linux-kernel - Re: [PATCH 1/3] kernel/sysctl: support setting sysctl parameters from kernel command line

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Message-ID: <202003311125.939F851A6@keescook>
Date:   Tue, 31 Mar 2020 11:26:51 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-mm@...ck.org, Ivan Teterevkov <ivan.teterevkov@...anix.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        "Guilherme G . Piccoli" <gpiccoli@...onical.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christian Brauner <christian.brauner@...ntu.com>
Subject: Re: [PATCH 1/3] kernel/sysctl: support setting sysctl parameters
 from kernel command line

On Tue, Mar 31, 2020 at 09:48:36AM +0200, Michal Hocko wrote:
> On Tue 31-03-20 09:42:46, Vlastimil Babka wrote:
> [...]
> > > Should we not do this, we'll have to live with the consequences of
> > > supporting the full swoop of sysctls are boot params, whatever
> > > consequences those may be.
> > 
> > Of course when the first user tries to set some particular sysctl as boot param
> > and finds and reports it doesn't work as intended, then it can be fixed or
> > blacklisted and it can't break anyone else?
> 
> Absolutely agreed. I would be really careful to not overengineer this
> whole thing.

Right -- this is supposed to be _simple_, and I think that's the primary
benefit here. If we encounter problems we can fix those cases. The
careful place, I think, needs to be with converting existing boot params
to be aliases. That's when timing considerations need to be taken into
account carefully.

-- 
Kees Cook