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[2002-11-30 12:38 UTC] heyjohnlim at yahoo dot com
When doing testing with ADOdb and PEAR DB, the following scripts crash PHP (when the delete statement is executed) with an illegal memory reference at 0xffffffff. I tried to duplicate the problem with native mssql functions, but could not.
While tracing through in ADOdb, I found that the crash occurs during the PHP return statement, and not within mssql code. Perhaps some form of subtle stack/data corruption.
Thanks, John Lim
Other useful info
=================
MSSQL 2000 (MSDE)
PEAR DB from PHP 4.23
ADOdb 2.50
SCRIPT
======
<?php
error_reporting(E_ALL);
ini_set('mssql.datetimeconvert',0);
function tmssql()
{
print "<h3>mssql</h3>";
$db = mssql_connect('JAGUAR\vsdotnet','adodb','natsoft') or die('No Connection');
mssql_select_db('northwind',$db);
$rs = mssql_query('select getdate() as date',$db);
$o = mssql_fetch_row($rs);
print_r($o);
mssql_free_result($rs);
print "<p>Delete</p>"; flush();
$rs2 = mssql_query('delete from adoxyz',$db);
$p = mssql_num_rows($rs2);
mssql_free_result($rs2);
}
function tpear()
{
include_once('DB.php');
print "<h3>PEAR</h3>";
$username = 'adodb';
$password = 'natsoft';
$hostname = 'JAGUAR\vsdotnet';
$databasename = 'northwind';
$dsn = "mssql://$username:$password@$hostname/$databasename";
$conn = &DB::connect($dsn);
print "date=".$conn->GetOne('select getdate()')."<br>";
@$conn->query('create table tester (id integer)');
print "<p>Delete</p>"; flush();
$rs = $conn->query('delete from tester');
/*** CRASH IN QUERY ABOVE ****/
print "date=".$conn->GetOne('select getdate()')."<br>";
}
function tadodb()
{
include_once('../adodb.inc.php');
print "<h3>ADOdb</h3>";
$conn = NewADOConnection('mssql');
$conn->Connect('JAGUAR\vsdotnet','adodb','natsoft','northwind');
// $conn->debug=1;
print "date=".$conn->GetOne('select getdate()')."<br>";
$conn->Execute('create table tester (id integer)');
print "<p>Delete</p>"; flush();
$rs = $conn->Execute('delete from tester');
/*** CRASH IN EXECUTE ABOVE ****/
print "date=".$conn->GetOne('select getdate()')."<br>";
}
?>
<a href=tmssql.php?do=tmssql>Test mssql</a>
<a href=tmssql.php?do=tpear>Test pear</a>
<a href=tmssql.php?do=tadodb>Test adodb</a>
<?php
if (!empty($_GET['do'])) {
$do = $_GET['do'];
$do();
}
?>
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Last updated: Sun Apr 20 01:01:28 2025 UTC |
This seems to be the problem - i suspect. Testing my existing SQL Server based sites with 4.3.0RC2 resulted in many memory access violations and crashes. I believe that I have tracked these down to two different changes made to the MSSQL extension since 4.2.3: 1) In version 1.82 of php_mssql.c there were 6 mallocs that were changed from "emalloc(res_length + 1);" to "emalloc(res_length);". I believe, however, that the code that uses those memory blocks in at least four of the cases required that extra space. This is the code as it is now for two of the changes in 4.3.0RC2: res_buf = (unsigned char *) emalloc(res_length); bin = ((DBBINARY *)dbdata(mssql_ptr->link, offset)); memcpy(res_buf, bin, res_length); res_buf[res_length] = '\0'; It's the setting of res_buf[res_length] illegal, as that would be beyond the bounds of emalloc(res_length)? Also this code (appearing in two of the changes): res_length = 19; res_buf = (unsigned char *) emalloc(res_length); sprintf(res_buf, "%d-%02d-%02d %02d:%02d:%02d" , . . . Since the length of the character string is going to be 19 characters, isn't the sprintf going to write an ASCIIZ ending beyond the size of res_buf? Does the way emalloc() works take care of these problems? Adding the "+ 1" back to these four emalloc() calls stopped one set of crashes. 2) In version 1.83 of php_mssql.c the mssql_query() function was altered from: if ((num_fields = dbnumcols(mssql_ptr->link)) <= 0) { RETURN_TRUE; } to: if ((num_fields = dbnumcols(mssql_ptr->link)) <= 0 && !dbdataready(mssql_ptr->link)) { RETURN_TRUE; } The CVS comment indicates that this change was for "fixing the mssql_query to handle multiple results correct if the first result does not return any data." If I now call mssql_query() with a query that doesn't return any values (like a SQL-T EXEC call), however, PHP will crash (removing the new dbdataready() check eliminates the crash). Michael Sisolak msisolak@yahoo.com