linux-kernel - Re: [PATCH 4/5] seccomp: add the synchronous mode for seccomp

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: <Y8AgiZqYSjozXbhP@tycho.pizza>
Date:   Thu, 12 Jan 2023 08:00:25 -0700
From:   Tycho Andersen <tycho@...ho.pizza>
To:     Andrei Vagin <avagin@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Christian Brauner <brauner@...nel.org>,
        Andrei Vagin <avagin@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Juri Lelli <juri.lelli@...hat.com>,
        Peter Oskolkov <posk@...gle.com>,
        Will Drewry <wad@...omium.org>
Subject: Re: [PATCH 4/5] seccomp: add the synchronous mode for seccomp_unotify

On Tue, Jan 10, 2023 at 01:30:09PM -0800, Andrei Vagin wrote:
> From: Andrei Vagin <avagin@...il.com>
> 
> seccomp_unotify allows more privileged processes do actions on behalf
> of less privileged processes.
> 
> In many cases, the workflow is fully synchronous. It means a target
> process triggers a system call and passes controls to a supervisor
> process that handles the system call and returns controls to the target
> process. In this context, "synchronous" means that only one process is
> running and another one is waiting.
> 
> There is the WF_CURRENT_CPU flag that is used to advise the scheduler to
> move the wakee to the current CPU. For such synchronous workflows, it
> makes context switches a few times faster.
> 
> Right now, each interaction takes 12µs. With this patch, it takes about
> 3µs.
> 
> This change introduce the SECCOMP_USER_NOTIF_FD_SYNC_WAKE_UP flag that
> it used to enable the sync mode.

What about just not having a flag and using the new primitives all the
time? Is there any reason not to?

Tycho