEC_BACKEND and not seen any failures.  Not many runs though.
> 
> > I get check-world failures in about 1/2-1/3 of the runs, and a plain check
> > fails in maybe 1/4 of the cases. It's pretty annoying because it often isn't
> > trivial to distinguish whether I've broken something or whether it's
> > randomization related...
> 
> I don't have numbers, but I do know that on Linux EXEC_BACKEND builds fail
> often enough to be annoying if you don't disable ASLR.  If we can do
> something not-too-invasive about that, it'd be great.

I now not sure if personality(NO_RANDOMIZE) in postmaster is actually
sufficient. It does seem to drastically reduce the frequency of issues, but
there's still conceivable failures where postmaster's layout would class with
the non-randomized children - obviously personality(NO_RANDOMIZE) cannot
retroactively change the layout of the already running binary.

So maybe we should put it into pg_ctl?

Greetings,

Andres Freund

Commits

  1. Make EXEC_BACKEND more convenient on Linux and FreeBSD.

  2. Make EXEC_BACKEND more convenient on macOS.