Re: Server crash with older tzload library

Hi Tom,

On Thu, Mar 11, 2010 at 8:29 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com> writes:
> > While setting timezone using SET command (say GMT+3:30), postgres
> sometimes
> > crashes randomly.
>
> I can't reproduce that:
>
> regression=# SET TimeZone = 'GMT+3:30';
> SET
> regression=# SELECT '1969-12-31 20:30:00'::timestamptz;
> timestamptz
> ---------------------------
> 1969-12-31 20:30:00-03:30
> (1 row)
>
>
Even we were fail to re-produce it always. It is crashing randomly. After
debugging, we found following values in tzstate variable when it crashed. So
I manually modified it at the beginning of pg_tzset() function.

/* Initialize tzstate with some arbitrary values */
tzstate.goback = 277946440;
tzstate.goahead = 0;
tzstate.ats[0] = 8892;

Also not that, tzstate variable remains uninitialized properly when tzload()
call returns -1. To mimic this, I have just renamed posixrules timezone file
to something else. So that tzload returns -1. And as tzload can return -1 in
any failure case and as we don't have that check at callee side tzstate
variable remains uninitialized which leading to a server crash. As above
garbage values too leads to a crash.

In summary, following are the steps to re-produce:
- Add above three lines at the beginning of the pg_tzset() function
- make install
- mv install/share/postgresql/timezone/posixrules
install/share/postgresql/timezoneposixrules_a (or remove it)
- start the server
- run these two statements on psql prompt
+ SET TimeZone = 'GMT+3:30';
+ SELECT '1969-12-31 20:30:00'::timestamptz;

BTW, after your commit, tzload() function now sets goback and goahead
variable to FALSE which fixes the server crash. MemSet in 2010c is just
doing it explicitly before calling tzload though.

Thanks for committing the part of the patch which stopped crashing the
server with above mentioned steps.

Thanks

> regards, tom lane
>

--
Jeevan B Chalke
Software Engineer, R&D
EnterpriseDB Corporation
The Enterprise Postgres Company

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