linux-kernel - Re: [RFC PATCH 2/4] sysctl: ipc: Do not use dynamic memory

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Date:   Wed, 1 Jun 2022 21:05:17 +0200
From:   Alexey Gladkov <legion@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christian Brauner <brauner@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Linux Containers <containers@...ts.linux.dev>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Vasily Averin <vvs@...tuozzo.com>
Subject: Re: [RFC PATCH 2/4] sysctl: ipc: Do not use dynamic memory

On Wed, Jun 01, 2022 at 11:34:18AM -0700, Linus Torvalds wrote:
> On Wed, Jun 1, 2022 at 11:25 AM Alexey Gladkov <legion@...nel.org> wrote:
> >
> > I'm not sure how to get rid of ctl_table since net sysctls are heavily
> > dependent on it.
> 
> I don't actually think it's worth getting rid of entirely, because
> there's just a lot of simple cases where it "JustWorks(tm)" and having
> just that table entry describe all the semantics is not wrong at all.
> 
> The name may suck, but hey, it's not a big deal. Changing it now would
> be more pain than it's worth.
> 
> No, I was more thinking that things that already need more
> infrastructure than that simple static ctl_table entry might be better
> off trying to migrate to your new "proper read op" model, and having
> more of that dynamic behavior in the read op.

This was part of my plan. I wanted to step by step try migrating other
sysctls to use open/read/write where it makes sense.

To be honest, it was Eric Biederman who came up with the idea to separate
open, read and write. I am very grateful to him.

> The whole "create dynamic ctl_table entries on the fly" model works,
> but it's kind of ugly.
> 
> Anyway, I think all of this is "I think there is more room for cleanup
> in this area", and maybe we'll never have enough motivation to
> actually do that.
> 
> Your patches seem to fix the extant issue with the ipc namespace, and
> the truly disgusting parts (although maybe there are other truly
> disgusting things hiding - I didn't go look for them).

I also hope to try and fix the f_cred issue.

-- 
Rgrds, legion