Re: A bug with ExecCheckPermissions - Mailing list pgsql-hackers

From Amit Langote
Subject Re: A bug with ExecCheckPermissions
Date
Msg-id CA+HiwqFPKnJqKxCdUO3szQ1hY7E973Z1CCaEDnvZfh=cN4xY0Q@mail.gmail.com
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In response to Re: A bug with ExecCheckPermissions  (Alvaro Herrera <alvherre@alvh.no-ip.org>)
Responses Re: A bug with ExecCheckPermissions
List pgsql-hackers
On Wed, Feb 8, 2023 at 16:19 Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
On 2023-Feb-08, o.tselebrovskiy@postgrespro.ru wrote:

> But if you debug function ExecCheckPermissions and look into what is passed
> to function (contents of rangeTable and rteperminfos to be exact),
> you'll see some strange behaviour:

> Both of RangeTableEntries have a perminfoindex of 0 and simultaneously have
> a RTEPERMISSIONINFO entry for them!

Ouch.  Yeah, that's not great.  As you say, it doesn't really affect
anything, and we know full well that these RTEs are ad-hoc
manufactured.  But as we claim that we still pass the RTEs for the
benefit of hooks, then we should at least make them match.

+1.   We don’t have anything in this (core) code path that would try to use perminfoindex for these RTEs, but there might well be in the future.

I think we should also patch ExecCheckPermissions to use forboth(),
scanning the RTEs as it goes over the perminfos, and make sure that the
entries are consistent.

Hmm, we can’t use forboth here, because not all RTEs have the corresponding RTEPermissionInfo, inheritance children RTEs, for example.   Also, it doesn’t make much sense to reinstate the original loop over range table and fetch the RTEPermissionInfo for the RTEs with non-0 perminfoindex, because the main goal of the patch was to make ExecCheckPermissions() independent of range table length.
--
Thanks, Amit Langote
EDB: http://www.enterprisedb.com

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