Re: BUG #16694: Server hangs in 100% CPU loop when decompressing a specific TOAST Postgis linestring

> 2 нояб. 2020 г., в 10:16, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> написал(а):
>
> Andrey Borodin <x4mmm(at)yandex-team(dot)ru> writes:
>> I'm not sure protection from corrupt input is complete within pglz. We
>> still do not protect from matches with offsets before source data.
>
> Yeah, I was wondering about that. Not quite sure it's worth adding
> cycles to defend against though.

I think so too. That's why I was not protecting from corruption at all when proposing c60e520.

Here we can have core dump too if *(srcend+1) produce SegFault:
len = (sp[0] & 0x0f) + 3;
off = ((sp[0] & 0xf0) << 4) | sp[1];
sp += 2;
if (len == 18)
len += *sp++;
if (sp > srcend || off == 0)
break;

And proper protection would cost nonzero time for branches. I think we should not protect against this.
I hope to see lz4 (or something else) in toast and other places one day :)

Best regards, Andrey Borodin.