| From: | Alexander Kuzmenkov <akuzmenkov(at)tigerdata(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de>, Anthonin Bonnefoy <anthonin(dot)bonnefoy(at)datadoghq(dot)com> |
| Cc: | Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Fix uninitialized xl_running_xacts padding |
| Date: | 2026-03-10 21:51:50 |
| Message-ID: | b607e42e-34ff-414a-b727-dd5ec70babe3@timescale.com |
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| Lists: | pgsql-hackers |
On 16/02/2026 21:10, Andres Freund wrote:
> I don't think it makes a whole lot of sense to tackle this specifically for
> xl_running_xacts. Until now we just accepted that WAL insertions can contain
> random padding. If we don't want that, we should go around and make sure that
> there is no padding (or padding is initialized) for *all* WAL records,
> document that as the rule, and remove the relevant valgrind suppressions.
That's not random, that's server memory, right? Probably not another
Heartbleed, but I'd rather initialize a few locals than find out.
Happy to see this being worked on, these uninitialized WAL records are a
major obstacle to enabling MemorySanitizer. I ran into this again today
and this is how I found this thread. Unfortunately the MemorySanitizer
can't even use the same suppressions as Valgrind, because the
suppression architecture is different (can only remove the checks from a
given function, not all stack traces that have this function like
Valgrind does).
Best regards
Alexander Kuzmenkov
TigerData
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