Re: Schema variables - new implementation for Postgres 15 - Mailing list pgsql-hackers

On 13.11.2022 20:59, Pavel Stehule wrote:
> fresh rebase

Hello,

Sorry, I haven't been following this thread, but I'd like to report a
memory management bug. I couldn't apply the latest patches, so I tested
with v20221104-1-* patches applied atop of commit b0284bfb1db.


postgres=# create variable s text default 'abc';

create function f() returns text as $$
begin
         return g(s);
end;
$$ language plpgsql;

create function g(t text) returns text as $$
begin
         let s = 'BOOM!';
         return t;
end;
$$ language plpgsql;

select f();
CREATE VARIABLE
CREATE FUNCTION
CREATE FUNCTION
server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.

LOG:  server process (PID 55307) was terminated by signal 11:
Segmentation fault
DETAIL:  Failed process was running: select f();


I believe it's a use-after-free error, triggered by assigning a new
value to s in g(), thus making t a dangling pointer.

After reconnecting I get a scary error:

postgres=# select f();
ERROR:  compressed pglz data is corrupt

Best regards,

--
Sergey Shinderuk                https://postgrespro.com/