Bug#396218: bind.c: bad handling of SQL_LEN_DATA_AT_EXEC breaks passing char buffer length at SQLExec time

[Enrico Zini]

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


-- System Information:
Debian Release: 4.0
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.18-1-686
Locale: LANG=it_IT.UTF-8, LC_CTYPE=it_IT.UTF-8 (charmap=UTF-8)

Versions of packages odbc-postgresql depends on:
ii  libc6                        2.3.6.ds1-7 GNU C Library: Shared libraries
ii  libpq4                       8.1.5-1     PostgreSQL C client library
ii  odbcinst1debian1             2.2.11-13   Support library and helper program

odbc-postgresql recommends no packages.

-- no debconf information

diff -Naur psqlodbc-08.01.0200/bind.c psqlodbc-08.01.0200.enrico/bind.c
--- psqlodbc-08.01.0200/bind.c	2005-11-25 11:43:25.000000000 +0100
+++ psqlodbc-08.01.0200.enrico/bind.c	2006-10-30 16:44:45.644656335 +0100
@@ -116,8 +116,8 @@
 	if (pcbValue && apdopts->param_offset_ptr)
 		pcbValue += (*apdopts->param_offset_ptr >> 2);
 	/* 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))
+	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;