From: | Amit Langote <amitlangote09(at)gmail(dot)com> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: CVE-2017-7484-induced bugs, or, btree cmp functions are not leakproof? |
Date: | 2019-11-27 02:03:34 |
Message-ID: | CA+HiwqF0P_xvNhGeCqx6_qinbSph_RaAxy3G+DRXyh_9JBNw=g@mail.gmail.com |
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On Wed, Nov 27, 2019 at 3:25 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Amit Langote <amitlangote09(at)gmail(dot)com> writes:
> > If inh_root_relid meant that, it would no longer be useful to
> > examine_variable. In examine_variable, we need to map a child table's
> > relid to the relid of its root parent table. If the root parent
> > itself is under a UNION ALL subquery parent, then inh_root_relid of
> > all relations in that ancestry chain would point to the UNION ALL
> > subquery parent, which is not what examine_variable would want to use,
> > because it's really looking for the root "table".
>
> Hm, I see. Still, the definition seems quite ad-hoc and of uncertain
> usefulness to any other use-case. Given that checking permissions for
> access to an expression index's stats is a pretty uncommon thing to
> be doing, I don't really want to let it drive the definition of a
> new RelOptInfo field.
>
> The other reason that I'm on the warpath against this field is that
> it makes the patch un-back-patchable, and I'd like to be able to fix
> this problem in the back branches.
Both arguments make sense.
> Given the existence of the append_rel_array array, it's not really
> difficult or expensive to use that to chain up to the root parent,
> as in the attached simplified patch. We could only use this back
> to v11 where append_rel_array was added, but that's still a lot
> better than no back-patched fix at all.
I agree.
> I've not studied the test case too closely yet, other than to verify
> that it does fail without the code fix :-). Other than that, though,
> I think this patch is committable for v11 through HEAD.
Thanks for committing.
Regards,
Amit
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