From: Kirill A. Korinsky <kirill@korins.ky>
Subject: Re: sys/uvm: fix uao_dropswap() index typo
To: Mark Kettenis <mark.kettenis@xs4all.nl>
Cc: tech@openbsd.org
Date: Wed, 22 Jul 2026 22:49:58 +0200

On Wed, 22 Jul 2026 22:28:23 +0200,
Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> 
> > Date: Wed, 22 Jul 2026 20:48:47 +0200
> > From: Kirill A. Korinsky <kirill@korins.ky>
> > 
> > tech@,
> > 
> > the loop variable indexes the current pgs[] batch, not the page within the
> > object. Pass the fetched page's object offset to uao_dropswap(), as the
> > other resident page callers do.
> > 
> > Thoughts? Ok?
> 
> Good find.  Trying to think about what the consequences would be of
> this bug.  I guess bad things may happen if we partially wire down an
> object and then unwire it again.  Some other pages in the object will
> get their swap dropped if they're swapped out.
> 
> Probably doesn't happen a lot.  Possibly cuases corruption of GPU
> memory?
>

Not sure that it is limited only to GPU memory.

My daily driver had random crashed processes when almost all ram was used
and machine started to touch swap.

Crashes was SIGABRT libc’s alloc. A few times it kills initd by the same
reason.

As soon as I fixed it, machine seems much stabled.

-- 
wbr, Kirill