Re: [PATCH v2] io_uring/rsrc: fix RLIMIT_MEMLOCK bypass by removing cross-buffer accounting

Yuhao Jiang
2026-01-19T23:34:55Z

On Mon, Jan 19, 2026 at 11:03 AM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 1/19/26 12:10 AM, Yuhao Jiang wrote:
> > The trade-off is that memory accounting may be overestimated when
> > multiple buffers share compound pages, but this is safe and prevents
> > the security issue.
>
> I'd be worried that this would break existing setups. We obviously need
> to get the unmap accounting correct, but in terms of practicality, any
> user of registered buffers will have had to bump distro limits manually
> anyway, and in that case it's usually just set very high. Otherwise
> there's very little you can do with it.
>
> How about something else entirely - just track the accounted pages on
> the side. If we ref those, then we can ensure that if a huge page is
> accounted, it's only unaccounted when all existing "users" of it have
> gone away. That means if you drop parts of it, it'll remain accounted.
>
> Something totally untested like the below... Yes it's not a trivial
> amount of code, but it is actually fairly trivial code.

Thanks, this approach makes sense. I'll send a v3 based on this.

--
Yuhao Jiang