Thread: ECPG CONNECT TO DEFAULT segfault

ECPG CONNECT TO DEFAULT segfault

From
Michael Fuhr
Date:
PostgreSQL 8.0.0rc2, 7.4.6
Solaris 9, FreeBSD 4.11-PRERELEASE

ECPG's CONNECT TO DEFAULT causes a segmentation fault.  This
originally came up in the "Connection without database name" thread
in pgsql-hackers:

http://archives.postgresql.org/pgsql-hackers/2004-12/msg00813.php

Example:

#include <stdlib.h>
int main(void)
{
    EXEC SQL CONNECT TO DEFAULT;
    EXEC SQL DISCONNECT;
    return 0;
}

% ./foo
Segmentation fault (core dumped)

% gdb ./foo core
...
(gdb) bt
#0  0xff2344e4 in strlen () from /usr/lib/libc.so.1
#1  0xff254224 in strdup () from /usr/lib/libc.so.1
#2  0xff368ecc in ECPGconnect (lineno=0, c=-1, name=0x0, user=0x0, passwd=0x0,
    connection_name=0x107b8 "DEFAULT", autocommit=-14465948) at connect.c:245
#3  0x00010704 in main () at foo.pgc:4

ecpg generates the following for CONNECT TO DEFAULT:

    { ECPGconnect(__LINE__, 0, NULL,NULL,NULL,"DEFAULT", 0); }

The problem appears to be when assigning dbname at the beginning
of ECPGconnect():

    char    *dbname = strdup(name),

"name" is the third argument to ECPGconnect() so it's NULL in this
case.  Many systems' standard libraries segfault when strdup() is
called with a NULL pointer.

Several other places in ECPGconnect() look like they'll have a
problem if dbname is NULL.  Lines 275-279, for example:

    if (dbname == NULL && connection_name == NULL)
            connection_name = "DEFAULT";

    /* get the detail information out of dbname */
    if (strchr(dbname, '@') != NULL)

The first "if" considers the possibility that dbname is NULL, but
then the second "if" and subsequent code passes that possibly-NULL
pointer to various functions that will probably segfault if dbname
is indeed NULL.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/

Re: ECPG CONNECT TO DEFAULT segfault

From
Michael Meskes
Date:
On Tue, Dec 28, 2004 at 11:15:52PM -0700, Michael Fuhr wrote:
> PostgreSQL 8.0.0rc2, 7.4.6
> Solaris 9, FreeBSD 4.11-PRERELEASE
> 
> ECPG's CONNECT TO DEFAULT causes a segmentation fault.  This
> originally came up in the "Connection without database name" thread
> in pgsql-hackers:
> ....


This is exactly what I did fix with the work mentioned in the hackers
thread. It should work nicely with CVS HEAD. Could you please try this?

BTW Tom, I just found that my problem with PGDATABASE was a local one.
It surely works, so the oracle style syntax will remain. That is you can also
write EXEC SQL CONNECT <username> to connect to the default database using the
given username.

Michael
-- 
Michael Meskes
Email: Michael at Fam-Meskes dot De
ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes@jabber.org
Go SF 49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!


Re: ECPG CONNECT TO DEFAULT segfault

From
Michael Fuhr
Date:
On Wed, Dec 29, 2004 at 10:32:21AM +0100, Michael Meskes wrote:
> On Tue, Dec 28, 2004 at 11:15:52PM -0700, Michael Fuhr wrote:
> > 
> > ECPG's CONNECT TO DEFAULT causes a segmentation fault.  This
> > originally came up in the "Connection without database name" thread
> > in pgsql-hackers:
> 
> This is exactly what I did fix with the work mentioned in the hackers
> thread. It should work nicely with CVS HEAD. Could you please try this?

Try what?  I don't see a patch, link, or suggested fix in the
thread -- just your original message and the two followups by
Tom Lane and me.  Or was the fix discussed in a different thread?

-- 
Michael Fuhr
http://www.fuhr.org/~mfuhr/


Re: ECPG CONNECT TO DEFAULT segfault

From
Michael Meskes
Date:
Zitat von Michael Fuhr <mike@fuhr.org>:

>> This is exactly what I did fix with the work mentioned in the hackers
>> thread. It should work nicely with CVS HEAD. Could you please try
>> this?
>
> Try what?  I don't see a patch, link, or suggested fix in the
> thread -- just your original message and the two followups by
> Tom Lane and me.  Or was the fix discussed in a different thread?

Sorry, something didn't work on my side as I thought they would. I just
noticed that I did not commit my changes. They are now. So using the cvs version
or the next release candidate should fix the problem. I'm sorry, but I do not
have a patch against 7.4 at the moment.

Michael
-- 
Michael Meskes
Email: Michael at Fam-Meskes dot De
ICQ: 179140304, AIM/Yahoo: michaelmeskes, Jabber: meskes@jabber.org
Go SF 49ers! Go Rhein Fire! Use Debian GNU/Linux! Use PostgreSQL!