linux-kernel - Re: [RFC PATCH 0/4] API extension for handling sysctl

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Date:   Thu, 9 Jun 2022 09:45:26 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Alexey Gladkov <legion@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        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@...r.kernel.org, Vasily Averin <vvs@...tuozzo.com>
Subject: Re: [RFC PATCH 0/4] API extension for handling sysctl

On Wed, Jun 01, 2022 at 03:20:28PM +0200, Alexey Gladkov wrote:
> On Fri, Apr 22, 2022 at 01:44:50PM -0700, Linus Torvalds wrote:
> > On Fri, Apr 22, 2022 at 5:53 AM Alexey Gladkov <legion@...nel.org> wrote:
> > >
> > > Yes, Linus, these changes are not the refactoring you were talking
> > > about, but I plan to try to do such a refactoring in the my next
> > > patchset.
> > 
> > Heh. Ok, I'm not saying these patches are pretty, and looking up the
> > namespace thing is a bit subtle, but it's certainly prettier than the
> > existing odd "create a new ctl_table entry because of field abuse".
> 
> As I promised, here is one of the possible options for how to get rid of dynamic
> memory allocation.
> 
> We can slightly extend the API and thus be able to save data at the time the
> file is opened. This will not only eliminate the need to allocate memory, but
> also provide access to file struct and f_cred.
> 
> I made an RFC because I'm not sure that I did the permissions check for
> ipc_sysctl. I also did not change all the places where this API can be applied
> to make the patch smaller. As in the case of /proc/sys/kernel/printk where
> CAP_SYS_ADMIN is checked[1] for the current process at the time of write.

Thanks for all this, can you also add respective selftests extensions
for this on lib/test_sysctl.c and tools/testing/selftests/sysctl/sysctl.sh ?

  Luis