Thread

Re: Fix bug of COPY (on_error set_null)

Chao Li <li.evan.chao@gmail.com> — 2026-05-18T22:22:15Z

> On May 16, 2026, at 13:17, jian he <jian.universality@gmail.com> wrote:
> 
> On Fri, May 15, 2026 at 9:13 AM Chao Li <li.evan.chao@gmail.com> wrote:
>> 
>> Hi,
>> 
>> I just tested “Add COPY (column list) (on_error set_null) option”. While tracing a normal case, I found a mistake:
>> 
>> In BeginCopyFrom(), cstate->domain_with_constraint is allocated using the length of the specified column list, and set using the index in that column list:
>> ```
>>                int                     attr_count = list_length(cstate->attnumlist);
>> 
>>                /*
>>                 * When data type conversion fails and ON_ERROR is SET_NULL, we need
>>                 * ensure that the input column allow null values.  ExecConstraints()
>>                 * will cover most of the cases, but it does not verify domain
>>                 * constraints.  Therefore, for constrained domains, the null value
>>                 * check must be performed during the initial string-to-datum
>>                 * conversion (see CopyFromTextLikeOneRow()).
>>                 */
>>                cstate->domain_with_constraint = palloc0_array(bool, attr_count); <== allocate with length of column list from SQL
>> 
>>                foreach_int(attno, cstate->attnumlist)
>>                {
>>                        int                     i = foreach_current_index(attno);
>> 
>>                        Form_pg_attribute att = TupleDescAttr(tupDesc, attno - 1);
>> 
>>                        cstate->domain_with_constraint[i] = DomainHasConstraints(att->atttypid, NULL); <= set with index of column list from SQL
>>                }
>> ```
>> 
>> However, cstate->domain_with_constraint is read in CopyFromTextLikeOneRow(), where it is accessed using the actual attribute number:
>> ```
>>        /* Loop to read the user attributes on the line. */
>>        foreach(cur, cstate->attnumlist)
>>        {
>>                int                     attnum = lfirst_int(cur);
>>                int                     m = attnum - 1;
>> 
>>        ...
>>                                if (!cstate->domain_with_constraint[m] ||
>> ```
>> 
>> So, if the column list specified in SQL is shorter than the table’s actual attribute list, this may cause an out-of-bounds read.
>> 
> Hi.
> 
> This appears to be the same issue as reported here:
> https://postgr.es/m/CAHg+QDdej0c0gWJi2FnbirzhgzyZNPiTwC1P5B_-dSNCzq-91A@mail.gmail.com

Thanks for pointing out that. I will review that patch.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/