Re: Fwd: Bug#396218: bind.c: bad handling of SQL_LEN_DATA_AT_EXEC

Peter Eisentraut wrote:
> A Debian bug report ...

Enrico is right at the point that the evaluation of *pcbValue here is
dangerous and has no meaning. So in my version I already invalidated
the code(#ifdef NOT_USED). Unfortunately his patch seems to have no
meaning.

regards,
Hiroshi Inoue

> ----------  Forwarded Message  ----------
>
> Subject: Bug#396218: bind.c: bad handling of SQL_LEN_DATA_AT_EXEC breaks
> passing char buffer length at SQLExec time
> Date: Monday 30 October 2006 17:00
> From: Enrico Zini <enrico@debian.org>
> To: Debian Bug Tracking System <submit@bugs.debian.org>
>
> Package: odbc-postgresql
> Version: 1:08.01.0200-2
> Severity: normal
> Tags: patch
>
> Hello,
>
> thanks for maintaining odbc-postgresql.
>
> In my package dballe (apt-get source dballe) I optimize some frequent
> query by preparing the ODBC statement for them and binding the input
> parameters, so that when I need the results I can just set some of the
> bound variables and call SQLExecute.
>
> This is an example of such variable bind code:
>
>     SQLBindParameter(res->istm, 3, SQL_PARAM_INPUT, SQL_C_CHAR,
>  SQL_CHAR, 0, 0, &(res->value), 0, &(res->value_ind));
>
> Note that I'm passing a pointer to the variable that will hold the
> string length as the last parameter, instead of using SQL_NTS.
>
> Now, this call eventually ends up in this code, found at bind.c:118:
>
>     /* Data at exec macro only valid for C char/binary data */
>     if (pcbValue && (*pcbValue == SQL_DATA_AT_EXEC ||
>                                      *pcbValue <=
>  SQL_LEN_DATA_AT_EXEC_OFFSET)) apdopts->parameters[ipar].data_at_exec =
>  TRUE;
>     else
>         apdopts->parameters[ipar].data_at_exec = FALSE;
>
> This code tries to dereferenciate the (still uninitialised) pointer I
> pass it ( that &(res->value_ind) ) and fails.  The test should be like
> this instead:
>
>     /* Data at exec macro only valid for C char/binary data */
>     if (pcbValue && (pcbValue == SQL_DATA_AT_EXEC ||
>                                      pcbValue <=
>  SQL_LEN_DATA_AT_EXEC_OFFSET)) apdopts->parameters[ipar].data_at_exec =
>  TRUE;
>     else
>         apdopts->parameters[ipar].data_at_exec = FALSE;
>
> ODBC has this dirty habit of passing negative integers as special
>  values for pointers, and SQL_DATA_AT_EXEC is one of those:
>
> from /usr/include/sql.h:29:
>
> #define SQL_NULL_DATA             (-1)
> #define SQL_DATA_AT_EXEC          (-2)
>
> same goes for the handling of SQL_LEN_DATA_AT_EXEC_OFFSET.
>
> I regret I can't test the patch with code that uses SQL_DATA_AT_EXEC,
> because that is an ODBC feature that I do not use.  However, with the
> patch my SQLBindParameter above works fine.
>
>
> Ciao,
>
> Enrico