Обсуждение: Fix pg_rewind which can be run as root user

Hi all,

I was just going through pg_rewind's code, and noticed the following
pearl:
    /*
     * Don't allow pg_rewind to be run as root, to avoid overwriting the
     * ownership of files in the data directory. We need only check for root
     * -- any other user won't have sufficient permissions to modify files in
     * the data directory.
     */
#ifndef WIN32
    if (geteuid() == 0)
    {
        fprintf(stderr, _("cannot be executed by \"root\"\n"));
        fprintf(stderr, _("You must run %s as the PostgreSQL superuser.\n"),
                progname);
    }
#endif

While that's nice to inform the user about the problem, that actually
does not prevent pg_rewind to run as root.  Attached is a patch, which
needs a back-patch down to 9.5.

Thanks,
--
Michael

On Mon, Apr 9, 2018 at 12:23 PM, Magnus Hagander <magnus@hagander.net> wrote:
> Seems simple enough and the right hting to do, but I wonder if we should
> really backpatch it. Yes, the behaviour is not great now, but there is also
> a non-zero risk of breaking peoples automated failover scripts of we
> backpatch it, isn't it?

+1 to committing to master as a documented behavioral change.

-- 
Peter Geoghegan

Magnus Hagander <magnus@hagander.net> writes:
> Seems simple enough and the right hting to do, but I wonder if we should
> really backpatch it. Yes, the behaviour is not great now, but there is also
> a non-zero risk of breaking peoples automated failover scripts of we
> backpatch it, isn't it?

Yeah, I'd vote against backpatching.  This doesn't seem like an essential
fix.

            regards, tom lane

On Mon, Apr 09, 2018 at 09:36:40PM +0200, Magnus Hagander wrote:
> Applied, and pushed this way.

OK, thanks for the commit.
--
Michael