linux-kernel - Re: [RFC] better visibility into kworkers

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] [day] [month] [year] [list]

Message-ID: <20180517155021.GA5480@gardel-login>
Date:   Thu, 17 May 2018 17:50:21 +0200
From:   Lennart Poettering <mzxreary@...inter.de>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     tj@...nel.org, torvalds@...ux-foundation.org, carlos@...ha.com,
        luto@...capital.net, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC] better visibility into kworkers

On Do, 17.05.18 10:42, Alexey Dobriyan (adobriyan@...il.com) wrote:

> > The kernel APIs for all this aren't really good
> > though, and I always was reluctant to check for PF_KTHREAD, as that
> > flag is neither documented for userspace, nor available in any
> > userspace-accessible headers. However, I wanted to tighten this a bit,
> > and hence we now define the flag in our own code, as it appeared to me
> > otherwise there was no chance to ever make this fully robust.
> 
> PF_KTHREAD was introduced in 2.6.27 and its value appears to be stable
> since then. I think it should be retroactively declared part of ABI
> otherwise people will continue to rediscover that all other means do not
> work.

Yes, I agree. And it's exposed to userspace after all, though not
symbolic, but simply as flags value.

> Empty /proc/*/exe is second best option for systemd and it's only one
> system call.

That doesn't really work for us as readlink() on that requires
CAP_SYS_PTRACE, and we need something that works unprivileged, which
PF_KTHREAD does.

Lennart

-- 
Lennart Poettering, Red Hat