linux-kernel - Re: userfaultfd: two-step UFFDIO

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <da978e8c-2a72-4b7b-ae67-41e6ff0d5089@yandex.ru>
Date: Mon, 25 Nov 2024 20:07:34 +0300
From: stsp <stsp2@...dex.ru>
To: Peter Xu <peterx@...hat.com>
Cc: Linux kernel <linux-kernel@...r.kernel.org>,
 Muhammad Usama Anjum <usama.anjum@...labora.com>,
 Axel Rasmussen <axelrasmussen@...gle.com>, Mike Rapoport <rppt@...nel.org>
Subject: Re: userfaultfd: two-step UFFDIO_API always gives -EINVAL

25.11.2024 19:58, Peter Xu пишет:
> On Mon, Nov 25, 2024 at 07:15:10PM +0300, stsp wrote:
>> Man page clearly talks about
>> "the userfaultfd object" (one object)
>> when mandating the "two-step handshake".
>> I spent hours of head-scratching
>> before went looking into the sources,
>> and even then I was confident the man
>> page is right: people should always assume
>> documentation is correct, code is buggy.
> Hmm yes.  I didn't pay much attention initially, but then after I read the
> latest man-pages/, especially "UFFDIO_API(2const)" I found it looks indeed
> wrong in the doc.
>
> In this case we can't change the code because we need to keep it working
> like before to not break ABI.  We may still update the doc.
I wonder if some non-ABI-breaker
is possible, like eg keep the current
behavior of "features=0", but allow
to (optionally) override that by a
non-0 request? Yes, I've seen kselftests
are trying to double-register after 0,
but IIRC they tried to register wrong
options, which would fail anyway.