Horton

Re: [PATCH] Fix segmentation fault and infinite loop in jsonb_{plperl,plpython}

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Aleksander Alekseev <aleksander@tigerdata.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2026-06-16T20:03:28Z
Lists: pgsql-hackers 
Aleksander Alekseev <aleksander@tigerdata.com> writes:
> The second bug affects only jsonb_plperl. It's possible to construct a
> Perl object with circular references which will cause
> SV_to_JsonbValue() to go into an infinite loop here:

>     while (SvROK(in))
>         in = SvRV(in);

> I suggest fixing it by rewriting the while loop into a recursion with
> check_stack_depth() call. This will make the behavior consistent with
> jsonb_plpython.

Unfortunately, your 0002 is too cute for its own good.  I tried it
here, with a not-especially-new gcc compiling at -O2, and found that
the tail recursion in SV_deref() is optimized into a loop.  So the
stack doesn't grow and we still have an uninterruptible loop.

I don't immediately see a way to write that function so that the
compiler is certain not to spot the tail recursion.  Tricks like
two mutually recursive functions might be seen through at
sufficiently high -O levels.

We could instead add a CHECK_FOR_INTERRUPTS, so that you can at
least break out of the infinite loop.  I'm not sure if the case
is worth more effort than that.

			regards, tom lane

Commits

  1. hstore_plperl: Add CHECK_FOR_INTERRUPTS() in reference-unwinding loop.

  2. jsonb_plperl, jsonb_plpython: Fix unguarded recursion and loops.