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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHYQsXTHfRKBuTDYWus9r5jDLO2WLBeopt4_bGH_vVm=0z7mWw@mail.gmail.com>
Date: Mon, 19 Jan 2026 17:34:43 -0600
From: Yuhao Jiang <danisjiang@...il.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: Pavel Begunkov <asml.silence@...il.com>, io-uring@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] io_uring/rsrc: fix RLIMIT_MEMLOCK bypass by removing
 cross-buffer accounting

On Mon, Jan 19, 2026 at 11:03 AM Jens Axboe <axboe@...nel.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