Thread

Re: Server crash: Use-after-free in AfterTriggerEndQuery()

Anthonin Bonnefoy <anthonin.bonnefoy@datadoghq.com> — 2026-05-06T08:13:57Z

Hi,

On Tue, May 5, 2026 at 8:38 AM Amul Sul <sulamul@gmail.com> wrote:
> Here is the reproducible test that has an AFTER INSERT trigger on a
> referenced table that recursively inserts rows into itself:
>
> --
> create table trigger_recursive_pk (id int primary key);
> create table trigger_recursive_fk (id int references trigger_recursive_pk(id));
> insert into trigger_recursive_pk select g from generate_series(1, 15) g;
>
> create function trigger_recursive_fn() returns trigger language plpgsql as $$
> begin
>     if new.id < 10 then
>         insert into trigger_recursive_fk values (new.id + 1);
>     end if;
>     return new;
> end$$;
>
> create trigger trigger_recursive after insert on trigger_recursive_fk
>     for each row execute function trigger_recursive_fn();
>
> insert into trigger_recursive_fk values (1);
> --

I've managed to reproduce the issue on the current HEAD thanks to the
script. Doing a git bissect, the failure was introduced with
34a30786293005 when the batch_callbacks list was added.

> The attached patch fixes the reported issue by recomputing qs
> immediately before calling FireAfterTriggerBatchCallbacks().

The patch fixes the issue and the change looks reasonable.

Regards,
Anthonin Bonnefoy