| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Petr Jelinek <petr(at)2ndquadrant(dot)com> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Dereferenced pointer in tablesample.c |
| Date: | 2015-06-30 16:47:52 |
| Message-ID: | 6975.1435682872@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Petr Jelinek <petr(at)2ndquadrant(dot)com> writes:
> On 2015-06-30 09:10, Michael Paquier wrote:
>> If the expression argstate is NULL when calling ExecInitExpr(), argstate
>> is going to be NULL and dereferenced afterwards, see execQual.c for more
>> details. Hence I think that the patch attached should be applied. Thoughts?
> Well, yes the ExecEvalExpr should be in the else block if we'd keep the
> NULL logic there.
> However after rereading the code, ISTM the ExecInitExpr will only return
> NULL if the argexpr is NULL and argexpr is added by ParseTableSample
> using the transformExpr on every argument which comes from grammar and
> those are a_exprs which AFAIK will never be NULL. So I actually think
> that the argstate can never be NULL in practice.
Indeed. ParseTableSample() is badly in need of a rewrite, but I agree
that it's not going to produce null expression trees.
> Patch attached.
Will push this shortly.
regards, tom lane
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